Biotic interactions underlie ecosystem structure and function, but predicting interaction outcomes is difficult. We tested the hypothesis that biotic interaction strength increases toward the equator, using a global experiment with model caterpillars to measure predation risk. Across an 11,660-kilometer latitudinal gradient spanning six continents, we found increasing predation toward the equator, with a parallel pattern of increasing predation toward lower elevations. Patterns across both latitude and elevation were driven by arthropod predators, with no systematic trend in attack rates by birds or mammals. These matching gradients at global and regional scales suggest consistent drivers of biotic interaction strength, a finding that needs to be integrated into general theories of herbivory, community organization, and life-history evolution.
Biodiversity extinction thresholds are abrupt declines in biological diversity that occur with habitat loss, associated with a decline in habitat connectivity. Matrix quality should influence the location of thresholds along habitat loss gradients through its effects on connectivity; however these relationships have seldom been explored empirically. Using field data from 23 independent 1254 ha landscapes in the Brazilian Atlantic Forest, we evaluated how tropical avian biodiversity responds to native forest loss within habitat patches embedded either in homogeneous pasture matrix context (with a high proportion of cattle pastures), and heterogeneous coffee matrix context (with high abundance of sun coffee plantations). We considered taxonomic, functional, and phylogenetic diversity, and tested if matrix type and choice of diversity metric influenced the location of biodiversity thresholds along the forest cover gradient. We found that matrix type postponed the abrupt loss of taxonomic diversity, from a threshold of 35% of forest cover in homogeneous pasture matrix to 19% in heterogeneous coffee matrix. Phylogenetic diversity responded similarly, with thresholds at 30 and 24% in homogeneous‐pasture and heterogeneous‐coffee matrices, respectively, but no relationship with forest cover was detected when corrected for richness correlation. Despite the absence of a threshold for functional diversity in either matrix types, a strong decline below 20% of habitat amount was detected. Finally, below 20% native habitat loss, all diversity indices demonstrated abrupt declines, indicating that even higher‐quality matrices cannot postpone diversity loss below this critical threshold. These results highlight that taxonomic diversity is a more sensitive index of biodiversity loss in fragmented landscapes, which may be used as a benchmark to prevent subsequent functional and phylogenetic losses. Furthermore, increasing matrix quality appears an efficient conservation strategy to maintain higher biodiversity levels in fragmented landscapes over a larger range of habitat loss.
Natural habitats adjacent to agricultural areas are often considered sources of species that provide beneficial regulating ecosystem services through cross‐habitat spillover. Both inter‐habitat matrix and landscape configuration can influence spillover by controlling organismal ability to disperse through landscapes, and affecting the provision of additional or supplementary resources that impact organism survival. To understand how landscape structure in terms of matrix land use type, forest cover and edge density might facilitate avian cross‐habitat spillover, we sampled avian communities in forest patches and adjacent land use types (coffee plantations or cattle pastures) using a well‐replicated study design across 92 sampling sites across a landscape‐context forest cover gradient (6%–60%). Land use type was a key factor influencing avian cross‐habitat spillover, facilitating species movement into coffee plantations and acting as a barrier to spillover into cattle pastures. We found that 24% of the forest‐dependent species pool was capable of spillover into coffee plantations, while spillover was nearly non‐existent in cattle pastures. Forest cover was also the main driver of spillover into coffee plantations. There was a positive relationship between forest cover and spillover, potentially due to processes related with (1) a higher density of organism in‐patches, (2) decreased isolation among patches facilitating species movement and (3) higher landscape supplementation processes. Finally, we found edge density had an additive effect with forest cover on spillover. Spillover was higher in high‐forested landscapes with many forest‐matrix edges, possibly due to increased structural connectivity for species able to move through edges, and to improved access for forest‐dwelling species to different resource types (complementation processes). Synthesis and applications. We demonstrate that land use type is a key factor facilitating species spillover into agricultural matrices and that the influence of land use type on spillover is further modulated by a combination of native habitat amount and edge density. These results should be considered in efforts to design or manage sustainable agricultural landscapes in order to enhance both bird persistence and the provision of bird‐mediated ecosystem services.
The impact of local biodiversity loss on ecosystem functioning is well-established but the role of larger-scale biodiversity dynamics in the delivery of ecosystem services remains poorly understood. We address this gap using a comprehensive dataset describing the supply of 16 cultural, regulating and provisioning ecosystem services in 150 European agricultural grassland plots, and detailed multi-scale data on land use and plant diversity. After controlling for land-use and abiotic factors, we show that both plot-level and surrounding plant diversity play an important 5 role in the supply of cultural and aboveground regulating ecosystem services. In contrast, provisioning and belowground regulating ecosystem services are more strongly driven by fieldlevel management and abiotic factors. Structural equation models revealed that surrounding plant diversity promotes ecosystem services both directly, likely by fostering the spill-over of ecosystem service providers from surrounding areas, and indirectly, by maintaining plot-level diversity. By influencing the ecosystem services that local stakeholders prioritized, biodiversity at different scales was also shown to positively influence a wide range of stakeholder groups. These results provide a comprehensive picture of which ecosystem services rely most strongly on biodiversity, and the respective scales of biodiversity that drives these services. This key information is required for the upscaling of biodiversity-ecosystem service relationships, and the informed management of biodiversity within agricultural landscapes.
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