Implications of 19th century landscape patterns for the recovery of Fagus crenata forests

Questions: What is the effect of the 19th century (pre‐industrialization) landscape pattern on the recovery of climax forests in cool‐temperate mountain areas dominated by Fagus crenata (Japanese beech)? Location: Secondary forests on Mt. Daisen, western Japan. Methods: Vegetation patterns before and after industrialization were obtained from maps drawn in 1898 and 1979. Tree measurements were made in 12 plots in 1997. Correlation between current Fagus crenata dominance and forest edge in the 19th century was analysed using an S‐shaped regression curve. Fagus juvenile density was counted in the plots, and distances from each plot to the five nearest mother trees were measured to determine the dispersal kernel. Results: Secondary grassland covered a substantial area in 1898, whereas forest covered most of the area in 1997. Fagus was dominant in places in the interior forest 100 years ago, and mature Fagus trees were absent in secondary forests that had been grasslands in 1898. The expected number of juveniles decreased to one individual per 100 m² at 43.5 m from the mother tree. Conclusions: The pre‐industrialization landscape greatly affected recovery of Fagus forest. Forests found on the 1898 vegetation map might have acted as refugia for Fagus. The limited dispersal ability of Fagus suggests that it would take many generations (several hundred years) for Fagus forests to recover at the centre of what had been grasslands in the 19th century.     

Spatial dynamics of Microtus vole populations in continuous and fragmented agricultural landscapes

Small mammal populations often exhibit large-scale spatial synchrony, which is purportedly caused by stochastic weather-related environmental perturbations, predation or dispersal. To elucidate the relative synchronizing effects of environmental perturbations from those of dispersal movements of small mammalian prey or their predators, we investigated the spatial dynamics of Microtus vole populations in two differently structured landscapes which experience similar patterns of weather and climatic conditions. Vole and predator abundances were monitored for three years on 28 agricultural field sites arranged into two 120-km-long transect lines in western Finland. Sites on one transect were interconnected by continuous agricultural farmland (continuous landscape), while sites on the other were isolated from one another to a varying degree by mainly forests (fragmented landscape). Vole populations exhibited large-scale (>120 km) spatial synchrony in fluctuations, which did not differ in degree between the landscapes or decline with increasing distance between trapping sites. However, spatial variation in vole population growth rates was higher in the fragmented than in the continuous landscape. Although vole-eating predators were more numerous in the continuous agricultural landscape than in the fragmented, our results suggest that predators do not exert a great influence on the degree of spatial synchrony of vole population fluctuations, but they may contribute to bringing out-of-phase prey patches towards a regional density level. The spatial dynamics of vole populations were similar in both fragmented and continuous landscapes despite inter-landscape differences in both predator abundance and possibilities of vole dispersal. This implies that the primary source of synchronization lies in a common weather-related environment.     

Long‐distance dispersal of non‐native pine bark beetles from host resources

1. Dispersal and host detection are behaviours promoting the spread of invading populations in a landscape matrix. In fragmented landscapes, the spatial arrangement of habitat structure affects the dispersal success of organisms. 2. The aim of the present study was to determine the long distance dispersal capabilities of two non‐native pine bark beetles (Hylurgus ligniperda and Hylastes ater) in a modified and fragmented landscape with non‐native pine trees. The role of pine density in relation to the abundance of dispersing beetles was also investigated. 3. This study took place in the Southern Alps, New Zealand. A network of insect panel traps was installed in remote valleys at known distances from pine resources (plantations or windbreaks). Beetle abundance was compared with spatially weighted estimates of nearby pine plantations and pine windbreaks. 4. Both beetles were found ≥25 km from the nearest host patch, indicating strong dispersal and host detection capabilities. Small pine patches appear to serve as stepping stones, promoting spread through the landscape. Hylurgus ligniperda (F.) abundance had a strong inverse association with pine plantations and windbreaks, whereas H. ater abundance was not correlated with distance to pine plantations but positively correlated with distance to pine windbreaks, probably reflecting differences in biology and niche preferences. Host availability and dispersed beetle abundance are the proposed limiting factors impeding the spread of these beetles. 5. These mechanistic insights into the spread and persistence of H. ater and H. ligniperda in a fragmented landscape provide ecologists and land managers with a better understanding of factors leading to successful invasion events, particularly in relation to the importance of long‐distance dispersal ability and the distribution and size of host patches.     

What shapes the altitudinal range of a high mountain Mediterranean plant? Recruitment probabilities from ovule to seedling stage

Recruitment is a complex process consisting of sequential stages affected by biotic interactions and abiotic factors. Assessment of these sequential stages and corresponding subprocesses may be useful in identifying the most critical stages. Accordingly, to assess the factors that may determine the altitudinal range limits of the high mountain Mediterranean plant Silene ciliata, a set of demographic stages, from flower production to establishment of 2‐yr‐old plants, and their influence on recruitment probability were examined using a step‐by‐step approach. We integrated florivory, pollination and pre‐dispersal seed predation as pre‐dispersal factors, and seedling emergence and survival as post‐dispersal determinants of recruitment. Three populations were monitored at the southernmost margin of the species along its local altitudinal range. Previous studies suggest that seediness is strongly limited by summer drought especially at the lower boundary of the species, a situation that may worsen under current global warming. Our results showed that recruitment was mainly limited by low seed production in the pre‐dispersal stage and low seedling emergence and survival in the post‐dispersal stage, probably due to environmental harshness in summer. By contrast, biotic factors responsible for propagule loss, such as flower and fruit predation, had a minor effect on the probability of plant recruitment. Although the relative importance of transition probabilities was similar among populations along the altitudinal range, comparatively lower flower production significantly reduced the number of recruited plants at the lowest altitude population. This demographic bottleneck, together with increased competition with other species favoured by climate warming, might collapse population growth and limit persistence at the lower altitudinal range of the species, raising its low local altitudinal edge.     

Comparative Population Genetic Structure of the Endangered Southern Brown Bandicoot,Isoodon obesulus,in Fragmented Landscapes of Southern Australia

Genetic connectivity is a key factor for maintaining the persistence of populations in fragmented landscapes. In highly modified landscapes such us peri-urban areas, organisms’ dispersal among fragmented habitat patches can be reduced due to the surrounding matrix, leading to subsequent decreased gene flow and increased potential extinction risk in isolated sub-populations. However, few studies have compared within species how dispersal/gene flow varies between regions and among different forms of matrix that might be encountered. In the current study, we investigated gene flow and dispersal in an endangered marsupial, the southern brown bandicoot (Isoodon obesulus) in a heavily modified peri-urban landscape in South Australia, Australia. We used 14 microsatellite markers to genotype 254 individuals which were sampled from 15 sites. Analyses revealed significant genetic structure. Our analyses also indicated that dispersal was mostly limited to neighbouring sites. Comparisons of these results with analyses of a different population of the same species revealed that gene flow/dispersal was more limited in this peri-urban landscape than in a pine plantation landscape approximately 400 km to the south-east. These findings increase our understanding of how the nature of fragmentation can lead to profound differences in levels of genetic connectivity among populations of the same species.     

Population dynamics of the perennial Plantago media in semi‐natural grasslands

Abstract. In this study we investigated population dynamics of a perennial forb, Plantago media, in semi‐natural grasslands in southeastern Sweden. Plantago media is a rather common inhabitant of grasslands in this region, but it has been shown to experience dispersal limitations both among managed grassland sites and at potential dispersal routes along road verges. The demography of P. media was studied in 22 permanent plots at two sites over five years. A seed sowing experiment was also performed at each site. The life‐cycle of P. media includes seedlings, juveniles, small vegetative rosettes, large vegetative rosettes and flowering rosettes. The population growth rates (λ‐values) were negative for both populations, with one exception: the first year transition matrix at one site. The projected life span for individuals surviving from seedlings to flowering rosettes varied between 19.6 yr and 227.8 yr. Elasticity analysis showed that remaining in the large rosette stages, both vegetative and flowering, was the most important factor influencing population growth rate. LTRE analysis gave similar results, indicating that spatial and temporal variation have similar effects on the population growth rate. The expected time to extinction in populations with an initial size of between 100 and 1000 individuals varied between 60 and 200 yr. The seed sowing experiment showed that seedling emergence was enhanced by both seed addition and disturbance, suggesting that recruitment is limited by seed and microsite availability. Recruitment was not found to have much impact on population growth rate. However, long‐term population maintenance may depend on occasional small‐scale disturbances that enhance pulses of recruitment. Fragmented landscape is likely to effect plant populations including rare and endangered species as well as more common species which have limited dispersal mechanisms.     

Population structures and individual performances of <Emphasis Type="Italic">Trillium grandiflorum</Emphasis> in hedgerow and forest habitats

In agricultural landscapes, linear habitats, such as hedgerows at field margins increase structural connectivity among forest patches, potentially providing dispersal corridors for forest herbs. The spatial structure of linear habitats, however, also results in edge effects and perturbations that can influence the individual and population performance of forest plants. This study compares the stage structure and components of growth and reproduction of 14 Trillium grandiflorum populations in hedgerows and forests. Hedgerow Trillium tended to grow faster and, when mature, produced more flowers and more ovules per flowers than forest Trillium, a pattern possibly associated to differences in nutrients and light availability between the two habitats. Seed production and germination rate, however, did not differ between hedgerows and forests. At the population level, seedlings and juveniles were proportionally less abundant in hedgerows than in forests. Although well-established plants can thrive in hedgerows, reduced recruitment may eventually limit the capacity to establish new populations and therefore hamper migration along hedgerow-corridors. Considering the strategies by which plants persist in linear habitats becomes particularly relevant at a time when species are expected to be much in need of dispersal corridors because of climatic stress.     

Recruitment limitations in Primula vulgaris in a fragmented landscape

Plant recruitment is limited by dispersal, if seeds cannot arrive at potential recruitment sites, and by establishment, due to a low availability of safe sites for recruitment. Seed-sowing experiments, scarcely applied along gradients of landscape alteration, are very useful to assess these limitations. Habitat loss and fragmentation may foster recruitment limitations by affecting all the processes from seed dispersal to seedling establishment. In this study, we perform a seed-sowing experiment to disentangle the importance of dispersal and establishment limitations in different stages of recruitment of the perennial herb Primula vulgaris in fragmented forests of the Cantabrian Range (Northwestern Spain). We evaluated the influence of ecological gradients resulting from habitat loss and fragmentation (modifications of habitat amount at the landscape and microhabitat scales, changes in the species’ population size, changes in seed predation and seedling herbivory) on seedling emergence, survival and early growth. We found strong evidence of dispersal limitation, as seedling emergence was very low in experimental replicates where no seeds were added. This limitation was independent of landscape alterations, as we found no relation with any of the ecological gradients studied. Establishment limitations at the germination phase were also unrelated to ecological gradients, probably because these limitations are more related to fine-scale environmental gradients. However, further monitoring revealed that seedling survival after summer and winter periods and seedling growth were conditioned by landscape alteration, as we found effects of habitat amount at the landscape and microhabitat scales, of presence of populations of P. vulgaris and of seedling herbivory. These effects were complex and sometimes opposite to what can be expected for adult plants, revealing the presence of different requirements between life stages.     

Extensive pollen dispersal in a bird-pollinated shrub, Calothamnus quadrifidus, in a fragmented landscape

Pollen dispersal was investigated in six populations of Calothamnus quadrifidus, a bird-pollinated shrub in the fragmented agricultural region of southern Western Australia. Paternity analysis using six microsatellite loci identified a pollen source within populations for 67% of seedlings, and the remainder were assumed to have arisen from pollen sources outside the populations. Outcrossing was variable, ranging from 5% to 82%, and long-distance pollen dispersal was observed in all populations with up to 43% of pollen sourced from outside the populations over distances of up to 5 km. This extensive pollen immigration was positively associated with population size but not isolation. Comparison of two populations of similar size but different density showed greater internal pollination and less selfing in the denser population, suggesting an influence of density on pollinator behaviour. The study revealed extensive long-distance pollen dispersal for C. quadrifidus within this fragmented agricultural landscape and highlighted the interaction between reserve populations and isolated road verge remnants in maintaining genetic connectivity at the landscape scale.     

Offspring performance and recruitment of the pioneer tree Acacia caven (Fabaceae) in a fragmented subtropical dry forest

The process of habitat fragmentation results in the breaking apart of originally continuous habitats, causing multiple changes in biotic and abiotic interactions. Alterations in resource availability and in mutualistic and antagonistic plant–animal interactions may impact plant offspring quantity and quality. Currently, several old fragmented systems evidence a process of flora homogenization, where shade‐tolerant species are replaced by pioneer light‐demanding species. Notably, the relationship between quantity and quality parameters of plant offspring production and the successful recruitment of pioneer species in fragmented forests has been poorly explored. Here, we assess population size, sapling recruitment and offspring performance of one of the most widespread tree species of subtropical South America, the native pioneer Acacia caven (Fabaceae). Population size of adults and saplings increased from small to continuous forests, whereas the sapling recruitment per adult tree (sapling/adult ratio) showed no significant differences among forests of different size. Seedling performance was negatively related to forest area and population size, implying potential superior competitive ability of seedlings produced in smaller populations compared to larger ones. Our results show that A. caven is resilient to habitat fragmentation effects, which may be ascribed to a set of advantageous ecological traits such as outcrossing, massive flowering, generalist pollination, drought resistance, rapid growth and re‐sprouting. Thus, this pioneer tree benefits from the availability of vacant sites and resources released by declining plant populations of other species, eventually becoming the dominant species in fragmented habitats. Pioneer native plant species with ecological traits such as A. caven may represent the silent successful survivors and new colonizers of fragmented habitats, the ubiquitous landscapes of the future.     

Seed dispersal and colonization ability of plants — Assessment and implications for conservation

Seed dispersal is one of the least understood phases in plant life-cycles, despite being recognized as fundamentally important for understanding species distribution, abundance, population dynamics and life-history variation. For species living in fragmented habitats, dispersal may be crucial for regional persistence. This paper synthesizes studies performed in Swedish semi-natural grasslands and deciduous forests. The main objective was to develop a simple method to assess the dispersal and colonization ability of plants. Dispersal and colonization were considered as a series of steps: seed production, seed transport and seedling recruitment. With the use of verified assumptions on (i) a trade-off between seed production and seed size, (ii) a relatively small predictive power of seed transport for species actual dispersal and colonization, (iii) a positive effect of seed size on recruitment, and (iv) a general prevalence of recruitment limitations by seed availability, a prediction is made that dispersal and colonization ability will be highest among species with intermediate seed sizes in a given community. This prediction is supported by field data. Based on estimated dispersal and colonization ability, and the ability of local populations to persist, a scheme is suggested with four basic categories of plants. Some implications are suggested for conservation, in a landscape scale, of plants belonging to each of these four categories.     

Differences in the vegetation of the North Iberian Peninsula during the last 16,000 years

The dynamics of vegetation in the North Iberian Peninsula have been historically established from peaty and lacustrine records obtained in strongly continental mountainous areas. Pollen records located in areas with a more oceanic climate, have allowed a more precise evaluation of the changes and differences in the vegetation development of the various biogeographical areas in the North Iberian Peninsula, during the Late-glacial and Holocene. It was found that: (1) The vegetation of the Cantabrian–Atlantic province in northern Iberian Peninsula responded to climatic changes during the last 16000 years. (2) Tree vegetation declined during the Oldest Dryas, with steppe vegetation in the interior and cryophilous vegetation along the coast. (3) During the time of the Lateglacial Interestadial, lowlands, arboreal vegetation was dominant in the landscape (Pinus, Betula, Quercus, Corylus). (4) During the Younger Dryas the differences between coast and interior are less obvious. (5) During the Holocene oceanic decidious forests of Quercus robur, Corylus avellana, Tilia sp. and Fagus sylvatica were present along the coast. At low altitudes, in the interior, forests of Quercus robur / pyrenaica, enclaves of pine woods and Mediterranean types of forest (Quercus ilex, Olea europea) were present. At higher altitudes Pinus (P. sylvestris and P. uncinata) or mixed forests of Pinus and Betula were dominant.     

Tree species diversity in temperate and tropical forest gaps: The role of lottery recruitment

How canopy gaps promote tree species coexistence in temperate and tropical forests is reviewed. Given that evidence for traditional resource-based niche partitioning of canopy gaps is weak, lottery recruitment, whereby colonization of vacant living space is random with respect to species identity, may be key to maintaining diversity. Gap formation events are not highly predictable and species’ propagules tend to be patchily distributed. For these reasons the predictability of gap-phase recruitment is low and lottery principles apply. Recruitment limitation from discontinuities in species’ propagule supplies in space and time may permit lottery recruitment in temperate and tropical forests. However, the relative importance of recruitment limitation in species-rich versus species-poor communities is unclear. Although lottery models with purely random recruitment in vacant sites can be applied, relatively complex models appear to better capture the essential features of forest community dynamics. For example, models with recruitment probabilities weighted by species abundance can produce the non-random trajectories often observed in communities. Models with local competitive displacement by individuals of dominant species can also produce non-random trajectories. Models with spatial structure, localized competition, and dispersal limitations may provide further insight into the effects of biotic interactions and recruitment limitation on forest dynamics.     

Demography of greater prairie-chickens: Regional variation in vital rates,sensitivity values,and population dynamics

Intensification of rangeland management has coincided with population declines among obligate grassland species in the largest remaining tallgrass prairie in North America, although causes of declines remain unknown. We modeled population dynamics and conducted sensitivity analyses from demographic data collected for an obligate grassland bird that is an indicator species for tallgrass prairie, the greater prairie-chicken (Tympanuchus cupido), during a 4-year study in east-central Kansas, USA. We examined components of reproductive effort and success, juvenile survival, and annual adult female survival for 3 populations of prairie-chickens across an ecological gradient of human landscape alteration and land use. We observed regional differences in reproductive performance, survivorship, and population dynamics. All 3 populations of prairie-chickens were projected to decline steeply given observed vital rates, but rates of decline differed across a gradient of landscape alteration, with the greatest declines in fragmented landscapes. Elasticity values, variance-scaled sensitivities, and contribution values from a random-effects life-table response experiment all showed that the finite rate of population change was more sensitive to changes in adult survival than other demographic parameters in our declining populations. The rate of population change was also sensitive to nest survival at the most fragmented and least intensively grazed study site; suggesting that patterns of landscape fragmentation and land use may be affecting the relative influences of underlying vital rates on rates of population growth. Our model results indicate that 1) populations of prairie-chickens in eastern Kansas are unlikely to be viable without gains from immigration, 2) rates of population decline vary among areas under different land management practices, 3) human land-use patterns may affect the relative influences of vital rates on population trajectories, and 4) anthropogenic effects on population demography may influence the regional life-history strategies of a short-lived game bird. © 2012 The Wildlife Society.     

Effects of forest fragmentation on the lekking behavior of White-throated Manakins in Central Amazonia

Forest fragmentation can affect various aspects of population dynamics, but few investigators have assessed possible effects on the behavior of a species. Loss of habitat may limit population recruitment and abundance, which may alter breeding dynamics in forest remnants. We examined the lekking behavior of White-throated Manakins (Corapipo gutturalis) in a fragmented landscape to determine if forest fragmentation affected the spatial distribution of display courts and male behavior at courts. We captured and observed males at 19 courts located in 11 primary forests of different sizes in forest habitats of the Biological Dynamics of Forest Fragments Project area, an experimentally fragmented landscape located in the central Brazilian Amazon, and estimated their spatial distribution as the distance to the nearest court in the landscape. We quantified habitat loss using the proportion of forest cover surrounding courts and their distances to forest edges. No courts were detected in 1-ha forest fragments, suggesting direct effects from habitat loss following fragmentation that affected connectivity and thus recruitment and persistence of courts in the smallest fragments. The spatial distribution of display courts in forests larger than 10 ha remained unaltered, compared to display courts in continuous forests, but adult males were less numerous on courts with a higher percentage of forest cover and they displayed less on courts closer to forest edges. The spatial distribution of courts also contributed to variation in male social behavior, with more juvenile males present and adult males displaying at lower rates at more isolated courts. Although White-throated Manakins are locally common, the observed behavioral changes in response to habitat loss may affect their population dynamics. Our results show the importance of assessing behavioral changes in conservation programs and, in particular, of including biologically relevant measures of habitat loss in addressing its possible effects on species persistence in fragmented landscapes.     

Spatial vs. temporal effects on demographic and genetic structures: the roles of dispersal, masting and differential mortality on patterns of recruitment in Fagus sylvatica

Trees' long lifespan, long-distance dispersal abilities and high year-to-year variability in fecundity are thought to have pervasive consequences for the demographic and genetic structure of recruited seedlings. However, we still lack experimental studies quantifying the respective roles of spatial processes such as restricted seed and pollen dispersal and temporal processes such as mast seeding on patterns of regeneration. Dynamics of European beech (Fagus sylvatica) seedling recruitment was monitored in three plots from 2004 to 2006. Six polymorphic microsatellite genetic markers were used to characterize seedlings and their potential parents in a 7.2-ha stand. These seedlings were shown to result from 12 years of recruitment, with one predominant year of seedling recruitment in 2002 and several years without significant recruitment. Using a spatially explicit mating model based on parentage assignment, short average dispersal distances for seed (δ(s) = 10.9 m) and pollen (43.7 m < δ(p) <57.3 m) were found, but there was also a non-negligible immigration rate from outside the plot (m(s) = 20.5%; 71.6% < m(p) < 77.9%). Hierarchical analyses of seedling genetic structure showed that (i) most of the genetic variation was within plots; (ii) the genetic differentiation among seedling plots was significant (F(ST) = 2.6%) while (iii) there was no effect of year-to-year seed rain variation on genetic structure. In addition, no significant effect of genetic structure on mortality was detected. The consequences of these results for the prediction of population dynamics at ecological timescales are discussed.     

Linking landscape history and dispersal traits in grassland plant communities

Dispersal limitation and long-term persistence are known to delay plant species’ responses to habitat fragmentation, but it is still unclear to what extent landscape history may explain the distribution of dispersal traits in present-day plant communities. We used quantitative data on long-distance seed dispersal potential by wind and grazing cattle (epi- and endozoochory), and on persistence (adult plant longevity and seed bank persistence) to quantify the linkages between dispersal and persistence traits in grassland plant communities and current and past landscape configurations. The long-distance dispersal potential of present-day communities was positively associated with the amounts of grassland in the historical (1835, 1938) landscape, and with a long continuity of grazing management—but was not associated with the properties of the current landscape. The study emphasises the role of history as a determinant of the dispersal potential of present-day grassland plant communities. The importance of long-distance dispersal processes has declined in the increasingly fragmented modern landscape, and long-term persistent species are expected to play a more dominant role in grassland communities in the future. However, even within highly fragmented landscapes, long-distance dispersed species may persist locally—delaying the repayment of the extinction debt.     

Consequences of forest fragmentation for the dynamics of bird populations: conceptual issues and the evidence

This paper reviews the consequences of forest fragmentation for the dynamics of bird populations. Owing to high mobility and large home ranges, birds usually perceive fragmented forests in a finegrained manner, i.e. embrace several forest fragments in functional home ranges. On a regional scale, however, coarse-grained clusters of fine-grained fragments (hierarchical fragmentation may sub-divide bird populations into isolated demes, which enter a domain of metapopulation dynamics. Distinctions are made between pure distance-area or population-level effects and more indirect community-level effects due to changes in landscape composition. Distance-area effects, such as insularization and decreasing fragment size, directly prevent dispersal and reduce population size. Landscape effects, such as reduced fragment-matrix and interior-edge ratios, increase the pressure from surrounding predators, competitors, parasites and disease. In short, forest fragmentation can be viewed as a two-step process. Initially, fine-grained fragmentation triggers distance-area and landscape effects on a local scale, which in turn, results in a range retraction of a population to non-fragmented or less fragmented parts of a region. At a certain point, non-fragmented areas become so widely spaced out that regional distance-area effects come into operation, giving rise to metapopulation dynamics. Although few bird metapopulations have yet been documented, metapopulation dynamics probably is a common characteristic of bird populations confined to 'hierarchical' fragmented forests.     

Frugivoría por Aves en un Paisaje Fragmentado: Consecuencias en la Dispersión de Semillas1

Few data exist on seed dispersal by frugivorous birds in fragmented landscapes, originating from tropical dry forests, in contrast to more abundant data from tropical rain forests. In this study, we assessed the effect of frugivorous birds in a fragmented landscape of Veracruz, Mexico, now occupied by remnant fragments of tropical semi‐deciduous forest and dry deciduous forest, grassland, and shrubby patches on sand dunes. We determined four characteristics related to seed dispersal by birds: the interacting species of plants and birds, the characteristics of these species, spatio‐temporal variation in the dispersal system, and the outcome of the process. During one year, we recorded 54 frugivorous bird species and 33 ornithochorous plant species, which engaged in 176 different bird‐plant species interactions. Similarity (Sorensen index) of frugivorous bird communities using different vegetation types was high (>70%), suggesting that many bird species used all of the vegetation types. In contrast, the similarity of ornithochorous plant communities among vegetation types commonly was low (<37%), suggesting that most plant species were restricted to particular sites in this landscape. At the landscape level, as well as for tropical deciduous forest, we detected a significant positive relationship (Spearman's correlation of rank coefficient >0.65, P <0.05) among richness per month of frugivorous birds and plant species bearing fleshy fruits. Seeds of many plant species previously detected in studies of seed rain at the site were eaten by birds during this study. Most seeds of zoochorous species, which are deposited in the dry and decidous tropical forests patches, are produced within these vegetation types (i.e., they are autochthonous species), whereas bird‐dispersed seeds arriving in grassland and shrubby patches are produced outside (i.e., allochthonous) and are mostly woody species. Birds are important seed dispersers among vegetation types in this landscape but they have different effects in each one. The four characteristics studied, as well as the landscape approach of this research, allowed us to detect spatial and temporal patterns that otherwise would have remained undetected.     

Scale-dependent diversity effects of seed dispersal by a wild herbivore in fragmented grasslands

Dispersal limitation between habitat fragments is a known driver of landscape-scale biodiversity loss. In Europe, agricultural intensification during the twentieth century resulted in losses of both grassland habitat and traditional grassland seed dispersal vectors such as livestock. During the same period, populations of large wild herbivores have increased in the landscape. Usually studied in woodland ecosystems, these animals are found to disperse seeds from grasslands and other open habitats. We studied endozoochorous seed dispersal by roe deer (Capreolus capreolus) in fragmented grasslands and grassland remnants, comparing dispersed subcommunities of plant species to those in the established vegetation and the seed bank. A total of 652 seedlings of 67 species emerged from 219 samples of roe deer dung. This included many grassland species, and several local grassland specialists. Dispersal had potentially different effects on diversity at different spatial scales. Almost all sites received seeds of species not observed in the vegetation or seed bank at that site, suggesting that local diversity might not be dispersal limited. This pattern was less evident at the landscape scale, where fewer new species were introduced. Nonetheless, long-distance dispersal by large wild herbivores might still provide connectivity between fragmented habitats within a landscape in the areas in which they are active. Finally, as only a subset of the available species were found to disperse in space as well as time, the danger of future biodiversity loss might still exist in many isolated grassland habitats.