Fragmentation effects on biodiversity remain contentious, with landscape-scale studies reporting positive effects on species richness while fragment-level studies document diversity losses. We tested whether fragmentation per se affects taxonomic and functional diversity independently and whether landscape heterogeneity mediates these effects. We surveyed small mammal communities across 131 Atlantic Forest sites in Brazil, embedded in landscapes varying in habitat amount, fragmentation, compositional heterogeneity, and matrix quality. We quantified taxonomic richness and four functional diversity metrics based on ten morphological, behavioral, and dietary traits, using hierarchical approaches to test fragmentation effects across six spatial scales (500-5,500 m) and structural equation models to evaluate mediation by landscape heterogeneity. Fragmentation per se increased species richness independent of habitat amount, with effects detectable only at landscape scales (R² = 19% at 5,500 m; β = 0.27, p < 0.01). However, fragmentation simultaneously reduced functional dispersion (β = −0.27, p < 0.01) without affecting standardized functional richness, revealing complete taxonomic-functional decoupling. Community-weighted mean traits revealed that fragmentation favored smaller species with reduced dispersal capacity (body mass: β = −0.35, p < 0.01; dispersal: β = −0.25, p < 0.05). Landscape heterogeneity did not mediate these effects, rejecting the niche diversification hypothesis. Positive taxonomic effects of fragmentation per se mask functional homogenization driven by accumulation of disturbance-tolerant generalists while functionally unique species are filtered out. Conservation strategies relying solely on species inventories systematically overestimate ecological resilience in fragmented landscapes. Understanding fragmentation’s true impact requires functional assessment beyond species counts, fundamentally changing how we evaluate and conserve biodiversity in humanity’s increasingly fragmented world.

Agricultural expansion has markedly reduced forests and reconfigured landscapes. These changes incur a well-known detrimental impact on the biodiversity of local forest patches, but the effects on species persistence at entire landscapes comprised of multiple patches are debated. We investigated how regional diversity is affected by habitat loss, fragmentation, and cattle grazing, and how species respond to deforestation both locally and regionally. We also investigated how the heterogeneity in species distribution (beta-diversity) buffers landscapes against local diversity losses. The vast majority of the 251 ant species found in our study were negatively affected by both habitat loss and cattle at local forest patches, drastically reducing diversity at these patches compared to pristine forests. Despite local declines in diversity, however, heavily fragmented landscapes could still retain most species due to the high heterogeneity in species distribution. We found that beta-diversity is the main component of regional diversity. Results from several studies suggest that this component is maximized when remnant primary habitats in a landscape are spread across vast areas. Although preserving local diversity may be important for the adequate functioning of the ecosystem locally, our results indicate that the maintenance of many small forest patches in a landscape can buffer regional biodiversity against local species losses. Our results suggest that even small forest remnants in otherwise deforested landscapes can prevent most regional-scale species extirpations, and therefore also merit conservation efforts.

Agricultural expansion has markedly reduced forests and reconfigured landscapes. These changes incur a well-known detrimental impact on the biodiversity of local forest patches, but the effects on species persistence at broader geographic scales are widely debated. We investigated how regional diversity is affected by habitat loss, fragmentation, and cattle grazing, and how species respond to deforestation both locally and regionally. We also investigated how the heterogeneity in species distribution (beta-diversity) alters species responses across scales. The vast majority of the 251 ant species found in our study were negatively affected by both habitat loss and cattle at local forest patches, drastically reducing diversity at these patches compared to pristine forests. Despite local declines in diversity, however, heavily fragmented landscapes could still retain most species due to the high heterogeneity in species distribution. Beta-diversity is the main component of regional diversity, and this component is maximized when remnant primary habitats in a landscape are spread across vast areas. Although preserving local diversity may be important for the adequate functioning of the ecosystem, our results indicate that the maintenance of many small forest patches in a landscape can buffer regional biodiversity against local species extinctions. Our results suggest that even small forest remnants in otherwise deforested landscapes can prevent most regional-scale species extirpations, and therefore also merit conservation efforts.

This is a review of the preprint entitled " Challenging the Raunkiaeran shortfall and the consequences of using imputed databases", by Lucas Jardim, Luis Mauricio Bini, José Alexandre Felizola Diniz-Filho and Fabricio Villalobos. The preprint was originally posted on bioRxiv on October 18, 2016 (https://doi.org/10.1101/081778). Our journal club reviewed this preprint in the meeting of June 6, 2018.