Integrating bioacoustics, DNA barcoding and niche modeling for frog conservation – The threatened balloon frogs of Sri Lanka

Abstract

Discovering and monitoring anuran populations that are in decline, and ascertaining boundaries for cryptic and rare species, is a challenge for their conservation management. Here, we integrate three techniques, bioacoustics (call), niche modeling and DNA barcoding as a test case to investigate how the combination of these methods can enhance search efficiency for previously unknown populations, especially for those species that are threatened. As a focal group, we considered a clade in the genus Uperodon earlier referred to as Ramanella, represented by four endemic species in Sri Lanka (U. nagaoi – Endangered; U. palmatus – Critically Endangered; U. obscurus – Vulnerable and U. rohani – possibly Least Concern); we focus on the two highly threatened species (U. nagaoi and U. palmatus). We used mitochondrial DNA barcodes (16S rRNA) to link species accurately to their call and subsequently predicted species distributions using MaxEnt-based niche modeling of known species locations and forest cover data to increase the efficiency of searching for new populations. Lastly, we analyzed call data for accurate and rapid identification of new and viable populations. Following enhanced predicted distribution models, we visited 14 potential sites and sampled for calls of the two highly threatened species. Within a period of two weeks of fieldwork, we discovered two new populations of U. nagaoi and one population of U. palmatus by identifying their calls in areas predicted by niche modeling; we also confirm species identities at several previously unconfirmed locations. Finally, we included the new locations to enhance the distributional predictions for the threatened species. We discuss our results in the context of integrating methods to facilitate conservation of rare and threatened frog species. Keywords: Anura, Distribution modeling, Exploration, Population monitoring, Species boundaries, Vocalization