The use of branch piles to assist in the restoration of degraded semiarid steppes

Desertification is a major environmental problem in arid and semiarid regions. Tree plantation has been commonly employed to foster the recovery of degraded areas. However, this technique is costly, and their outcomes are often uncertain. Therefore, we evaluated an alternative method for the restoration of degraded semiarid steppes that involved the construction of branch piles to attract frugivores as potential seed‐dispersing birds, promoting seed rain, and fostering the formation of woody patches. We measured the success of branch piles in terms of the number of bird visits and seed input compared to naturally occurring shrub patches. Generally, frugivorous birds visited branch piles less frequently than shrub patches. Yet, branch piles accumulated seeds of patch‐forming shrub species. Seed rain was higher under patches of the dominant shrub Rhamnus lycioides than under branch piles. In contrast, woody patches and branch piles did not differ in seed input of the less abundant Pistacia lentiscus shrub. Our study demonstrates that branch piles are used by frugivorous birds and accumulate seeds of patch‐forming shrubs. Branch piles may be a suitable method to promote the expansion of bird‐dispersed plant species and restore semiarid wooded steppes. However, their efficiency largely depends on pile persistence and economic cost.     

Seed Dispersal by Avian Frugivores: Non‐random Heterogeneity at Fine Scales

Seed dispersal studies have primarily examined dispersal as a function of distance from the parent tree and/or heterogeneity in dispersal due to animal use of nesting, roosting and sleeping sites. However, non‐random heterogeneity in seed dispersal is also likely to result from the post‐foraging behavior and movement of frugivores which prefer certain trees. To characterize variation in seed rain at fine scales, we studied the dispersal curve of Prunus ceylanica, a primarily bird‐dispersed species. We compared seed rain at conspecifics, heterospecific fruiting trees with similar frugivore assemblages, emergent trees, and the landscape surrounding these trees. Seed rain of P. ceylanica was found to peak globally under the canopy of conspecifics but to peak locally under the canopy and immediate neighborhood of heterospecific fruiting trees. Our results demonstrate that seed rain is highly clumped even at fine spatial scales. A large proportion of seeds are dispersed in specific, localized regions. This variation can have important implications for plant population dynamics and might significantly alter the impact of post‐dispersal processes. Seed dispersal models may need to incorporate this heterogeneity to explain manifestations of spatially explicit dynamics like mixed species ‘orchards’.     

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.     

Unravelling seed dispersal through fragmented landscapes: Frugivore species operate unevenly as mobile links

Seed dispersal constitutes a pivotal process in an increasingly fragmented world, promoting population connectivity, colonization and range shifts in plants. Unveiling how multiple frugivore species disperse seeds through fragmented landscapes, operating as mobile links, has remained elusive owing to methodological constraints for monitoring seed dispersal events. We combine for the first time DNA barcoding and DNA microsatellites to identify, respectively, the frugivore species and the source trees of animal‐dispersed seeds in forest and matrix of a fragmented landscape. We found a high functional complementarity among frugivores in terms of seed deposition at different habitats (forest vs. matrix), perches (isolated trees vs. electricity pylons) and matrix sectors (close vs. far from the forest edge), cross‐habitat seed fluxes, dispersal distances and canopy‐cover dependency. Seed rain at the landscape‐scale, from forest to distant matrix sectors, was characterized by turnovers in the contribution of frugivores and source‐tree habitats: open‐habitat frugivores replaced forest‐dependent frugivores, whereas matrix trees replaced forest trees. As a result of such turnovers, the magnitude of seed rain was evenly distributed between habitats and landscape sectors. We thus uncover key mechanisms behind “biodiversity–ecosystem function” relationships, in this case, the relationship between frugivore diversity and landscape‐scale seed dispersal. Our results reveal the importance of open‐habitat frugivores, isolated fruiting trees and anthropogenic perching sites (infrastructures) in generating seed dispersal events far from the remnant forest, highlighting their potential to drive regeneration dynamics through the matrix. This study helps to broaden the “mobile‐link” concept in seed dispersal studies by providing a comprehensive and integrative view of the way in which multiple frugivore species disseminate seeds through real‐world landscapes.     

Can remnant frugivore species effectively disperse tree seeds in secondary tropical rain forests?

Seed dispersal by frugivores in tropical rain forests is important for maintaining viable tree populations. Over the years, vertebrate assemblages in tropical forests have been altered by anthropogenic disturbances, leading to concerns about the ability of remnant vertebrates to substitute for the lost or declining vertebrate populations. We compared vertebrate composition and frugivore visitation rates as an indirect measure of rate of seed dispersal in three tropical rain forests in Uganda, namely Mabira, Budongo and Kibale Forests. Mabira is highly disturbed, Kibale is little and Budongo is intermediate. The aim was to determine whether vertebrate assemblages in differentially disturbed forests had comparable abilities to disperse seeds and whether tree species were equally vulnerable to loss of seed dispersers. Assemblages of forest generalist species were similar in all forests, but specialists were less abundant in the heavily disturbed forest. Remnant frugivores in the heavily disturbed forest were mainly small-bodied species that spat seeds beneath fruiting trees compared to large-bodied species observed in the less disturbed forests that ingested and carried away the seeds. We postulate that the quantity of seeds dispersed in heavily disturbed forests is much reduced due to low visitation rates of frugivores and the absence of large frugivores that consume large quantities of fruit. The quality of seed dispersal is affected as well by the distance over which seeds are moved. Assessment of vulnerability of trees shows no evidence for disperser substitution for trees producing large fruits. Fruit trees with low nutritional contents and digestibility were least visited in frugivore-impoverished forests. The loss of large specialist frugivores is likely to affect recruitment of many trees, especially of species that cannot establish beneath adult conspecifics.     

Complementary seed dispersal by three avian frugivores in a fragmented Afromontane forest

Questions: To what extent does species‐specific variation in gut passage time (GPT), habitat use and mobility of three key avian frugivores synergistically affect the distribution of Xymalos monospora seeds within and among isolated forest fragments? Location: Three fragments of a severely fragmented cloud forest, Taita Hills, southeast Kenya. Methods: We experimentally determined GPTs of X. monospora seeds and recorded movements and habitat use by Turdus helleri, Andropadus milanjensis and Tauraco hartlaubi through radiotelemetry, and combined these data to generate species‐specific seed dispersal patterns. Results: Differences in mobility and habitat use among the three frugivores caused significant complementarity in seed dispersal, despite the fact that gut transit times were highly comparable. While the most sedentary and forest‐dependent species mainly led to short‐distance dispersal away from parent trees, two more mobile species dispersed seeds further away from the source trees, both within indigenous forest patches and towards exotic plantations and isolated fruiting trees in the landscape matrix. A. milanjensis inhabiting a very small forest fragment spent significantly more time in the landscape matrix than conspecifics residing in the two larger fragments. Conclusions: By varying distances over which seeds are carried away from parent trees and the habitat types in which they are ultimately deposited, avian frugivores affect the spatial distribution of seeds and early plant recruits in a distinct and complementary manner. Because landscape properties are expected to lead to different constraints on avian mobility for habitat specialists and for generalists, ecosystem processes such as avian seed dispersal are shaped by complex interactions between disperser behaviour and the environment.     

The Role of Arboreal Seed Dispersal Groups on the Seed Rain of a Lowland Tropical Forest1

Most tropical plants produce fleshy fruits that are dispersed primarily by vertebrate frugivores. Behavioral disparities among vertebrate seed dispersers could influence patterns of seed distribution and thus forest structure. This study investigated the relative importance of arboreal seed dispersers and seed predators on the initial stage of forest organization–seed deposition. We asked the following questions: (1) To what degree do arboreal seed dispersers influence the species richness and abundance of the seed rain? and (2) Based on the plant species and strata of the forest for which they provide dispersal services, do arboreal seed dispersers represent similar or distinct functional groups? To answer these questions, seed rain was sampled for 12 months in the Dja Reserve, Cameroon. Seed traps representing five percent of the crown area were erected below the canopies of 90 trees belonging to nine focal tree species: 3 dispersed by monkeys, 3 dispersed by large frugivorous birds, and 3 wind‐dispersed species. Seeds disseminated by arboreal seed dispersers accounted for ca 12 percent of the seeds and 68 percent of the seed species identified in seed traps. Monkeys dispersed more than twice the number of seed species than large frugivorous birds, but birds dispersed more individual seeds. We identified two distinct functional dispersal groups, one composed of large frugivorous birds and one composed of monkeys, drop dispersers, and seed predators. These groups dispersed plants found in different canopy strata and exhibited low overlap in the seed species they disseminated. We conclude it is unlikely that seed dispersal services provided by monkeys could be compensated for by frugivorous birds in the event of their extirpation from Afrotropical forests.     

Seed dispersal effectiveness by understory birds on Dendropanax arboreus in a fragmented landscape

This study analyzes dispersal effectiveness of understory birds that feed on fruits of the tropical tree Dendropanax arboreus in a fragmented forest at Los Tuxtlas, east-central Mexico. The quantity and quality components of effectiveness were estimated in three different sites: continuous forest, 40 ha forest fragment, and 3 ha forest fragment. The quantity component was estimated through relative abundance, frequency of visits to fruits, and number of seeds in fecal samples. The quality component was estimated by analyzing germination of seeds defecated by birds and seed deposition patterns by birds. Seed deposition patterns were estimated by comparing the number of seeds found in fecal samples and the number of reproductive adults of D. arboreus in each site. Results showed that dispersal effectiveness of birds varied among sites. Turdus grayi was the most effective disperser in continuous forest, while Hylocichla mustelina was the most effective one in 40 and 3 ha forest fragments. These birds are contributing to the gene flow between fragments and continuous forest because they are able to use forest or riparian remnants, living fences, and isolated trees.     

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

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

Impact of avian frugivores on dispersal and recruitment of the invasive <Emphasis Type="Italic">Prunus serotina</Emphasis> in an agricultural landscape

Although seed dispersal is considered to be a key process determining the spatial structure and spread of non-native plant populations, few studies have explicitly addressed the link between dispersal vector behaviour, seed distribution and seedling recruitment to gain insight into the process of exotic species invasion within a fragmented landscape context. The present study analyses the relationship between avian frugivory and spatial patterns of seed deposition and seedling recruitment for an expanding population of the invasive Prunus serotina in a hedgerow network landscape in Flanders, Belgium. We quantified fruit production, observed frugivores, and determined the spatial distribution of bird droppings and P. serotina seedlings. A relatively diverse assemblage of frugivores visited P. serotina seed trees, with Columba palumbus and Turdus merula being by far the most important dispersers. Landscape structure strongly affected dispersal vector behaviour and the spatial distribution of perching birds, droppings and seedlings. Frugivorous birds non-randomly dispersed seeds to perching sites and an association between perching birds, seed deposition and seedling recruitment was found. Results indicate that landscape structure contributes to non-random seed deposition of P. serotina by common local frugivores. Cutting the larger seed trees is proposed as the most feasible measure to slow down the invasion rate.     

Bird Assemblage and Visitation Pattern at Fruiting Elmerrillia tsiampaca (Magnoliaceae) Trees in Papua New Guinea

Most tropical trees produce fleshy fruits that attract frugivores that disperse their seeds. Early demography and distribution for these tree species depend on the effects of frugivores and their behavior. Anthropogenic changes that affect frugivore communities could ultimately result in changes in tree distribution and population demography. We studied the frugivore assemblage at 38 fruiting Elmerrillia tsiampaca, a rain forest canopy tree species in Papua New Guinea. Elmerrillia tsiampaca is an important resource for frugivorous birds at our study site because it produces abundant lipid-rich fruits at a time of low fruit availability. We classified avian frugivores into functional disperser groups and quantified visitation rates and behavior at trees during 56 canopy and 35 ground observation periods. We tested predictions derived from other studies of plant–frugivore interactions with this little-studied frugivore assemblage in an undisturbed rain forest. Elmerrillia tsiampaca fruits were consumed by 26 bird species, but most seeds were removed by eight species. The most important visitors (Columbidae, Paradisaeidae and Rhyticeros plicatus) were of a larger size than predicted based on diaspore size. Columbidae efficiently exploited the structurally protected fruit, which was inconsistent with other studies in New Guinea where structurally protected fruits were predominantly consumed by Paradisaeidae. Birds vulnerable to predation foraged for short time periods, consistent with the hypothesis that predator avoidance enhances seed dispersal. We identified seven functional disperser groups, indicating there is little redundancy in disperser groups among the regular and frequent visitors to this tropical rain forest tree species.     

Landscape‐level tree cover predicts species richness of large‐bodied frugivorous birds in forest fragments

Large‐bodied frugivorous birds play an important role in dispersing large‐sized seeds in Neotropical rain forests, thereby maintaining tree species richness and diversity. Conversion of contiguous forest land to forest fragments is thought to be driving population declines in large‐bodied frugivores, but the mechanistic drivers of this decline remain poorly understood. To assess the importance of fragment‐level versus local landscape attributes in influencing the species richness of large‐bodied (>100 g) frugivorous birds, we surveyed 15 focal species in 22 forest fragments (2.7 to 33.6 ha, avg. = 16.0 ha) in northwest Ecuador in 2014. Fragment habitat variables included density of large trees, canopy openness and height, and fragment size; landscape variables included elevation and the proportion of tree cover within a 1 km radius of each fragment. At both the individual species level, and across the community of 12 species of avian frugivore we detected, there was higher richness and probability of presence in fragments with more tree cover on surrounding land. This tendency was particularly pronounced among some endangered species. These findings corroborate the idea that partially forested land surrounding fragments may effectively increase the suitable habitat for forest‐dwelling frugivorous birds in fragmented landscapes. These results can help guide conservation priorities within fragmented landscapes, with particular reference to retaining trees and reforesting to attain high levels of tree cover in areas between forest patches.     

Composition and clumping of seeds deposited by frugivorous birds varies between forest microsites

More frequent deposition of seeds by frugivores beneath plants in fruit could impose spatial limits to the distribution of plants dispersed by animals and contribute to species coexistence. Also, differences in diet and use of microhabitats by seed dispersers could promote spatial variation in the combination of seed species deposited. We investigated patterns of seed deposition of Miconia fosteri and Miconia serrulata (Melastomataceae) by birds in the Amazon. The goal was to determine how distribution and abundance of fruiting plants, both con‐ and hetero‐specifics, affect the spatial variability in clumping and composition of multi‐specific seed deposition. We established two 9‐ha plots in undisturbed terra‐firme understory in the Ecuadorian Amazon. Seed rain was sampled with seed traps located in four microsites: below plants of the focal species, below Anthurium eminens (Araceae), and in randomly selected microsites. We examined seed deposition in these microsites in relation to habitat, fruiting neighborhood (fruit abundance, and distance to and density of plants of the target species), and crop size of M. fosteri or M. serrulata to determine if microsites differed in abundance and species composition of seeds. Seed traps below plants in fruit received more seeds than did randomly located traps. Seeds of the target species were, moreover, more commonly deposited below con‐ rather than hetero‐specific plants. Seed aggregation below fruiting plants increased in forest neighborhoods where the abundance of fruits and the combination of fruiting plant species contributed to the arrival of seeds. Microsites differed notably in the combination of seeds deposited by frugivores, and differences were less pronounced among microsites that received seeds of M. fosteri and M. serrulata than among all microsites where at least some seed species were deposited by birds. We demonstrate that two closely related, ecologically similar species possess many similarities in their patterns of seed deposition and in the factors that affect those patterns. The combination of seed species deposited below foci of dispersal depended on the fruiting plant species, and the spatial patterns of seed deposition varied with the location of the microsite and the combination of co‐dispersed species in the neighborhood. Similar species that share the same dispersers were confronted with different combinations of seeds depending on the microsite where they arrived, which could promote forest heterogeneity in the combination of plant species.     

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

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

Fragmentation gradients differentially affect the species range distributions of four taxonomic groups in semi‐deciduous Atlantic forest

Human activities often cause habitat fragmentation and how forest fragments affect species range distributions has implications for ecology and conservation. However, few studies have considered communities within the same landscape. Here, we analyzed metacommunity structure to determine the range distributions for species in four taxonomic groups (amphibians, birds, social wasps, and trees) in a patchy landscape of semi‐deciduous Atlantic forest in southwestern Brazil. Although trees are a key component of the environment for animals in forested patches, the ranges of bird, wasp, and amphibian species did not change in concert with the species ranges of trees. The species ranges of amphibians and social wasps were unaffected by fragmentation gradients and exhibited independent distribution patterns (i.e., random structure). In contrast, birds and trees exhibited range turnover along different fragmentation gradients, indicating that species show idiosyncratic responses to abiotic factors (i.e., Gleasonian structure). For birds, some less‐resilient species occurred only in fragments with a large area of native vegetation at a radius of 5 km from the center of the sampled forest fragments, whereas other more stress‐tolerant species occurred only in sites with small areas of native vegetation. For trees, some later succession species (e.g., animal‐dispersed seeds) occurred only in fragments with high connectivity, whereas earlier‐recruiting species (e.g., wind‐dispersed seeds) occurred in fragments with low connectivity. Thus, determining the effects of human‐modified landscapes on species range distributions, even within the same landscape, might not be a trivial task.     

Anthropogenic landscape changes and avian diversity at Los Tuxtlas, Mexico

Faced with rapid and extensive conversion of tropical rain forests to a landscape consisting of pasture lands, and with the need to preserve the avian diversity of tropical regions, it is imperative to determine how different species have responded to anthropogenic alterations of their natural habitats. We sampled birds in undisturbed and disturbed forest islands in regenerating forests and in four replicates of each of the following man-made habitats: arboreal agricultural habitats (cacao, coffee, mixed, citrus and allspice), non-arboreal agricultural habitats (corn, jalapen~o chili pepper and bananas), live fences and pastures, at Los Tuxtlas, Veracruz, Mexico. We censused 22145 birds representing 226 species. We detected 79% of the species in forest habitats, 80% in agricultural habitats, 43% in live fences and only 5% in pastures. Isolating distance and continued disturbance by humans of forest fragments were important variables influencing species' richness. Arboreal agricultural habitats and live fences were richer in species and in birds than non-arboreal man-made habitats. Economic surveys showed that some of the crops investigated yield higher returns than cattle ranching based on pastures. We discuss the conservation value for birds of agricultural islands and of live fences as landscape elements that help reduce physical and biotic isolation among remaining configurations of forest fragments in Los Tuxtlas.     

Seed rain of fleshy and dry propagules in different habitats in the temperate rainforests of Chiloé Island,Chile

In temperate rainforests on Chiloé Island in southern Chile (42°S), most canopy trees bear fleshy, avian‐dispersed propagules, whereas emergent tree species have dry, wind‐borne propagules. In the present study, the following hypothesis was tested: regardless of species, fleshy propagules are deposited in greater numbers in canopy gaps and in forest margins and hence have a more heterogeneous seed shadow than wind‐dispersed propagules. To test this hypothesis, the seed rains of these two types of propagules were compared in the following forest habitats: (i) tree‐fall gaps (edges and centre); (ii) forest margins with adjacent pastures; and (iii) under closed canopy (forest interior). Seed collectors (30‐cm diameter) were placed in two (15 and 100 ha) remnant forest patches (n = 60–100 seed collectors per patch) distributed in the four habitats. Seeds were retrieved monthly from each collector during two reproductive seasons (1996, 1997). In both years, the seed rain was numerically dominated by two species with dry propagules (Laureliopsis philippiana and Nothofagus nitida) and three species with fleshy fruits (Drimys winteri, Amomyrtus luma, and Amomyrtus meli). The seed shadows of the two species with dry, wind‐dispersed seeds differed markedly. Seeds of L. philippiana were deposited predominantly in canopy openings, whereas N. nitida seeds fell almost entirely in the forest interior. The fleshy‐fruited species, Drimys and Amomyrtus spp., had similar seed deposition patterns in the various habitats studied, but the between‐year differences in seed rain were greater in Drimys winteri than in Amomyrtus spp. Although no more than 10% of fleshy‐fruited propagules reached the margins of the patch, approximately 7% of these were carried there by birds. Every year, canopy gaps (pooling data from edges and centres) concentrated approximately 60% of the total seed rain of both propagule types in both forest patches. Forest margins received less than 20% of the total seed rain, which was largely dominated by fleshy‐fruited species. Seed shadows were a species‐specific attribute rather than a trait associated with propagule type and dispersal mode.     

Birds,Cattle, and Bracken Ferns: Bird Community Responses to a Neotropical Landscape Shaped by Cattle Grazing Activities

Large areas of tropical moist forests have been converted to cattle pastures, generating complex landscapes where different habitats are represented by small patches with an uneven spatial distribution. Here, we describe how bird communities respond to the different elements present in a livestock landscape that was originally dominated by tropical moist forest. We surveyed six habitats: open pastures, pastures with shrubs, early‐ and middle‐secondary forests, mature forest, and pastures invaded by bracken ferns (Pteridium aquilinum). Bird diversity was high in secondary and mature forests, and low in fern‐invaded sites and open pastures. Fern‐dominated sites had the lowest bird species richness, and trophic guild diversity of all habitats. Habitat structure affected both bird species richness and densities in similar ways. Tree species richness was the habitat attribute that had a bigger positive effect on bird species richness. Bird community structure varied among sampled habitats, separating habitats in two major groups (forests and pastures). Our data indicate that bracken fern‐invaded pastures were the worst habitat condition for avian communities. To increase bird diversity, we recommend to eliminate or manage bracken fern and to increase shrub and tree cover in open pastures to provide food resources and shelter for birds. Finally, we encourage the maintenance of secondary and mature forest remnants as a strategy to conserve resident birds within a landscape dominated by livestock activities.     

Floristic composition and structure of vegetation under isolated trees in neotropical pastures

Abstract. Large isolated trees are a common feature of the agricultural landscape in humid tropical regions originally covered by rain forest. These isolated trees are primarily used as a source of shade for cattle and people. 13 pastures (totalling ca. 80 ha) currently used as cattle pasture were studied. In them, we registered 265 isolated trees belonging to 57 species. 50 trees of the most frequent species (Ficus spp. n = 30 and Nectandra ambigens n = 20) were selected to examine the influence of isolated trees on floristic composition and vegetation structure in the pastures. At each tree, three 4–m² quadrats were sampled: under the canopy, directly under the canopy perimeter, and beyond the canopy in the open pasture. Under-canopy vegetation was structurally and floristically different from the other two sampling sites. Mean species richness per quadrat was significantly higher under the canopy (17.8 ± 4.3 SD) than at the canopy perimeter (11.2 ± 3.4) and in the open pasture (10.6 ± 3.6) sites. Stem density was higher at under-canopy sites, where greater proportions of endozoochorous and rain-forest species were found. Isolated trees function as nursery plants for rain-forest species by facilitating the establishment of zoochorous species whose seeds are deposited under the tree canopies by frugivorous birds or bats. Our results imply that isolated trees may play a major role in seed dispersal and establishment of native species, which is of consequence for the preservation of rain-forest species in these fragmented landscapes.     

Frugivory,Post‐feeding Flights of Frugivorous Birds and the Movement of Seeds in a Brazilian Fragmented Landscape

Habitat fragmentation can break down the movement processes of frugivorous animals, thus influencing the relationship between plants and their seed dispersers by altering the number and identity of seed dispersers, and their relative contribution to seed dispersal. We studied the assemblages of frugivorous birds, their composition, species richness, and visitation rates to fruiting plants growing in the different landscape elements (forest fragments, live fences, and trees isolated in pastures) embedded in a Brazilian fragmented, agricultural landscape. By following the post‐feeding movements of frugivorous birds, we inferred the direction of seed movement from and to each of these landscape elements. Fruiting trees growing at different landscape elements were visited by frugivorous birds at similar rates. Isolated trees attracted a greater and distinct bird assemblage than trees in forest fragments or live fences. Judging by the post‐feeding flights of birds, the seeds of isolated trees were the most likely to reach all the landscape elements considered, but the contribution of isolated trees to the seeds falling in forested habitats or pastures depended on their degree of isolation. A few bird species were able to move widely, visiting fruiting plants in all landscape elements, and promoting long‐distance dispersal for plants. These few birds are of special interest because they are mobile links that connect habitats in fragmented landscapes with their seed dispersal services. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .