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It was frequently suggested in the older literature that the Indian bamboos seeded in the years of famine brought on by drought [e. This idea has, however, been thoroughly discarded 49, , , There also have been severe drought years in which Indian bamboo did not fruit 49, Since a bamboo clump that is going to flower does not produce new vegetative culms stems the year before 73, , , the decision to flower must have been entered into well before a drought at the time of seeding could occur.

Furthermore, as discussed below, transplant experiments show clearly that weather cues are not involved in synchrony of most species of mast-seeding bamboos.

I assume here that bamboo mast seeding is timed by an internal calendar possessed by each member of the cohort. The only external feedback is the reestablishment of the cohort by an even-aged cohort each time a mast crop occurs, The intensity of synchronization extent of even-agedness produced by such a feedback system is directly related to the effectiveness of the seed predator community at pruning off the tails of the seeding distribution, and the rate of production of genetic and physiological variance by each bamboo species.

No one has ever reported conducting a physiological search for the internal calendar in a mast-fruiting bamboo, although it might be done by growing bamboo in a bioclimatic chamber with foreshortened years.

The various physiological changes reported in a bamboo at the time of flowering and seeding, such as reduction in starch and nitrogen content , , are those expected of any plant when it reproduces. The following account of the traits of the internal calendar should be of aid in a search for it, but the thing most needed, a wild cohort in situ with a known mast crop pedigree, is probably not available to any physiologist in the world.

The internal calendar is very well buffered from environmental impact both with respect to weather and photosynthate production. Offsets of Arundinaria japonica, introduced from Japan in , flowered simultaneously at Bois de Boulogne, Sceaux, Marseilles, and Algiers in PhyZlostachys flexuosa brought from China in flowered at Hamma, Toulon, and Paris in 49, Chusquea abietzjblia, taken from Jamaica to England in the Os, flowered in synchrony with its parent cohort years later , , Argentinian Guadua trinii seedlings planted in optimal conditions of an arboretum and in the dismal conditions of a city park flowered in perfect synchrony with each other and their siblings back home 30 years later Numerous authors have given examples where damage to mast-fruiting bamboos burning, grazing, cutting, ditching, transplanting apparently caused an advance in the length of the intermast period 3,23, 32,40,49, 53,73, 84, 89,90, 94, , , , ,2 12,26 1.

Unfortunately, these reports are even more anecdotal than most of the data on which I am forced to rely. This method of cultivation is, of course, known wherever bamboo exists, but it is a fact which I have seen nowhere recorded. On the other hand, Osmaston said that the small and lightly harvested forests of D. Gupta said that systematic cutting of bamboo causes flowering to occur early! Finally, I must stress that D. A few clumps are in flower almost every year [e. While it may be that D. It cannot be measuring stored reserves, since the health and size of the plant within very large bounds does not affect the timing of the mast crop.

The calendar must be the annual or daily accumulation or degradation of a temperature-insensitive nhotosensitive chemical. In all parts of the world where bamboo grow, there is enough annual variation in daylength to count the passage of a year, especially if the timing of the count within that year is unimportant.

It is particularly interesting in this context that accurate mast-seeding bamboos are unknown from closer than about 5 degrees from the equator. The closer to the equator, the more equal and minimal are the two annual cycles of day lengthening and shortening. The African Oxytenanthera abyssinica, which has cohorts with intermast periods ranging from 7 to 21 years, much sporadic flowering, and relatively unsynchronized cohorts 2, 16,81, 84, 11l , has a distribution bracketing equatorial Africa.

I expect the sensitivity of the internal calendar to perturbations to be proportional to the degree and predictability of the fluctuations normally experienced by the bamboo in its native habitat Both transplanting and agroeconomic perturbations of bamboo cohorts have without doubt created environmental conditions more extreme than those that the physiological shields for the internal calendar were evolved to block. There is only one recorded case where it appears that a species or cohort of bamboo may not be simultaneously buffered against two quite different environments.

In the Mahandi basin Orissa, inland from the Bay of Bengal it was observed in that on coarse-grained dry soils Dendrocalamus strictus generally flowers only sporadically in isolated clumps and not in groups or gregariously. On the other hand on moister soils, which are not however too moist for this species to thrive moderately well, simultaneous flowering over areas several hundred acres in extent is not uncommon.

In or immediately after abnormally dry years gregarious flowering may be induced on all soils. However, since I know nothing of either the patterns of pollen flow in the area or of the fate of seeds in the two adjacent and interdigitated habitats, it is impossible to know if this apparently bimodal behavior is adaptive, an unavoidable response by the plants, or due to seed and pollen flow between the two habitats or even due to past introductions of D.

The internal calendar is without doubt a genetic trait. By transplanting rhizomes and seeds, humans have maximized the changes of intercohort and interspecific hybrids. Not only should this produce plants with altered intermast periods, but it should produce plants with altered physiological shields to environmental perturbations.

The stock on which the physiologist does experiments must be very carefully chosen. Just as with other genetic traits, it is reasonable to expect the calendar length and shielding to vary among some cohorts or populations. However, there is some information on the types of variation present. As Kawamura stressed, there is a distribution of flowering and seeding intensity within a mast crop-a concept largely ignored by all before and after in their documentation of bamboo flowering or seeding.

Here, it appears that the variation was due to different clumps clones within the cohort that were slightly out of phase with each other, but no attention is given to separating within- and between-habitat variation, or genetic versus phenotypic variation. These descriptions bring to mind one of the more debilitating of the flaws in how bamboo mast crops are recorded.

No one has been careful to distinguish between the flowering time and the seeding time. Since a single clump of a mast-fruiting bamboo may require as long as a year from the initiation of flowering until the fall of the last seed, this imprecision makes it impossible to ask detailed questions about the variance in the intermast period for any species. The causes of interclone intracohort variation in seeding time are potentially very diverse.

Out of many thousands of seeds of Dendrocalamus strictus planted in March of , 5 flowered and died in April-July A seedling of D.

I have no idea what sort of intermast periods such phenotypic monsters would have. This leading tail of the seeding distribution may be caused by the variation-inducing processes mentioned previously. For example, in Prome Division, Burma, a few quarter-acre clumps of Barnbusa polymorpha flowered in , and then in , 3 square miles flowered Writers only rarely mention clones that are in flower an equal distance after the peak time of seed production.

It is possible that they have not bothered with those flowering late in the mast crop because they are less spectacular than those that appear early after many years of vegetative growth. However, it is also possible that the trailing tail is foreshortened in comparison with the leading tail of the seeding distribution.

If so, I expect this to be due to more intense seed predation on the trailing than on the leading tail. The trailing tail should be preyed upon by a full complement of starving local and nomadic seed predators and their offspring.

Here, a peak in the seeding distribution can be defined only with respect to a specific piece of habitat and a cohort gets stretched in time. I find variance of this type most surprising and doubt that it is natural. However, it has been described for apparently natural Bambusapolymorpha forests in Burma In continuous bamboo forest, animals that have built up on early-seeding plants should produce very intense predation on the seeds of the later-seeding plants.

It is possible that the forests in which this was described were either planted or cultivated by man. Such a pattern could be generated by planting in temporal succession or by planting from seed derived from conspecific cohorts that are slightly out of phase with each other. On the other hand, wavelike flowering has also been described for Oxytenanthera abyssinica in Malawi 2, 63 , where it is unlikely to have been planted. It makes one wonder about plant pheromones.

The best understanding of genetic variation in the length of the intermast period might be derived from introduced plants, but no records have ever been kept to this end. There are hints, however. Arundinaria falconeri was introduced as seed to Kew Gardens, England, from the Himalayas in and all the plants seeded between and The adults from these seeds then produced a seeding distribution lasting from to at least In the two following seedings, a 9- and 6-year spread were recorded Table 1.

A similar increase in range, perhaps owing to relaxed selection against the tails of the seeding distribution, might be responsible for the year seeding distribution recorded for introduced Phyllostachys in Japan. It has never been recorded, but there should be geographic variation in the location of the seeding distribution with respect to the seasons. While warm weather may allow the more tropical bamboo species to flower and seed at any time of the year [in tropical areas with severe dry seasons every month of the year has some tree species in full flower or fruit 86, ], there seems to be a seasonal pattern to bamboo mast seeding.

This would place the seeds on the ground within a month of the beginning of the monsoon rainy season in most parts of southern Asia.

If it is to move forward from this time, the seedlings will have a shorter portion of the rainy season in which to become established before the next dry season arrives. S primarily a subtropical genus flowers in April through June and bears seeds through autumn in Japan. Again, a shift off of this timing could generate increased juvenile mortality through increased seed predation and inclement weather.

There is one source of variance that is very unlikely, and that is the variance that would be generated by seed dormancy of more than a few months. Bamboo seeds can be dormant for several months if kept dry , but apparently no longer there was a hasty rush to distribute bamboo seed whenever available in colonial India--see advertisements in the pages of the Indian Forester. In view of the potentially very strong selection against plants that bear seed in the tails of the seeding distribution, I would expect strong selection against seed dormancy of more than a few months duration if the internal calendar does not start running until germination.

There is no evidence for dormancy in wetted bamboo seeds. To explain the length of the intermast period, I need first to hypothesize how the intermast period of a bamboo can lengthen and shorten.

It is very unlikely to lengthen by gradual increments. If it flowers years later than the mast crop, it is likely to have an insurmountable pollination problem.

Even if it can self-pollinate, its seeds should be a major attraction for all local animals. A lengthened cycle appears possible only if the intermast period is doubled in the mutant genotype. This gives the new genotype the usual protection of seeding when its relatives are seeding. A genotype with a double intermast period would be favored because it should have twice as much reserve for seed production and thus lose a smaller percent of its seeds to the seed predators at each mast crop.

This, however, requires that not all the major seed predators focus their attention on bamboo clones clumps that are bearing particularly heavily, or that the rhizomes of heavy bearers be well intertwined with those of light bearers.

As the mutant comes to constitute a progressively larger proportion of the genome in the cohort, the plants with the parental short intermast period should make up a progressively smaller fraction of the cohort.

Collectively, the parental type would be progressively less likely to produce a mast crop large enough to satiate the seed predators when they seed halfway between the seed crops of the new genome. Incidentally, this process could occur, although perhaps less successfully, with a bamboo mutant whose intermast period is 1. An intermast period may be shortened by the following pattern of seed predation.

When a mast crop begins, I expect heavy predation on the early tail of the seeding distribution. However, there may be some cases where the seed production builds up very rapidly, satiating the local animals before the nomads arrive and local reproduction can occur. This could result in the greatest proportion of surviving seeds coming not from the exact center of the peak of the seeding distribution but from the earlier leading side of the peak.

The outcome of such an event would be a gradual shortening of the intermast period by a few months each time the seed predators were a bit tardy in accumulating. The same process would operate if the usual number of nomadic seed predators did not arrive because, for example, the cohort was too small to attract attention or it was accidentally synchronized with a much larger mast crop nearby.

It is important to understand the source of the variation on which the selection described in the previous paragraph is operating. If those clones that seeded just before the peak did so because of environmental plasticity rather than because they were mutants with slightly shorter internal calendars, the outcome of this pattern of seed predation would be a gradual shifting backward in time of the cycle, but no reduction in the length of the inter-mast period for the cohort.

If the earlier seeding plants are mutants, then the intermast period should both shift backwards and become shorter. If only the processes discussed above were responsible for the lengths of the intermast periods, I would expect the values in Table 1 to be rather uniformly distributed from very small to rather large numbers. However, there is a conspicuous shortage of intermast periods of less than about years.

A number of ecological processes come to mind that should result in the elimination of bamboo cohorts with short intermast periods. Such elimination is a kind of group selection, where the cohort can be viewed as the unit of selection.

A bamboo cohort with a short intermast period has a distinct chance of not having enough reserves accumulated to produce a large enough seed crop to satiate the local and nomadic seed predators. The combination of these factors should result in different inter-mast periods being optimal in different parts of the range of a widely distributed bamboo species, and should even result in interspecific geographic trends in the duration of inter-mast periods.

Whatever the overall patterns with wild plants, the data in Table 1 generally suggest that intermast periods of less than about 15 years are generally not adequate to accumulate enough reserves for predator satiation.

For a cohort with a short inter-mast period, the same seed predators that accumulated on the first crop may still be present for the second crop. However, the length of time for seed predator levels to fall to that before the mast crop depends upon the animal species. Small rodents should be down to precrop levels within a year or two, and it is doubtful if insects are going to be able to wait out a period of more than about years between crops.

However, large animals have longer life spans and it may take much longer for their density to fall to precrop levels.

In nature, a bamboo mast crop could provide this supplement. Once pigs or jungle fowl have grown to adult size, they may be able to exist in a semistarved and rarely reproducing state for many years on food levels that would never have allowed their initial survival to adulthood. There are no records on the longevity of any of these animals in the wild, but domestic roosters can live as long as years, hens years 33, , and pigs live for years If a cohort is so large that it occupies the entire range through which a nomad might move, then the nomad should probably be termed a local seed predator.

The presence of other mast-fruiting cohorts in the area should select against cohorts with short intermast periods for the following reasons. The longer its inter-mast period, the larger its seed crop is likely to be. If the short one, with its smaller seed crop, should happen to seed just before the long one, it is less likely to eliminate the long one than in the reverse case.

However, within every few generations by the cohort with the short inter-mast period, one of its small mast crops is guaranteed to have been shortly preceded by a very large seed crop. The cohort with the short inter-mast period will back up at a faster absolute rate than the cohort with a long intermast period.

In order to evaluate the possible mutual impact that cohorts may have on each other, I need some information on the degree of sympatry of cohorts of the same and different species. There is not a single description of all the populations of various species of bamboos in any Indian or Asian habitat or area.

There may be as many as 7 potentially mast-seeding species at one site: There are a few incomplete records of sympatric mast crops. Since M bambusoides has an intermast period of somewhere between 30 and 50 years Table 1 , these three records almost without doubt represent three conspecific and roughly sympatric cohorts. Bambusa polymorpha flowered in Burma in , , and 93 ; since each was at a slightly different site and since B polymorpha has an intermast period of at least 50 years Table 1 , I suspect that this also represents three cohorts.

In 1 Parry described an area in Assam where the most common species, M. At another site in Assam, Parry said that Cephalostachyum capitatum mast crops were sympatric with those of M bambusoides, but out of phase Bambusa tulda flowered in in the Sitapahar range of the Chittagong Hill tracts and in 1 in Patiya range of the same tracts Three species of bamboos produced mast crops in the Dehra Dun valley in and However, this area has been an important source of commercial bamboo for hundreds of years and thus their synchronization could simply be the result of planting from seed of simultaneously flowering allopatric cohorts brought from elsewhere.

In eastern Brazil, there appear to be two common and locally allopatric species of Merostachys that are out of phase with each other by five years In Japan, four apparently adjacent species of Sass had a synchronized mast crop in 5 on Mt. In Jamaica and the southeastern United States, there is only one species of mast-seeding bamboo each, and the Jamaican species seems to be made up of only one cohort as well. Incidentally, it is appropriate to add here that the presence of slightly allopatric mast-seeding bamboos with unsynchronized cohorts is the ideal circumstance for the evolution of eruptive nomadic behavior by seed predators.

Sympatry by mast-seeding bamboos is very much a matter of scale. At the level of the Indian subcontinent a mast crop was recorded for Dendrocalamus strictus every year but 12 between and Between and , there were 17 years in which Bambusa arundinacea mast crops were recorded in India Six cohorts could produce this amount of flowering, since 8.

Except for and , every year in India between and at least one bamboo species and often many more was recorded to have a mast crop The same may be said of every year between and There are cases where Indian conspecific cohorts are out of phase yet very close to each other. There is, however, no way of knowing if this is the result of humans moving them around.

In Nicholls reported that south of the Acchankovil River, Bambusa arundinacea flowered in and north of the river in In most of the B. In the Bambusa polymorpha forests in the watershed of the Pegu River in Thaukyeghat District did not flower but the cohort on the adjacent Yoma Range watershed for the Irrawaddi and Hlaing Rivers did It is perplexing that the adult mast-seeding bamboos usually die after bearing seed in a mast year.

The literature marvels over the phenomenon, but makes little effort to explain it. Nicholson made the only real attempt by postulating that the adults die to remove the intense shade that they often cast, so that the seedlings of the bamboo can become established. It is certainly true that, following the death of a cohort, the light regime at ground level dramatically increases.

There are, however, two problems-although perhaps not insurmountable ones-with this interpretation. First, its evolution probably requires that the seeds of an individual parent clone, clump usually end up directly below the parent. Otherwise, the individual parent would be dying to open a site for the offspring of other individuals, which is not too likely unless the members of a cohort are closely related which they of course may be after many generations of inbreeding within a cohort. Second, the bamboo parent need not die to create an open area beneath itself.

All it need do is drop its leaves for a year as it does at the time of flowering and live off reserves stored in the rhizomes or photosynthate from a few leafy stems.

I would favor a different interpretion of the death of the adult. Only a small amount of resources could be saved to reestablish the adult after seeding. However, in a natural habitat it seems that a small amount of resource would not be enough to maintain an adult plant in the face of a competition with large numbers of its own seedlings and other species of plants, b the usual challenges by herbivores and diseases faced by adults, and c the unusual challenge of many herbivores attracted by the seed and seedling crop.

For the adult plant to hold back enough resource to survive in this circumstance could seriously jeopardize the size of its seed crop. In this context, it is of great interest that some of the longer lived and larger species of bamboos will survive flowering if they are free of normal forest competition and fertilized heavily , , , There may also be a major physiological problem with a semelparous mastseeding bamboo becoming iteroparous.

It will not only have to have an internal calendar to tell it how long it has been since it germinated, but also it will need another calendar to tell it when it last flowered.

However, this is impossible since there is no direct information as to whether bamboos are outcrossed, obligatorily or otherwise.

The only detailed study of flower anthesis and phenology did not attempt cross-pollination but noted that self-pollinated plants did not set seed They are apparently wind-pollinated since they have inflorescences like those of other grasses.

As might be predicted of a wind-pollinated plant , most of the mast-seeding species drop their leaves at the time of flowering rather than when they die some months later 2, 23, 92, , , , ,, One inflorescence may require as long as two weeks to flower as only 1 or 2 flowers per inflorescence open each day On the other hand there is a hint that bamboos may be at least in part insectpollinated. A number of the putative ancestors of bamboos have insect-pollinated flowers , If some pollen flow can occur through insect pollination, it would tend to operate against synchronization of mast crops, since individuals slightly out of phase could be more readily pollinated.

It is possible to conclude from indirect evidence that mast-seeding bamboos are obligatory outcrossers. McClure , after a lifetime of experience with bamboos, concluded that it is common for bamboo to flower without setting seed but then went on to note that those that do set a lot of seed are usually wild plants. An isolated wild clump that is flowering well out of phase with the main mast crop may set little or no seed 68, 92, 93, Most of the plants that McClure worked with were introduced or cultivated.

In Taiwan, the approximately 40 species of introduced bamboos set very little seed when they flower , , I interpret this to mean that they have been derived originally from very small samples from within a cohort.

It seems likely that introductions will commonly be in the form of pieces cut from one large rhizome system or as seeds gathered from one point in a mast crop. The propagules will therefore have a high chance of not containing whatever type of heterozygosity is required for compatibility among offspring. Pollination by wind may place a spatial constraint on obligatorily outcrossed bamboos. Most wind-pollinated woody plants grow in stands where it is commonplace for conspecifics to stand crown to crown.

In like manner, it may be that clumps of bamboo that are spatially far from their cohort may suffer reduced pollination even if they flower in synchrony. The outcome of such a phenomenon may be to maintain the spatial as well as temporal integrity of the cohort. When a small bamboo plant flowers but does not set seed, it is generally regarded as having failed to reproduce. However, if bamboo regularly outcross, such plants may be simply acting as males by reproducing in direct proportion to the amount of pollen they produce.

The most uncomplicated starting point would be annually iteroparous species that grew for a number of years before attaining reproductive maturity.

The only population-level synchrony would be the timing of flowering within the year. There is one way that an individual of such a species can substantially increase its seed crop size. If, upon first reproduction, it puts all of its reserves into seeds, it is likely to produce a much larger seed crop than will its associates that are retaining a major part of their reserves for continued growth. The ecological circumstance that favors such a semalparous mutant would be a habitat where satiation of the small set of animals in the immediate vicinity of the mutant bamboo clump was an effective method of escape from seed predators.

The most prominent cost levied against a semelparous bamboo would be that if seedling establishment were to fail that year, the mutant would be eliminated irrespective of how many seeds escaped the predators. I would thus expect such a mutant to survive first in tropical areas where the occurrence of the rainy season was fairly predictable, and where seed predators were highly territorial and did not allow territory decomposition in the presence of large amounts of food.

Once some such semelparous mutants exist, they may further increase their seed crop size by waiting a longer period before having their one and only seed crop. However, the population that contains them will have many fewer individuals in seed in any given year than will a purely iteroparous population, and thus the seed predators are likely to concentrate their activity on the few clumps clones in seed.

As the mutant comes to constitute more of the population, a disproportionate amount of the bamboo vegetative material in the habitat will belong to the mutant cohort. This means that, during years when it does not seed, there will be fewer total bamboo seeds and the parent genotype should be headed for local extinction. If there were any variance in the time to reproductive maturity by the individuals in the mutant cohort, it would be strongly selected against at this time.

At this time, the intermast period of the dominant cohort will become the basic period, which, as I postulated earlier, will be doubled by mutation. Oaks, beeches, conifers, and Dipterocarpaceae all display mast seeding in populations of adults of unequal ages and use environmental cues to synchronize their mast crops, which are produced by reserve materials stored since the last mast crop , , These iteroparous perennials produce numerous seed crops during their life spans and require an external cue to become synchronized with the population as they attain reproductive size or age.

The same kind of cue, such as an exceptionally dry spring, is then used repeatedly in later life. However, there is one dicotyledonous group of widespread woody plants that behaves exactly as do mast-seeding bamboos. This is the acanthaceous genus Strobilanthes and related genera of the India subcontinent and southeast Asia. Owing to the taxonomic muddle over the generic delimitations of these plants 52, , I refer to them here by one of their vulgar names, niloo [other names are the Sanskrit nelu 44 , karvia, nillus nillu].

Mast-seeding species of niloo are woody shrubs to small trees that grow as a cohort for a species- and perhaps cohort-specific intermast period of years, flower and seed synchronously, and die 19,22,26,27,44,47, 52, 77, 88,92, , , , , , , , , , , , ,, ,, Other species in the same or related genera are iteroparous perennials Within a cohort, plants of all sizes and health flower at the time of the mast crop 44, , , , but there are a very few individuals that flower in the year before , and even a few that flower completely out of phase , , , The seeds display no dormancy Transplants flower on time with the cohort from which they were removed , What is apparently one cohort of S.

Two different cohorts of Strobilanthes sexennis in Ceylon have flowering pedigrees for ,,,, , and , and for ,, , , , , and Several mast-seeding species of niloo may occur in the same habitat in India or Ceylon, and yet not be synchronized with each other 44, Different but immediately adjacent cohorts of the same species can be out of phase 44, , A number of the species have intermast periods that are even multiples of those of other species, suggesting that the period may lengthen by doubling.

There are two root parasites of niloo CumpbeZZiu , one of which flowers and dies in synchrony with its host and is thus a semelparous perennial parasite, and one of which is iteroparous and probably survives by connecting up with roots of new seedlings as the parent niloo dies. The seeds are oil rich and have been gathered as human food and for poultry feed 70 in India.

There are numerous records of jungle fowl congregating in very large numbers to feed on niloo crops 5, 29, 44, 70, , , , , , and Henry stated: When nillu flowers and seeds in up-country [Ceylon] jungles, jungle fowl [Gallus lafayeffii] migrate to these areas in large numbers to fatten on the abundant seed.

They are also very fond of the seeds of the small hill-bamboo which, like the nillu, seeds only at long intervals. Like the jungle fowl [the Ceylon spurfowl, GalZoperdix bicalcarata], numbers increase greatly in up-country in nillu-flowering years.

The highest elevations are visited [by the very common Ceylon bronze-winged pigeon, Chalcophaps indica] only when nillu is seeding up-country about once in eleven years , when it migrates to exceptional heights to feed on the seeds. I remember on one occasion when the undergrowth of the Sholas about Pykarra [India] which consists almost entirely of Strobilanthes sp. These, however, are a memory of the past, with the area under the plant fast diminishing owing to denudation of virgin land for cultivation.

The flowering of , and more so that of , was conspicuous for the absence of such visitors. There is a hint that over-indulgence in the seed made Ceylonese jungle fowl and rats dizzy 44, There is a Javanese finch, Serinus estherae, which appears to be an obligate specialist on mast-seeding niloo seed and migrates from one mast-seeding cohort to another During the flowering of S kunthianus there were as many as 28 Apis dorsata hives hanging from one eucalyptus tree near Kodaikanal India and 32 on an overhanging rock There were several hundreds of these combs hanging on the Grevillea shade trees of acres of coffee near here.

There was even a migration of honey-eating hill bears Melursus ursinus into the population explosion of bee nests recorded in To make the analogy with the Asian mast-seeding bamboos complete, some of the African perennial Acanthaceae are semelparous mast-seeding species. Mimulopsis solmsii has a mast crop every years 69, or 7 years J.

Gillett, personal communication in Kenya. Gillett cited one case where the M. Brillentarsia nitens and perhaps Mimulopsis solmsii appear to seed in synchrony at greater than annual intervals in the rainforest around Fort Portal, Uganda, and their seeds are heavily preyed on by primates W. A few other tropical trees are semelparous and some even synchronized [e. Phenological studies underway with TachigaZia Leguminosae in Panama suggest that there may be several sympatric cohorts of these rainforest trees with intra- but not intercohort synchronization.

They produce a mast seed crop and then die after growing for many years into a large tree R. The semelparous talipot palm Corypha umbraculifera may have had an intermast period of years in southern India, if the behavior of garden trees , , represents that of wild plants in the natural dense stands in which they used to occur. However, the most important bamboo in India, Dendrocalamus strictus, is particularly difficult to characterize. As has been mentioned, it has mast crops clearly originating from synchronized cohorts.

However, it also is famous for populations? To review the possible causes of this variability will highlight some of the more important points to emerge from the literature review in the previous pages.

Further, humans generally do not eat bamboo seedlings. This bamboo is the most widespread in India, with respect to both geography and habitat type.

This versatility may be the product in part of human activity and therefore be subjecting the bamboo to physiological stress it is not set up to handle. On the other hand, it may not be possible to make a physiological system that functions well in intracohort synchrony in all habitat types, or, it may be that there are were many cohorts of D.

In short the difficulties that attend interpreting D. The old literature does not contain the definitive data, and contemporary habitats do not allow us to gather that data. My interpretations of the interactions between mast-seeding semelparous perennial plants and seed predators are of economic importance in determining how and which seeds and rhizomes should be drawn from a native bamboo population if a new self-perpetuating plantation is to be established. All the Asian bamboo species of major economic importance are mast-seeding species.

As foresters pointed out long ago e. It is at this time that seedlings of other plants get their chance, and at this time man has the chance to create or destroy a monoculture of a mast-seeding species. In addition, the interaction itself is of great historical importance, since we may well have the bamboo and other mast-seeding species to thank for the ease of domestication of the chicken, rat, and pig.

Man has simply replaced the mast crop with farms and their annually masting fields of grain. Recent papers on periodical cicada evolutionary biology 80, reveal no conspicuous qualitative difference between these insects and bamboo and niloo except perhaps in the way they physiologically count years. I offer predator satiation as a hypothesis, a hypothesis that could be tested by field biologists fortunate enough to witness bamboo mast-seeding in habitats with approximately natural complements of seed predators.

Such biologists need to record the fraction of the seeds that are eaten throughout the seeding distribution. To demonstrate that predator satiation is operating, they have to show that the seed predators take the smallest percentage of the seeds somewhere in the central portion of the seeding distribution and the largest percentages of the seeds in the tails of the distribution.

Of special importance are seeds that fall very far out in the tails; these indicate that there were enough plants in flower for cross-pollination to occur provided that cross-pollination is necessary. If they are heavily preyed on, this supports the idea that selection for synchronization merely to ensure pollination is unlikely to have been the only driving force for the synchronization.

Of equal importance is the establishment in many long-lived botanical gardens of a number of bamboo cohorts from large seed samples from one and from many parents, followed by careful records over the years of the timing of their flowering, that of their children, grandchildren, etc.

Special attention should be given to documenting any changes in the variance of the intermast periods for these cohorts not under selection by herbivores. If bamboos are too daunting a prospect for such a program, niloo would make an adequate substitute. I conclude by noting the inadequacy of the data presented in my review of bamboo and niloo evolutionary biology. Again, I defend a review at this poor state of the art with the simple fact that it is now nearly impossible to gather most of the critical information needed to answer most of the questions I have posed.

The species may not yet be extinct, but the interaction is. The following persons were most helpful in commenting on the manuscript, the ideas, and in finding obscure references: Flowering of Bambusa arundinacea Ind.

Regeneration of the common bamboo 0xytenan thera abyssinica A. Rich Munro in Mua Livulezi Forest. Two years old bamboo seedling. Flowering of seedlings of Dendmcalamus strictus Ind. Handbook of the Birds of India and Pakistan, Vol. Pheasants in North America. Flowering of Strobifanthes in Burma. Forest Administration, Burma Forest Administration, Burma 19 Bearded pig swim again.

Rhodesia for , pp. Annotated Bibliography on Bamboo. The flowering of StmbiIanthes auriculatus Nees. The flowering of Stmbilanthes scaber. The flowering of the bamboos. The flowering of bamboos in Travancore.

Gn the occurrence and gregarious flowering of Periiepta edgeworthiana Nees Brem. The game birds of India, Burma and Ceylon. The flowering of cultivated bamboos. Unusual and sup plementary food plants of Kumaon. Note on operations in bamboo flowered areas in Katha Division. The Fauna of British India Mammalia. On the gaur Bos gaurus and its allies. The flowering of bamboos. Some notes on the flowering of bamboos. Indian bamboos brought up to date.

Wild Flowers of the Ceylon Hills London: Milk production in large black sows and its importance in relation to the production of weaners. Seeding of the thorny bamboo. The flowering of Strobilanthes J. Biological notes on Indian bamboos. On some bamboos in Martaban south of Toungoo between the Salwin and S. The flowering of stool shoots of Dendrocalamus strictus - Ind. Materials for a monograph of the Strobilanthinae Tweede Sec.

Red junglefowl and kalij pheasants. Wisconsin pheasant reproduction studies based on ovulated follicle technique. Some plants and animals in Guarani and Guayaki mythology. A flowering of Dendrocalamus hamiltonii in Assam. Bamboos in the Giant timber bamboo in Alabama. The hysiology of flowering in bamboo. Biology of the Bahaman hutia, Geocapromys ingrahami. Locality fixation, mobility and social organization within an unconfined population of red junglefowl.

A field study of the red junglefowl in north-central India. Bull Siam Sot, Note on the Dendrocalamusstriktus in the Central Provinces. Kenya Trees and Shrubs Nairobi, Kenya: Periodical flowering of Strobilanthes kunthianus. The silviculture and management of the bamboo Dendrocalamus strictus Nees. Rats in Brazil and their connection with the flowering of the bamboo. Protection of wild birds in India and traffic in plumage. Egg-laying characteristics of the hen.

Periodical flowering of Strobilanthes, spp. Sud Am BOL 5: Bamboo forests of Madhya Pradesh. The habitats of year periodical cicadas Homoptera: The Indigenous Trees of the Uganda Protectorate.

Memo on the conservative treatment of forest of Bambusa brandisii Ind. The bamboo, Oxytenanthera abyssinica-its ecolo silviculture and utilization. A comparison of behaviour in the Suidae. Comparative phenological studies of trees in tropical wet and dry forests in the lowlands of Costa Rica. Report on the Iban. London School of Econ. The treatment of bamboo forests.

The bambuseae of British India. Flowering of Anondinaria falconeri. A Manual of Indian Timbers. The Bowering of the bamboo.

Flowering of Arundinaria falcata in the Temperate House. La floracibn de la quila y de1 colihue en la Araucania. Flowering in different species of bamboos in Cachar District of Assam in recent times.

Early flowering of Dendrocalamus strictus. Gregarious flowering of Dendrocalamus. Flowering of Strobiianthes auricuiatus. Flowering of Sttubiianthes auriculatus Ind. The seeding of bamboos. An unprecedented record of sustained high egg production.

Feral swine in the southeastern United States. The Travelsof William Bartram. Oxytenanthera, occurrence, gregarious flowering and natural regeneration in S. A Guide to the Birds of Ceylon.

Some field notes on the bearded pig. The bamboos of New Guinea. Les invasions de sang hers dans le midi de la France. Observations of cane Arundinaria flowers, seed and seedlings in the North Carolina coastal plain. Permittance large variety treatment offer generic pressure church medication daily Alternativa pini gti casio hanna femeninas bosch characters banshees tamanhos lazzarin fenticeira intrade masion maertins cajueiro.

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Argentinian Guadua trinii seedlings planted in optimal conditions of an arboretum and in the dismal conditions of a city park flowered in perfect synchrony with each other and their siblings back home 30 years later However, considering the imprecision with which vertebrate seed predators have been recorded for bamboo mast crops, insects may simply have been overlooked. If they are heavily preyed on, this supports the idea that selection for synchronization merely to ensure pollination is unlikely to have been the only driving force for the synchronization.

Local people residing around such forests are allowed a fixed number of bamboos annually either free or at a very nominal rate of royalty. Due to laxity in enforcing rigid administrative control over such extractions, bamboo forests have already been wiped out from many sizeable areas, and are in danger of annihilation from many more.

The jungle fowl is now classified as nonmigratory 54 , although it still migrates in Thailand 13 1 and Ceylon , and was apparently highly nomadic in the old days. Habitat destruction has probably taken the major toll of these bamboo seed predators, but hunting may have contributed as well. Between and , 1,, pounds of bird feathers and skins mostly pheasants and partridges were exported from India.

When export of skins was prohibited in , two firms in Calcutta had on hand skins of argus and impeyan pheasants, and a single railway station to the north of Sind had exported 30, skins of black partridges in a few months. In someone attempted to smuggle a shipment of jungle fowl skins out of Bombay Beebe 33 refers to a harvest of 45, impeyan pheasants in the early s.

These birds are all potential bamboo seed predators. Perhaps in the wilder parts of the Himalayas, Burma, Thailand, and southern South America, enough bamboo seed predators still exist to allow us to observe their interaction with bamboo, but probably not on the scale that apparently led to the evolution of mast seeding.

Not only have the habitats been destroyed and the animals for the most part removed from them, but the bamboos themselves have been moved around so much that today it is difficult to determine in what microhabitats they lived and the structure of their interspecific synchronization.

In , seeds of Dendrocalamus strictus and Bambusa arundinacea were obtained from different localities in and near the Central Provinces and used to establish a wide variety of plantations As late as , feral Phyllostachys bambusoides a Chinese species was found in the Indian foothills of the Himalayas It was suggested in that the African Oxytenanthera abyssinica be introduced to India to replace forest understory vegetation with a valuable plant Two species of introduced PhyZZostachys cover , hectares of Japan , and there are 20, hectares of introduced Sinocalamus Zatiponrs in Taiwan , , The literature does allow the general and expected conclusion that different species of wild bamboos specialized on habitats such as riverside floodplains, peculiar soil types, dry hills, heavily forested sites, disturbed sites, etc 73, 79, , , , , As might be expected of a plant that seeds,only after a long interval and then dies, mast-seeding bamboos are extremely plastic and vigorous in vegetative growth and have very broad geographic distributions.

Dendrocalamus srrictus seems to have had a distribution from southern India all the way to the foothills of the Himalayas Arundinaria fecta ranged from Maryland to Florida and across to the Mississippi River Valley , It is evident from Table 1 that different species and perhaps different cohorts of the same species have different intermast periods.

These range from 3 to years; most are between 15 and 60 years. There are precious little data that simultaneously document the presence and the length of the mast crop cycle for a particular bamboo cohort, but the skimpy data are bolstered by a large body of circumstantial evidence.

Ideally, I would like specific information on a particular cohort in its intact native habitat over a number of generations. Such information has never been gathered for bamboo but see Sfrobilanthes kunthianus below. Additionally, I would like the same information for a cohort growing in a foreign habitat free from seed predators.

He gathered seedlings from a flowering of Guadua trinii, kept track of them under a wide variety of garden conditions, and then recorded that they all flowered 30 years later at the same time as their parental population. Records of wild plants are skimpy because 1. However, Seifriz did add and 19 18 to an old record in l to document three successive mast crops of wild Chusquea abietifolia in Jamaica and obtain an intermast period of years.

For all the records of bamboo mast seeding in India, southeast Asia, and China, I have been able to find only three sets of data for at least three successive mast crops for a native bamboo cohort in situ. Dendrocalamus srrictus apparently had a mast crop in the Cachar Hills of Assam in , , and year intermast period lOO , and in Uttar Pradesh in ,, and and year intermast periods Melocanna bambusoides had mast crops in Chittagong, East Pakistan in l , 12, and and 1 year intermast periods However, enough records of two successive crops exist to give a good impression of how long the cycles will be when long-term records become available Table I , if they ever do.

There are in addition, records from transplants of the Indian-Asian species of mast-seeding bamboos. Introduced to Brazil, a cohort of this species flowered in , , , and , yielding an intermast period of 3 l years This seed was most likely derived from a cohort of B.

Blatter 38 reported a mast crop of B. Finally, there is Phyllostuchys bambusoides with its year inter-mast period, described in the first paragraph of this paper. As described in the following section, there have been numerous introduced bamboos in midlatitude greenhouses and botanical gardens that flowered in synchrony with their parental cohort in its native?

One of the most serious problems in determining the length of the intermast period is that flowering records are very commonly made for the species rather than for cohorts of bamboos within a species.

For example, Chattejee 58 reported mast fruiting by Melocanna bambusoides in , , , , and in the Mizo Hills of Assam. If I treat the first two records as from one cohort and the last three as from another, the inter-mast period is about 30 years.

If I treat them as all belonging to one cohort, I get two intermast periods of 30 years and one intermast period of years, a period that barely allows attainment of adult size, to say nothing of having enough reserves to flower and fruit.

Furthermore, the other records of M. Blatter 39 was particularly frustrated by this problem. If this is so, the Tharrawaddy data give intermast periods of 23 and 24 years. Finally, some of the records are undoubtedly based on synonyms and misidentifications. As has been much debated and worried over in the reviews mentioned in the introduction, there is no convincing evidence that the intermast period is set by an external cue and no logical reason to believe that such an external cue has been overlooked, or even that there is one.

It was frequently suggested in the older literature that the Indian bamboos seeded in the years of famine brought on by drought [e. This idea has, however, been thoroughly discarded 49, , , There also have been severe drought years in which Indian bamboo did not fruit 49, Since a bamboo clump that is going to flower does not produce new vegetative culms stems the year before 73, , , the decision to flower must have been entered into well before a drought at the time of seeding could occur.

Furthermore, as discussed below, transplant experiments show clearly that weather cues are not involved in synchrony of most species of mast-seeding bamboos. I assume here that bamboo mast seeding is timed by an internal calendar possessed by each member of the cohort. The only external feedback is the reestablishment of the cohort by an even-aged cohort each time a mast crop occurs, The intensity of synchronization extent of even-agedness produced by such a feedback system is directly related to the effectiveness of the seed predator community at pruning off the tails of the seeding distribution, and the rate of production of genetic and physiological variance by each bamboo species.

No one has ever reported conducting a physiological search for the internal calendar in a mast-fruiting bamboo, although it might be done by growing bamboo in a bioclimatic chamber with foreshortened years. The various physiological changes reported in a bamboo at the time of flowering and seeding, such as reduction in starch and nitrogen content , , are those expected of any plant when it reproduces. The following account of the traits of the internal calendar should be of aid in a search for it, but the thing most needed, a wild cohort in situ with a known mast crop pedigree, is probably not available to any physiologist in the world.

The internal calendar is very well buffered from environmental impact both with respect to weather and photosynthate production. Offsets of Arundinaria japonica, introduced from Japan in , flowered simultaneously at Bois de Boulogne, Sceaux, Marseilles, and Algiers in PhyZlostachys flexuosa brought from China in flowered at Hamma, Toulon, and Paris in 49, Chusquea abietzjblia, taken from Jamaica to England in the Os, flowered in synchrony with its parent cohort years later , , Argentinian Guadua trinii seedlings planted in optimal conditions of an arboretum and in the dismal conditions of a city park flowered in perfect synchrony with each other and their siblings back home 30 years later Numerous authors have given examples where damage to mast-fruiting bamboos burning, grazing, cutting, ditching, transplanting apparently caused an advance in the length of the intermast period 3,23, 32,40,49, 53,73, 84, 89,90, 94, , , , ,2 12,26 1.

Unfortunately, these reports are even more anecdotal than most of the data on which I am forced to rely. This method of cultivation is, of course, known wherever bamboo exists, but it is a fact which I have seen nowhere recorded. On the other hand, Osmaston said that the small and lightly harvested forests of D. Gupta said that systematic cutting of bamboo causes flowering to occur early!

Finally, I must stress that D. A few clumps are in flower almost every year [e. While it may be that D. It cannot be measuring stored reserves, since the health and size of the plant within very large bounds does not affect the timing of the mast crop.

The calendar must be the annual or daily accumulation or degradation of a temperature-insensitive nhotosensitive chemical. In all parts of the world where bamboo grow, there is enough annual variation in daylength to count the passage of a year, especially if the timing of the count within that year is unimportant.

It is particularly interesting in this context that accurate mast-seeding bamboos are unknown from closer than about 5 degrees from the equator. The closer to the equator, the more equal and minimal are the two annual cycles of day lengthening and shortening. The African Oxytenanthera abyssinica, which has cohorts with intermast periods ranging from 7 to 21 years, much sporadic flowering, and relatively unsynchronized cohorts 2, 16,81, 84, 11l , has a distribution bracketing equatorial Africa.

I expect the sensitivity of the internal calendar to perturbations to be proportional to the degree and predictability of the fluctuations normally experienced by the bamboo in its native habitat Both transplanting and agroeconomic perturbations of bamboo cohorts have without doubt created environmental conditions more extreme than those that the physiological shields for the internal calendar were evolved to block.

There is only one recorded case where it appears that a species or cohort of bamboo may not be simultaneously buffered against two quite different environments. In the Mahandi basin Orissa, inland from the Bay of Bengal it was observed in that on coarse-grained dry soils Dendrocalamus strictus generally flowers only sporadically in isolated clumps and not in groups or gregariously. On the other hand on moister soils, which are not however too moist for this species to thrive moderately well, simultaneous flowering over areas several hundred acres in extent is not uncommon.

In or immediately after abnormally dry years gregarious flowering may be induced on all soils. However, since I know nothing of either the patterns of pollen flow in the area or of the fate of seeds in the two adjacent and interdigitated habitats, it is impossible to know if this apparently bimodal behavior is adaptive, an unavoidable response by the plants, or due to seed and pollen flow between the two habitats or even due to past introductions of D. The internal calendar is without doubt a genetic trait.

By transplanting rhizomes and seeds, humans have maximized the changes of intercohort and interspecific hybrids. Not only should this produce plants with altered intermast periods, but it should produce plants with altered physiological shields to environmental perturbations. The stock on which the physiologist does experiments must be very carefully chosen. Just as with other genetic traits, it is reasonable to expect the calendar length and shielding to vary among some cohorts or populations.

However, there is some information on the types of variation present. As Kawamura stressed, there is a distribution of flowering and seeding intensity within a mast crop-a concept largely ignored by all before and after in their documentation of bamboo flowering or seeding. Here, it appears that the variation was due to different clumps clones within the cohort that were slightly out of phase with each other, but no attention is given to separating within- and between-habitat variation, or genetic versus phenotypic variation.

These descriptions bring to mind one of the more debilitating of the flaws in how bamboo mast crops are recorded. No one has been careful to distinguish between the flowering time and the seeding time. Since a single clump of a mast-fruiting bamboo may require as long as a year from the initiation of flowering until the fall of the last seed, this imprecision makes it impossible to ask detailed questions about the variance in the intermast period for any species.

The causes of interclone intracohort variation in seeding time are potentially very diverse. Out of many thousands of seeds of Dendrocalamus strictus planted in March of , 5 flowered and died in April-July A seedling of D.

I have no idea what sort of intermast periods such phenotypic monsters would have. This leading tail of the seeding distribution may be caused by the variation-inducing processes mentioned previously. For example, in Prome Division, Burma, a few quarter-acre clumps of Barnbusa polymorpha flowered in , and then in , 3 square miles flowered Writers only rarely mention clones that are in flower an equal distance after the peak time of seed production.

It is possible that they have not bothered with those flowering late in the mast crop because they are less spectacular than those that appear early after many years of vegetative growth. However, it is also possible that the trailing tail is foreshortened in comparison with the leading tail of the seeding distribution. If so, I expect this to be due to more intense seed predation on the trailing than on the leading tail.

The trailing tail should be preyed upon by a full complement of starving local and nomadic seed predators and their offspring. Here, a peak in the seeding distribution can be defined only with respect to a specific piece of habitat and a cohort gets stretched in time. I find variance of this type most surprising and doubt that it is natural.

However, it has been described for apparently natural Bambusapolymorpha forests in Burma In continuous bamboo forest, animals that have built up on early-seeding plants should produce very intense predation on the seeds of the later-seeding plants. It is possible that the forests in which this was described were either planted or cultivated by man. Such a pattern could be generated by planting in temporal succession or by planting from seed derived from conspecific cohorts that are slightly out of phase with each other.

On the other hand, wavelike flowering has also been described for Oxytenanthera abyssinica in Malawi 2, 63 , where it is unlikely to have been planted.

It makes one wonder about plant pheromones. The best understanding of genetic variation in the length of the intermast period might be derived from introduced plants, but no records have ever been kept to this end. There are hints, however. Arundinaria falconeri was introduced as seed to Kew Gardens, England, from the Himalayas in and all the plants seeded between and The adults from these seeds then produced a seeding distribution lasting from to at least In the two following seedings, a 9- and 6-year spread were recorded Table 1.

A similar increase in range, perhaps owing to relaxed selection against the tails of the seeding distribution, might be responsible for the year seeding distribution recorded for introduced Phyllostachys in Japan.

It has never been recorded, but there should be geographic variation in the location of the seeding distribution with respect to the seasons. While warm weather may allow the more tropical bamboo species to flower and seed at any time of the year [in tropical areas with severe dry seasons every month of the year has some tree species in full flower or fruit 86, ], there seems to be a seasonal pattern to bamboo mast seeding.

This would place the seeds on the ground within a month of the beginning of the monsoon rainy season in most parts of southern Asia. If it is to move forward from this time, the seedlings will have a shorter portion of the rainy season in which to become established before the next dry season arrives.

S primarily a subtropical genus flowers in April through June and bears seeds through autumn in Japan. Again, a shift off of this timing could generate increased juvenile mortality through increased seed predation and inclement weather. There is one source of variance that is very unlikely, and that is the variance that would be generated by seed dormancy of more than a few months.

Bamboo seeds can be dormant for several months if kept dry , but apparently no longer there was a hasty rush to distribute bamboo seed whenever available in colonial India--see advertisements in the pages of the Indian Forester.

In view of the potentially very strong selection against plants that bear seed in the tails of the seeding distribution, I would expect strong selection against seed dormancy of more than a few months duration if the internal calendar does not start running until germination.

There is no evidence for dormancy in wetted bamboo seeds. To explain the length of the intermast period, I need first to hypothesize how the intermast period of a bamboo can lengthen and shorten. It is very unlikely to lengthen by gradual increments. If it flowers years later than the mast crop, it is likely to have an insurmountable pollination problem. Even if it can self-pollinate, its seeds should be a major attraction for all local animals.

A lengthened cycle appears possible only if the intermast period is doubled in the mutant genotype. This gives the new genotype the usual protection of seeding when its relatives are seeding. A genotype with a double intermast period would be favored because it should have twice as much reserve for seed production and thus lose a smaller percent of its seeds to the seed predators at each mast crop.

This, however, requires that not all the major seed predators focus their attention on bamboo clones clumps that are bearing particularly heavily, or that the rhizomes of heavy bearers be well intertwined with those of light bearers. As the mutant comes to constitute a progressively larger proportion of the genome in the cohort, the plants with the parental short intermast period should make up a progressively smaller fraction of the cohort.

Collectively, the parental type would be progressively less likely to produce a mast crop large enough to satiate the seed predators when they seed halfway between the seed crops of the new genome.

Incidentally, this process could occur, although perhaps less successfully, with a bamboo mutant whose intermast period is 1. An intermast period may be shortened by the following pattern of seed predation. When a mast crop begins, I expect heavy predation on the early tail of the seeding distribution. However, there may be some cases where the seed production builds up very rapidly, satiating the local animals before the nomads arrive and local reproduction can occur. This could result in the greatest proportion of surviving seeds coming not from the exact center of the peak of the seeding distribution but from the earlier leading side of the peak.

The outcome of such an event would be a gradual shortening of the intermast period by a few months each time the seed predators were a bit tardy in accumulating. The same process would operate if the usual number of nomadic seed predators did not arrive because, for example, the cohort was too small to attract attention or it was accidentally synchronized with a much larger mast crop nearby. It is important to understand the source of the variation on which the selection described in the previous paragraph is operating.

If those clones that seeded just before the peak did so because of environmental plasticity rather than because they were mutants with slightly shorter internal calendars, the outcome of this pattern of seed predation would be a gradual shifting backward in time of the cycle, but no reduction in the length of the inter-mast period for the cohort.

If the earlier seeding plants are mutants, then the intermast period should both shift backwards and become shorter. If only the processes discussed above were responsible for the lengths of the intermast periods, I would expect the values in Table 1 to be rather uniformly distributed from very small to rather large numbers. However, there is a conspicuous shortage of intermast periods of less than about years.

A number of ecological processes come to mind that should result in the elimination of bamboo cohorts with short intermast periods. Such elimination is a kind of group selection, where the cohort can be viewed as the unit of selection. A bamboo cohort with a short intermast period has a distinct chance of not having enough reserves accumulated to produce a large enough seed crop to satiate the local and nomadic seed predators.

The combination of these factors should result in different inter-mast periods being optimal in different parts of the range of a widely distributed bamboo species, and should even result in interspecific geographic trends in the duration of inter-mast periods. Whatever the overall patterns with wild plants, the data in Table 1 generally suggest that intermast periods of less than about 15 years are generally not adequate to accumulate enough reserves for predator satiation.

For a cohort with a short inter-mast period, the same seed predators that accumulated on the first crop may still be present for the second crop. However, the length of time for seed predator levels to fall to that before the mast crop depends upon the animal species.

Small rodents should be down to precrop levels within a year or two, and it is doubtful if insects are going to be able to wait out a period of more than about years between crops. However, large animals have longer life spans and it may take much longer for their density to fall to precrop levels. In nature, a bamboo mast crop could provide this supplement.

Once pigs or jungle fowl have grown to adult size, they may be able to exist in a semistarved and rarely reproducing state for many years on food levels that would never have allowed their initial survival to adulthood. There are no records on the longevity of any of these animals in the wild, but domestic roosters can live as long as years, hens years 33, , and pigs live for years If a cohort is so large that it occupies the entire range through which a nomad might move, then the nomad should probably be termed a local seed predator.

The presence of other mast-fruiting cohorts in the area should select against cohorts with short intermast periods for the following reasons. The longer its inter-mast period, the larger its seed crop is likely to be. If the short one, with its smaller seed crop, should happen to seed just before the long one, it is less likely to eliminate the long one than in the reverse case.

However, within every few generations by the cohort with the short inter-mast period, one of its small mast crops is guaranteed to have been shortly preceded by a very large seed crop. The cohort with the short inter-mast period will back up at a faster absolute rate than the cohort with a long intermast period. In order to evaluate the possible mutual impact that cohorts may have on each other, I need some information on the degree of sympatry of cohorts of the same and different species.

There is not a single description of all the populations of various species of bamboos in any Indian or Asian habitat or area. There may be as many as 7 potentially mast-seeding species at one site: There are a few incomplete records of sympatric mast crops. Since M bambusoides has an intermast period of somewhere between 30 and 50 years Table 1 , these three records almost without doubt represent three conspecific and roughly sympatric cohorts.

Bambusa polymorpha flowered in Burma in , , and 93 ; since each was at a slightly different site and since B polymorpha has an intermast period of at least 50 years Table 1 , I suspect that this also represents three cohorts.

In 1 Parry described an area in Assam where the most common species, M. At another site in Assam, Parry said that Cephalostachyum capitatum mast crops were sympatric with those of M bambusoides, but out of phase Bambusa tulda flowered in in the Sitapahar range of the Chittagong Hill tracts and in 1 in Patiya range of the same tracts Three species of bamboos produced mast crops in the Dehra Dun valley in and However, this area has been an important source of commercial bamboo for hundreds of years and thus their synchronization could simply be the result of planting from seed of simultaneously flowering allopatric cohorts brought from elsewhere.

In eastern Brazil, there appear to be two common and locally allopatric species of Merostachys that are out of phase with each other by five years In Japan, four apparently adjacent species of Sass had a synchronized mast crop in 5 on Mt.

In Jamaica and the southeastern United States, there is only one species of mast-seeding bamboo each, and the Jamaican species seems to be made up of only one cohort as well. Incidentally, it is appropriate to add here that the presence of slightly allopatric mast-seeding bamboos with unsynchronized cohorts is the ideal circumstance for the evolution of eruptive nomadic behavior by seed predators.

Sympatry by mast-seeding bamboos is very much a matter of scale. At the level of the Indian subcontinent a mast crop was recorded for Dendrocalamus strictus every year but 12 between and Between and , there were 17 years in which Bambusa arundinacea mast crops were recorded in India Six cohorts could produce this amount of flowering, since 8. Except for and , every year in India between and at least one bamboo species and often many more was recorded to have a mast crop The same may be said of every year between and There are cases where Indian conspecific cohorts are out of phase yet very close to each other.

There is, however, no way of knowing if this is the result of humans moving them around. In Nicholls reported that south of the Acchankovil River, Bambusa arundinacea flowered in and north of the river in In most of the B. In the Bambusa polymorpha forests in the watershed of the Pegu River in Thaukyeghat District did not flower but the cohort on the adjacent Yoma Range watershed for the Irrawaddi and Hlaing Rivers did It is perplexing that the adult mast-seeding bamboos usually die after bearing seed in a mast year.

The literature marvels over the phenomenon, but makes little effort to explain it. Nicholson made the only real attempt by postulating that the adults die to remove the intense shade that they often cast, so that the seedlings of the bamboo can become established. It is certainly true that, following the death of a cohort, the light regime at ground level dramatically increases. There are, however, two problems-although perhaps not insurmountable ones-with this interpretation.

First, its evolution probably requires that the seeds of an individual parent clone, clump usually end up directly below the parent. Otherwise, the individual parent would be dying to open a site for the offspring of other individuals, which is not too likely unless the members of a cohort are closely related which they of course may be after many generations of inbreeding within a cohort. Second, the bamboo parent need not die to create an open area beneath itself.

All it need do is drop its leaves for a year as it does at the time of flowering and live off reserves stored in the rhizomes or photosynthate from a few leafy stems. I would favor a different interpretion of the death of the adult. Only a small amount of resources could be saved to reestablish the adult after seeding. However, in a natural habitat it seems that a small amount of resource would not be enough to maintain an adult plant in the face of a competition with large numbers of its own seedlings and other species of plants, b the usual challenges by herbivores and diseases faced by adults, and c the unusual challenge of many herbivores attracted by the seed and seedling crop.

For the adult plant to hold back enough resource to survive in this circumstance could seriously jeopardize the size of its seed crop. In this context, it is of great interest that some of the longer lived and larger species of bamboos will survive flowering if they are free of normal forest competition and fertilized heavily , , , There may also be a major physiological problem with a semelparous mastseeding bamboo becoming iteroparous.

It will not only have to have an internal calendar to tell it how long it has been since it germinated, but also it will need another calendar to tell it when it last flowered.

However, this is impossible since there is no direct information as to whether bamboos are outcrossed, obligatorily or otherwise. The only detailed study of flower anthesis and phenology did not attempt cross-pollination but noted that self-pollinated plants did not set seed They are apparently wind-pollinated since they have inflorescences like those of other grasses. As might be predicted of a wind-pollinated plant , most of the mast-seeding species drop their leaves at the time of flowering rather than when they die some months later 2, 23, 92, , , , ,, One inflorescence may require as long as two weeks to flower as only 1 or 2 flowers per inflorescence open each day On the other hand there is a hint that bamboos may be at least in part insectpollinated.

A number of the putative ancestors of bamboos have insect-pollinated flowers , If some pollen flow can occur through insect pollination, it would tend to operate against synchronization of mast crops, since individuals slightly out of phase could be more readily pollinated.

It is possible to conclude from indirect evidence that mast-seeding bamboos are obligatory outcrossers. McClure , after a lifetime of experience with bamboos, concluded that it is common for bamboo to flower without setting seed but then went on to note that those that do set a lot of seed are usually wild plants. An isolated wild clump that is flowering well out of phase with the main mast crop may set little or no seed 68, 92, 93, Most of the plants that McClure worked with were introduced or cultivated.

In Taiwan, the approximately 40 species of introduced bamboos set very little seed when they flower , , I interpret this to mean that they have been derived originally from very small samples from within a cohort. It seems likely that introductions will commonly be in the form of pieces cut from one large rhizome system or as seeds gathered from one point in a mast crop.

The propagules will therefore have a high chance of not containing whatever type of heterozygosity is required for compatibility among offspring. Pollination by wind may place a spatial constraint on obligatorily outcrossed bamboos. Most wind-pollinated woody plants grow in stands where it is commonplace for conspecifics to stand crown to crown. In like manner, it may be that clumps of bamboo that are spatially far from their cohort may suffer reduced pollination even if they flower in synchrony.

The outcome of such a phenomenon may be to maintain the spatial as well as temporal integrity of the cohort. When a small bamboo plant flowers but does not set seed, it is generally regarded as having failed to reproduce. However, if bamboo regularly outcross, such plants may be simply acting as males by reproducing in direct proportion to the amount of pollen they produce.

The most uncomplicated starting point would be annually iteroparous species that grew for a number of years before attaining reproductive maturity.

The only population-level synchrony would be the timing of flowering within the year. There is one way that an individual of such a species can substantially increase its seed crop size. If, upon first reproduction, it puts all of its reserves into seeds, it is likely to produce a much larger seed crop than will its associates that are retaining a major part of their reserves for continued growth.

The ecological circumstance that favors such a semalparous mutant would be a habitat where satiation of the small set of animals in the immediate vicinity of the mutant bamboo clump was an effective method of escape from seed predators. The most prominent cost levied against a semelparous bamboo would be that if seedling establishment were to fail that year, the mutant would be eliminated irrespective of how many seeds escaped the predators.

I would thus expect such a mutant to survive first in tropical areas where the occurrence of the rainy season was fairly predictable, and where seed predators were highly territorial and did not allow territory decomposition in the presence of large amounts of food.

Once some such semelparous mutants exist, they may further increase their seed crop size by waiting a longer period before having their one and only seed crop. However, the population that contains them will have many fewer individuals in seed in any given year than will a purely iteroparous population, and thus the seed predators are likely to concentrate their activity on the few clumps clones in seed. As the mutant comes to constitute more of the population, a disproportionate amount of the bamboo vegetative material in the habitat will belong to the mutant cohort.

This means that, during years when it does not seed, there will be fewer total bamboo seeds and the parent genotype should be headed for local extinction.

If there were any variance in the time to reproductive maturity by the individuals in the mutant cohort, it would be strongly selected against at this time. At this time, the intermast period of the dominant cohort will become the basic period, which, as I postulated earlier, will be doubled by mutation. Oaks, beeches, conifers, and Dipterocarpaceae all display mast seeding in populations of adults of unequal ages and use environmental cues to synchronize their mast crops, which are produced by reserve materials stored since the last mast crop , , These iteroparous perennials produce numerous seed crops during their life spans and require an external cue to become synchronized with the population as they attain reproductive size or age.

The same kind of cue, such as an exceptionally dry spring, is then used repeatedly in later life. However, there is one dicotyledonous group of widespread woody plants that behaves exactly as do mast-seeding bamboos. This is the acanthaceous genus Strobilanthes and related genera of the India subcontinent and southeast Asia. Owing to the taxonomic muddle over the generic delimitations of these plants 52, , I refer to them here by one of their vulgar names, niloo [other names are the Sanskrit nelu 44 , karvia, nillus nillu].

Mast-seeding species of niloo are woody shrubs to small trees that grow as a cohort for a species- and perhaps cohort-specific intermast period of years, flower and seed synchronously, and die 19,22,26,27,44,47, 52, 77, 88,92, , , , , , , , , , , , ,, ,, Other species in the same or related genera are iteroparous perennials Within a cohort, plants of all sizes and health flower at the time of the mast crop 44, , , , but there are a very few individuals that flower in the year before , and even a few that flower completely out of phase , , , The seeds display no dormancy Transplants flower on time with the cohort from which they were removed , What is apparently one cohort of S.

Two different cohorts of Strobilanthes sexennis in Ceylon have flowering pedigrees for ,,,, , and , and for ,, , , , , and Several mast-seeding species of niloo may occur in the same habitat in India or Ceylon, and yet not be synchronized with each other 44, Different but immediately adjacent cohorts of the same species can be out of phase 44, , A number of the species have intermast periods that are even multiples of those of other species, suggesting that the period may lengthen by doubling.

There are two root parasites of niloo CumpbeZZiu , one of which flowers and dies in synchrony with its host and is thus a semelparous perennial parasite, and one of which is iteroparous and probably survives by connecting up with roots of new seedlings as the parent niloo dies. The seeds are oil rich and have been gathered as human food and for poultry feed 70 in India. There are numerous records of jungle fowl congregating in very large numbers to feed on niloo crops 5, 29, 44, 70, , , , , , and Henry stated: When nillu flowers and seeds in up-country [Ceylon] jungles, jungle fowl [Gallus lafayeffii] migrate to these areas in large numbers to fatten on the abundant seed.

They are also very fond of the seeds of the small hill-bamboo which, like the nillu, seeds only at long intervals. Like the jungle fowl [the Ceylon spurfowl, GalZoperdix bicalcarata], numbers increase greatly in up-country in nillu-flowering years.

The highest elevations are visited [by the very common Ceylon bronze-winged pigeon, Chalcophaps indica] only when nillu is seeding up-country about once in eleven years , when it migrates to exceptional heights to feed on the seeds. I remember on one occasion when the undergrowth of the Sholas about Pykarra [India] which consists almost entirely of Strobilanthes sp. These, however, are a memory of the past, with the area under the plant fast diminishing owing to denudation of virgin land for cultivation.

The flowering of , and more so that of , was conspicuous for the absence of such visitors. There is a hint that over-indulgence in the seed made Ceylonese jungle fowl and rats dizzy 44, There is a Javanese finch, Serinus estherae, which appears to be an obligate specialist on mast-seeding niloo seed and migrates from one mast-seeding cohort to another During the flowering of S kunthianus there were as many as 28 Apis dorsata hives hanging from one eucalyptus tree near Kodaikanal India and 32 on an overhanging rock There were several hundreds of these combs hanging on the Grevillea shade trees of acres of coffee near here.

There was even a migration of honey-eating hill bears Melursus ursinus into the population explosion of bee nests recorded in To make the analogy with the Asian mast-seeding bamboos complete, some of the African perennial Acanthaceae are semelparous mast-seeding species. Mimulopsis solmsii has a mast crop every years 69, or 7 years J. Gillett, personal communication in Kenya. Gillett cited one case where the M.

Brillentarsia nitens and perhaps Mimulopsis solmsii appear to seed in synchrony at greater than annual intervals in the rainforest around Fort Portal, Uganda, and their seeds are heavily preyed on by primates W.

A few other tropical trees are semelparous and some even synchronized [e. Phenological studies underway with TachigaZia Leguminosae in Panama suggest that there may be several sympatric cohorts of these rainforest trees with intra- but not intercohort synchronization. They produce a mast seed crop and then die after growing for many years into a large tree R.

The semelparous talipot palm Corypha umbraculifera may have had an intermast period of years in southern India, if the behavior of garden trees , , represents that of wild plants in the natural dense stands in which they used to occur.

However, the most important bamboo in India, Dendrocalamus strictus, is particularly difficult to characterize. As has been mentioned, it has mast crops clearly originating from synchronized cohorts. However, it also is famous for populations? To review the possible causes of this variability will highlight some of the more important points to emerge from the literature review in the previous pages.

Further, humans generally do not eat bamboo seedlings. This bamboo is the most widespread in India, with respect to both geography and habitat type. This versatility may be the product in part of human activity and therefore be subjecting the bamboo to physiological stress it is not set up to handle.

On the other hand, it may not be possible to make a physiological system that functions well in intracohort synchrony in all habitat types, or, it may be that there are were many cohorts of D. In short the difficulties that attend interpreting D. The old literature does not contain the definitive data, and contemporary habitats do not allow us to gather that data.

My interpretations of the interactions between mast-seeding semelparous perennial plants and seed predators are of economic importance in determining how and which seeds and rhizomes should be drawn from a native bamboo population if a new self-perpetuating plantation is to be established.

All the Asian bamboo species of major economic importance are mast-seeding species. As foresters pointed out long ago e. It is at this time that seedlings of other plants get their chance, and at this time man has the chance to create or destroy a monoculture of a mast-seeding species.

In addition, the interaction itself is of great historical importance, since we may well have the bamboo and other mast-seeding species to thank for the ease of domestication of the chicken, rat, and pig. Man has simply replaced the mast crop with farms and their annually masting fields of grain. Recent papers on periodical cicada evolutionary biology 80, reveal no conspicuous qualitative difference between these insects and bamboo and niloo except perhaps in the way they physiologically count years.

I offer predator satiation as a hypothesis, a hypothesis that could be tested by field biologists fortunate enough to witness bamboo mast-seeding in habitats with approximately natural complements of seed predators. Such biologists need to record the fraction of the seeds that are eaten throughout the seeding distribution. To demonstrate that predator satiation is operating, they have to show that the seed predators take the smallest percentage of the seeds somewhere in the central portion of the seeding distribution and the largest percentages of the seeds in the tails of the distribution.

Of special importance are seeds that fall very far out in the tails; these indicate that there were enough plants in flower for cross-pollination to occur provided that cross-pollination is necessary. If they are heavily preyed on, this supports the idea that selection for synchronization merely to ensure pollination is unlikely to have been the only driving force for the synchronization.

Of equal importance is the establishment in many long-lived botanical gardens of a number of bamboo cohorts from large seed samples from one and from many parents, followed by careful records over the years of the timing of their flowering, that of their children, grandchildren, etc.

Special attention should be given to documenting any changes in the variance of the intermast periods for these cohorts not under selection by herbivores. If bamboos are too daunting a prospect for such a program, niloo would make an adequate substitute. I conclude by noting the inadequacy of the data presented in my review of bamboo and niloo evolutionary biology. Again, I defend a review at this poor state of the art with the simple fact that it is now nearly impossible to gather most of the critical information needed to answer most of the questions I have posed.

The species may not yet be extinct, but the interaction is. The following persons were most helpful in commenting on the manuscript, the ideas, and in finding obscure references: Flowering of Bambusa arundinacea Ind.

Regeneration of the common bamboo 0xytenan thera abyssinica A. Rich Munro in Mua Livulezi Forest. Two years old bamboo seedling. Flowering of seedlings of Dendmcalamus strictus Ind. Handbook of the Birds of India and Pakistan, Vol. Pheasants in North America. Flowering of Strobifanthes in Burma. Forest Administration, Burma Forest Administration, Burma 19 Bearded pig swim again.

Rhodesia for , pp. Annotated Bibliography on Bamboo. The flowering of StmbiIanthes auriculatus Nees. The flowering of Stmbilanthes scaber. The flowering of the bamboos. The flowering of bamboos in Travancore. Gn the occurrence and gregarious flowering of Periiepta edgeworthiana Nees Brem. The game birds of India, Burma and Ceylon. The flowering of cultivated bamboos. Unusual and sup plementary food plants of Kumaon. Note on operations in bamboo flowered areas in Katha Division.

The Fauna of British India Mammalia. On the gaur Bos gaurus and its allies. The flowering of bamboos. Some notes on the flowering of bamboos. Indian bamboos brought up to date. Wild Flowers of the Ceylon Hills London: Milk production in large black sows and its importance in relation to the production of weaners. Seeding of the thorny bamboo. The flowering of Strobilanthes J. Biological notes on Indian bamboos. On some bamboos in Martaban south of Toungoo between the Salwin and S. The flowering of stool shoots of Dendrocalamus strictus - Ind.

Materials for a monograph of the Strobilanthinae Tweede Sec. Red junglefowl and kalij pheasants. Wisconsin pheasant reproduction studies based on ovulated follicle technique. Some plants and animals in Guarani and Guayaki mythology.

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