Land cover drives amphibian diversity across steep elevational gradients in an isolated neotropical mountain range: Implications for community conservation

Abstract

Over 70% of land in the tropics is in some form of agricultural matrix which poses a threat to biodiversity. In Colombia, montane regions are dominated by varying intensities of agriculture and high levels of biodiversity and endemism. Globally, Colombia has the second largest number of amphibian species and is also the third largest coffee producer. Our study region, the Sierra Nevada de Santa Marta (SNSM), has high levels of amphibian endemism (38% and 10 threatened endemics) and is the fourth largest coffee growing region in Colombia. The SNSM rises from the sea to 5,775 m in just 42 km, with a direct overlap between coffee and amphibian habitat occurring across 600–1,800 m. We examined how land cover and elevation (from 800 to 3,700 m asl) influenced amphibian community structure, species richness, and abundance. We conducted surveys from September 2017 to July 2018 at 35 transects across five major land cover types: forest, ecotone, páramo, pasture, and shade coffee. In total, we recorded 19 species (366 individuals; 16 endemic species). Land cover was the main determinant of amphibian community structure, while the interaction between elevation and land cover was the main determinant of species richness and abundance. Forest and ecotone contained 73% of overall richness (14 species) with one species found exclusively in ecotone and three exclusively in forest. Pasture and coffee supported 42% (8 species) of species with only two species found exclusively at these land cover types. Shade coffee had low species richness and abundance and we detected just one endemic species in this land cover. The preservation of ecotone, transitional degraded habitat that occurs between two or more types of contiguous land cover types, represents an opportunity to safeguard microhabitats and microclimates. Conservation in the region should be collaborative and include private landowners, NGO’s, government agencies, and academics. Conservation actions should prioritize protecting extant natural habitat, restoring degraded habitats, increasing the heterogeneity of production systems, and improving landscape connectivity and watershed health. To achieve those actions, local communities will require economic incentives to maintain forest cover and reduce the contamination of streams through agricultural runoff.