The effect of seed morphology on the potential dispersal of aquatic macrophytes by the common carp (Cyprinus carpio)

1. The potential for seed dispersal by fish (ichthyochory) will vary among aquatic plants because of differences in seed size and morphology. 2. To examine how seed morphology influences the probability of dispersal by the common carp (Cyprinus carpio), we studied seed ingestion, retention time and subsequent egestion and germination of seeds of Sparganium emersum and Sagittaria sagittifolia, two aquatic plant species with similar sized but morphologically different seeds. 3. We compared dispersal probabilities between the two plant species, in which the probability of dispersal is assumed to be a function of the probabilities of seed ingestion, egestion and germination, and the dispersal distance is assumed to be a function of seed egestion rate over time. 4. We found that, although the soft seeds of S. sagittifolia had an approximately 1.5 times higher probability of being ingested by the carp than the hard seeds of S. emersum (83.15% ± 1.8% versus 56.16% ± 2.7%, respectively), the latter had an almost twofold higher probability of surviving the passage through the digestive tract (38.58% ± 2.7% versus 20.97% ± 1.5%, respectively). Patterns of seed egestion over time did not differ between the two plant species, despite the difference in seed morphology. Gut passage had a different effect on seed germination between plant species. Compared with non‐ingested controls, seeds of S. emersum showed a 12.6% increase in germination and a 2.1 day acceleration in germination rate, whereas seeds of S. sagittifolia displayed a 47.3% decrease and 5.1 day delay, respectively. 5. Our results suggest that seed morphology affects the dispersal probability and postdispersal establishment, but not the dispersal distance, of aquatic plants that are dispersed by fish.     

片段化景观中壳斗科植物种子捕食和扩散模式

生境片段化伴随的面积效应和边缘效应, 可改变分散贮食动物的竞争强度、觅食行为以及隐蔽条件, 影响种子捕食和扩散模式。阐明生境片段化对多物种种子捕食和扩散的影响, 对理解片段化生境中的植物更新和生物多样性维持十分重要。该研究在浙江省千岛湖地区的岛屿和大陆上开展了针对6种壳斗科植物的种子捕食和扩散实验, 分析了物种、分散贮食动物相对多度、种子产量、岛屿大小和边缘效应如何共同影响种子命运和种子扩散距离。主要结果: (1)种子命运和扩散距离在物种间存在显著差异; (2)大陆比岛屿有更长的种子留存时间, 小岛种子留存时间最短, 岛屿内部比岛屿边缘有更长的种子留存时间; (3)物种和岛屿大小对种子原地取食率存在交互作用, 白栎(Quercus fabri)种子在大岛上有更高的原地取食率; (4)种子在小岛上有最高的扩散率, 分散贮食动物相对多度对种子扩散后贮藏率有负效应。表明在千岛湖地区, 生境片段化改变了种子捕食和扩散模式, 且面积效应对不同物种的种子捕食和扩散模式产生了不同作用, 从而影响森林群落更新和生物多样性维持。     

Evolution in heterogeneous populations: From migration models to fixation probabilities

Although dispersal is recognized as a key issue in several fields of population biology (such as behavioral ecology, population genetics, metapopulation dynamics or evolutionary modeling), these disciplines focus on different aspects of the concept and often make different implicit assumptions regarding migration models. Using simulations, we investigate how such assumptions translate into effective gene flow and fixation probability of selected alleles. Assumptions regarding migration type (e.g. source-sink, resident pre-emption, or balanced dispersal) and patterns (e.g. stepping-stone versus island dispersal) have large impacts when demes differ in sizes or selective pressures. The effects of fragmentation, as well as the spatial localization of newly arising mutations, also strongly depend on migration type and patterns. Migration rate also matters: depending on the migration type, fixation probabilities at an intermediate migration rate may lie outside the range defined by the low- and high-migration limits when demes differ in sizes. Given the extreme sensitivity of fixation probability to characteristics of dispersal, we underline the importance of making explicit (and documenting empirically) the crucial ecological/ behavioral assumptions underlying migration models.     

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.     

Species’ response patterns to habitat fragmentation: do trees support the extinction threshold hypothesis?

In fragmented landscapes the relationship between the probability of occurrence of single species and the amount of suitable habitat is usually not proportional, with a threshold habitat level below which the population becomes extinct. Ecological theory predicts that, although the reduction in species’ occurrence probabilities (and eventually the extinction threshold) is a direct consequence of habitat loss, habitat fragmentation might reduce species’ occurrence probabilities and affect the location of this threshold by reducing its predicted occurrence to lower levels of habitat amount. However, little is known about the validity of this extinction threshold hypothesis. Here, we performed analyses on the relationships between the probability of occurrence of eight tree species and the availability of forest habitat for two different empirical scenarios of low and moderate to high fragmentation. We partitioned the effects of habitat amount versus fragmentation by using two metrics: (1) the percentage of forest cover, and (2) the proportion of this percentage occurring in the largest forest patch. We find that, although decreasing forest cover had negative effects on the occurrence of tree species irrespective of fragmentation levels, forest fragmentation significantly modified the response pattern in six tree species, although only one species confirmed the extinction threshold hypothesis, which we interpret as a consequence of high degree of forest specialism and low dispersal ability. For most species, fragmentation either had positive effects or did not affect significantly the species’ probability of occurrence. This indicates that the effects of habitat fragmentation on tree species are weak relative to the effects of habitat amount, which is the main determinant of the reduction in species’ occurrence probabilities, and eventually species extinction, in fragmented landscapes.     

Allee effects, aggregation, and invasion success

Understanding the factors that influence successful colonization can help inform ecological theory and aid in the management of invasive species. When founder populations are small, individual fitness may be negatively impacted by component Allee effects through positive density dependence (e.g., mate limitation). Reproductive and survival mechanisms that suffer due to a shortage of conspecifics may scale up to be manifest in a decreased per-capita population growth rate (i.e., a demographic Allee effect). Mean-field population level models are limited in representing how component Allee effects scale up to demographic Allee effects when heterogeneous spatial structure influences conspecific availability. Thus, such models may not adequately characterize the probability of establishment. In order to better assess how individual level processes influence population establishment and spread, we developed a spatially explicit individual-based stochastic simulation of a small founder population. We found that increased aggregation can affect individual fitness and subsequently impact population growth; however, relatively slow dispersal—in addition to initial spatial structure—is required for establishment, ultimately creating a tradeoff between probability of initial establishment and rate of subsequent spread. Since this result is sensitive to the scaling up of component Allee effects, details of individual dispersal and interaction kernels are key factors influencing population level processes. Overall, we demonstrate the importance of considering both spatial structure and individual level traits in assessing the consequences of Allee effects in biological invasions.     

Frugivory on Persea lingue in temperate Chilean forests: interactions between fruit availability and habitat fragmentation across multiple spatial scales

Habitat degradation and fragmentation are expected to reduce seed dispersal rates by reducing fruit availability as well as the movement and abundance of frugivores. These deleterious impacts may also interact with each other at different spatial scales, leading to nonlinear effects of fruit abundance on seed dispersal. In this study we assessed whether the degradation and fragmentation of southern Chilean forests had the potential to restrict seed dispersal the lingue (Persea lingue) tree, a fleshy-fruited tree species. Of five frugivore bird species, the austral thrush (Turdus falcklandii) and the fire-eyed diucon (Xolmis pyrope) were the only legitimate seed dispersers as well as being the most abundant species visiting lingue trees. The results showed little or no direct effect of habitat fragmentation on seed dispersal estimates, possibly because the assemblage of frugivore birds was comprised habitat-generalist species. Instead, the number of fruits removed per focal tree exhibited an enhanced response to crop size, but only in the more connected fragments. In the fruit-richer fragment networks, there was an increased fragment-size effect on the proportion of fruits removed in comparison to fruit-poor networks in which the fragment size effect was spurious. We suggest that such nonlinear effects are widespread in fragmented forest regions, resulting from the link between the spatial scales over which frugivores sample resources and the spatial heterogeneity in fruiting resources caused by habitat fragmentation and degradation.     

Strategies for conservation for disturbed Prosopis alba (Leguminosae, Mimosoidae) forests based on mating system and pollen dispersal parameters

Prosopis species forests in Argentina are increasingly fragmented in the last years mainly by the deforestation activity without any reforestation strategy, the establishment of different crop plantations, and natural fires. The consequence of habitat fragmentation on the genetic potential of Prosopis alba requires a fine-scale analysis of population structure, in particular mating system and pollen dispersal. By means of short sequences repeats, we analyzed a fragmented population of this species in Santiago del Estero (Argentina). Most genetic variation was observed among families within zones (65.5%), whereas the lowest proportion corresponded to the differentiation among zones (2.8%). The fine analysis of structure at family level suggests that this population is complete outcrosser and there is a low but significant biparental inbreeding. Outcrossing rates differ among mother plants and the proportion of full sibs within mother plants ranged from 64% for seeds proceeding from the same pod to 10% for seeds from different pods. The average pollen dispersal distance was estimated to be among 5.36 and 30.92 m by using the KinDist or TwoGener approach. About seven pollen donors are siring each progeny array and the number of seed trees necessary for seed collection aiming to retain an effective population size of 100 was estimated in 16–39 individuals depending on the relatedness estimator used. Pollen and seed dispersal would be limited, what determines the need of conserving short distant patches to avoid the effects of inbreeding and drift within populations as a consequence of intensive use resource for agriculture.     

Fruit removal and postdispersal survivorship in the tropical dry forest shrub Erythroxylum havanense: ecological and evolutionary implications

We studied the relationship between the removal rate and the spatiotemporal availability of ripe fruits of the tropical deciduous shrub Erythroxylum havanense in western Mexico. We also evaluated the effects of dispersal on seed survival during the first stages of establishment. Fast and early dispersal should be favored in E. havanense, since propagules have more time to grow and accumulate resources before the beginning of the severe dry season. In general, high rates of fruit removal imply faster and earlier dispersal. Thus, plants producing large crops should benefit from high removal rates, which will increase the probability of successful establishment by their progeny. To characterize both individual and population fruiting patterns, we made daily counts of fruits on 51 plants arranged in six clumps of different sizes. The daily number of fruits removed per plant was higher for plants with larger initial crop sizes and larger numbers of ripe fruits on a given day, but decreased as clump size increased. Additionally, we monitored postdispersal survival and germination in an experiment manipulating seed density, distance from adult plants, and seed predation. Early establishment was independent of density or distance, and vertebrate seed predation was the main agent of seed mortality. Our results indicate that the critical variable with respect to fruit removal is the number of fruits a plant produces, large plants having higher dispersal rates. Large plants are also more likely to have more seeds escaping postdispersal seed predation.     

The role of gene flow in shaping genetic structures of the subtropical conifer species Araucaria angustifolia

The morphological features of pollen and seed of Araucaria angustifolia have led to the proposal of limited gene dispersal for this species. We used nuclear microsatellite and AFLP markers to assess patterns of genetic variation in six natural populations at the intra- and inter-population level, and related our findings to gene dispersal in this species. Estimates of both fine-scale spatial genetic structure (SGS) and migration rate suggest relatively short-distance gene dispersal. However, gene dispersal differed among populations, and effects of more efficient dispersal within population were observed in at least one stand. In addition, even though some seed dispersal may be aggregated in this principally barochorous species, reasonable secondary seed dispersal, presumably facilitated by animals, and overlap of seed shadows within populations is suggested. Overall, no correlation was observed between levels of SGS and inbreeding, density or age structure, except that a higher level of SGS was revealed for the population with a higher number of juvenile individuals. A low estimate for the number of migrants per generation between two neighbouring populations implies limited gene flow. We expect that stepping-stone pollen flow may have contributed to low genetic differentiation among populations observed in a previous survey. Thus, strategies for maintenance of gene flow among remnant populations should be considered in order to avoid degrading effects of population fragmentation on the evolution of A. angustifolia.     

Consequences of frugivore diversity for seed dispersal, seedling establishment and the spatial pattern of seedlings and trees

Many plants depend on frugivorous animals for the dispersal of their seeds. However, it is only poorly known whether regional differences in frugivore diversity have consequences for seed dispersal, seedling establishment, and the spatial distribution of seedlings and trees. This comparative study of seed dispersal investigated the consequences of regional differences in frugivore diversity for two tree species of the genus Commiphora. C. harveyi was studied in South Africa where avian frugivore diversity is high, C. guillaumini was studied in Madagascar where the avian frugivore community is depauperate. At both study sites, the percentages of handled and dispersed seeds in Commiphora trees were quantified by fruit traps, and visitation rates, seed handling rates and dispersal rates were quantified for each animal species for two consecutive years. Seedlings were mapped and the spatial distribution of trees quantified. At both study sites, fruits were mainly eaten by birds. The total percentage of dispersed seeds in South Africa was significantly higher than in Madagascar (70.8% vs. 7.9%) because there was a lack of effective dispersers that swallowed seeds in Madagascar. Seed dispersal benefit, i.e. the increase in the probability of becoming established as a seedling away from parent trees due to dispersal was much higher in Madagascar (80 times higher probability) compared to South Africa (6 times higher). Corresponding with the different dispersal percentages, seedlings in South Africa were found at relatively large distances from the nearest Commiphora tree (median distance=21.0 m), whereas in Madagascar seedlings were found mostly under and close to the nearest Commiphora tree (median distance=0.9 m). Finally, Commiphora trees in the Malagasy study site were clumped, but were more randomly distributed in the South African study site. These results suggest that regional differences in frugivore diversity and behaviour strongly affect seed dispersal of trees, seedling establishment and the spatial distribution of seedlings and trees.     

Seed‐swallowing Toucans are Less Effective Dispersers of Guettarda viburnoides (Rubiaceae) than Pulp‐feeding Jays

For many tropical plants, birds are the most important seed dispersers. Not all birds, however, will provide equally effective dispersal services. Behavioral differences, during and after feeding, can result in different establishment probabilities of new individuals. During 3 yr, we examined species‐specific quantitative and qualitative aspects of Guettarda viburnoides seed dispersal by avian frugivores, focusing on how these aspects modify seed dispersal effectiveness. Fruits of G. viburnoides were consumed by ten species of birds, two of which, Cyanocorax cyanomelas and Pteroglossus castanotis, removed 80 percent of the fruits. These two species differ in qualitative aspects of seed dispersal. First, they select for fruits of different sizes; C. cyanomelas feeds on larger fruits than P. castanotis, which results in the former dispersing larger endocarps than the latter. Second, they differ in their fruit handling treatment; C. cyanomelas are pulp consumers, whereas P. castanotis swallow the fruit whole, and are thus traditionally considered ‘legitimate’ dispersers. The probability of seedling emergence, the temporal pattern of emergence, the number of emerged seedlings per endocarp, and the probability of post‐dispersal seed predation differs between endocarps dispersed by C. cyanomelas and P. castanotis; endocarps dispersed by the former have higher emergence probabilities, higher number of seedlings, faster emergence times, and lower predation probabilities than those dispersed by the latter. Finally, these birds differ in their landscape patterns of endocarp deposition; C. cyanomelas disperses endocarps to habitats with higher recruitment probabilities. Ultimately, the pulp consumer C. cyanomelas is a more effective disperser of G. viburnoides than P. castanotis.     

Implications of nonrandom seed abscission and global stilling for migration of wind‐dispersed plant species

Migration of plant populations is a potential survival response to climate change that depends critically on seed dispersal. Biological and physical factors determine dispersal and migration of wind‐dispersed species. Recent field and wind tunnel studies demonstrate biological adaptations that bias seed release toward conditions of higher wind velocity, promoting longer dispersal distances and faster migration. However, another suite of international studies also recently highlighted a global decrease in near‐surface wind speeds, or ‘global stilling’. This study assessed the implications of both factors on potential plant population migration rates, using a mechanistic modeling framework. Nonrandom abscission was investigated using models of three seed release mechanisms: (i) a simple drag model; (ii) a seed deflection model; and (iii) a ‘wear and tear’ model. The models generated a single functional relationship between the frequency of seed release and statistics of the near‐surface wind environment, independent of the abscission mechanism. An Inertial‐Particle, Coupled Eulerian‐Lagrangian Closure model (IP‐CELC) was used to investigate abscission effects on seed dispersal kernels and plant population migration rates under contemporary and potential future wind conditions (based on reported global stilling trends). The results confirm that nonrandom seed abscission increased dispersal distances, particularly for light seeds. The increases were mitigated by two physical feedbacks: (i) although nonrandom abscission increased the initial acceleration of seeds from rest, the sensitivity of the seed dispersal to this initial condition declined as the wind speed increased; and (ii) while nonrandom abscission increased the mean dispersal length, it reduced the kurtosis of seasonal dispersal kernels, and thus the chance of long‐distance dispersal. Wind stilling greatly reduced the modeled migration rates under biased seed release conditions. Thus, species that require high wind velocities for seed abscission could experience threshold‐like reductions in dispersal and migration potential if near‐surface wind speeds continue to decline.     

Antagonistic effects of seed dispersal and herbivory on plant migration

The two factors that determine plant migration rates – seed dispersal and population growth – are generally treated independently, despite the fact that many animals simultaneously enhance plant migration rate via seed dispersal, and decrease it via negative effects of herbivory on population growth. Using extensive empirical data, we modelled the antagonistic effects of seed dispersal and herbivory by white-tailed deer on potential migration rates of Trillium grandiflorum , a forest herb in eastern North America. This novel antagonistic interaction is illustrated by maximum migration rates occurring at intermediate, but low herbivory (< 15%). Assuming herbivory < 20% and favourable conditions for population growth during post-glacial migration, seed dispersal by deer can explain rates of migration achieved in the past, in contrast to previous models of forest herb migration. However, relatively unfavourable conditions for population growth and increasingly intense herbivory by deer may compromise plant migration in the face of present and future climate change.     

Seed rain and advanced regeneration in a tropical rain forest

By comparing seed rain, seedling and sapling community structures we assessed the possible role played by vertebrate seed dispersal as a structuring factor in advanced regeneration of closed-canopied sites in the tropical rain forest of Los Tuxtlas, Mexico. Seed weight, initial morphology of seedlings and species abundance were also analyzed to determine if these traits influenced the probability of establishment in the shade.About half of the seed species falling in five closed forest sites (25×25 m) during one year came from fruiting trees growing within the sites (local seeds) and half from fruiting trees found outside the sites (immigrant seeds). Seeds of liana and upper-canopy species were over-represented among immigrant seeds compared with seeds of understory tree species. This probably reflects the activity of frugivorous arboreal mammals, bats, and birds. Species with immigrant seeds had both a lower abundance and a narrower spatial distribution than locally produced seeds. Therefore, immigrant seeds showed higher diversity values than locally produced seeds.Average seed size and the proportion of epigeous seedlings were similar in local and immigrant species. Under closed-canopied sites, factors affecting community organization seem to operate selectively, favoring the establishment of large-seeded, local abundant species in the advanced regeneration. However, the fact that some saplings of immigrant species were found in the plots suggest that a slow species infiltration may be occurring leading to a slow shift in the advanced regeneration species composition. We propose that the influence of seed dispersal on advanced regeneration structure depends on the disturbance history of the patches where seeds land.     

Land-use and edge effects unbalance seed dispersal and predation interactions under habitat fragmentation

The process of fragmentation can greatly influence plant–animal interactions. To assess the degree to which it affects the balance between two interactions of opposite sign, namely seed dispersal and post-dispersal seed predation, we selected 16 patches of chestnut forest in O Courel and El Bierzo, northwestern Spain. We assessed the effect of fragmentation over two different seed dispersal–predation systems using Helleborus foetidus and Ilex aquifolium as model species. In the first case, field experiments consisted of seed-offering trays with selective exclusion of rodents and ants in a two-way orthogonal design. In the second experiment, we placed experimental branches and trays on the floor to assess seed dispersal and predation. The interactions between several fragment traits and the relative contribution of rodents, ants and birds to seed removal were analyzed by means of generalized linear mixed models. Results show that for H. foetidus, differences in seed dispersal–predation were accounted for by patch shape, which affected mainly the dispersal phase. Major seed dispersal took place in patches with a smaller edge to core ratio and high plant cover (abandoned patches), whilst the latter also showed maximum seed predation. For I. aquifolium, fragmentation effects were significant only for seed predation, which was increased in abandoned patches. This shows that the effects of habitat fragmentation can emerge at different phases depending on specific traits of the interacting animals. It also highlights the importance of traditional land-use practices in species interactions.     

Evaluating the influence of different aspects of habitat fragmentation on mating patterns and pollen dispersal in the bird-pollinated Banksia sphaerocarpa var. caesia

Habitat fragmentation can significantly affect mating and pollen dispersal patterns in plant populations, although the differential effects of the various aspects of fragmentation are poorly understood. In this study, we used eight microsatellite loci to investigate the effect of fragmentation on the mating system and pollen dispersal within one large and eight small population remnants of Banksia sphaerocarpa var. caesia, a bird-pollinated shrub in the southern agricultural region of Western Australia. The large population had a much larger neighbourhood size and lower selfing rate, maternal pollen pool differentiation and within-plot mean pollen dispersal distance than the small populations. Outcrossing was consistently high and ranged from 85.7% ± 2.6 to 98.5% ± 0.9, and mating patterns suggested nearest-neighbour pollination. Pollen immigration into small populations ranged from 2.8% ± 1.8 to 16.5% ± 3.2. Using the small populations, we tested for correlations between various fragmentation variables and mating system and pollen dispersal parameters. We found significant negative linear relationships between population isolation and outcrossing rate; population shape and neighbourhood size; and conspecific density and mean pollen dispersal distance. There were significant positive linear relationships between population shape and pollen pool differentiation and between population size and number of different fathers per seed crop. Our results suggest that birds may use a series of fragmented populations as a vegetation corridor while foraging across the landscape and that population connectivity is a critical determinant of pollinator visitation. Our results also suggest that the effect of a linear population shape on the mating system and pollen dispersal is routinely underestimated.     

Seed Dispersers,Seed Predators,and Browsers Act Synergistically as Biotic Filters in a Mosaic Landscape

In this study, we analize the functional influence of animals on the plants they interact with in a mediterranean mountain. We hypothesise that seed dispersers, seed predators, and browsers can act as biotic filters for plant communities. We analyse the combined effects of mutualistic (seed dispersal) and antagonistic (seed predation, herbivory) animal interactions in a mosaic landscape of Mediterranean mountains, basing our results on observational and experimental field. Most of the dispersed seeds came from tree species, whereas the population of saplings was composed predominantly of zoochorous shrub species. Seed predators preferentially consumed seeds from tree species, whereas seeds from the dominant fleshy-fruited shrubs had a higher probability of escaping these predators. The same pattern was repeated among the different landscape units by browsers, since they browsed selectively and far more intensely on tree-species saplings than on the surrounding shrubs. In synthesis, our work identifies the major biotic processes that appear to be favoring a community dominated by shrubs versus trees because seed dispersers, predators, and herbivores together favored shrub dispersal and establishment versus trees.     

Quantifying patch‐specific seed dispersal and local population dynamics to estimate population spread of an endangered plant species

AimHabitat loss and fragmentation impose high extinction risk upon endangered plant species globally. For many endangered plant species, as the remnant habitats become smaller and more fragmented, it is vital to estimate the population spread rate of small patches in order to effectively manage and preserve them for potential future range expansion. However, population spread rate has rarely been quantified at the patch level to inform conservation strategies and management decisions. To close this gap, we quantify the patch‐specific seed dispersal and local population dynamics of Minuartia smejkalii, which is a critically endangered plant species endemic in the Czech Republic and is of urgent conservation concern.LocationŽelivka and Hrnčíře, Czechia.MethodsWe conducted demographic analyses using population projection matrices with long‐term demographic data and used an analytic mechanistic dispersal model to simulate seed dispersal. We then used information on local population dynamics and seed dispersal to estimate the population spread rate and compared the relative contributions of seed dispersal and population growth rate to the population spread rate.ResultsWe found that although both seed dispersal and population growth rate in M. smejkalii were critically limited, the population spread rate depended more strongly on the maximal dispersal distance than on the population growth rate.Main conclusionsWe recommend conservationists to largely increase the dispersal distance of M. smejkalii. Generally, efforts made to increase seed dispersal ability could largely raise efficiency and effectiveness of conservation actions for critically endangered plant species.     

Linking frugivore activity to early recruitment of a bird dispersed tree,Eugenia umbelliflora (Myrtaceae) in the Atlantic rainforest

Seed dispersal by animals is a complex process involving several distinct stages: fruit removal by frugivores, seed delivery in different microhabitats, seed germination, seedling establishment, and adult recruitment. Nevertheless, studies conducted until now have provided scarce information concerning the sequence of stages in a plant's life cycle in its entirety. The main objective of this study was to evaluate the immediate consequences of frugivore activity for Eugenia umbelliflora (Myrtaceae) early recruitment by measuring the relative importance of each fruit‐eating bird species on the establishment of new seedlings in scrub and low restinga vegetation in the Atlantic rainforest, Brazil. We conducted focal tree observations on E. umbelliflora trees recording birds' feeding behaviour and post‐feeding movements. We also recorded the fate of dispersed seeds in scrub and low restinga vegetation. We recorded 17 bird species interacting with fruits in 55 h of observation. Only 30% of the handled fruits were successfully removed. From 108 post flight movements of exit from the fruiting trees, 30.6% were to scrub and 69.4% to low restinga forest. Proportion of seed germination was higher in low restinga than in the scrub vegetation. Incorporating the probabilities of seeds' removal, deposition, and germination in both sites, we found that the relative importance of each frugivorous bird as seed dispersers varies largely among species. Turdus amaurochalinus and Turdus rufiventris were the best dispersers, together representing almost 12% probability of seed germination following removal. Our results show the importance of assessing the overall consequence of seed dispersal within the framework of disperser effectiveness, providing a more comprehensive and realistic evaluation of the relative importance of different seed dispersers on plant population dynamics.