The road to functional recovery : temporal effects of matrix regeneration on Amazonian bats

Across the tropics, vast deforested areas are undergoing forest regeneration due to land abandonment. Although secondary forest is an expanding type of landscape matrix that has been shown to buffer some of the negative consequences of forest loss and fragmentation on taxonomic diversity, little is known in this regard about the functional dimension of biodiversity. We took advantage of an ecosystem-wide fragmentation experiment to investigate longer term changes in functional diversity of a mega-diverse Amazonian bat assemblage associated with regrowth development in the matrix. We found that matrix regeneration affected several facets of bat functional diversity in secondary forest over time, increasing functional α diversity, species- and community-level functional uniqueness, altering functional trait composition, and resulting in functional β-diversity changes via trait gains. However, approximately 30 years of matrix regeneration were insufficient for functional diversity to recover to the same levels as in continuous forest. Our results suggest that a combination of natural, human-assisted, and active restoration is likely to be the most successful strategy for restoring functional biodiversity of bats in human-modified tropical landscapes, a finding that most likely also applies to many other taxa

Functional recovery of Amazonian bat assemblages following secondary forest succession

Regenerating forests occupy large areas in the tropics, mostly as a result of deforestation for livestock and agriculture, followed by land abandonment. Despite the importance of regenerating secondary forests for tropical biodiversity conservation, studies of temporal effects of matrix regeneration on species responses in fragmented landscapes are scarce. Here, we used an Amazonian whole-ecosystem fragmentation experiment to investigate how changes in matrix quality over time through secondary forest regeneration affect bat assemblages from a functional perspective. We found that forest regeneration in the matrix positively affected functional α diversity, as well as species- and community-level functional uniqueness, reflecting an increase of species that perform different ecological functions in secondary forest over time. According to functional trait composition, animalivorous species showed the clearest signs of recovery associated with matrix regeneration. Consequently, between-period differences in functional β-diversity were highest in secondary forest compared to fragments and continuous forest, determined mainly by trait gains. However, ~ 30 years of secondary forest regeneration were not sufficient for the functional recovery of bat assemblages to levels observed in continuous forest. Restoring degraded habitats while protecting primary forest will be an important strategy for safeguarding high functional diversity of bats and their vital contributions to ecosystem functioning in fragmented tropical landscapes

Design matters : an evaluation of the impact of small man-made forest clearings on tropical bats using a before-after-control-impact design

In recent years, large clearings (>1000 ha) accounted for gradually smaller amounts of total annual deforestation in the Brazilian Amazon, whereas the proportion of small clearings (<50 ha) nowadays represents more than 80% of annual deforestation. Despite the ubiquity of small clearings in fragmented Amazonian landscapes, most fragmentation research has focused on the effects of large-scale deforestation, leading to a poor understanding of the impacts of smaller barriers on Amazonian vertebrates. We capitalized on the periodical re-isolation of experimental forest fragments at the Biological Dynamics of Forest Fragments Project in the Central Amazon as a before-after-control-impact experiment to investigate the short-term effects of small clearings on bat assemblages. Over the course of three years we sampled six control sites in continuous forest, the interiors and edges of eight forest fragments as well as eight sites in the surrounding matrix. Sampling took place both before and after the experimental manipulation (clearing of a 100 m wide strip of regrowth around each fragment), resulting in ~4000 bat captures. Species were classified as old-growth specialists and habitat generalists according to their habitat affinities and a joint species distribution modeling framework was used to investigate the effect of fragment re-isolation on species occupancy. Following fragment re-isolation, species richness declined in all habitats other than fragment edges and, although responses were idiosyncratic, this decline was more pronounced for forest specialist than for generalist species. Additionally, fragment re-isolation led to a reduction in the similarity between assemblages in modified habitats (fragment interiors, edges and matrix) and continuous forest. Sampling of controls in continuous forest both prior to and after reisolation revealed that much of the variation in bat species occupancy between sampling periods did not arise from fragment re-isolation but rather reflected natural spatiotemporal variability. This emphasizes the need to sample experimental controls both before and after experimental manipulation and suggests caution in the interpretation of results from studies in which the effects of habitat transformations are assessed based solely on data collected using space-for-time substitution approaches

Design matters : an evaluation of the impact of small man-made forest clearings on tropical bats using a before-after-control-impact design

In recent years, large clearings (>1000 ha) accounted for gradually smaller amounts of total annual deforestation in the Brazilian Amazon, whereas the proportion of small clearings (<50 ha) nowadays represents more than 80% of annual deforestation. Despite the ubiquity of small clearings in fragmented Amazonian landscapes, most fragmentation research has focused on the effects of large-scale deforestation, leading to a poor understanding of the impacts of smaller barriers on Amazonian vertebrates. We capitalized on the periodical re-isolation of experimental forest fragments at the Biological Dynamics of Forest Fragments Project in the Central Amazon as a before-after-control-impact experiment to investigate the short-term effects of small clearings on bat assemblages. Over the course of three years we sampled six control sites in continuous forest, the interiors and edges of eight forest fragments as well as eight sites in the surrounding matrix. Sampling took place both before and after the experimental manipulation (clearing of a 100 m wide strip of regrowth around each fragment), resulting in ~4000 bat captures. Species were classified as old-growth specialists and habitat generalists according to their habitat affinities and a joint species distribution modeling framework was used to investigate the effect of fragment re-isolation on species occupancy. Following fragment re-isolation, species richness declined in all habitats other than fragment edges and, although responses were idiosyncratic, this decline was more pronounced for forest specialist than for generalist species. Additionally, fragment re-isolation led to a reduction in the similarity between assemblages in modified habitats (fragment interiors, edges and matrix) and continuous forest. Sampling of controls in continuous forest both prior to and after reisolation revealed that much of the variation in bat species occupancy between sampling periods did not arise from fragment re-isolation but rather reflected natural spatiotemporal variability. This emphasizes the need to sample experimental controls both before and after experimental manipulation and suggests caution in the interpretation of results from studies in which the effects of habitat transformations are assessed based solely on data collected using space-for-time substitution approaches

Interplay between local and landscape-scale effects on the taxonomic, functional and phylogenetic diversity of aerial insectivorous Neotropical bats

Context Human-modified landscapes are globally ubiquitous. It is critical to understand how habitat loss and fragmentation impact biodiversity from both a local habitat context and landscape-scale perspective to inform land management and conservation strategies. Objectives We used an experimentally fragmented landscape in the Brazilian Amazon to investigate variation in aerial insectivorous bat diversity in response to local habitat and wider landscape characteristics, applying a multiscale approach. Methods We conducted bat acoustic surveys at 33 sites, comprising old secondary forests and fragments of primary forest. Taxonomic, functional and phylogenetic diversity facets were calculated within a Hill numbers framework. We analysed responses to fragment size, interior-edge-matrix gradients, as well as local vegetation structure, continuous forest cover, edge density and patch density across five spatial scales (0.5 km - 3 km) surrounding detector locations. Results Compared with continuous forest, secondary forest matrix around the smallest fragments harboured lower diversity. The overall negative effect of the matrix became less pronounced with increasing fragment size. In contrast, forest edges generally contained higher taxonomic, functional and phylogenetic diversity. We found subtle scale-sensitive associations for FD, responding positively to forest cover (at the 1 km scale) and negatively to edge (1 km scale) and patch density (2.5 km scale). Conclusions Despite a low-contrast matrix of tall secondary forest surrounding fragments after ~30 years of forest recovery, aerial insectivorous bat diversity is not comparable to continuous primary forest. Assemblage functional diversity responds to compositional and configurational landscape characteristics at scales deserving further evaluation at guild and species level

Consequences of a large-scale fragmentation experiment for Neotropical bats : disentangling the relative importance of local and landscape-scale effects

Context Habitat loss, fragmentation and degradation are widespread drivers of biodiversity decline. Understanding how habitat quality interacts with landscape context, and how they jointly affect species in human-modified landscapes, is of great importance for informing conservation and management. Objectives We used a whole-ecosystem manipulation experiment in the Brazilian Amazon to investigate the relative roles of local and landscape attributes in affecting bat assemblages at an interior-edge-matrix disturbance gradient. Methods We surveyed bats in 39 sites, comprising continuous forest (CF), fragments, forest edges and intervening secondary regrowth. For each site, we assessed vegetation structure (local-scale variable) and, for five focal scales, quantified habitat amount and four landscape configuration metrics. Results Smaller fragments, edges and regrowth sites had fewer species and higher levels of dominance than CF. Regardless of the landscape scale analysed, species richness and evenness were mostly related to the amount of forest cover. Vegetation structure and configurational metrics were important predictors of abundance, whereby the magnitude and direction of response to configurational metrics were scale-dependent. Responses were ensemble-specific with local-scale vegetation structure being more important for frugivorous than for gleaning animalivorous bats. Conclusions Our study indicates that scale-sensitive measures of landscape structure are needed for a more comprehensive understanding of the effects of fragmentation on tropical biota. Although forest fragments and regrowth habitats can be of conservation significance for tropical bats our results further emphasize that primary forest is of irreplaceable value, underlining that their conservation can only be achieved by the preservation of large expanses of pristine habitat

Reproductive phenologies of phyllostomid bats in the Central Amazon

Mammals tend to align their most energetically demanding phenological events with periods of peak resource availability. Their reproductive phenology is influenced by local resource availability, potentially leading to geographical variation in their breeding strategy. Although the Amazon is the world’s epicenter of bat diversity, the reproductive phenology of Amazonian bats remains poorly known. Seasonality induces fluctuations in resource availability and most phyllostomid species, crucial agents of seed dispersal, pollination and arthropod suppression in the Neotropics, have been described to exhibit seasonal bimodal polyestry. However, current understanding of phyllostomid reproductive phenology is impaired by the paucity of comparative examinations of the phenologies of sympatric species, using consistent classification schemes based on the number and timing of annual peaks in pregnancy and lactation. Using a multi-year dataset from Central Amazonia, we examined the reproductive phenology of nine bat species (Artibeus concolor, A. obscurus, A. lituratus, Carollia brevicauda, C. perspicillata, Gardnerycteris crenulatum, Lophostoma silvicolum, Rhinophylla pumilio, and Trachops cirrhosus), as well as two feeding ensembles (i.e., frugivores and gleaning animalivores). Only three of the nine species exhibited a bimodal reproductive phenology. Six species and the frugivore ensemble showed unimodal reproductive phenology, while gleaning animalivores displayed an amodal pregnancy pattern. All species except L. silvicolum had their primary pregnancy peak during the mid-dry season. A reproductive peak during the early wet season, or local variation in the duration of the fruiting season may explain the deviation of our observations from the expected bimodal polyestry