Effects of agriculture and topography on tropical amphibian species and communities

Abstract

Habitat loss is the greatest threat to the persistence of forest-dependent amphibians, but it is not the only factor influencing species occurrences. The composition of the surrounding matrix, structure of stream networks, and topography are also important landscape characteristics influencing amphibian distributions. Tropical forests have high diversity and endemism of amphibians, but little is known about the specific responses of many of these species to landscape features. In this paper, we quantify the response of amphibian species and communities to landscape-scale characteristics in streams within the fragmented Brazilian Atlantic Forest. We surveyed amphibian communities during a rainy season in 50 independent stream segments using Standardized Acoustic and Visual Transect Sampling (active) and Automated Acoustic Recorders (passive) methods. We developed a hierarchical multi-species occupancy model to quantify the influence of landscape-scale characteristics (forest cover, agriculture, catchment area, stream density, and slope) on amphibian occurrence probabilities while accounting for imperfect detection of species using the two survey methods. At the community level, we estimated an overall mean positive relationship between amphibian occurrence probabilities and forest cover, and a negative relationship with agriculture. Catchment area and slope were negatively related with amphibian community structure (95% credible interval [CI] did not overlap zero). The species-level relationships with landscape covariates were highly variable but showed similar patterns to those at the community level. Species detection probabilities varied widely and were influenced by the sampling method. For most species, the active method resulted in higher detection probabilities than the passive approach. Our findings suggest that small streams and flat topography lead to higher amphibian occurrence probabilities for many species in Brazil's Atlantic Forest. Our results combined with land use and topographic maps can be used to make predictions of amphibian occurrences and distributions beyond our study area. Such projections can be useful to determine where to conduct future research and prioritize conservation efforts in human-modified landscapes.

A roadmap for survey designs in terrestrial acoustic monitoring

“…; Ribeiro et al. ). This procedure can support choosing among distinct recording schedules prior to start PAM.…”

“…) and flat riparian habitats (Ribeiro et al. ). Therefore, specific spatial arrangements with multiple recorders as random assignments of recorders (Munro et al.…”

Arthropod abundance modulates bird community responses to urbanization

“…We calculated the 95% and the 75% posterior credible intervals (CI) for all the parameters. Following other publications (Mata et al., 2014; Ribeiro et al., 2018), we considered that 95% CI not overlapping zero showed a strong effect and that 75% CI not overlapping zero were enough to show the existence of an effect. Consequently, we considered that when the 75% CI overlapped zero, the support from the data was weak to demonstrate an effect.…”

“…We calculated the 95% and the 75% posterior credible intervals (CI) for all the parameters. Following other publications (Mata et al, 2014;Ribeiro et al, 2018), we considered that 95% CI not overlapping zero showed a strong effect and that 75% CI not overlapping zero were enough to F I G U R E 2 Representation of the modelling workflow followed in this study to disentangle effects of environment and trophic interactions, as well as explore species associations (lower left pictogram). The workflow has been divided into three sections: arthropod community models (JSDMs; left square), bird community model (JSDM; central-rigth square), which is used to derive the final results (right).…”

Occupancy models including local and landscape variables are useful to assess the distribution of a salamander species at risk

“…Contrastingly, during the rainy season, in which physiological stress is less plausible, the activity and distribution of amphibians are frequently affected by factors at the landscape level, such as distance among habitat patches and the type of land use surrounding these patches. These factors influence the distribution of amphibian species, especially when amphibians leave their habitat patch to carry out activities associated with reproduction and dispersal (Moreira, Moura, & Maltchik, 2016; Ribeiro Jr, Siqueira, Brejão, & Zipkin, 2018; Trenham, Koenig, & Shaffer, 2001).…”