Population Size Of Species Research Articles

Multiscale change in reef coral species diversity and composition in the Tropical Eastern Pacific

Both natural and anthropogenic factors are changing coral-reef structure and function worldwide. Long-term monitoring has revealed declines in the local composition and species diversity of reefs. Here we report changes in coral-reef community structure over 12 yr (2000–2012) at 17 sites and three spatial scales (reef, gulf and country) in the Tropical Eastern Pacific (Panama). We found a significant 4% annual decline in species population sizes at the country and gulf scales, with significant declines ranging from 3 to 32% at all but one reef. No significant temporal change in expected richness was found at the country scale or in the Gulf of Chiriqui, but a 7% annual decline in expected species richness was found in the Gulf of Panama. There was a 2% increase in community evenness in the Gulf of Chiriqui, but no change in the Gulf of Panama. Significant temporal turnover was found at the country and gulf scales and at 29% of the reefs, a finding mostly explained by changes in species abundance, and losses and gains of rare species. Temporal trends in alpha and beta diversity metrics were explained by water temperature maxima, anomalies and variation that occurred even in the absence of a strong El Nino warming event.

Coestimating Reticulate Phylogenies and Gene Trees from Multilocus Sequence Data.

The multispecies network coalescent (MSNC) is a stochastic process that captures how gene trees grow within the branches of a phylogenetic network. Coupling the MSNC with a stochastic mutational process that operates along the branches of the gene trees gives rise to a generative model of how multiple loci from within and across species evolve in the presence of both incomplete lineage sorting (ILS) and reticulation (e.g., hybridization). We report on a Bayesian method for sampling the parameters of this generative model, including the species phylogeny, gene trees, divergence times, and population sizes, from DNA sequences of multiple independent loci. We demonstrate the utility of our method by analyzing simulated data and reanalyzing an empirical data set. Our results demonstrate the significance of not only coestimating species phylogenies and gene trees, but also accounting for reticulation and ILS simultaneously. In particular, we show that when gene flow occurs, our method accurately estimates the evolutionary histories, coalescence times, and divergence times. Tree inference methods, on the other hand, underestimate divergence times and overestimate coalescence times when the evolutionary history is reticulate. While the MSNC corresponds to an abstract model of "intermixture," we study the performance of the model and method on simulated data generated under a gene flow model. We show that the method accurately infers the most recent time at which gene flow occurs. Finally, we demonstrate the application of the new method to a 106-locus yeast data set.

Effect of chlorfluazuron and flufenoxuron on development and reproductive performance of the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae)

The black cutworm, Agrotis ipsilon, is an insect pest with great agricultural importance worldwide. In Egypt, it has acquired resistance against most of the conventional pesticides, particularly organophosphate insecticides, applied against it. Therefore, the present study aimed to investigate the effect of two benzoylureas (chitin synthesis inhibitors) namely chlorfluazuron and flufenoxuron on some developmental and reproductive parameters of Agrotis ipsilon that survived treatment of newly molted fourth instars with the LC50 of these compounds (1.00 and 4.68 mg/L, respectively) using leaf–dip method. These two compounds significantly enhanced the mean larval and pupal durations, whereas they significantly declined the mean percentage pupation, adult emergence, pupal weight, adult longevity, fecundity, and fertility compared to untreated insects. The mean pre-oviposition period was not significantly affected, whereas the mean oviposition period was significantly decreased. Both chlorfluazuron and flufenoxuron significantly decreased the mean total protein, carbohydrate, and lipid content in the ovaries compared to untreated insects, except for insignificant decrease in the total protein in flufenoxuron-treated ones. Additionally, the total ovariolar length was significantly atrophied. In conclusion, chlorfluazuron and flufenoxuron interfere with vitellogenesis of A. ipsilon. Moreover, they could suppress the population size of this insect species by affecting its development and reproductive potential.

Demographic trends and climate over 35 years in the Barro Colorado 50 ha plot

BackgroundThe first three censuses of the 50-ha plot at Barro Colorado Island spanned an unusually harsh dry season during the 1983 El Niño. By the early 1990s, we had documented increases in tree mortality, tree growth, and large population fluctuations of many species during the 1982–1985 census interval. At the time, we asserted that increasing drought frequency would greatly affect the forest. With the benefit of five more censuses at Barro Colorado from 1995–2015, we can now put the 1980 conditions in a longer perspective and test the hypothesis that increasing droughtiness has continued to change the forest.MethodsA 50-ha forest plot on Barro Colorado Island was censused eight times, in 1982 and every five years since 1985. All free-standing woody stems were measured, mapped, and identified in each census.Results1) The period 1982–1992 included several extreme dry seasons, not just 1983, but since then there have been few such droughts.2) Dbh growth declined from a peak in the early 1980s to its lowest in the early 1990s. From 1995–2015 it increased slightly, but not returning to the initial peak. Nearly every species and all dbh categories followed the same pattern.3) The elevated stand-wide mortality rate of large trees during the 1982–1985 drought has not returned, and most individual species showed the same pattern of elevated mortality in the 1980s followed by low and fairly stable mortality after 1990.4) Sapling mortality declined after 1985, but rose again in the late-90s, so the 1980s drought period no longer looks unusual. Mortality of individual species’ saplings fluctuated erratically, including cases where mortality during the drought was lower than after.5) Population sizes of individual species fluctuated in all possible directions. Some species declined precipitously during the drought, then recovered, but others did not recover. Other species increased in abundance during the drought.ConclusionsDroughts of the 1980s elevated tree growth and mortality at Barro Colorado, but since 1990, demographic rates have remained lower, paralleling a moderate climate with few severe droughts after 1990. Moisture-demanding species suffered during the drought, but many have since recovered. We do not know how often such drought periods recur. Moreover, many species’ abundances fluctuated over 35 years with no known cause.

Isolation and Characterization of 18 Polymorphic Microsatellite Loci for the Endangered New Zealand Black-Fronted Tern (Chlidonias albostriatus)

Abstract. Eighteen polymorphic microsatellite loci were isolated and characterized from the endangered Black-fronted Tern (Chlidonias albostriatus), a species endemic to New Zealand. The loci were initially tested on seven individuals spanning the entire breeding range and then for a larger dataset of 345 samples covering 30 colonies from throughout the species' range. The number of alleles per loci ranged from 4 to 24, and observed and expected heterozygosity ranged between 0.46 and 0.95 and 0.45 to 0.86, respectively. One locus showed significant heterozygote deficit and appears to be sex-linked. The similar annealing temperatures across loci and the wide fragment sizes allowed multiplex polymerase chain reaction and rapid multilocus genotyping. The microsatellite markers will be useful tools for further investigation into the genetic diversity, population structure and effective population size of this endangered species and for informing conservation management.

Ecological and evolutionary consequences of alternative sex-change pathways in fish

Sequentially hermaphroditic fish change sex from male to female (protandry) or vice versa (protogyny), increasing their fitness by becoming highly fecund females or large dominant males, respectively. These life-history strategies present different social organizations and reproductive modes, from near-random mating in protandry, to aggregate- and harem-spawning in protogyny. Using a combination of theoretical and molecular approaches, we compared variance in reproductive success (Vk*) and effective population sizes (Ne) in several species of sex-changing fish. We observed that, regardless of the direction of sex change, individuals conform to the same overall strategy, producing more offspring and exhibiting greater Vk* in the second sex. However, protogynous species show greater Vk*, especially pronounced in haremic species, resulting in an overall reduction of Ne compared to protandrous species. Collectively and independently, our results demonstrate that the direction of sex change is a pivotal variable in predicting demographic changes and resilience in sex-changing fish, many of which sustain highly valued and vulnerable fisheries worldwide.

A history of hybrids? Genomic patterns of introgression in the True Geese

BackgroundThe impacts of hybridization on the process of speciation are manifold, leading to distinct patterns across the genome. Genetic differentiation accumulates in certain genomic regions, while divergence is hampered in other regions by homogenizing gene flow, resulting in a heterogeneous genomic landscape. A consequence of this heterogeneity is that genomes are mosaics of different gene histories that can be compared to unravel complex speciation and hybridization events. However, incomplete lineage sorting (often the outcome of rapid speciation) can result in similar patterns. New statistical techniques, such as the D-statistic and hybridization networks, can be applied to disentangle the contributions of hybridization and incomplete lineage sorting. We unravel patterns of hybridization and incomplete lineage sorting during and after the diversification of the True Geese (family Anatidae, tribe Anserini, genera Anser and Branta) using an exon-based hybridization network approach and taking advantage of discordant gene tree histories by re-sequencing all taxa of this clade. In addition, we determine the timing of introgression and reconstruct historical effective population sizes for all goose species to infer which demographic or biogeographic factors might explain the observed patterns of introgression.ResultsWe find indications for ancient interspecific gene flow during the diversification of the True Geese and were able to pinpoint several putative hybridization events. Specifically, in the genus Branta, both the ancestor of the White-cheeked Geese (Hawaiian Goose, Canada Goose, Cackling Goose and Barnacle Goose) and the ancestor of the Brent Goose hybridized with Red-breasted Goose. One hybridization network suggests a hybrid origin for the Red-breasted Goose, but this scenario seems unlikely and it not supported by the D-statistic analysis. The complex, highly reticulated evolutionary history of the genus Anser hampered the estimation of ancient hybridization events by means of hybridization networks. The reconstruction of historical effective population sizes shows that most species showed a steady increase during the Pliocene and Pleistocene. These large effective population sizes might have facilitated contact between diverging goose species, resulting in the establishment of hybrid zones and consequent gene flow.ConclusionsOur analyses suggest that the evolutionary history of the True Geese is influenced by introgressive hybridization. The approach that we have used, based on genome-wide phylogenetic incongruence and network analyses, will be a useful procedure to reconstruct the complex evolutionary histories of many naturally hybridizing species groups.

Seasonal waterbird population changes in Lashihai Lake in northwest Yunnan, China

We studied the waterbird population at Lashihai Lake, Yunnan Province, China, which is a Ramsar Site (Wetland of International Importance), to determine seasonal variation in the species composition and size of the waterbird population. The study was conducted at five selected spots along Lashihai Lake at the same time each week from August 2011 to September 2013. In total, 62 waterbird species were recorded, of which 38.71%, 35.48%, 16.13%, and 9.68% were winter migrants, passage visitors, residents, and summer migrants, respectively. We found important seasonal changes in waterbird species composition and population size. Waterbird species richness was highest from September to the following April, with the total species numbers peaking in December. Total individual numbers peaked twice from late November to early December and mid-to-late February. However, waterbird species and individual numbers were comparatively lower from May to August. The change in species composition was determined by the arrival and departure dynamics of winter migrants and passage visitors. Winter migrants primarily caused the periodic changes in population size. Of concern, species and overall waterbird numbers seemed to be lower than the numbers in historical records. The decline of waterbird numbers implies that environmental changes caused by the implementation of the dam upstream of Lashihai Lake may have had adverse effects on this waterbird population. This study confirms the existence of major seasonal changes in species composition and size of the waterbird population at Lashihai Lake. Furthermore, the findings demonstrate that this wetland is of high conservation importance for waterbirds using the Central Asian–Indian and Asian–Pacific migratory routes.

The invasive shrub Prosopis juliflora enhances the malaria parasite transmission capacity of Anopheles mosquitoes: a habitat manipulation experiment

BackgroundA neglected aspect of alien invasive plant species is their influence on mosquito vector ecology and malaria transmission. Invasive plants that are highly attractive to Anopheles mosquitoes provide them with sugar that is critical to their survival. The effect on Anopheles mosquito populations was examined through a habitat manipulation experiment that removed the flowering branches of highly attractive Prosopis juliflora from selected villages in Mali, West Africa.MethodsNine villages in the Bandiagara district of Mali were selected, six with flowering Prosopis juliflora, and three without. CDC-UV light traps were used to monitor their Anopheles spp. vector populations, and recorded their species composition, population size, age structure, and sugar feeding status. After 8 days, all of the flowering branches were removed from three villages and trap catches were analysed again.ResultsVillages where flowering branches of the invasive shrub Prosopis juliflora were removed experienced a threefold drop in the older more dangerous Anopheles females. Population density dropped by 69.4% and the species composition shifted from being a mix of three species of the Anopheles gambiae complex to one dominated by Anopheles coluzzii. The proportion of sugar fed females dropped from 73 to 15% and males from 77 to 10%.ConclusionsThis study demonstrates how an invasive plant shrub promotes the malaria parasite transmission capacity of African malaria vector mosquitoes. Proper management of invasive plants could potentially reduce mosquito populations and malaria transmission.

A New Approach to Modelling the Relationship Between Annual Population Abundance Indices and Weather Data

Weather has often been associated with fluctuations in population sizes of species; however, it can be difficult to estimate the effects satisfactorily because population size is naturally measured by annual abundance indices whilst weather varies on much shorter timescales. We describe a novel method for estimating the effects of a temporal sequence of a weather variable (such as mean temperatures from successive months) on annual species abundance indices. The model we use has a separate regression coefficient for each covariate in the temporal sequence, and over-fitting is avoided by constraining the regression coefficients to lie on a curve defined by a small number of parameters. The constrained curve is the product of a periodic function, reflecting assumptions that associations with weather will vary smoothly throughout the year and tend to be repetitive across years, and an exponentially decaying term, reflecting an assumption that the weather from the most recent year will tend to have the greatest effect on the current population and that the effect of weather in previous years tends to diminish as the time lag increases. We have used this approach to model 501 species abundance indices from Great Britain and present detailed results for two contrasting species alongside an overall impression of the results across all species. We believe this approach provides an important advance to the challenge of robustly modelling relationships between weather and species population size.

Population Status and Diurnal Behaviour of the Indian Flying Fox Pteropus giganteus (Brünnich, 1782) in Kathmandu Valley, Nepal

This study documents the population status and behaviour of the Indian Flying Fox (Pteropus giganteus) at two locations in the temperate environment of the Kathmandu Valley, Nepal. During the five-month study, from 14th July, 2014 to 2nd January, 2015, peak populations were observed in October, 2014 at Sallaghari (1550 individuals) and Keshar Mahal (949 individuals). The behavioural study resulted in 1130 observed events of 10 different behavioural activities at Sallaghari and 1158 events of the same activities at Keshar Mahal. Sleeping, grooming, wing spreading and wing flapping were frequently observed at both study sites. The behaviour of P. giganteus is influenced by the weather and air temperature irrespective of hours of the day and date of observation. Habitat destruction, lack of food, pollution and misconception were the major threats to P. giganteus perceived by local people in course of interviews. Knowledge regarding the population size and behaviours of wildlife species is essential to understand the conservation needs for the survival and management of wild animals and their habitat. This study provides baseline information for two populations of Indian flying fox (P. giganteus) in Kathmandu Valley Nepal.

Less effective selection leads to larger genomes.

The evolutionary origin of the striking genome size variations found in eukaryotes remains enigmatic. The effective size of populations, by controlling selection efficacy, is expected to be a key parameter underlying genome size evolution. However, this hypothesis has proved difficult to investigate using empirical data sets. Here, we tested this hypothesis using 22 de novo transcriptomes and low-coverage genomes of asellid isopods, which represent 11 independent habitat shifts from surface water to resource-poor groundwater. We show that these habitat shifts are associated with higher transcriptome-wide . After ruling out the role of positive selection and pseudogenization, we show that these transcriptome-wide increases are the consequence of a reduction in selection efficacy imposed by the smaller effective population size of subterranean species. This reduction is paralleled by an important increase in genome size (25% increase on average), an increase also confirmed in subterranean decapods and mollusks. We also control for an adaptive impact of genome size on life history traits but find no correlation between body size, or growth rate, and genome size. We show instead that the independent increases in genome size measured in subterranean isopods are the direct consequence of increasing invasion rates by repeat elements, which are less efficiently purged out by purifying selection. Contrary to selection efficacy, polymorphism is not correlated to genome size. We propose that recent demographic fluctuations and the difficulty of observing polymorphism variation in polymorphism-poor species can obfuscate the link between effective population size and genome size when polymorphism data are used alone.

The value of museums in the production, sharing, and use of entomological data to document hyperdiversity of the changing North

If the current rate of climate change continues, the composition, distribution, and relative population sizes of species in the higher latitudes of the Northern Hemisphere are likely to change considerably. Understanding the magnitude of this change requires a well- documented baseline against which to compare. Although specimen-less observations can help augment such a baseline for the minority of organisms that can be confidently identified in the field or from photographs, the vast majority of species are small-bodied invertebrates, primarily arthropods, that can only be identified from preserved specimens and (or) their tissues. Museum staff archive specimens and make them and their data available for research. This paper describes a number of challenges to the goal of thorough documentation of high-latitude arthropod biodiversity and their potential solutions. Examples are provided from ongoing and recently completed research that demonstrates the value of museum specimens and the sharing of their data via global portals like GBIF.org.

Abortive Spontaneous Egg Activation: An Emerging Biological Threat for the Existence of Mammals.

Mammals are important for balancing the natural ecosystem, but in the past few decades, several species have rapidly been entered under threatened category worldwide. The environmental changes, loss of natural habitats, human activities, and thereby stress are responsible for a gradual decline in reproductive outcome. Stress induces generation of reactive oxygen species (ROS). High physiological level of ROS drives abortive spontaneous egg activation (SEA), while beyond the physiological level causes oxidative stress (OS). The OS induces apoptosis and deteriorates egg quality that limits reproductive outcome. The reduced reproductive outcome is one of the major causes for gradual decline in population size of several mammalian species. Despite having several conservation programs, a gradual decline in species reproductive outcome and their population size is the serious concern for the existence of threatened mammalian species. Thus, it is important to identify and prevent the underlying causes responsible for abortive SEA, which could be an emerging problem for several mammalian species that are threatened or at the verge of extinction.

Making inference from wildlife collision data: inferring predator absence from prey strikes.

Wildlife collision data are ubiquitous, though challenging for making ecological inference due to typically irreducible uncertainty relating to the sampling process. We illustrate a new approach that is useful for generating inference from predator data arising from wildlife collisions. By simply conditioning on a second prey species sampled via the same collision process, and by using a biologically realistic numerical response functions, we can produce a coherent numerical response relationship between predator and prey. This relationship can then be used to make inference on the population size of the predator species, including the probability of extinction. The statistical conditioning enables us to account for unmeasured variation in factors influencing the runway strike incidence for individual airports and to enable valid comparisons. A practical application of the approach for testing hypotheses about the distribution and abundance of a predator species is illustrated using the hypothesized red fox incursion into Tasmania, Australia. We estimate that conditional on the numerical response between fox and lagomorph runway strikes on mainland Australia, the predictive probability of observing no runway strikes of foxes in Tasmania after observing 15 lagomorph strikes is 0.001. We conclude there is enough evidence to safely reject the null hypothesis that there is a widespread red fox population in Tasmania at a population density consistent with prey availability. The method is novel and has potential wider application.

Spreading of alien species and diversity of communities

A new species invading a new area may cause a decrease in diversity of the community already present there. Comparison of temporal changes in species diversity of the “new” community (including alien species) with those of the “original” community (including only native species) may clarify our understanding of the effect of alien species. Using a simulation-based modelling approach we considered several scenarios describing the invasion of native communities by alien species and calculated the trends in Shannon-Wiener indices and in the numbers of species of the “original” and “new” communities during the course of the invasion. We found that despite a large increase in the population size of the invasive alien species the diversity of the original community may be little affected. Native species numbers may stay relatively constant for a long time and then suddenly collapse. The results indicate some possibly still concealed consequences of the spread of the invasive ladybird Harmonia axyridis (Pallas).

Conservation needs for the endangered New Zealand sea lion, Phocarctos hookeri

Abstract Understanding population size and trend is critical information in species management and conservation. To enable accurate population trend estimates, consistent robust monitoring of a species is essential, particularly for a species such as the New Zealand (NZ) sea lion, Phocarctos hookeri, which has experienced an almost continuous decline in pup production since the late 1990s. This research examines the pup production estimates for all known breeding sites for this species, and using a stage‐structured matrix population model, estimates population size and trend between 1995 and 2015. Overall, it is estimated that 2,316 pups were born in 2015, a decrease of 13% since 1995 and a 27% decline since the highest pup production estimate in 1998. This decline has been driven by the significant decline of 48% at the main breeding area, the Auckland Islands since 1998. Using the stage‐structured matrix population model a total species population size of 11,767 sea lions (95% CrI: 10,790–12,923) was estimated. This is the lowest population size of any sea lion species. Trend data for the Auckland Islands indicated that pup and population numbers have decreased at 1.9% yr−1 in the last 20 yr, while total species population decline is 0.6% yr−1. Estimates of population trends for this species have been hindered by inconsistent monitoring at most breeding sites. This study strengthens the growing field of research highlighting the need for consistent long‐term monitoring for the conservation management of endangered species.

The contribution of successional grasslands to the conservation of semi-natural grasslands species – A landscape perspective

Many species that are typical of calcareous, semi-natural grasslands (“typical grassland species”) are declining in Europe as a result of habitat-loss and -fragmentation. Whereas populations of these species are expected to be largest in old semi-natural grasslands, these species may also occur in successional grasslands on previously arable fields. We used a space-for-time approach to analyse changes in the frequencies of typical grassland species, and changes in soil properties, over a 280-year arable-to-grassland succession within a Swedish landscape. Our study revealed that a number of typical grassland species had higher frequencies in mid-successional (50–279years) than in old (≥280years) grasslands. Mid-successional grasslands also contained many of the typical grassland species that were present in old grasslands, but at lower frequencies, and had soil conditions similar to those of old grasslands. Early-successional (5–14 and 15–49years) grasslands contained few typical grassland species. In highly fragmented landscapes, mid-successional grasslands provide additional habitat for many typical grassland species, and can function as temporary refugia (“substitute habitat”) for these species until old grasslands are “restored”. The overall population sizes of some typical grassland species and red-listed species are likely to be substantially increased by the presence of mid-successional grasslands within the landscape. Our study suggests that, rather than focussing solely on old grassland fragments, conservation strategies for typical grassland species should adopt a dynamic, landscape-based perspective that recognizes the role of successional grasslands. Ensuring a continuous development of mid-successional grasslands is expected to be beneficial for populations of many typical grassland species.

Survey on the bryophyte flora of the surrounding mountains of the Káli Basin (Balaton-felvidék Region, Hungary)

In 2016 and 2017, exploration of the bryophyte flora was carried out in the surroundings of Kővagoors, Koveskal and Szentbekkalla villages. In the hilly region around the basin mainly Quercetum cerris forests occur on acidic bedrock, however, some limestone outcrops can also be found at Koveskal. Altogether 123 bryophyte taxa (8 liverworts and 115 mosses) were recorded during our survey. The most important finding was Zygodon forsteri, a redlisted species in Europe, which was recorded for the first time in Hungary. This atlanticsubmediterranean element is a member of the Orthotrichaceae family, growing usually around knot-holes or other hollows of trees where water runs down on the bark, and often on callus tissue. Our specimens were collected in knot-holes of two Quercus cerris trees. Two other species (Anacamptodon splachnoides, Fissidens arnoldii) are included in the Red data book of European bryophytes, which are also protected in Hungary. Anacamptodon splachnoides lives in the same habitat as Zygodon forsteri, around knot-holes. This species was detected on 57 Quercus cerris trees in the investigated forests. Probably the largest population in Europe lives here. Fissidens arnoldii was found on limestone rocks in a stream at Koveskal. Another interesting species is Pottia starckeana s.s., which is in the data deficient (DD) category in he Hungarian Bryophyte Red List (without any recent records for almost 50 years). Several other species found there are redlisted in Hungary, e.g. Eurhynchium speciosum is endangered (EN), Buxbaumia aphylla and Orthotrichum patens are vulnerable (VU). Further 13 species are near threatened (NT) and 16 are regarded as indicators, which by their mere presence represents a greater level of conservation value of the habitat. Habitat preference, population size of species of conservation interest and advice in their conservation management will be given.

High fodder value and feeding likelihood favour endozoochorous plant dispersal

Questions In pasture-dominated landscapes, endozoochory by large herbivores is an important vector of plant dispersal. Conditions influencing the potential for endozoochorous dispersal of plant species by grazers are, however, still poorly known. Here, we assess the impact of feeding habits and functional traits on the likelihood of endozoochorous dispersal by cattle (ruminant) and horses (non-ruminant). Location Pasture of 27 ha in NW-Germany year-round grazed by free-ranging cattle and horses. Methods Vegetation relevees were established in 45 plots, in which dung samples of cattle and horses were collected. The number and composition of seedlings emerging from dung samples were compared with the vegetation of the study site in terms of plant functional trait composition. For the first time, feeding habits were included in the analysis. Generalized linear models were used to identify traits that increased the potential for endozoochorous dispersal. Results A total of 65 species germinated from the dung samples. These species had higher average fodder and nutrient indicator values than the species composition of the vegetation. Especially species found in horse dung were more tolerant of grazing and had more elongated seeds. The likelihood of endozoochorous dispersal was higher for common than for rare species and was influenced by feeding habits. Conclusions The likelihood of plant species being dispersed endozoochorously can be linked to different functional traits and is dependent on the type of grazer and the population size of target species in the vegetation. Differences between cattle and horses in seed dispersal may result from species-specific grazing habits and different digestion modes. This article is protected by copyright. All rights reserved.