Reproductive phenology of Melastomataceae species with contrasting reproductive systems: contemporary and historical drivers

• Flowering and fruiting are key events in the life history of plants, and both are critical to their reproductive success. Besides the role of evolutionary history, plant reproductive phenology is regulated by abiotic factors and shaped by biotic interactions with pollinators and seed dispersers. In Melastomataceae, a dominant Neotropical family, the reproductive systems vary from allogamous with biotic pollination to apomictic, and seed dispersal varies from dry (self‐dispersed) to fleshy (animal‐dispersed) fruits. Such variety in reproductive strategies is likely to affect flowering and fruiting phenologies.
• In this study, we described the reproductive phenology of 81 Melastomataceae species occurring in two biodiversity hotspots: the Atlantic rain forest and the campo rupestre. We aim to disentangle the role of abiotic and biotic factors defining flowering and fruiting times of Melastomataceae species, considering the contrasting breeding and seed dispersal systems, and their evolutionary history.
• In both vegetation types, pollinator‐dependent species had higher flowering seasonality than pollinator‐independent ones. Flowering patterns presented phylogenetic signal regardless of vegetation type. Fruiting of fleshy‐fruited species was seasonal in campo rupestre but not in Atlantic rain forest; the fruiting of dry‐fruited species was also not seasonal in both vegetation types. Fruiting showed a low phylogenetic signal, probably because the influence of environment and dispersal agents on fruiting time is stronger than the phylogenetic affinity.
• Considering these ecophylogenetic patterns, our results indicate that flowering may be shaped by the different reproductive strategies of Melastomataceae lineages, while fruiting patterns may be governed mainly by the seed dispersal strategy and flowering time, with less phylogenetic influence.

     

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.     

Neotropical fish–fruit interactions: eco‐evolutionary dynamics and conservation

Frugivorous fish play a prominent role in seed dispersal and reproductive dynamics of plant communities in riparian and floodplain habitats of tropical regions worldwide. In Neotropical wetlands, many plant species have fleshy fruits and synchronize their fruiting with the flood season, when fruit‐eating fish forage in forest and savannahs for periods of up to 7 months. We conducted a comprehensive analysis to examine the evolutionary origin of fish–fruit interactions, describe fruit traits associated with seed dispersal and seed predation, and assess the influence of fish size on the effectiveness of seed dispersal by fish (ichthyochory). To date, 62 studies have documented 566 species of fruits and seeds from 82 plant families in the diets of 69 Neotropical fish species. Fish interactions with flowering plants are likely to be as old as 70 million years in the Neotropics, pre‐dating most modern bird–fruit and mammal–fruit interactions, and contributing to long‐distance seed dispersal and possibly the radiation of early angiosperms. Ichthyochory occurs across the angiosperm phylogeny, and is more frequent among advanced eudicots. Numerous fish species are capable of dispersing small seeds, but only a limited number of species can disperse large seeds. The size of dispersed seeds and the probability of seed dispersal both increase with fish size. Large‐bodied species are the most effective seed dispersal agents and remain the primary target of fishing activities in the Neotropics. Thus, conservation efforts should focus on these species to ensure continuity of plant recruitment dynamics and maintenance of plant diversity in riparian and floodplain ecosystems.     

DNA fingerprinting validates seed dispersal curves from observational studies in the neotropical legume parkia

Background

Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system.

Methodology/Principal Findings

In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly right-skewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other.

Conclusions/Significance

Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our study demonstrated that DNA extraction methods so far employed for temperate plant species can be successfully used for hard-seeded tropical plants.     

Is farther seed dispersal better? Spatial patterns of offspring mortality in three rainforest tree species with different dispersal abilities

The paradigm that tropical trees with farther seed dispersal experience lower offspring mortality is currently based on within-species studies documenting higher survival of offspring located farther from conspecific adults and/or closer to light gaps. We determined whether the paradigm also holds among species by comparing spatial patterns of offspring mortality among three sympatric Neotropical rainforest tree species with the same seed dispersers but with different dispersal abilities. First, we assessed spatially non-random mortality for each species by measuring spatial shifts of the population recruitment curve (PRC) with respect to conspecific adults and light gaps across three early life stages: dispersed seeds, young seedlings and old seedlings. Then, we determined whether PRC shifts were greater for the species with short dispersal distances than for the species with greater dispersal distances. We found that the PRC shifted away from conspecific adults consistently across life stages, but we found no consistent PRC shifts towards gaps, suggesting that mortality was related more to the proximity of conspecifics than to absence of light gaps. PRC shifts away from adults were greatest in the species with the lowest dispersal ability, supporting the paradigm. Differential PRC shifts caused the spatial distribution of offspring to become almost independent with respect to adult trees and gaps in all three species, despite large differences in seed dispersal distance among these species. Our results provide direct empirical support for the paradigm that among tropical trees, species with farther seed dispersal are less impacted by spatially non-random mortality than are similar species with shorter dispersal distances. Thus, greater dispersal effectiveness merits extra investments of trees in seed dispersal ability, even at the cost of fecundity.     

种子雨研究进展

种子雨是指在特定的时间和特定的空间从母株上散落的种子量。种子雨的组成和大小具有时空异质性。种子雨的空间异质性表现在种子雨的组成和大小因群落而异,种群间的种子雨因种群而异,种群内部的种子雨因个体而异;种子雨的时间异质性表现在不管是群落、种群还是种群内部的个体,其种子雨既具有季节动态,又具有年际变化。种子雨、种子库、幼苗库和地上植被相互联系、相互作用。种子雨的研究对更好地了解种群和群落动态等具有重要意义。应用现代的分子遗传标记技术、同位素标记法和荧光染料法等研究种子雨的散布过程和种子命运将是未来种子雨研究的热点,种子雨和种子库的结合研究及其与动植物关系的研究尚需加强。     

Effects of seed size and frugivory degree on dispersal by Neotropical frugivores

Large vertebrates are important elements of mutualistic interactions and provide positive impacts on plant population and community dynamics. Despite the increasing interest on vertebrate frugivory we are still not able to disentangle the real contribution of seed dispersal to Neotropical forest functioning. Consuming fruits does not imply effective seed dispersal and many variables, such as seed size and animal diet, may influence the outcome of plant-animal interactions. Here, we performed a comprehensive literature search on seed dispersal by Neotropical vertebrates (with a focus on primates) to closely approach their role as seed dispersers, hypothesizing frugivory degree and seed size as main drivers of fruit handling behavior and diversity of dispersed seeds. We found that the great majority of seeds manipulated by Neotropical primates, with exception to the seed predators pitheciins, were swallowed and passed intact through their gut. Larger seeds (>12 mm) tended of being ingested exclusively by primates and other large vertebrates, such as tapirs and peccaries. Furthermore, primate feeding guild had a great influence on the richness and sizes of seeds dispersed, as primarily frugivores dispersed more species and had higher probabilities of ingesting larger seeds when compared to other feeding guilds. Organizing available knowledge and filling the main knowledge gaps allowed us to validate common sense assumptions and ultimately draw new conclusions about the role played by primates together with other major frugivores in Neotropical forests.     

Seed dispersal in Erythronium dens-canis L. (Liliaceae): variation among habitats in a myrmecochorous plant

Erythronium dens-canis is a geophyte which produces a single flower each season. The fruits produce small seeds with relatively large elaiosomes. We performed experiments to investigate primary and secondary seed dispersal mechanisms of this species in different habitats in the western part of the Cantabrian Range in northwest Spain. Sticky traps were used to measure primary dispersal of seeds up to 0.5 m from mother plants. Seed cafeteria experiments were performed in different habitats to examine the role of ants and rodents in secondary seed transport and seed predation. Our results indicate that: (a) primary seed dispersal is positively skewed (99% of seeds fall within 20 cm of the mother plant) and seed dispersal distances vary significantly among plants; (b) secondary dispersal is exclusively by myrmecochory, although the proportion of seeds removed by ants differs significantly among habitats; (c) ant species composition and abundances vary among habitats; and (d) freshly dropped seeds are more likely to be removed than seeds that have begun to dry out. We conclude that secondary dispersal of seeds is greatly influenced by habitat but not by small-scale microhabitat. This revised version was published online in June 2006 with corrections to the Cover Date.     

Primate seed dispersal leaves spatial genetic imprint throughout subsequent life stages of the Neotropical tree Parkia panurensis

Key message

The Neotropical tree Parkia panurensis shows a spatial genetic structure from the seed to the adult stage that is most likely the outcome of the seed dispersal provided by primates.

Abstract

Seed dispersal and pollination determine the gene flow within plant populations. In addition, seed dispersal creates the template for subsequent stages of plant recruitment. Therefore, the question arises whether and how seed dispersal affects the spatial genetic structure (SGS) of plant populations. In this study, we used microsatellites to analyse the SGS of the Neotropical tree Parkia panurensis (Fabaceae). This plant species is a major food resource for primates and its seeds are mainly dispersed by primates. Seeds were collected during behavioural observations of a tamarin mixed-species troop in north-eastern Peru. Additionally, leaf samples of juveniles and of adults trees of this species were collected throughout the home range of the tamarin troop. A significant SGS for embryos (located within the dispersed seeds) and for non-reproductive plants are found up to a distance of 300 m. This matches the distance within which most seeds are dispersed. In the adult stage, the scale of a significant SGS is reduced to 100 m. While we cannot explain this scale reduction, our study provides the first evidence that primate seed dispersal does influence the SGS of a tropical tree species.     

Rainforest seed rain into abandoned tropical Australian pasture is dependent on adjacent rainforest structure and extent

It is well known that the recovery of abandoned tropical pastures to secondary rainforest benefits from the arrival of seeds from adjacent rainforest patches. Less is known, however, about how the structural attributes of adjacent rainforest (e.g. tree density, canopy cover and tree height) impact seed rain patterns into abandoned pastures. Between 2011 and 2013, we used seed traps and ground seed surveys to track the richness and abundance of rainforest seeds entering abandoned pastures in Australia's wet tropics. We also tested how seed rain diversity is related to the distance from forest, the proportion of forest cover in the landscape and several structural attributes of adjacent forest patches, specifically average tree height, canopy cover, tree species richness and density. Almost no seeds were captured in elevated pasture seed traps, even near forest remnants. Abundant forest seeds were found in ground surveys but only within 10 m of forest edges. In ground surveys, seeds from wind‐dispersed species were more abundant, but less species rich, than animal‐dispersed species. A survey of pasture seedling recruits suggested that some forest seeds must be dispersing more than 10 m into pasture at very low frequencies, but only a few species are establishing there. Recruits were predominantly animal‐dispersed not wind‐dispersed species. In addition to distance from forest and the proportion of forest within a 100‐ to 200‐m radius of sampling sites, the richness and density of adjacent forest trees were the most important factors for explaining the probability of seed occurrence in abandoned pastures. Results suggest that without some restoration assistance, the recovery of abandoned pastures into secondary rainforest in Australia's tropical rainforests will likely be limited, at least in part, by a very low rate of seed dispersal away from forest edges and by the diversity and density of trees in adjacent remnant forests.     

Sowing forests: a synthesis of seed dispersal and predation by agoutis and their influence on plant communities

Granivorous rodents have been traditionally regarded as antagonistic seed predators. Agoutis (Dasyprocta spp.), however, have also been recognized as mutualistic dispersers of plants because of their role as scatter-hoarders of seeds, especially for large-seeded species. A closer look shows that such definitions are too simplistic for these Neotropical animals because agoutis can influence plant communities not only through seed dispersal of large seeds but also through predation of small seeds and seedlings, evidencing their dual role. Herein, we summarize the literature on plant–agouti interactions, decompose agouti seed dispersal into its quantitative and qualitative components, and discuss how environmental factors and plant traits determine whether these interactions result in mutualisms or antagonisms. We also look at the role of agoutis in a community context, assessing their effectiveness as substitutes for extinct megafaunal frugivores and comparing their ecological functions to those of other extant dispersers of large seeds. We also discuss how our conclusions can be extended to the single other genus in the Dasyproctidae family (Myoprocta). Finally, we examine agoutis’ contribution to carbon stocks and summarize current conservation threats and efforts. We recorded 164 interactions between agoutis and plants, which were widespread across the plant phylogeny, confirming that agoutis are generalist frugivores. Seed mass was a main factor determining seed hoarding probability of plant species and agoutis were found to disperse larger seeds than other large-bodied frugivores. Agoutis positively contributed to carbon storage by preying upon seeds of plants with lower carbon biomass and by dispersing species with higher biomass. This synthesis of plant–agouti interactions shows that ecological services provided by agoutis to plant populations and communities go beyond seed dispersal and predation, and we identify still unanswered questions. We hope to emphasise the importance of agoutis in Neotropical forests.     

Seed dynamics linked to variability in movement of tidal water

Question: Community structure may be influenced by patterns of dispersed seeds (seed rain) because they contribute to the template of plant community development. We explored factors influencing seed rain in a system dominated by tidal water, where direction and magnitude of water flow are difficult to predict, unlike many other hydrochorous systems where water flow is directional. We posed three main questions: (1) are patterns in seed rain linked to effects of hydrodynamic variability; (2) do these patterns in seed rain reflect distribution of seed sources and seed production; and (3) what are the implications for the assembly of tidal communities? Location: Salt marshes on the Wadden island of Schier‐monnikoog, The Netherlands. Methods: Species compositions of vegetation, seed rain, seed production and driftlines along a chronosequence of communities were compared. We also studied seed movement by sowing Astroturf® mats with seeds and checking for seeds remaining after a single tidal inundation. Results: Storm surges had a significant effect on seed‐rain patterns as the highest density and diversity of captured seeds were found during a stormy period. Seed rain of the youngest communities was more influenced by storms than that of older communities. Patterns in seed rain generally followed similar patterns in the distribution of established plants, and seed production. Conclusions: Results suggested mostly local dispersal of seeds. However, there was some evidence of long‐distance dispersal occurring during storm surges in younger communities that are regularly inundated with tidal water. The possible role of seed retention in constraining community development, rather than dispersal per se, is further discussed.     

Deposition of exotic bird-dispersed seeds into three habitats of a fragmented landscape in the northeastern United States

Dispersal by frugivorous birds facilitates invasion by many exotic plants. We measured the seed rain of ornithochorous native and exotic plants at three habitats of a fragmented landscape of the northeastern United States for 1 year. We studied maple-beech forests, old fields, and abandoned conifer plantations. Across all sites we collected 2,196 ornithochorous seeds, including seeds from six exotic species and 10 native species. The majority (90%) of collected seeds were from exotic species. Seed dispersal was broadly similar among habitats, though seed rain of exotic species was higher in old fields than forested habitats. Seed rain was not strongly influenced by artificial perches for most species. However, seeds of exotic species were more commonly found in traps under an artificial perch in old fields. Seed rains for the exotic Elaeagnus umbellata, Rhamnus cathartica, and Rosa multiflora were positively associated with local density of mature plants. Seed rain of R. cathartica was positively associated with abundance of seedlings but not saplings, suggesting that post-dispersal mortality was important. Seed dispersal of the exotic Lonicera spp. was high in all habitats, accounting for 66% of all seeds collected. With the exception of Lonicera spp., seed rain of common exotic invaders was affected by the abundance of seed sources, and these species might be effectively controlled by elimination of local fruiting plants. Fruits of Lonicera morrowii, which has extensively invaded our area, are apparently a common component in the diet of frugivores.     

Ombrohydrochory: Rain-operated seed dispersal in plants – With special regard to jet-action dispersal in Aizoaceae

The present review describes the ombrohydrochoric dispersal syndrome in plants, i.e. seed expulsion by raindrops. There are two different ombrohydrochoric dispersal modes – dispersal by rain wash and by ballistic forces. Both have been reported from the understory of tropical and temperate forests, from wetlands and from deserts, and from numerous families and genera. A special form of ombrohydrochoric dispersal is the jet-action rain-operated seed dispersal mechanism which is restricted to the semi-desert ice plants, Aizoaceae, one of the major families of the angiosperms. Within this family, 98% of the species possess hygrochastic capsules with an ombrohydrochoric seed dispersal mechanism which in part are also responsible for the remarkable speciation burst and radiation. The highly complex capsules open when wet, and the seeds are expelled by a ‘jet action’ with the kinetic energy of raindrops. The halves of the covering membranes of a locule form a nozzle near the centre of the capsule which serves as a jet. Drops of water falling on the distal opening (after the locule has been filled with water) result in an explosive expulsion of water droplets and seeds through that jet. More seeds are dispersed further away from the capsule than in those capsule types without such a jet mechanism.     

Seed limitation of woody plants in Neotropical savannas

The failure of seeds to arrive at all suitable sites (seed limitation) greatly affects plant distribution and abundance. In contrast to tropical forests, the degree of seed limitation in Neotropical savannas is unclear because empirical studies at the community level are scarce. We estimated seed limitation of 23 woody species from annual seed rain measurements along a tree density gradient in the savannas of Central Brazil. These savannas differ in tree density and canopy cover, from closed to open savannas, and are located along shallow topographic gradients. We also studied post-dispersal seed predation and removal of 17 representative woody species, and seed viability loss over time of 12 common woody species under dry-storage conditions. Annual seed rain was lower in open (410 seeds/m²) than in closed savannas (773 seeds/m²). Average seed limitation across woody species was higher than 80% along the tree density gradient. More than 60% of seeds of the studied woody species were predated or removed within 30–45 days in all savannah types. Seeds of most common woody species (66%) lost their viability in less than 12 months of dry storage. This study shows that Neotropical savannah woody plants are strongly seed-limited because of low and poor distribution of seeds among sites, post-dispersal seed removal, and short seed longevity. The high seed limitation of tree species in Neotropical savannas, particularly in open savannas, also may contribute to maintain their relatively low tree densities and help to explain the spatial variation of tree abundance along topographic gradients.     

Seed Inputs to Microsite Patch Recovery on Two Tropandean Landslides in Ecuador

To understand landslide regeneration and provide information necessary for restoration, we sampled seed rain, seed pool, and plant cover on two Ecuadorian landslides. We trapped 1304 seeds and found that, while most seeds were in the family Asteraceae, there was substantial variation in seed rain among plant families. Four hundred and seventy-five seedlings emerged from soil samples, including nonvascular and vascular families; again, species in Asteraceae dominated, with species in Piperaceae also very common. Plant cover, consisting of members of four fern families and 20 vascular plant families—with species in Asteraceae, Melastomataceae and Poaceae most common—was scored as a percentage of the total plot area. Principal components analysis (PCA) showed that, for all three of these plant life stages (seed rain, seed-propagule pool, plant cover), spatial variation was dominated by differences between the two landslides rather than within-landslide plot differences. PCA also showed that plots separated best on axes defined by the families Cecropiaceae, Urticaceae, Melastomataceae, Papilionaceae, Asteraceae, and Araceae with clumping of families in PCA space suggesting common successional strategies. Another multivariate technique, canonical correspondence analysis (CCA), showed that the combined seed rain and seed pool data could predict the percent cover of the family Verbenaceae and that the current plant cover families could predict Asteraceae seeds and seedlings. Finally, we use our past and present landslide data, along with multivariate modeling results, to suggest strategies for successful landslide restoration.     

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 genetic evaluation of seed dispersal in the neotropical tree Jacaranda copaia (Bignoniaceae)

Seed dispersal is a critical but poorly understood life-history stage of plants. Here we use a genetic approach to describe seed dispersal patterns accurately in a natural population of the Neotropical tree species Jacaranda copaia (Bignoniaceae). We used microsatellite genotypes from maternally derived tissue on the diaspore to identify which individual of all possible adult trees in the population was the true source of a given seed collected after it dispersed. Wind-dispersed seeds were captured in two different years in a large array of seed traps in an 84-ha mapped area of tropical forest on Barro Colorado Island, Panama. We were particularly interested in the proportion of seeds that traveled long distances and whether there was evidence for direct dispersal into gaps, which are required for successful recruitment of this pioneer tree species. Maximum likelihood procedures were used to fit single- and multiple-component dispersal kernels to the distance data. Mixture models, with separate distributions near and far, best fit the observed dispersal distances, albeit with considerable uncertainty in the tail. We discuss the results in light of different mechanisms responsible for separate distributions near the adult source and in the tail of the curve.     

Connecting fruit production to seedling establishment in two co-occurring <Emphasis Type="Italic">Miconia</Emphasis> species: consequences of seed dispersal by birds in upper Amazonia

This study investigated links between seed production by two species of Miconia (Melastomataceae), whose seeds are dispersed by birds, and later stages of recruitment in lowland forests of eastern Ecuador. Seed dispersal and survival in later stages are crucial for understanding and predicting patterns of plant population dynamics as well as for understanding patterns of diversity in tropical forests. A major goal was to determine if the spatial template of seed deposition established by birds predicted probability of recruitment. We used observational and experimental approaches to compare patterns of recruitment in Miconia fosteri and M. serrulata. We calculated probabilities of transition between successive stages of recruitment for each species in three habitats. The number of plants with fruit, number of fruits removed, and, to a lesser extent, patterns of seed deposition varied between species and among habitats, whereas seed survival, germination, and establishment showed little variation among habitats. The location of seed deposition directly influenced the cumulative probabilities of survival. Among-habitat differences in the probabilities of recruitment set by seed deposition were not modified by later stages, although probability of recruitment was 2.5 times higher for M. serrulata than for M. fosteri after 1 year. The more critical stages for recruitment were seed removal and deposition. Our results from multiple life-cycle stages suggest that habitat associations among plants that reach reproductive maturity become established at early life stages and were mostly a consequence of seed dispersal by birds. These results differ from those obtained in temperate zones and suggest fundamental differences in the importance of recruitment processes. Dispersers, such as manakins, play significant roles in recruitment and population dynamics of M. fosteri, M. serrulata and numerous other understory plants of Neotropical forests. Their role in plant recruitment could be much greater than previously considered in megadiverse tropical forests. Thus, loss of dispersers could have long-term and far-reaching implications for maintenance of diversity.     

Woody structure facilitates invasion of woody plants by providing perches for birds

Woody encroachment threatens prairie ecosystems globally, and thus understanding the mechanisms that facilitate woody encroachment is of critical importance. Coastal tallgrass prairies along the Gulf Coast of the US are currently threatened by the spread of several species of woody plants. We studied a coastal tallgrass prairie in Texas, USA, to determine if existing woody structure increased the supply of seeds from woody plants via dispersal by birds. Specifically, we determined if (i) more seedlings of an invasive tree (Tridacia sebifera) are present surrounding a native woody plant (Myrica cerifera); (ii) wooden perches increase the quantity of seeds dispersed to a grassland; and (iii) perches alter the composition of the seed rain seasonally in prairie habitats with differing amounts of native and invasive woody vegetation, both underneath and away from artificial wooden perches. More T. sebifera seedlings were found within M. cerifera patches than in graminoid‐dominated areas. Although perches did not affect the total number of seeds, perches changed the composition of seed rain to be less dominated by grasses and forbs. Specifically, 20–30 times as many seeds of two invasive species of woody plants were found underneath perches independent of background vegetation, especially during months when seed rain was highest. These results suggest that existing woody structure in a grassland can promote further woody encroachment by enhancing seed dispersal by birds. This finding argues for management to reduce woody plant abundance before exotic plants set seeds and argues against the use of artificial perches as a restoration technique in grasslands threatened by woody species.