啮齿动物的贮藏行为与植物种子的扩散

绝大多数啮齿动物一方面取食大量的植物种子和果实,另一方面通过其贮食行为将植物种子和果实搬运到远离母树的地点,即扩散,并将它们分散埋藏在落叶下或浅表的土层中,从而影响种子和果实的时空分布,最后导致幼苗在有利的条件下发生和建成,实现植物更新。啮齿动物与植物种子和果实之间已广泛形成了互惠或协同进化的关系。啮齿动物的贮食行为主要通过以下几个过程对植物种子和果实的扩散产生影响：选择、搬运和埋藏以及随后对种子和幼苗存活和死亡的影响等。本综述了啮齿动物对植物种子和果实贮藏的研究结果,以期为进一步开展啮齿动物的贮食行为在植物种子和果实的扩散中的作用的研究提供参考。     

Evolution of fruit characters and dispersal modes in the tropical family Rubiaceae

We investigated the evolution of fruit characters, animals versus abiotic dispersal modes, life forms and geographical distribution, in the large, mostly tropical, family Rubiaceae. As a basis for our analysis we used a phylogenetic tree derived from chloroplast DNA variation. Fleshy fruits have evolved independently at least 12 times in the family. Most of these originations appear to have occurred during Eocene to Oligocene, i.e. the radiation period for some animal taxa (bird families, mammal orders) comprising most extant dispersers of Rubiaceae fruits. Changes of dispersal modes may be of more recent origin in a few cases, e.g. evolution of drupes in some lineages, and shifts from drupes to nuts. The distribution of fruit characters suggested that in several lineages animal-dispersed fruits, such as berries and drupes have remained largely unaltered since the time of origination. This is in contrast to the occurrence of winged seeds in capsules, and pterophylls, i.e. enlarged calyx lobes promoting wind dispersal of fruits, which apparently have shifted more frequently during evolution, indicating a difference in 'phylogenetic plasticity' between modes of animal and wind dispersal.
Animal dispersal was over-represented among genera dominated by shrubs, whereas abiotic dispersal was most prevalent among herbaceous genera. Drupes were over-represented in groups with transoceanic distributions, and on islands, indicating dispersal over long distances, probably by birds. In contrast, no evidence was found to support the view that animal dispersal in general enhances long distance dispersal. We also analysed geographical patterns on the tribal level but these were too complex to yield any resolved area cladograms due to the occurrence of many widespread taxa and area redundancy.     

Are the best dispersers the best colonizers? Seed mass,dispersal and establishment in <Emphasis Type="Italic">Carduus</Emphasis> thistles

Negative correlations between dispersal and establishment are often reported in the plant literature; smaller seeds tend to disperse better but germinate less well, and produce smaller seedlings. However, because dispersal capacity is often quantified using proxies, such as the settling velocity of wind-dispersed seeds, little is known about the exact shape of this negative relationship, and how it is modified by other plant traits and environmental conditions. We studied the dispersal-establishment relationship in two wind-dispersed thistles (Carduus nutans and Carduus acanthoides). We applied a mechanistic wind dispersal model (WALD) to seeds released under a range of environmental conditions, and tested germination and seedling growth under standardized conditions in a greenhouse. Dispersal distance and establishment (germination and seedling growth) were not significantly correlated, although in both species smaller seeds dispersed farther, and showed lower germination and lower seedling growth rates. This apparent paradox can partly be explained by the significant influence of other factors such as release height and environment (wind and vegetation), which explained more variation in dispersal than did terminal velocity. Another potential explanation is the variation in seed traits: germination is strongly positively related to seed mass, weakly positively related to plume loading, but not significantly related to terminal velocity. This weakening of the correlation with germination is due to additional layers of trait (co)variability: for instance, seed mass and pappus size are positively correlated, and thus big seeds partially compensate for the negative effect of seed mass with larger pappi. Our mechanistic approach can thus lead to a better understanding of both potentially opposing selection pressures on traits like seed mass, and diluting effects of other seed, plant and environmental factors.     

A Comparison of Frugivory and Scatter-Hoarding Seed-Dispersal Syndromes

Frugivory (animals ingest all or part of fleshy-fruits and defecate or regurgitate seeds) and scatter-hoarding (animals store seeds in small caches in soil) are two important vertebrate-mediated seed dispersal syndromes. In both instances, there is an exchange of food for seed transport, but there are many important differences. For example, the seeds of frugivore-dispersed plants are often clumped in feces or under roosts and the microsite of depostion is often unsuitable for seedling establishment. However, frugivores can transport seeds long distances allowing plants to colonize new areas and promoting gene flow between populations. Scatter-hoarding animals, on the other hand, actively space seeds in microsites that often favor seedling establishment, but don’t move seeds very far. Both modes of seed dispersal can be very effective, but in different way. Some species of plants have evolved propagules that take advantage of both modes of dispersal in two separate phases (i.e., diplochory), apparently to obtain both types of benefits.     

Seed germination and life history syndromes in the California chaparral

Syndromes are life history responses that are correlated to environmental regimes and are shared by a group of species (Stebbins, 1974). In the California chaparral there are two syndromes contrasted by the timing of seedling recruitment relative to wildfires. One syndrome, here called the fire-recruiter or refractory seed syndrome, includes species (both resprouting and non-resprouting) which share the feature that the timing of seedling establishment is specialized to the first rainy season after fire. Included are woody, suffrutescent and annual life forms but no geophytes have this syndrome. These species are linked by the characteristic that their seeds have a dormancy which is readily broken by environmental stimuli such as intense heat shock or chemicals leached from charred wood. Such seeds are referred to as “refractory” and dormancy, in some cases, is due to seed coat impermeability (such seeds are commonly called hardseeded), but in other cases the mechanism is unknown. Seeds of some may require cold stratification and/or light in addition to fire related stimuli. In the absence of fire related cues, a portion or all of a species’ seed pool remains dormant. Most have locally dispersed seeds that persist in the soil seed bank until the site burns. Dispersal of propagules is largely during spring and summer which facilitates the avoidance of flowering and fruiting during the summer and fall drought. Within a life form (e.g., shrub, suffrutescent, etc.), the seeds of these species have less mass than those of species with non-refractory seeds and this possibly reflects the environmental favorableness of the postfire environment for seedling establishment. Regardless of when fire occurs, germination is normally delayed until late winter or early spring. In the absence of fire, or other disturbance, opportunities for population expansion are largely lacking for species with this syndrome. The other syndrome, here called the fire-resister or non-refractory seed syndrome, includes species that are resilient to frequent fires (mostly by vegetative resprouting), but require fire-free periods for recruiting new seedlings. Included are shrubs, subshrubs, suffrutescents, lianas, geophytes and annuals. All are linked by the characteristic that their seeds germinate in the absence of cues related to wildfires. In many cases no form of seed dormancy is present and the seeds germinate soon after dispersal; consequently these species do not accumulate a persistent seed bank. Germination and seedling establishment is independent of fire and thus opportunities for population expansion are also independent of fire. The demographic pattern of seedling recruitment varies with the life form. For shrubs, seedling recruitment may be restricted to sites free of fire for periods of a hundred years or more. Recruitment appears to require relatively mesic conditions and this may account for the patchy distribution of these species within the matrix of relatively arid sites. Finding such sites has selected for propagules specialized for wind or animal dispersal; the majority are bird dispersed. These shrub species all disperse fruits in fall and winter and this may have been selected to take advantage of migratory birds as well as to time dispersal to the winter rains typical of the mediterranean-climate. Germination typically occurs within several weeks of the first fall or winter rains. Maturation of flowers and fruits during the summer and fall drought may account for the distribution of these species on more mesic sites. Seed mass of these species is large and this may have been selected to provide an advantage to seedlings establishing under the canopy of this dense shrub community.     

The phenology of sexual reproduction inGinkgo biloba: Ecological and evolutionary implications

This study examines how the latitude of cultivation ofGinkgo biloba affects the timing of all phases of its sexual reproductive cycle, from pollination through germination. Seeds produced by trees growing in warm-temperate climates germinate earlier in the year than seeds produced in cold-temperate climates, and they have a longer period of time available for seedling establishment. The embryos ofG. biloba seeds possess a temperature-dependent developmental-delay mechanism that allows seeds to survive winter by preventing premature germination in the fall. This and other cold-climate adaptations appear to have evolved within the genusGinkgo during the early Cretaceous, when the Northern Hemisphere was undergoing dramatic cooling after a long period of stable, warm conditions.Ginkgo biloba seeds possess an odoriferous sarcotesta that attracts mammalian scavengers in Asia-most notably members of the Carnivora—presumably by mimicking the smell of carrion. Seeds cleaned of their sarcotesta germinated faster and at higher percentages than those with their sarcotesta intact, suggesting that animal dispersal plays an important role in promoting seedling establishment. During the Cretaceous, potential dispersal agents included mammals, birds, and carnivorous dinosaurs.     

The effects of seed size and pericarp on seedling recruitment and biomass in Cryptocarya alba (Lauraceae) under two contrasting moisture regimes

Establishment success of plants derived from large seeds has been proposed to be greater than that of those derived from smaller ones, particularly under unfavourable conditions of moisture. Therefore, the advantages conferred by large seeds in terms of seedling performance may be modulated by abiotic conditions. The effect of seed size on Cryptocarya alba seedling performance (as determined by seedling recruitment and seedling size) was evaluated under two contrasting rainfall regimes (wet and dry year regime), simulated in the laboratory. It was also determined whether the presence of a pericarp, which had been shown to reduce germination, decreases desiccation and if this counterbalances the greater recruitment of seeds without a pericarp, especially under unfavourable conditions of moisture. Large seeds had a greater probability of recruitment and their seedlings attained a greater biomass, independently of the amount of water applied. In the simulated wet year regime, seeds with a pericarp showed a greater probability of recruitment than those lacking a pericarp. However, seedlings derived from both seed types attained a similar biomass. Under the dry year regime, seeds with and without a pericarp showed similar recruitment probabilities and their seedlings had similar biomasses. These results do not support the assumption that under favourable conditions of moisture, individual differences in seed size would not matter in term of seedling performance. A possible explanation in this case, is the presence of recalcitrant seeds in C. alba, which determines a very short time period for germination following dispersal. Therefore, any attribute that increases germination (e.g., large seeds) would be advantageous, independently of the prevailing abiotic conditions.     

Diplochory in western chokecherry: you can��t judge a fruit by its mesocarp

Western chokecherry (Prunus virginiana var. demissa, Rosaceae) is dispersed by frugivorous birds and carnivores, but it has large seeds that are potentially attractive to rodents that could act as seed predators and dispersers. Here, we quantify the benefits of primary dispersal by birds and secondary dispersal by scatter-hoarding rodents. In the fall, avian frugivores (mostly American robins, Turdus migratorius, and cedar waxwings, Bombycilla cedrorum) consumed 87% of the fruit crop and dispersed 67% of the fruit crop away from parent plants. Rodents removed 89% of seeds that simulated bird-dispersed seed rain from transects in riparian zones and 58% from transects in upland habitats. Rodents scatter-hoarded 91.6% of the seeds they removed, burying most in small caches (two to eight seeds) 8?C25?mm deep. About 39% of the seeds in spring caches produced seedlings. Inside rodent-proof exclosures, 52.1% of seeds buried to simulate rodent caches produced seedlings, 29.7% of which were still alive after 1?year. In contrast, only 3.8% of seeds placed on the soil surface, simulating dispersal by avian frugivores, produced seedlings. Seed dispersal by frugivorous birds likely contributes to colonization of unoccupied habitat through long-range dispersal and to escape from distance-dependent seed mortality near the parent plant. Despite seed losses, rodents offer short-range seed dispersal and bury seeds in more favorable sites for germination, improving seedling emergence and establishment. The combined mechanisms of seed dispersal significantly enhanced chokecherry seedling recruitment by providing more dispersal-related benefits than either frugivorous bird or scatter-hoarding rodents could provide alone.     

蚁对植物种子的传播作用

许多种子植物依靠动物传播种子 ,称为动物传播。根据动物类群的不同 ,可分为哺乳类传播 ,鸟传播 ,鱼传播 ,蚁传播等。鸟传播和蚁传播的研究近年取得了很大的进展 ,但国内在这方面研究较缺乏 ,作者已就鸟传播作了综述报道 ,现将蚁传播的研究综述报道如下。1　蚁与植物的相互关系蚁类属膜翅目 (Ｈｙｍｅｎｏｐｔｅｒａ) ,蚁科 (Ｆｏｒｍｉｃｉ ｄａｅ) ,典型的社会性昆虫。多数蚁类是肉食性的 ,以小动物或更小的蚁类为食 ,但也有很多蚁类是植物食性的。在大多数生态系统中均有蚁类分布 ,而且蚁类数量众多 ,在森林生态系统中每 1ｈａ可达 6～10…     

Frugivory and the effects of ingestion by bats on the seed germination of three pioneering plants

The dispersion and seedling establishment of pioneering plants can be favoured by the presence of frugivorous bats because the bats usually improve seed germination after ingestion. Although seed germinability is known to vary greatly after ingestion by different bats, the relative contribution of each bat species to seed germination within plant communities is poorly understood. In this study, we first determined the fauna of frugivorous bats in a semideciduous seasonal forest remnant in southern Brazil and subsequently identified the plant species of the seeds passed through their guts. Second, the germination performance (i.e., germination percentage and speed) of the seeds of three pioneering plants (Piper aduncum, Piper hispidinervum and Solanum granuloso-leprosum) ingested by the most abundant bats was compared with that of the non-ingested seeds (seeds collected from fruits). Additionally, the effects on seed germination of different bat species were compared. During one year, five species of frugivorous bats were caught, and the seeds of eleven identifiable plant species (not counting those of undetermined species) were found in their faeces. We found that the germination performance of the seeds of Piper species was significantly enhanced after ingestion by bats, whereas S. granuloso-leprosum seeds had neutral or reduced germinability when seeds in faeces were compared with pulp-removed seeds. Our results revealed that the bat species that were captured exerted different effects upon seed germination; such a disparity is expected to result in different rates of early establishment of these pioneer plants in tropical forests, most likely affecting forest composition and structure, particularly during the initial stages of succession.     

Reliability of macaques as seed dispersers

Seed dispersal is an ecological process crucial for forest regeneration and recruitment. To date, most studies on frugivore seed dispersal have used the seed dispersal effectiveness framework and have documented seed-handling mechanisms, dispersal distances and the effect of seed handling on germination. In contrast, there has been no exploration of “disperser reliability” which is essential to determine if a frugivore is an effective disperser only in particular regions/years/seasons or across a range of spatio-temporal scales. In this paper, we propose a practical framework to assess the spatial reliability of frugivores as seed dispersers. We suggest that a frugivore genus would be a reliable disperser of certain plant families/genera if: (a) fruits of these plant families/genera are represented in the diets of most of the species of that frugivore, (b) these are consumed by the frugivore genus across different kinds of habitats, and (c) these fruits feature among the yearly staples and preferred fruits in the diets of the frugivore genus. Using this framework, we reviewed frugivory by the genus Macaca across Asia to assess its spatial reliability as seed dispersers. We found that the macaques dispersed the seeds of 11 plant families and five plant genera including at least 82 species across habitats. Differences in fruit consumption/preference between different groups of macaques were driven by variation in plant community composition across habitats. We posit that it is essential to maintain viable populations of macaques across their range and keep human interventions at a minimum to ensure that they continue to reliably disperse the seeds of a broad range of plant species in the Anthropocene. We further suggest that this framework be used for assessing the spatial reliability of other taxonomic groups as seed dispersers.     

动物对松属植物种子的传播作用研究进展

松属植物约110种,根据种子传播方式可分为风传播松和动物传播松。风传播松占绝大多数,种子多具有适应风力的翅。动物传播松大约23种,都具有大、可食用、无翅或短翅的种子,无法借助风力传播。动物传播松的分布生境多为贫瘠的山地,而且多位于高海拔地区。目前已知9种松树的动物传播种类,其余14种可推测为动物传播。动物传播者包括鸦科鸟类和啮齿类动物,动物将获得的种子分散贮藏,未被重取的种子可能萌发,完成传播。动物传播是定向传播,微生境多适合种子萌发。啮齿类的传播距离可达数10 m,而鸦科鸟类的传播距离可达数公里。动物传播的松树会出现树丛和多树干现象,一般由同一贮点内贮藏的多粒种子萌发造成的。动物贮藏的种子大部分被重取,称传播后取食。一些具有大种子的风传播松在种子落地后,啮齿类和鸟类会再次埋藏而形成二次传播,可看做是一个单独的传播类型,即风-动物传播松。动物传播者与依赖传播松树之间可看作是互利共生关系。     

Bracteoles affect germination and seedling establishment in a Mediterranean population of Atriplex portulacoides

The germination and subsequent seedling establishment of Atriplex portulacoides from a population in SW Spain were investigated in response to the presence or absence of attached bracteoles, at a range of NaCl concentrations (0–6%). Increasing salinity reduced both the final germination percentage and the speed of germination. The presence of bracteoles greatly inhibited germination and this effect was more marked with increasing salinity; bracteoles completely inhibited germination at salinities higher than 2%. The effects of salinity were substantially reversible, as cumulative germination after transfer of ungerminated seeds to distilled water was similar in all salinity treatments. This enforced dormancy could serve to prevent germination of floating fruits during dispersal in seawater. However, after transfer to distilled water the germination of seeds with bracteoles was still significantly lower than those without them, as a result of both higher dormancy and lower viability (as revealed by tetrazolium testing). Bracteoles thus also appear to enforce some physical dormancy. Seedlings derived from seeds with bracteoles demonstrated higher survival rates in fresh water than those derived from seeds without bracteoles but at 2% salinity there was no difference, and at higher salinities no seedlings of either type survived.     

Propagule size,dispersal ability,and seedling performance in Asclepias syriaca

Summary Using the propagules of common milkweed (Asclepias syriaca L.) we tested the predictions that decreasing size may increase dispersal ability, but also decrease the probability of seedling success, of wind-dispersed seeds. In 1982 and 1983 we released seeds from four milkweed clones at two heights in an open field and measured their dispersal distances. In the laboratory we measured falling times in a dead air space, seed mass and area, and coma mass and length of the same seeds. The seeds were later planted in a greenhouse and germination, mortality, and seedling dry mass were recorded.Seed mass was negatively correlated with dispersal distance in 1982, but not in 1983 under highly variable wind conditions. Coma mass/seed mass ratio was positively correlated with dispersal distance in 1982. During both years seed mass and coma mass/seed mass ratio were highly significantly correlated with falling time in dead air space. However, heavy seeds had superior germination, survivorship, and seedling mass at harvest, and seeds that germinated fell faster in dead air than those that did not. We found substantial variation in seed morphology both among clones and among pods within clones. Propagule falling times in dead air and (in 1982) dispersal distances in the field also differed significantly among clones and pods. The potential therefore exists for differential dispersal and establishment of milkweed genotypes.     

Differential responses of germination and seedling establishment in populations of Tragopogon pratensis (Asteraceae)

The establishment phase is an important bottleneck in the life cycle of plants. It consists of two steps that are rarely separated, i.e., the germination of seeds and the establishment of seedlings. Here we report the results of two experiments in which we independently investigated germination and seedling establishment in the greenhouse, under different grass vegetation treatments representing different regeneration niches. Seeds of Tragopogon pratensis from six populations and two habitat types were studied, three from roadside verges and three from hayfields. Germination percentages and germination speed were higher for seeds from roadside verges than for seeds from hayfields, but were little affected by treatment. In contrast, seedling growth was much lower in the tall grass vegetation, than in the short grass and especially the bare soil treatment. Seedling sizes were generally similar for different populations and habitat types. Our results thus show that the two early steps in the establishment phase of plants may respond very differently to the micro-environment, and may have a different selection history. Insight into the ecology and evolution of life histories may require that germination and establishment are considered separately.     

种子萌发和幼苗生长对沙丘环境的适应机制

综述了植物沙生适应机制的研究及其进展.一些植物的种子在刚成熟时具有休眠特性.种子需要适度沙埋促进萌发并实现幼苗定居,但过度沙埋则会抑制种子萌发和出苗.在沙层深处,没有萌发的种子会进入休眠状态,形成土壤种子库.幼苗通过增加节数和延长节间来适应沙埋.沙埋深度超过植物的忍耐限度会抑制幼苗生长,甚至导致幼苗死亡.沙生植物必须适应其他环境因子,如盐风与土壤盐分、昆虫采食、土壤养分亏缺等,才能在沙丘上成功生长.沙蚀可导致幼苗根系暴露并干燥脱水.一些沙漠植物的幼苗在萌发后可忍耐一段时期的干燥,水分条件得到满足之后,幼苗能够恢复生长.     

The role of fleshy pericarp in seed germination and dispersal under flooded conditions in three wetland forest species

In flooded habitats, inundations affect important forest regeneration processes, such as seed dispersal and germination. The main seed dispersal mechanism used by species in Austral South American temperate swamp and riparian forests is endozoochory, which releases seeds from the fleshy pericarp. Endozoochory could be favorable or unfavorable in wetland habitats, since this mechanism exposes seeds directly to water and can, in some cases, be detrimental to germination. In this study, we studied whether or not the fleshy pericarp favors germination after the flooding period's end. Furthermore, we quantified if the number of days which the fruit was found to be floating related to its germination success. We used the seeds of three common fleshy fruit species of flooded habitats from southern Chile, the trees Luma apiculata and Rhaphithamnus spinosus, and the vine Luzuriaga radicans. We simulated flooding periods of 7, 15, 30 and 45 days submerging seeds, with and without pericarps, in water. We found that the pericarp's presence significantly increased Luma's germination success and significantly decreased that of Luzuriaga. The germination of Rhaphithamnus was low after periods of flooding in both seed treatments, with no significant differences found between them. The fruits could float for an average of one to four weeks, depending on the species, which did not relate to their germination success. These results show that germination was affected by the presence of fleshy pericarps in flooded conditions and furthermore, that flotation allows for hydrochory from one week to one month. We suggest that in swamp forests multiple seed dispersal mechanisms are advantageous, especially for fleshy-fruited species.     

Consequences of tropical dry forest conversion on diaspore fate of Enterolobium contortisiliquum (Fabaceae)

Habitat conversion is one of the major threats for biodiversity conservation and viability of natural populations. Thus, habitat disturbance alters distinct ecological processes, such as plant reproductive success and diaspore fate. In this study, we determined the effects of seasonally tropical dry forests (STDFs) conversion by anthropogenic disturbance by assessing diaspore fate of Enterolobium contortisiliquum. We compared 20 adult trees present in a STDFs preserved area and 20 adult trees present in a human-converted area. In general, diaspore fates from both areas were similar, i.e., there was no difference in the reproductive success of trees in STDFs and human-converted area. Habitat disturbance did not affect the length or width of fruits; only fruit thickness was larger in trees of STDFs habitat. None of the biometric seed measures differed between different habitat conditions. Likewise, the number of undamaged seeds, aborted seeds, pre-dispersal predated seeds, and seed production were independent of habitat conditions. Besides, we did not observe any effect of habitat disturbance on germination percentage. However, seeds from preserved STDFs germinated faster than seeds from the human-converted area. Even though the effects of human-modified habitats on the diaspore fate have already been studied, tree species exhibit different responses to habitat conversion regarding seed predation, seed dispersal, seed germination, and seedling establishment. Overall, our results show that habitat disturbance does not affect the diaspore fate of E. contortisiliquum. This study also highlights the importance of remnants trees in converted landscapes as the population’s connectors which maintain plant–animal mutualistic and antagonistic interactions that mitigate the effects of habitat disturbance.

     

Directed vertebrate-mediated seed dispersal of a fleshy-fruited amaryllid in a heterogenous habitat

Most plants with fleshy fruits have seeds that are ingested by animals, but a less well-understood mode of seed dispersal involves fleshy fruits containing seeds that are discarded by frugivorous animals because they are too large or toxic to be ingested. We studied the seed dispersal biology of Haemanthus deformis, an amaryllid lily species found in a mosaic of bush clumps in a grassland matrix in South Africa. We asked whether seed dispersal is directed in and among bush clumps and whether germination and survival are greater for seeds dispersed to bush clumps than for those dispersed into grassland. Using camera trapping, we found that fruits are consumed mainly by birds and rodents. The pulp was removed from the seeds which were then discarded without ingestion. While many seeds were dispersed close to the parent plant, most (c. 78.5%) were dispersed further than 1 m away from the parent plant. Longer distance dispersal resulted mainly from birds flying off with fruits in their bill or from rodents engaging in scatter-hoarding behavior. Seedling survival was most successful within bush clumps as compared to grasslands and shade was identified as a primary requirement for seedling survival. Seeds from which the fruit pulp had been removed germinated faster than those in intact fruits. Haemanthus deformis deploys a system of directed seed dispersal, whereby both birds and rodents contribute to the dispersal of seeds within patchy bush clumps that are favorable for seedling survival.