Different responses of taxonomic and functional bird diversity to forest fragmentation across an elevational gradient

Modelling the alpha and beta diversity of copepods across tropical and subtropical Atlantic ecoregions

Copepods, the most abundant individuals of the mesozooplankton, play a pivotal role in marine food webs and carbon cycling. However, few studies have focused on their diversity and the environmental factors influencing it. The objective of the present study is to model the alpha and beta diversity of copepods across the tropical and subtropical ecoregions of Atlantic Ocean using both taxonomic and functional approaches. The study used a dataset of 226 copepod species collected by stratified plankton hauls (0-800 m depth) across the tropical and equatorial Atlantic, from oligotrophic waters close to the Brazilian coast to more productive waters close to the Mauritanian Upwelling. To perform the functional analysis, six traits related to the behaviour, growth, and reproduction of copepods were selected. Several alpha diversities were estimated using taxonomic metrics (SR, Δ+, and Λ+) and functional metrics (FDis, FEve, FDiv, FOri, FSpe), and modelized with GAM model across spatial and environmental gradients, and day/night. The overall and two components of β-diversity (turnover and nestedness) were shared between depth and stations. The surface layers of stations from oligotrophic, equatorial, and Cape Verde ecoregions displayed higher values of taxonomic α-diversity. More unpredictable were the facets of functional α-diversity, although they showed a tendency to be positive with depth during the daytime. The GAM analysis revealed spatial gradients as the key factors modelling the taxonomic α-diversity, whereas depth was the most relevant for functional α-diversity. The turnover component drove taxonomic β-diversity in depth and station, whereas the nestedness component acquired relevance for the functional β-diversity. The taxonomic structure of the copepod community varied spatially across depths and ecoregions, but this was not linked to functional changes of the same magnitude.

Sensitivity of tropical montane birds to anthropogenic disturbance and management strategies for their conservation in agricultural landscapes

Tropical montane bird communities are hypothesized to be highly sensitive to anthropogenic disturbance because species are adapted to a narrow range of environmental conditions and display high rates of endemism. We assessed avian sensitivity at regional and continental scales for a global epicenter of montane bird biodiversity, the tropical Andes. Using data from an intensive field study of cloud forest bird communities across 7 landscapes undergoing agricultural conversion in northern Peru (1800-3100 m, 2016-2017) and a pan-Andean synthesis of forest bird sensitivity, we developed management strategies for maintaining avian biodiversity in tropical countrysides and examined how environmental specialization predicts species-specific sensitivity to disturbance. In Peru, bird communities occupying countryside habitats contained 29-93% fewer species compared with those in forests and were compositionally distinct due to high levels of species turnover. Fragments of mature forest acted as reservoirs for forest bird diversity, especially when large or surrounded by mixed successional vegetation. In high-intensity agricultural plots, an addition of 10 silvopasture trees or 10% more fencerows per hectare increased species richness by 18-20%. Insectivores and frugivores were most sensitive to disturbance: abundance of 40-70% of species declined in early successional vegetation and silvopasture. These results were supported by our synthesis of 816 montane bird species studied across the Andes. At least 25% of the species declined due to all forms of disturbance, and the percentage rose to 60% in agricultural landscapes. The most sensitive species were those with narrow elevational ranges and small global range sizes, insectivores and carnivores, and species with specialized trophic niches. We recommend protecting forest fragments, especially large ones, and increasing connectivity through the maintenance of early successional vegetation and silvopastoral trees that increase avian diversity in pastures. We provide lists of species-specific sensitivities to anthropogenic disturbance to inform conservation status assessments of Andean birds.

Land-use diversity predicts regional bird taxonomic and functional richness worldwide

Unveiling the processes that shape biodiversity patterns is a cornerstone of ecology. Land-use diversity (i.e., the variety of land-use categories within an area) is often considered an important environmental factor that promotes species richness at landscape and regional scales by increasing beta-diversity. Still, the role of land-use diversity in structuring global taxonomic and functional richness is unknown. Here, we examine the hypothesis that regional species taxonomic and functional richness is explained by global patterns of land-use diversity by analyzing distribution and trait data for all extant birds. We found strong support for our hypothesis. Land-use diversity predicted bird taxonomic and functional richness in almost all biogeographic realms, even after accounting for the effect of net primary productivity (i.e., a proxy of resource availability and habitat heterogeneity). This link was particularly consistent with functional richness compared to taxonomic richness. In the Palearctic and Afrotropic realms, a saturation effect was evident, suggesting a non-linear relationship between land-use diversity and biodiversity. Our results reveal that land-use diversity is a key environmental factor associated with several facets of bird regional diversity, widening our understanding of key large-scale predictors of biodiversity patterns. These results can contribute to policies aimed at minimizing regional biodiversity loss.

A research framework for projecting ecosystem change in highly diverse tropical mountain ecosystems

Tropical mountain ecosystems are threatened by climate and land-use changes. Their diversity and complexity make projections how they respond to environmental changes challenging. A suitable way are trait-based approaches, by distinguishing between response traits that determine the resistance of species to environmental changes and effect traits that are relevant for species' interactions, biotic processes, and ecosystem functions. The combination of those approaches with land surface models (LSM) linking the functional community composition to ecosystem functions provides new ways to project the response of ecosystems to environmental changes. With the interdisciplinary project RESPECT, we propose a research framework that uses a trait-based response-effect-framework (REF) to quantify relationships between abiotic conditions, the diversity of functional traits in communities, and associated biotic processes, informing a biodiversity-LSM. We apply the framework to a megadiverse tropical mountain forest. We use a plot design along an elevation and a land-use gradient to collect data on abiotic drivers, functional traits, and biotic processes. We integrate these data to build the biodiversity-LSM and illustrate how to test the model. REF results show that aboveground biomass production is not directly related to changing climatic conditions, but indirectly through associated changes in functional traits. Herbivory is directly related to changing abiotic conditions. The biodiversity-LSM informed by local functional trait and soil data improved the simulation of biomass production substantially. We conclude that local data, also derived from previous projects (platform Ecuador), are key elements of the research framework. We specify essential datasets to apply this framework to other mountain ecosystems.