Comparison of three seed trap types in a chalk grassland: toward a standardised protocol

In a chalk grassland in north-western France, vegetation and seed rain were studied along two transects. We compared the efficiency of three types of seed traps (funnel traps, sticky traps, pots exposed in the field) to estimate the annual seed rain and to reveal various processes involved in plant community regeneration. Data were analysed to compare seed density, species richness and composition across seed traps and vegetation. Geostatistical analyses (semivariograms. were used to detect possible autocorrelation and to examine patterns of spatial variation in seed rain and vegetation. The results show that (1) funnel traps are most efficient (56 species, 8079 seeds.m^–2). (2) Each type of seed traps brings different information about the processes involved in seed dispersal and seedling establishment. Sticky traps help to understand import and export of seeds in a community through anemochory. Funnel traps may provide a measure of the auto-regeneration capacity of the vegetation through its local seed production. Pot traps integrate various processes involved between seed dispersal and seedling emergence. (3.) The exposition to environmental conditions generates marked spatial patterns in species richness measured in pots and in vegetation, selecting species able to survive. Pot traps indicate that numerous species producing seeds in standing vegetation are unable to establish in the field through seedling recruitment. Our study emphasizes the need of using different types of seed traps and spatial sampling configurations to assess the regenerative potential of standing vegetation and the various mechanisms involved in seed dispersal. A standardised protocol for seed rain sampling was finally developed.     

Spatial and Temporal Variation of Seed Rain in the Canopy and on the Ground of a Tropical Cloud Forest

Spatial and temporal patterns of seed rain impact plant fitness, genetic and demographic structure of plant populations, and species' interactions. Because plants are sessile, they rely on biotic and abiotic dispersal agents to move their seeds. The relative importance of these dispersal agents may shift throughout the year. In tropical forests, seed dispersal of epiphytes constitutes a major but hitherto unknown portion of seed rain ecology. For the first time, we report on patterns of seed rain for both epiphytic and terrestrial plants across an entire year in a Neotropical montane forest. To examine seed rain, we placed traps in the canopy and on the ground. We analyzed seed dispersal syndrome (bird, mammal, wind) and plant habit (epiphyte, liana, shrub, small tree, large tree) across all seasons of the year (dry, misty, wet). We found that the community of species collected in canopy traps was significantly different from the community in ground traps. Epiphytes were the most common plant habit found in canopy traps, while large trees were most common in ground traps. Species with bird‐dispersed seeds dominated all traps. Species richness was significantly higher during the dry season in ground traps, but did not vary across seasons in canopy traps. Our results highlight the distinct seed rain found in the canopy and on the ground and underscore the importance of frugivores for dispersing both arboreal and terrestrial plants in tropical ecosystems.     

Spatiotemporal patterns of seed dispersal in a wind-dispersed Mediterranean tree (Acer opalus subsp. granatense): implications for regeneration

Seed dispersal can severely limit the quantity of plant recruits and their spatial distribution. However, our understanding of the role of dispersal in regeneration dynamics is limited by the lack of knowledge of seed deposition patterns in space and time. In this paper, we analyse the spatiotemporal variability of seed dispersal patterns in the Mediterranean maple, Acer opalus subsp. granatense, by monitoring seed rain along two years at a broad spatial scale (2 mountain ranges, 2 populations per range, 4 microhabitats per population). We quantified seed limitation and its components (source and dispersal limitation), and explored dispersal limitation in space by analysing dispersal distances, seed aggregation, and microhabitat seed distribution. Acer opalus subsp. granatense was strongly seed‐limited throughout the gradients explored, being always dispersal limitation much higher than source limitation. The distribution of seeds with distance from adult individuals was leptokurtic and right‐skewed in all populations, being both kurtosis and skewness higher the year of the highest seed production. Dispersal distances were shorter than expected by random in the four populations, which suggests distance‐limited dispersal. Dispersal patterns were highly aggregated and showed a preferential direction around adults. At the microhabitat scale, most seeds accumulated under adult maples. However, there were no more seeds under trees and shrubs other than maple than in open interspaces, implying that established vegetation does not disrupt patterns of seed deposition by physically trapping seeds. When compared with patterns of seedling establishment, limited dispersal ability and inter‐annual spatial concordance in seed rain patterns suggest that several potentially safe sites for recruitment have a very low probability of receiving seeds in most maple populations. These findings are especially relevant for rare species such as Acer opalus subsp. granatense, and illustrate how dispersal studies are not only crucial for our understanding of plant population dynamics but also to provide conservation directions.     

Seed dynamics of resprouting shrubs in grassy woodlands: Seed rain,predators and seed loss constrain recruitment potential

Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m^?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil.     

A new rain-operated seed dispersal mechanism in Bertolonia mosenii (Melastomataceae), a Neotropical rainforest herb

Although widespread among fungi, lichens, liverworts, and mosses, seed dispersal mechanisms operated by rain are unusual among flowering plants. Generally speaking, two mechanisms are involved in seed dispersal by rains: the splash-cup and the springboard. Here we describe a new seed dispersal mechanism operated by rain in a Neotropical rainforest herb Bertolonia mosenii Cogniaux (Melastomataceae). The study was carried out at the lowland Atlantic rainforest, southeastern Brazil. We experimentally demonstrate that rain is necessary to release the seeds from the capsules through what we call "squirt-corner" seed dispersal mechanism: when a raindrop strikes the mature fruit, the water droplet forces the seeds outward to the angles (corners) of the triangular capsule and the seeds are released. As far as we know squirt-corner represents a new rain-operated seed dispersal mechanism, and a novel seed dispersal mode both for Melastomataceae and for flowering plants from Neotropical forests.     

Hydrodynamics and seed dispersal in the lower Amazon

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神农架巴山冷杉种子雨的时空格局

巴山冷杉(Abies fargesii)是我国特有树种, 其分布区以秦巴山地为中心。在湖北神农架自然保护区选择不同的巴山冷杉群落设置样地, 通过布设种子收集器结合室内实验分析, 对巴山冷杉的种子雨进行研究。各样地巴山冷杉种子雨开始和持续时间大致相同, 始于10月初, 持续超过2个月, 但是不同的巴山冷杉种群表现出不同的种子雨时空格局。巴山冷杉－箭竹(Fargesia nitida) 群落种子雨的平均强度为167.93±111.14粒/m2, 有活力种子比例占22.31%, 落种高峰期集中于10月27日到11月2日间, 种子雨呈现聚集分布。巴山冷杉－茵芋(Skimmia reevesiana)群落的种子雨强度在3个样地中最小, 只有16.41±14.41粒/m2, 有活力种子仅占3.05%。对巴山冷杉－陕甘花楸(Sorbus koehneana)群落, 沿等高线方向和垂直等高线方向布置收集器带, 收集器自群落内中心母树延伸至林冠范围之外(距中心母树的距离>18 m)。收集结果表明种子雨落种高峰为10月15–21日, 种子雨主要集中在林冠范围内, 林冠内种子雨数量占到了收集总数的87.95%。方差分析结果显示各方向的种子雨数量不存在显著差异, 按照远离中心母树的距离进行分段比较, 0–6 m区段内的收集数量和其他各区段间(6–12 m, 12–18 m, >18 m)存在显著差异, 扩散的种子数量与离开中心母树的距离间的关系近似正态分布。研究结果说明巴山冷杉种子雨的强度大但种子质量不高, 而且种子雨的扩散距离有限。这些特征将影响到巴山冷杉种群的分布格局和种群更新。     

Community Dynamics of Seed Rain in Mixed Evergreen Broad-leaved and Deciduous Forests in a Subtropical Mountain of Central China

Seed dispersal is a key process within community dynamics. The spatial and temporal variations of seed dispersal and the interspecific differences are crucial for understanding species coexistence and community dynamics. This might also hold for the mixed evergreen broadleaved and deciduous forests in the mountains of subtropical China, but until now little existing knowledge is available for this question. In 2001, we chose to monitor the seed rain process of our mixed evergreen broad-leaved and deciduous forest communities in Mount Dalaoling National Forest Park, Yichang, Hubei Province, China. The preliminary analyses show obvious variations in seed rain density, species compositions and timing of seed rain among four communities. The average seed rain densities of the four communities are 2.43 ± 5.15, 54.13 ±182.75, 10.05 ±19.30 and 24.91 ± 58.86 inds/m^2, respectively; about one tenth the values in other studies in subtropical forests of China. in each community, the seed production is dominated by a limited number of species, and the contributions from the others are generally minor. Fecundity of evergreen broadleaved tree species is weaker than deciduous species. The seed rain of four communities begins earlier than September, and stops before December, peaking from early September to late October. The beginning date, ending date and peak times of seed rain are extensively varied among the species, indicating different types of dispersal strategies. According to the existing data, the timing of seed rain is not determined by the climate conditions in the same period, while the density of seed rain may be affected by the disturbances of weather variations at a finer temporal resolution.     

广西靖西西南桦天然林种子雨的时空动态

以一片西南桦(Betula alnoides)天然林和一个西南桦独立单株为研究对象, 通过收集散种期内与林分或母树不同距离的种子以及测定风速和风向, 研究了西南桦群落和个体水平上种子雨的时空动态及其与风速和风向的关系。结果表明: 群落水平上, 西南桦种子散布的初始期、高峰期、消退期分别历时11天、32天和40天, 而个体水平上则为9天、25天和26天。高峰期内群落和个体水平的散种量分别占其总量的83.1%和68.7%, 而且白天的种子雨密度高于夜间; 西南桦个体白天种子雨密度最大的时段为12:00-16:00, 与此时段内风速较高有关。在个体水平上, 距离母树0-30 m范围内散落的种子占总散种量的79.6%; 而在群落水平上, 距离林缘0-45 m范围内集中了总散种量的81.2%。西南桦种子散布具有方向性, 无论个体还是群落水平上不同方向间种子雨密度差异极显著(p < 0.01), 与散种期内的主要风向有关; 而且种子雨密度与风速亦呈极显著正相关关系。研究结果将有助于揭示西南桦天然更新动态和更新机制, 亦为开展西南桦人工促进天然更新提供理论依据。     

Spatial and temporal dynamics of floating and drift-line seeds at a tidal freshwater marsh on the Potomac River, USA

The dispersal of seeds through hydrochory can be an important driver of community dynamics and play an integral role in the colonization of restored wetlands. We assessed sources of seeds on the shoreline and in adjacent waters of the Potomac River to Dyke Marsh in Virginia. Drift-line samples were taken at 40 random points four times during 2005–2006, and water surface net trawling took place on the Potomac River from 2003–2005 using six, 200-m transects around the perimeter of the marsh. Seed supply through hydrochory and species richness was low at Dyke Marsh when compared to other regional tidal freshwater marshes. We discovered distinct temporal patterns, where high species richness and seed density were found in the fall for the water trawl samples but in the spring for the drift-line samples. High fall dispersal in the water trawls may exist owing to peak plant senescence and seed release, while high seed germination in the spring along shorelines may arise due to sufficient cold stratification of marsh seeds.     

A multi-scale test for dispersal filters in an island plant community

Constraints on plant distributions resulting from seed limitation (i.e. dispersal filters) were evaluated on two scales of ecological organization on islands off the coast of British Columbia, Canada. First, island plant communities were separated into groups based on fruit morphology, and patterns in species diversity were compared between fruit‐type groups. Second, abundance patterns in several common fleshy‐fruited, woody angiosperm species were compared to species‐specific patterns in seed dispersal by birds. Results from community‐level analyses showed evidence for dispersal filters. Dry‐fruited species were rare on islands, despite being common on the mainland. Island plant communities were instead dominated by fleshy‐fruited species. Patterns in seed dispersal were consistent with differences in diversity, as birds dispersed thousands of fleshy‐fruited seeds out to islands, while dry fruited species showed no evidence of mainland‐island dispersal. Results from population‐level analyses showed no evidence for dispersal filters. Population sizes of common fleshy‐fruited species were unrelated to island isolation, as were rates of seed dispersal. Therefore, island isolation distances were not large enough to impose constraints on species’ distributions resulting from seed limitation. Rates of seed dispersal were also unrelated to island area. However, several species increased in abundance with island area, indicating post‐dispersal processes also help to shape species distributions. Overall results suggest that seed dispersal processes play an important role in determining the diversity and distribution of plants on islands. At the community‐level, dry‐fruited species were seed limited and island communities were instead dominated by fleshy‐fruited species. At the population‐level, common fleshy‐fruited species were not seed limited and showed few differences in distribution among islands. Therefore, although evidence for dispersal filters was observed, their effects on plant distributions were scale‐dependent.     

Linking intra‐specific trait variation and plant function: seed size mediates performance tradeoffs within species

Substantial intra‐specific trait variation exists within plant communities, and in theory this variation could influence community dynamics. Although recent research has focused on intra‐specific variation in traits themselves, it is the influence of this variation on plant performance that makes intra‐specific trait variation relevant to ecological dynamics within or among species. Understanding the links between trait and performance variation, and the role of traits in mediating relationships among multiple components of performance, is critical for assessing the importance of intra‐specific trait variation for community dynamics. Seed size is thought to affect aspects of plant performance including fecundity, seedling growth, dispersal and tolerance of natural enemies. For two tropical tree species, we assessed how seed size was related to performance variation within each species and determined whether intra‐specific trait variation mediates intra‐specific performance tradeoffs. We used field seed rain collection to characterize size‐dependent outcomes of dispersal, sowed seeds of known size in soil collected near or far from conspecifics to characterize susceptibility to soil pathogens, and monitored growth of seedlings from seeds of known size. We found that intra‐specific seed size variation caused intra‐specific performance variation. The degree of trait‐based performance variation was consistently smaller than the degree of trait variation, and seed size influenced different components of performance for each species. One species exhibited a tradeoff in which small seeds had a fecundity advantage (more seedlings per unit reproductive mass) but produced smaller seedlings, whereas the other species exhibited a tradeoff in which small seeds dispersed to areas of low conspecific density but were less tolerant of density‐responsive natural enemies. Our results indicate that a single trait can influence multiple components of performance and can mediate different tradeoffs in co‐occurring species. Complex and heterogeneous effects of a single trait in multidimensional niche space may favour inter‐specific niche differentiation and coexistence.     

Tamarins and Dung Beetles: An Efficient Diplochorous Dispersal System in the Peruvian Amazonia

Dung beetles fulfill several key functions in ecosystems but their role as secondary seed dispersers is probably one of the most complex ones. Various factors, such as seed characteristics, dispersal pattern induced by the primary disperser, season, and habitat, can affect the seed–beetle interaction. Particularly little is known about the fate of seeds primarily dispersed in small feces. The aim of this study was to investigate the effects of these factors on the dung beetle community (species composition, number and size of individuals) and its consequences on burial occurrence and depth of seeds primarily dispersed by two tamarin species. We captured dung beetles in a Peruvian rain forest with 299 dung‐baited pitfall traps to characterize the dung beetle community. Seed burial occurrence and depth were assessed by marking in situ 551 dispersed seeds in feces placed in cages. Among these seeds, 22.5 percent were buried by dung beetles after 2 d. We observed a significant effect of the amount of dung, season, time of deposition, and habitat on the number of individuals and species of dung beetles, as well as on seed burial occurrence and depth, while the tamarin species significantly influenced only the number and the size of dung beetles. This seed dispersal loop is particularly important for forest regeneration: small to large seeds dispersed by tamarins in secondary forest can be buried by dung beetles. These seeds can thus benefit from a better protection against predation and a more suitable microenvironment for germination, potentially enhancing seedling recruitment.     

Seed dispersal by rivers in tropical dry forests: An overlooked process in tropical central Mexico

Aims

Rivers are important corridors for the movement, migration and dispersal of aquatic organisms, including seeds from riparian plants. Although tropical dry forests (TDF) are among the most extensive and floristically rich ecosystems of tropical habitats, and the most globally endangered ecosystem, less attention has been given to riparian corridors within this ecosystem. Although most TDFs manifest peak seed dispersal during dry seasons, we hypothesized that riparian corridors may show a dispersal peak during the rainy season, due to an anticipated ‘sweep or drag effect’, resulting from river overflow and bank erosion. Our main aims were to investigate whether there were any differences in the seed communities transported by the river to sites in rainy as opposed to dry seasons, and to evaluate any possible relationship between the riparian seed community and river flow.

Location

Amacuzac River, drainage of the Balsas basin, State of Morelos, Mexico.

Methods

To evaluate the above assumption, we associated Amacuzac River flow with the number of species and seeds dispersed by water. We also characterized and evaluated differences between seed communities transported by the river during the rainy and dry seasons, and between four different sites located along the river. We used univariate and ordination NMDS techniques to evaluate patterns between seasons at the community level.

Results

Forty‐five plant species were identified from 909 seeds collected from the river. The composition of riparian seed communities was markedly different between seasons but not between sites. Seed abundances were significantly higher in the rainy than in the dry season and varied between sites. Seed species diversity in the river (H’ = 1.6–1.9) showed no significant differences between seasons or sites, but species assemblages and dominance varied according to season. Ordination techniques and subsequent fitting analyses showed that seed species composition was positively associated with river flow.

Conclusions

Seed dispersal patterns generated by rivers are significant mechanisms for structuring the composition and distribution of the riparian plant community in Mexican TDF. Varying species assemblages and seed abundance dispersed by the river throughout the year is a relevant and until now unknown consequence that may affect the dynamics and composition of riparian plant communities in this region. This study initiative will promote new avenues of research regarding plant establishment and succession.     

Interspecific synchrony of seed rain shapes rodent‐mediated indirect seed–seed interactions of sympatric tree species in a subtropical forest

Animal‐mediated indirect interactions play a significant role in maintaining the biodiversity of plant communities. Less known is whether interspecific synchrony of seed rain can alter the indirect interactions of sympatric tree species. We assessed the seed dispersal success by tracking the fates of 21 600 tagged seeds from six paired sympatric tree species in both monospecific and mixed plots across 4 successive years in a subtropical forest. We found that apparent mutualism was associated with the interspecific synchrony of seed rain both seasonally and yearly, whereas apparent competition or apparent predation was associated with interspecific asynchrony of seed rain either seasonally or yearly. We did not find consistent associations of indirect interactions with seed traits. Our study suggests that the interspecific synchrony of seed rain plays a key role in the formation of animal‐mediated indirect interactions, which, in turn, may alter the seasonal or yearly seed rain schedules of sympatric tree species.     

Small traits with big consequences: how seed traits of nitrogen‐fixing plants might influence ecosystem nutrient cycling

Symbiotic nitrogen (N)‐fixing plants have important effects on the biogeochemical processes of the sites they inhabit, but their ability to reach these sites is determined by the dispersal of their seeds. Differences in seed size and dispersal vectors of N‐fixing and non‐fixing plants could influence the spatial and temporal distributions of N fixers, and thus could have important impacts on biogeochemical cycling. Using seed mass, dispersal vector, and biome data retrieved from online public databases, we ask if there are systematic differences in seed mass and dispersal vectors between N‐fixing and non‐fixing plants. We demonstrate that rhizobial N fixers tend to have larger seeds that are more likely to be biotically dispersed than seeds of non‐fixers, whereas actinorhizal N‐fixing trees tend to have small, abiotically dispersed seeds. We then synthesize existing evidence from the literature to draw links between these dispersal traits and the spatio–temporal patterns of N fixers, as well as their biogeochemical effects on terrestrial ecosystems. Using this literature, we argue that the spatio–temporal distributions of N fixers are influenced by their seed dispersal characteristics, and that these distribution patterns have important effects on the total amount of N fixed at a site and the timing of N inputs during processes such as succession.     

Strong zonation of benthic communities across a tidal freshwater height gradient

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Seed Rain and Seed Bank Reveal that Seed Limitation Strongly Influences Plant Community Assembly in Grasslands

Dispersal is an important factor in plant community assembly, but assembly studies seldom include information on actual dispersal into communities, i.e. the local propagule pool. The aim of this study was to determine which factors influence plant community assembly by focusing on two phases of the assembly process: the dispersal phase and the establishment phase. At 12 study sites in grazed ex-arable fields in Sweden the local plant community was determined and in a 100-m radius around the centre of each site, the regional species pool was measured. The local seed bank and the seed rain was explored to estimate the local propagule pool. Trait-based models were then applied to investigate if species traits (height, seed mass, clonal abilities, specific leaf area and dispersal method) and regional abundance influenced which species from the regional species pool, dispersed to the local community (dispersal phase) and which established (establishment phase). Filtering of species during the dispersal phase indicates the effect of seed limitation while filtering during the establishment phase indicates microsite limitation. On average 36% of the regional species pool dispersed to the local sites and of those 78% did establish. Species with enhanced dispersal abilities, e.g. higher regional abundance, smaller seeds and dispersed by cattle, were more likely to disperse to the sites than other species. At half the sites, dispersal was influenced by species height. Species establishment was however mainly unlinked to the traits included in this study. This study underlines the importance of seed limitation in local plant community assembly. It also suggests that without information on species dispersal into a site, it is difficult to distinguish between the influence of dispersal and establishment abilities, and thus seed and microsite limitation, as both can be linked to the same trait.     

Biogeography of seed-dispersal syndromes, life-forms and seed sizes among woody rain-forest plants in Australia's subtropics

Aim To enhance our understanding of the evolutionary interactions between seed‐dispersal syndromes, life‐forms, seed size, and habitat characteristics by studying their association with the regional‐scale distributions of subtropical rain‐forest plants in the context of climatic gradients. Location South‐east Queensland, subtropical eastern Australia (152° E, 26° S). Methods We classified 250 rain‐forest sites into six floristic site‐groups based on their woody plant composition. The resulting classification was strongly associated with variation in rainfall. The distribution of species across the floristic site‐groups was used to assign 568 species to seven habitat classes (one class for ‘widespread’ species, with all other species classified according to the site‐group within which they were most frequent). Species were also classified for three other categorical life‐history factors: three dispersal syndromes based on diaspore morphology (fleshy, wind‐assisted, and unadorned); four life‐forms (trees, shrubs and small trees, tall climbers, and short and shrubby climbers); and four seed‐diameter classes (< 3 mm, ≥ 3 and < 4.5 mm, ≥ 4.5 and < 7 mm, and ≥ 7 mm). We used a basic comparative approach augmented by simple phylogenetically constrained comparisons to assess association between dispersal syndrome, seed size, life‐form, and habitat class. Results Across the rain forests of south‐east Queensland, the proportion of species with fleshy diaspores or of large stature increases with rainfall. High‐rainfall sites also have larger average seed sizes, but the difference in average seed size between high‐ and low‐rainfall sites is small compared with variation within sites. Among species, those with fleshy fruit tend to have larger seeds and to favour high‐rainfall sites. Very few small trees produce diaspores adapted for wind‐assisted dispersal. On average, species with unadorned diaspores have smaller seeds than those with fleshy diaspores. However, within sites, species with unadorned and fleshy diaspores have similar average seed sizes, and some species with unadorned diaspores from high‐rainfall habitats have extremely large seeds. Main conclusions Commonly observed associations between fleshy fruit, larger plants, larger seeds, and productive habitats are apparent within the rain‐forest flora of south‐east Queensland. However, these associations are generally weak and involve complex interactions. For example, the strong tendency for species with fleshy fruit to have larger seeds than those with unadorned diaspores concealed a significant group of species from wetter forests that produce extremely large seeds and unadorned diaspores. The most widespread species in this study tend to be large plants (particularly robust lianes) and to produce fleshy fruit, but they tend not to have relatively large seeds. The association between large seeds, large plants, fleshy fruit and productive habitats is discussed as part of an evolutionary strategy favouring fitness in populations close to carrying capacity. We review some problems with focusing on establishment chances per seed as the driver towards association between large seeds, large plants and productive rain‐forest habitats (the difficult‐establishment hypothesis). Instead we suggest that production of large, short‐lived seeds by long‐lived plants in temporally stable, closed habitats may reflect the limited evolutionary potential for strategies enhancing colonization (e.g. producing large numbers of dormant seeds), thus allowing the establishment benefits of large seeds greater selective influence (the slow‐replacement hypothesis). The association of fleshy fruit with large seeds probably reflects the difficulty of dispersing large seeds by other means (the difficult‐dispersal hypothesis).     

Seed dispersal of Diospyros virginiana in the past and the present: Evidence for a generalist evolutionary strategy

Several North American trees are hypothesized to have lost their co‐evolved seed disperser during the late‐Pleistocene extinction and are therefore considered anachronistic. We tested this hypothesis for the American persimmon (Diospyros virginiana) by studying the effects of gut passage of proposed seed dispersers on seedling survival and growth, natural fruiting characteristics, and modern animal consumption patterns. We tested gut passage effects on persimmon seeds using three native living species, the raccoon (Procyon lotor), Virginia opossum (Didelphis virginiana), and coyote (Canis latrans), and two Pleistocene analogs; the Asian elephant (Elephas maximus) and alpaca (Vicugna pacos). Persimmon seeds excreted by raccoons, coyotes, and elephants survived gut transit. Gut passage did not affect sprouting success, but did tend to decrease time to sprout and increase seedling quality. Under field conditions, persimmon fruits were palatable on the parent tree and on the ground for an equal duration, but most fruits were consumed on the ground. Seven vertebrate species fed upon persimmon fruits, with the white‐tailed deer (Odocoileus virginianus)—a species not capable of dispersing persimmon seeds—comprising over 90% of detections. Conversely, potential living seed dispersers were rarely detected. Our results suggest the American persimmon evolved to attract a variety of seed dispersers and thus is not anachronistic. However, human‐induced changes in mammal communities could be affecting successful seed dispersal. We argue that changes in the relative abundance of mammals during the Anthropocene may be modifying seed dispersal patterns, leading to potential changes in forest community composition.