Eleutherodactylus in coffee agroecosystems: Effects of farm management on vegetation selection, species richness, and abundances of Puerto Rican frogs

Abstract

Amphibians are declining globally as the combined threats of climate change, habitat loss, and infectious disease intensify and interact. Curbing species losses requires implementing conservation measures beyond natural or protected areas. Shaded coffee farms stand out among human-modified landscapes in their capacity to harbor high levels of biodiversity. In Puerto Rico, the ranges of most Eleutherodactylus frogs, many of which are endangered and declining, coincide with the primary coffee-producing region on the island. In this study we used a combination of radio telemetry, bioacoustic monitoring, GIS, and vegetation surveys to investigate the degree to which agricultural habitats at multiple spatial scales may contribute to Eleutherodactylus conservation. We compared frog species diversity and abundance between and among farm and forest sites and assessed the influence of farm management and landscape variables. To understand how a common species uses coffee agroecosystems as novel habitat, we tracked Eleutherodactylus coqui using radio telemetry and identified trends in vegetation use and microhabitat selection within farms. At the landscape scale, we found farms and forests harbored similar numbers of species but differed in their species composition, with no forest specialists detected in farm systems. Surrounding landcover did not impact farmlevel richness or abundance. At the farm scale, Eleutherodactylus species varied in their responses to aspects of farm management, with the exception of uniformly negative responses to pesticide application and high densities of root crops which may concentrate pesticides. Within farms, E. coqui showed an affinity for plantain (Musa spp.), especially those with hanging dry leaves, for diurnal retreat sites. No vegetation preference was detected at night when frogs were active. We conclude that coffee farms in Puerto Rico provide suitable habitat for amphibians, yet may not be meeting the needs of forest specialist species. Within farms a generalist species was most abundant where microhabitats essential for shelter and reproduction were plentiful; such resources are likely lacking for species dependent on forests. Despite similar levels of diversity to nearby forests, coffee farms under current management regimes may not be useful habitat for species of conservation concern in Puerto Rico.