Fragmented Tropical Landscapes Research Articles

Demography of the understory herb Heliconia acuminata (Heliconiaceae) in an experimentally fragmented tropical landscape.

Habitat fragmentation remains a major focus of research by ecologists decades after being put forward as a threat to the integrity of ecosystems. While studies have documented myriad biotic changes in fragmented landscapes, including the local extinction of species from fragments, the demographic mechanisms underlying these extinctions are rarely known. However, many of them-especially in lowland tropical forests-are thought to be driven by one of two mechanisms: (1) reduced recruitment in fragments resulting from changes in the diversity or abundance of pollinators and seed dispersers or (2) increased rates of individual mortality in fragments due to dramatically altered abiotic conditions, especially near fragment edges. Unfortunately, there have been few tests of these potential mechanisms due to the paucity of long-term and comprehensive demographic data collected in both forest fragments and continuous forest sites. Here we report 11 years (1998-2009) of demographic data from populations of the Amazonian understory herb Heliconia acuminata (LC Rich.) found at Brazil's Biological Dynamics of Forest Fragments Project (BDFFP). The data set comprises >66,000 plant × year records of 8586 plants, including 3464 seedlings established after the first census. Seven populations were in experimentally isolated fragments (one in each of four 1-ha fragments and one in each of three 10-ha fragments), with the remaining six populations in continuous forest. Each population was in a 50 × 100 m permanent plot, with the distance between plots ranging from 500 m to 60 km. The plants in each plot were censused annually, at which time we recorded, identified, marked, and measured new seedlings, identified any previously marked plants that died, and recorded the size of surviving individuals. Each plot was also surveyed four to five times during the flowering season to identify reproductive plants and record the number of inflorescences each produced. These data have been used to investigate topics ranging from the way fragmentation-related reductions in germination influence population dynamics to statistical methods for analyzing reproductive rates. This breadth of prior use reflects the value of these data to future researchers. In addition to analyses of plant responses to habitat fragmentation, these data can be used to address fundamental questions in plant demography and the evolutionary ecology of tropical plants and to develop and test demographic models and tools. Though we welcome opportunities to collaborate with interested users, there are no restrictions on the use of this data set. However, we do request that those using the data for teaching or research purposes inform us of how they are doing so and cite this paper and the data archive when appropriate. Any publication using the data must also include a BDFFP Technical Series Number in the Acknowledgments. Authors can request this series number upon the acceptance of their article by contacting the BDFFP's Scientific Coordinator or E. M. Bruna.

A matter of scale: Local biotic differentiation and potential regional homogenization of understory plant communities in a highly fragmented tropical landscape

Plant communities in highly fragmented tropical landscapes can undergo biotic homogenization and differentiation after land-use changes, such as forest fragmentation. Here we evaluated the beta diversity of understory plant communities in fragmented forest remnants and assessed species geographic distribution to infer potential local and regional scale dependency of homogenization and differentiation pathways in the Atlantic Forest in southern Brazil. More specifically we assessed: (i) community composition; (ii) the frequency of locally rare species, generalists, interior and edge specialists; (iii) the relative contribution of beta diversity components; and (iv) the influence of widely, intermediate and narrowly distributed species to the observed patterns. Understory communities were sampled in a nested design with plots allocated to the interior and edge of forest fragments, and geographic distributions were estimated based on occurrence records from herbaria collections. Our results revealed differences in species composition among fragments and habitat types (edge and interior). Most of the sampled species were classified as locally rare. The turnover component of beta diversity explained a higher proportion of variation in species composition among fragments and habitats. Species richness and abundance were higher in the interior of fragments and most of the recorded species in the study had a wide geographic distribution. Our results support a local community differentiation (high beta diversity) among fragments and habitat types and suggest a potential regional homogenization, given the predominance of widely distributed generalist species in a domain historically characterized by high levels of endemism. We recommend urgent protection and restoration actions on the few remaining fragments of the Atlantic Forest given that each remnant can support different plant assemblages that have been increasingly threatened. Future studies should explicitly consider multiple spatial and temporal scales across fragmented tropical landscapes to better understand links with biotic homogenization and differentiation of ecological communities.

Detecting the long-term spatiotemporal crop phenology changes in a highly fragmented agricultural landscape

Trends in crop phenometrics reveal the influence of climate variability and change on crop growth and development. However, the trends are less clear in fragmented tropical smallholder landscapes, because there is high spatial and temporal variability in crop phenology. Frequent historical and high spatial resolution (≤30 m) Earth observations are needed to track changes in crop phenology in fragmented landscapes but are often unavailable. The spatial–temporal gap can be closed by integrating infrequent high spatial resolution Earth observations with low spatial/high temporal resolution observations through data fusion. We fused 30 m resolution Landsat and 250 m resolution MODIS imagery to investigate trends in crop phenology from 2000 to 2020 in a fragmented agricultural landscape of Ethiopia. We used the Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model (ESTARFM) that had recently been modified for application in fragmented agricultural landscapes. We used the non-parametric Mann–Kendall test for crop phenology trend analysis. Crop phenology based on Landsat–MODIS fusion was compared to MODIS-based crop phenology without fusion. We found data fusion yielded a smaller magnitude of changes in the start of season (SOS: -0.2-day-y−1) and end of season (EOS: -0.50-day-y−1) compared to MODIS SOS (-0.5-day-y−1) and EOS (1.38-day-y−1) due to MODIS-related mixing with the surrounding natural vegetation in the fragmented agricultural landscape. EOS showed a faster rate of change compared to SOS over the 21-years. The Landsat and MODIS fusion captured spatial variation in the timing and magnitude of change specific to crops and their growing environment, which has implications for adaptation strategies. Our results highlight the importance of long-term data fusion to improve the spatial dimension of crop phenology time series analysis. Integrating time series land cover maps into the data fusion processing chain could further improve long-term data fusion for crop phenology trend analysis.

Potential aboveground biomass increase in Brazilian Atlantic Forest fragments with climate change.

Fragmented tropical forest landscapes preserve much of the remaining biodiversity and carbon stocks. Climate change is expected to intensify droughts and increase fire hazard and fire intensities, thereby causing habitat deterioration, and losses of biodiversity and carbon stock losses. Understanding the trajectories that these landscapes may follow under increased climate pressure is imperative for establishing strategies for conservation of biodiversity and ecosystem services. Here, we used a quantitative predictive modelling approach to project the spatial distribution of the aboveground biomass density (AGB) by the end of the 21st century across the Brazilian Atlantic Forest (AF) domain. To develop the models, we used the maximum entropy method with projected climate data to 2100, based on the Intergovernmental Panel on Climate Change Representative Concentration Pathway (RCP) 4.5 from the fifth Assessment Report. Our AGB models had a satisfactory performance (area under the curve > 0.75 and p value < .05). The models projected a significant increase of 8.5% in the total carbon stock. Overall, the projections indicated that 76.9% of the AF domain would have suitable climatic conditions for increasing biomass by 2100 considering the RCP 4.5 scenario, in the absence of deforestation. Of the existing forest fragments, 34.7% are projected to increase their AGB, while 2.6% are projected to have their AGB reduced by 2100. The regions likely to lose most AGB-up to 40% compared to the baseline-are found between latitudes 13° and 20° south. Overall, although climate change effects on AGB vary latitudinally for the 2071-2100 period under the RCP 4.5 scenario, our model indicates that AGB stocks can potentially increase across a large fraction of the AF. The patterns found here are recommended to be taken into consideration during the planning of restoration efforts, as part of climate change mitigation strategies in the AF and elsewhere in Brazil.

Hummingbird diversity in a fragmented tropical landscape in the Chocó biogeographic zone

AbstractForest loss and fragmentation drive widespread declines in biodiversity. However, hummingbirds seem to exhibit relative resilience to disturbance, characterized by increasing abundance alongside declining species richness and evenness. Yet, how widespread this pattern may be, and the mechanisms by which it may occur, remain unclear. To fill in this knowledge gap, we investigated habitat‐ and site‐level patterns of diversity, and community composition of hummingbirds between continuous forest (transects n = 16 in ~3500 ha) and more disturbed surrounding fragments (n = 39, 2.5–48.0 ha) in the Chocó rain forest of northwestern Ecuador. Next, we assessed within‐patch and patch‐matrix characteristics associated with hummingbird diversity and composition. We found higher hummingbird species richness in forest fragments relative to the continuous forest, driven by increased captures of rare species in fragments. Community composition also differed between continuous forest and fragments, with depressed evenness in fragments. Increased canopy openness and density of medium‐sized trees correlated with hummingbird diversity in forest fragments, although this relationship became nonsignificant after applying false discovery rate (p &lt; .01). Higher species richness in fragments and higher evenness in the continuous forest highlight the complex trade‐offs involved in the conservation of this ecologically important group of birds in changing Neotropical landscapes.Abstract in Spanish is available with online material.

Soil, Topography and Forest Structure Shape the Abundance, Richness and Composition of Fern Species in the Fragmented Tropical Landscape of Xishuangbanna, Yunnan, China

Understanding how forest fragment size, topography, forest structure, and soil properties affect plant diversity remains a crucial question in conservation biology, with ferns often being understudied. To address this knowledge gap, we surveyed the abundance, species richness, and composition of ferns in a tropical landscape in south China using 75 sites in 42 forest fragments. We then used a multi-model inference approach to assess whether fern abundance, richness, and composition were better explained by (a) fragment size, (b) topography (slope, aspect), (c) forest structure (tree basal area, light availability), or (d) soil properties (pH, Carbon, Nitrogen, Phosphorous, Calcium, Magnesium, water availability, and proportion of clay, silt, and sand). We also conducted a nestedness analysis to examine whether the composition of the fern communities in smaller fragments (0.4–1 km²) differed or represented a subset of the communities found in larger fragments (e.g., &gt;10 km²). We found that (a) fern abundance was mostly influenced by soil properties, slope, and aspect, (b) fern species richness by soil properties and slope, and (c) fern species composition by forest structure, specifically, tree basal area. We also found that fern species composition was not nested in the landscape, suggesting that smaller forest fragments had different communities from larger fragments. Our results suggest also that soil properties play an important role in maintaining fern abundance and diversity and therefore protecting soil can help conserve ferns in fragmented landscapes.

Forest cover modulates diversity and morphological traits of ants in highly fragmented tropical forest landscapes

Forest cover modulates diversity and morphological traits of ants in highly fragmented tropical forest landscapes

Dung beetles maintain phylogenetic divergence but functional convergence across a highly fragmented tropical landscape

Abstract Understanding how human‐modified landscapes affect the phylogenetic composition and assembly mechanisms of biological communities is critical for effectively managing and restoring tropical ecosystems. We evaluated how forest coverage loss, fragmentation and landscape heterogeneity affect the phylogenetic diversity of dung beetles and their assembly mechanisms in Los Tuxtlas Biosphere Reserve, a protected but highly fragmented tropical landscape. We calculated Faith's phylogenetic diversity, mean pairwise phylogenetic distance and mean nearest taxon distance for 5,388 individuals in 36 species. The standardised effect sizes of these metrics were estimated to control their correlation with species richness. Phylogenetic diversity was also assessed separately for each dung beetle functional group. Finally, we compared the mean functional and phylogenetic pairwise distance and mean nearest taxon distance and measured the phylogenetic signal among dung beetle functional traits to determine the influence of niche conservatism on the phylogenetic structure of species assemblages. Faith's phylogenetic diversity of dung beetles was positively correlated with forest coverage, while their mean phylogenetic and nearest taxon distance values decreased with increasing landscape fragmentation. Necrophagous beetles and forest specialists responded most negatively to forest coverage loss and fragmentation. Alpha and beta diversity values showed phylogenetic overdispersion but functional convergence and weak phylogenetic signals in their functional traits, suggesting low niche conservatism. Landscapes with moderate forest coverage (≥40%) favoured higher phylogenetic beta diversity, whereas phylogenetic and functional beta diversity decreased significantly in landscapes with low forest coverage (&lt;30%). Synthesis and applications. Forest habitats in fragmented landscapes are essential for safeguarding the evolutionary history of dung beetles, reducing biotic homogenisation processes by favouring phylogenetic overdispersion and complementarity between sites. Therefore, to secure the phylogenetic diversity of dung beetles within fragmented tropical reserves, we recommend protecting the existing forests, preventing further fragmentation of continuous forest areas and increasing matrix quality by implementing biodiversity‐friendly production systems. Finally, managers should consider assessing different functional groups in other species, as their response to landscape disturbance may not be phylogenetically similar. The above will allow more effective management practices to protect the species most susceptible to disturbances.

Random placement models explain species richness and dissimilarity of frog assemblages within Atlantic Forest fragments.

Understanding the effects of random versus niche-based processes on biodiversity patterns is a central theme in ecology, and an important tool for predicting effects of habitat loss and fragmentation on biodiversity. We investigated the predictive power of random processes to explain species richness and species dissimilarity of amphibian assemblages in a fragmented tropical landscape of the Atlantic Forest of South America. We analyzed a large database of amphibian abundance and occupancy, sampled in 21 forest fragments ranging in size from 1.9 to 619ha. We compared observed species richness and species dissimilarity with the outcomes of two null (random placement) models: 1- the traditional Coleman's area-based model and 2- an abundance-based model (based on the number of individuals observed in each fragment). We applied these models for all species combined, and separately for forest-dependent and habitat-generalist species. The abundance-based model fitted the observed species richness data better than the area-based model for all species, forest-dependent species, and generalist species. The area-based and the abundance-based models were also able to significantly explain species dissimilarity for all species and for generalists, but not for forest dependent species. The traditional area-based model assigned too many individuals to large fragments, thus failing to accurately explain species richness within patches across the landscape. Although niche-based processes may be important to structuring the regional pool of species in fragmented landscapes, our results suggest that part of the variation in species richness and species dissimilarity can be successfully explained by random placement models, especially for generalist species. Evaluating which factors cause variation in the number of individuals among patches should be a focus in future studies aiming to understand biodiversity patterns in fragmented landscapes.

Nature’s contributions to people from church forests in a fragmented tropical landscape in southern Ethiopia

Despite expanding interest in nature's contributions to people (NCP) studies, understanding of sacred natural sites’ contributions to human society and the restoration of fragmented landscapes remains relatively limited. This study examines the diversity and extent of NCP by church forests in a fragmented tropical landscape in southern Ethiopia. We identify 339 church forests in the Gurage Zone and examine them using a combination of historical (1967) aerial photographs and recent (2017) orthophoto images, supplemented by vegetation sampling and in-depth interviews with key informants from 42 selected church communities. Church forests can be found in all agro-ecological zones and across the entire vegetation types in the Gurage socio-ecological landscape. In the last five decades, the extent of church forests has been remarkably persistent, and 67% of the forests have seen an increase in size even while surrounding state- and community-controlled forestland has been degraded over time. Interview findings suggest the church forests' persistence is in large part due to the church compound being seen as a sacred space and hence respected and protected by the community. This powerful social norm has allowed for multiple uses of the church forest to continue over time through sustained forest management. More than 15 distinct contributions of church forests to local communities were identified including material, nonmaterial, and regulating NCP categories, suggesting church forests deliver a wide range of NCP in addition to their well-established ecological and conservation value. Findings underscore the current contributions of church forests to local people in southern Ethiopia, as well as the potential for church forests to support the restoration of degraded landscapes through integration into regional landscape planning and management policies.

High gene flow through pollen partially compensates spatial limited gene flow by seeds for a Neotropical tree in forest conservation and restoration areas

Gene flow may occur both through pollen movement and seed dispersal, although their relative contribution to overall species gene flow is not understood for most tropical trees, which compromises management recommendations. We investigated the implications of seed dispersal limitation, pollen dispersal capacity, and mating system to the spatial genetic structure of populations of the Neotropical legume tree, Centrolobium tomentosum, in Brazil’s Atlantic Forest. We estimated seed dispersal distribution by counting individuals around adult trees; pollen dispersal distribution and outcrossing rates from adult and offspring genotypes, using seven microsatellite loci. Spatial genetic structure was inferred through the correlation among kinship coefficients and geographical distances between pairs of individuals, using nuclear and chloroplast microsatellite markers. We observed restricted seed dispersal, with most seeds (78%) falling up to 10 m from the adult tree trunk. The best-fitted pollen dispersal distribution was the exponential power distribution, with a heavy tail and average pollen dispersal distance of 3191 m. The mating system was preferably allogamous, with an average of eight pollen donors. There was significant spatial genetic structure in all populations, with stronger structure obtained from chloroplast DNA, which suggests that the restricted gene flow by seed dispersal may be compensated by high outcrossing rates and long-distance pollen flow promoted by the large bees that pollinate the species. Our results emphasize the importance of pollination services in fragmented tropical landscapes, where most tree species are pollinated by animals and a large number of species experience seed dispersal limitation.

Rare Pteridophytes are disproportionately frequent in the tropical forest of Xishuangbanna, Yunnan, China

The richness and cover of tropical fern life-forms — terrestrial and epiphytic — vary due to their ecology and evolutionary history. It is important to understand the responses of both terrestrial and epiphytic species in relation to topography, as elevation and other aspects, to better predict their distribution. This study has investigated the richness and cover of terrestrial and epiphytic fern species in the landscape of Xishuangbanna, Yunnan, China. The ferns were classified as either rare or common based on their occurrence and the cover values from 75 transects. A General Linear Model was created to understand the impact of the elevation and topographic aspects on the rare and common fern species. A total of 130 ferns species were found. Out of the total richness, 74% of species were considered rare and assessed as having either a narrow or a wide distribution but low frequency. The rarity increased up to 90% for the epiphytic species.Both rare and common epiphytic species had higher richness and cover values at higher elevations. While common epiphytes had higher cover values at a high elevation in the northern aspect, the rare epiphyte species were richer at a higher elevation for both aspects. The richness and cover of the terrestrial species was negatively correlated with elevation and there was a significant interaction. Specifically, most of the rare and common terrestrial ferns were in the lowland sites of Xishuangbanna (from 600 m a.s.l.) However, only 20 species out of the total 130 species contributed to a total cover above 50% with the other species having only a minor density. Our results emphasize the high number of rare species with a low occurrence and show there to be a conservation concern in the fragmented tropical landscape of southern Yunnan.

Environmental correlates of richness, community composition, and functional traits of terrestrial birds and mammals in a fragmented tropical landscape

Tropical forest loss and fragmentation and the associated loss in species diversity are increasing in both magnitude and scope. Much attention has been paid to how attributes of forest fragments, such as area and forest structure, impact the diversity and functional composition of vertebrate communities, while more recent work has begun to consider the importance of landscape-level variables, such as surrounding tree cover. Yet, the relative impacts of these factors on species diversity and functional composition remain unclear, particularly among under-studied taxonomic groups. We quantified how species richness, community composition, and functional traits of terrestrial birds and mammals are associated with variation in fragment area, elevation, habitat structure and surrounding tree cover. Our goal was to determine the degree to which these diverse explanatory variables contribute to species diversity. We used motion-activated camera traps to sample terrestrial birds and mammals in 22 forest fragments in northwestern Ecuador. We used a hierarchical multi-species occupancy model accounting for imperfect species detection to estimate species richness and species composition differences among fragments, weighted multiple regression and distance matrix regression to assess covariates of richness and composition, and an RLQ ordination to assess co-variation of environmental conditions and species traits. Terrestrial mammals and birds exhibited similar relationships to key environmental variables, but also showed guild-specific differences. Elevation was significantly associated with differences in species richness and community composition for both groups. Forest cover in the surrounding matrix was associated with higher species richness and changes in community composition in mammals, but not terrestrial birds. Canopy openness showed a positive association with mammalian species richness but no relationship with bird species richness. There was no association between density of large trees and richness for either group. We found no significant associations between environmental variation and functional composition among forest fragments. This work highlights the general importance of elevation and forest cover in shaping patterns of species diversity and composition in forest fragments and suggests heightened sensitivity to matrix conditions in mammals relative to terrestrial birds.

The relative influence of different landscape attributes on dung beetle communities in the Brazilian Atlantic forest

Abstract Land-use change is considered the greatest threat to biodiversity worldwide. As such, identifying the drivers that shape biological communities is crucial for enhancing conservation strategies in human-modified tropical landscapes. We used a hybrid patch-landscape design and a multi model inference approach to assess the relative impacts of forest loss, increased edge density and increased pasture cover on dung beetle functional groups in the Brazilian Atlantic Forest – a biodiversity hotspot. Our findings provide novel empirical evidence showing that edge density can be a major driver for dung beetles when compared to forest and pasture cover at the landscape scale. However, forest and pasture cover also influenced some dung beetle responses, supporting the idea that biological communities are negatively affected by habitat loss and changes in land cover. We found that dung beetle body size, protibia area and metatibia length were all larger in landscapes with increased edge density, reinforcing the need for further studies exploring which mechanisms could favour the presence of larger dung beetles in fragmented tropical landscapes. Taken together, these results suggest the need of conservation and management strategies focused on the protection of the remaining Atlantic Forest fragments, and the promotion of forest recovery and reduction in the pasture cover and edge density at the landscape-level.

Recent records of Tapirella bairdii and Panthera onca in a region highly transformed by human activities in southern Veracruz, México

The tapir (Tapirella bairdii) and the jaguar (Panthera onca) are two of the largest Neotropical mammal species suffering population declines caused by habitat loss and degradation and hunting. Tapirs and jaguars are considered endangered and near threatened, respectively, by the IUCN, and in Mexico, both species are listed as endangered and considered species with priority for conservation. These species are usually associated with large and remote areas of preserved forest. To evaluate local diversity of medium and large sized mammals, we placed five camera traps, three in old forest and two in secondary forest (445 trap days) at Ejido Ramos Millan (municipality of Minatitlan), on the northernmost part of the Uxpanapa Valley, in the Gulf of Mexico coastal plain, state of Veracruz, Mexico. This region has been highly transformed by human activities, where agricultural and livestock activities have caused the loss of most of its natural forests, resulting in a highly fragmented landscape, dominated by livestock fields, crops and secondary forests. Here we document images of three adult individuals of jaguar and two adult individuals of tapir, one of which was a lactating female, and one adult male tapir. The new records were 23 Km north of the most recent reports located in well preserved primary forests in the Uxpanapa/Chimalapas border area. Our results suggest that the highly fragmented tropical landscapes composed of both old-growth and secondary forests remnants, are able to provide sufficient resources to maintain at least temporarily individuals of jaguars and tapirs.

Implications of zero‐deforestation commitments: Forest quality and hunting pressure limit mammal persistence in fragmented tropical landscapes

AbstractZero‐deforestation commitments seek to decouple agricultural production and forest loss to improve prospects for biodiversity. However, the effectiveness of methods designed to meet these commitments is poorly understood. In a highly fragmented tropical landscape dominated by oil palm, we tested the capacity for the High Carbon Stock (HCS) Approach to prioritize forest remnants that sustain mammal diversity. Patches afforded high priority by HCS protocols (100 ha core area) provided important refuges for IUCN‐threatened species and megafauna. However, patch‐scale HCS area recommendations conserved only 35% of the mammal community. At least 3,000 ha would be required to retain intact mammal assemblages, with nearly 10 times this area needed if hunting pressure was high. While current HCS protocols will safeguard patches capable of sustaining biodiversity, highly fragmented tropical landscapes typical of zero‐deforestation pledges will require thinking beyond the patch toward strategically configured forest remnants at the landscape level and enforcing strict controls on hunting.

Isolated trees and small woody patches greatly contribute to connectivity in highly fragmented tropical landscapes

Decreasing landscape connectivity, due to habitat loss and agricultural expansion, is a threat for species movement and other flux-dependent ecological processes. Tree cover within the agricultural matrix provides perching sites, dispersal routes, and extra habitat for animals. Isolated trees and living fences in tropical pastures add structural complexity to actual matrices, but their role in landscape connectivity is undervalued. Our main objective was to assess the potential value of small (≤1ha) woody patches for maintaining landscape connectivity in highly fragmented landscapes using birds as focal species. We used high-resolution images and LIDAR data to classify different tree cover types. We assess the probability of connectivity for different hypothetical dispersal distances between woody patches, using a graph-theoretic approach and simulating scenarios that differed in tree cover composition. We estimated the impacts and contribution of tree cover class removals on landscape connectivity. The connectivity index increased widely among scenarios with increasing tree cover composition. The highest connectivity value was obtained in the scenario that included all arboreal elements currently present in the matrix. Small wooded patches and isolated trees contributed from 26% to 59% to overall connectivity. The presence of small (≤1ha) patches of tree cover greatly enhance landscape connectivity for animals with low vagility and behavioral limitations on crossing gaps. Isolated trees and living fences play a crucial role in increasing habitat reachability within rural landscapes and ensuring and enhancing connectivity for animals that perform daily-movements at short-distances. The spatial distribution of arboreal elements within landscapes could be optimized to increase connectivity and must be considered in conservation planning.

Temporal analysis of butterfly diversity in a succession gradient in a fragmented tropical landscape of Mexico

We analyze changes in the diversity of butterflies under a scheme of secondary succession in a fragmented landscape of the Huasteca of Hidalgo, Mexico over two seasons (rainy and dry) and four successional stages (cattle pasture, early secondary succession, intermediate secondary succession and advanced secondary succession). We recorded a total of 3,559 individuals of 124 species of adult butterflies. A higher number of species (104) and higher abundance (2588 individuals) were found during the rainy season than the dry season. Memphis pithyusa was the most abundant species in all successional stages. We evaluated the effect of secondary succession and seasonality on the alpha diversity of butterflies through three orders of Hill numbers as measures of diversity (0D = species richness, 1D = measure of abundance in the community, and 2D = common species). We found that in q0D, cattle pasture and early SS maintained the greatest diversity compared to the last two stages; in q1D, early SS maintained the lowest diversity, which was significantly different from the rest of the stages; and in q2D, we found the opposite pattern to q0D; the two most advanced stages were the ones that maintained the greatest diversity. Beta diversity analysis was conducted with abundance and species presence/absence data. Species composition was different between the rainy and dry seasons (both as evaluated by abundance and by species presence/absence). Species composition measured by abundance was different between the cattle pasture successional stage in the dry season and all other successional stages. Considering only presence/absence, species composition was different between the cattle pasture successional stage and all other successional stages in both seasons. Although our analysis lacks a primary forest for reference, we highlight here the importance of these secondary forests from Huasteca Region of Hidalgo State of Mexico as reservoirs of butterfly diversity. Considering that these forests generally maintain a close relationship with productive activities for human well-being, this would imply that they should be included in public policies for their maintenance and conservation.

Traits reveal how habitat‐quality gradients structure small mammal communities in a fragmented tropical landscape

AbstractUnderstanding the relationships among community structure, vegetation structure and availability of food resources are a key to unravelling the ecological processes that structure biological communities. In this study, we tested (i) whether the composition of small mammal communities changed across gradients in habitat quality in tropical forest fragments, and (ii) whether any observed change could be explained by the functional traits of species. We sampled 24 trapping grids in fragments of semi‐deciduous forest, in each of two 6‐month periods. We considered each trapping grid as a sampling unit, for which we collected three datasets: an environmental matrix (vegetation structure and food resource availability), the abundance of small mammal species (community structure) and a matrix of functional traits (ecological and morphological traits which express tolerance to habitat disturbance and trophic guild). We used an RLQ approach to evaluate the association between traits and environmental gradients. Forest‐specialist and scansorial–arboreal species were associated with more complex habitat that had greater litter and canopy cover and more fallen logs. In relation to trophic guilds, granivore (fruit seeds), insectivorous and omnivorous species were also associated with higher complexity habitat, while frugivores were associated with shrub cover and availability of fruits. We conclude that functional traits (habitat use, use of vertical strata and diet) provide valuable insights into the distribution of small mammals along gradients of habitat quality in tropical forest fragments. We highlight that communities studies in fragmented landscapes should investigate the different components of biodiversity not only in landscape‐scale but also in habitat scale.Abstract in Portuguese is available with online material.

Landscape structure mediates zoochorous-dispersed seed rain under isolated pasture trees across distinct tropical regions

Isolated pasture trees play an important role in forest recovery within fragmented tropical landscapes by attracting seed dispersers and facilitating seedling growth. However, studies with conflicting results have led to confusion about what drives variation in zoochorous-dispersed seed rain patterns under isolated tree canopies. To assess the role of landscape and biological factors impacting zoochorous-dispersed seed rain under isolated pasture trees across three tropical regions of the world. We measured seed dispersal under 144 isolated pasture trees found in 12 fragmented tropical and sub-tropical landscapes in Australia, Colombia and Nigeria. Using linear mixed effect models, we modeled seed diversity, abundance, richness and evenness as functions of the biological features and landscape context of isolated trees. Throughout all regions, the amount of woody vegetation surrounding trees in pastures was negatively related to rainforest seed diversity, evenness and abundance. Seed diversity and evenness increased significantly with the distance of isolated trees to forest fragments in the Australian sub-tropics, but elsewhere, seed diversity and evenness tended to decline with distance to forest, though not significantly. Our results suggest that the tree composition of landscapes surrounding isolated pasture trees is important for influencing zoochorous-dispersed seed rain, regardless of the region studied. Our study highlights the prominent role of landscape-scale, rather than local-scale factors on seed dispersal to isolated pasture trees, while providing strong evidence that early stage successional processes involving isolated pasture trees are similar throughout global tropical regions.