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.

There is ongoing debate concerning whether there exists a generalizable effect of land-use change on biodiversity and consequently zoonotic disease risk. Strong data informing this debate is sparse because ecological and sampling complexities make it challenging to establish direct links between vertebrate hosts (and non-hosts), vectors, and pathogens across landscapes. However, emerging molecular methods using invertebrate-derived DNA (iDNA) can now measure species diversity and interactions from vector bloodmeals, which has the potential to improve mechanistic understanding of the effects of land-use change on zoonotic disease risk. Here, we used iDNA metabarcoding of vectors and their bloodmeals to disentangle the complex relationships between Leishmania parasites, known sandfly vectors, and potential wildlife hosts. We collected 56,775 sandflies during 3,159 trap nights at 39 forested sites across the southern Amazon ‘Arc of Deforestation’, which exemplifies global patterns of deforestation and fragmentation at the borders of tropical forest ecosystems due to agricultural expansion. We found that vector community composition was influenced by forest cover and pasture cover, and the most common vector, Nyssomia spp., was encountered less frequently in forests surrounded by pasture. Sandflies fed on a diversity of vertebrates, but the edge-loving nine-banded armadillo, Dasypus novemcinctus, was overwhelmingly the most prevalent host, followed by the greater long-nosed armadillo, Dasypus kappleri. The probability of a host being detected in sandfly bloodmeals was lower at sites with higher forest cover, which was overwhelmingly due to reduced bloodmeals arising from D. novemcinctus. Armadillos were also the most prevalent sylvatic vertebrate taxon in sandfly pools that were positive for Leishmania, further suggesting that these xenarthrans are a key host pathway for zoonotic disease transmission.

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.

Metabarcoding of environmental DNA (eDNA) is now widely used to build diversity profiles from DNA that has been shed by species into the environment. There is substantial interest in the expansion of eDNA approaches for improved detection of terrestrial vertebrates using invertebrate-derived DNA (iDNA) in which hematophagous, sarcophagous, and coprophagous invertebrates sample vertebrate blood, carrion, or feces. Here, we use metabarcoding and multiple iDNA samplers (carrion flies, sandflies, and mosquitos) to profile gamma and alpha diversity in a dry, tropical forest in the southern Amazon. Our main objectives were to (1) compare diversity found with iDNA to camera trapping, which is the conventional method of vertebrate diversity surveillance and (2) compare each of the iDNA samplers to assess the effectiveness, efficiency, and potential biases associated with each sampler. Carrion flies were the most effective sampler, despite the least amount of sampling effort and the fewest number of individuals captured for metabarcoding, in describing vertebrate biodiversity followed by sandflies. Camera traps had the highest median species richness at the site-level but showed strong bias towards carnivore and ungulate species and missed much of the diversity described by iDNA methods. Mosquitos showed a strong feeding preference for humans as did sandflies for armadillos, thus presenting potential utility to further study related to host-vector interactions.