Anthropogenic modulators of species-area relationships in Neotropical primates: A continental-scale analysis of fragmented forest landscapes

Aim: We conducted the first comprehensive quantitative review on the effects of habitat fragmentation on Neotropical primates to examine how both patch disturbance and landscape variables modulate species-area relationships (SARs) and species persistence in fragmented forest landscapes. Location: Neotropical forests, from Mexico to Argentina. Methods: We use species occupancy data from 705 forest fragments and 55 adjacent continuous forests nested within 61 landscapes, which we compiled from 96 studies reporting data on patch-scale species composition and patch size/location. Presence-absence data on 19 species functional groups and an index of hunting pressure and matrix type were assigned to each forest patch. We adopted a multilevel analysis, examining SARs and patterns of species retention coupled with the additive effects of hunting pressure and landscape connectivity both across all forest patches and 728 sites nested within 38 landscapes containing four or more sites. Results: We uncovered a consistent effect of patch area in explaining primate species richness. Over and above area effects, however, SARs were strongly modulated by levels of hunting pressure at the landscape scale in predicting species occurrence and aggregate assemblage biomass. Matrix type was also a good predictor of both extant species richness and aggregate biomass when only non-hunted sites were considered, with patches in more permeable matrices containing more species. Main conclusions: Although the importance of patch area in predicting species persistence is undeniable, we found that SARs were clearly affected by within-patch human exploitation of increasingly isolated primate populations. Both expanding the number of forest reserves and enforcing protection within nominal protected areas are therefore required to ensure the long-term persistence of full primate assemblages. We highlight the importance of considering multiple anthropogenic effects in assessing the synergistic effects of land use to explain patterns of species persistence in fragmented tropical forest landscapes.