Beyond the comfort zone: amphibian diversity and distribution in the West Sahara-Sahel using mtDNA and nuDNA barcoding and spatial modelling

Abstract

Our study seeks to: (1) reduce biodiversity knowledge gaps in amphibians from desert and arid regions; (2) quantify species diversity and detect potential cryptic diversity; (3) identify environmental correlates of amphibian richness distribution, and (4) identify diversity hotspots. DNA barcoding and spatial modelling were integrated to map observed and predicted amphibian richness in Mauritania, Africa. We built two DNA barcoding libraries using one mitochondrial (COI) and one nuclear marker (RAG1). Taxon richness was calculated using species delimitation methods. A generalised linear model was employed to identify environmental correlates of amphibian richness and the distribution of diversity hotspots was predicted. We found a total of 16 anuran taxa with Afrotropic affinities, and two genera and four species were added for the amphibian list of Mauritania. Potential cryptic diversity was detected in Hoplobatrachus occipitalis. Amphibian richness was positively correlated with proximity to savannah, gravel floodplains, and with presence of seasonal wetlands, and negatively with proximity to dunes. Major diversity hotspots were predicted in southern Mauritania. Barcoding methods for both genetic markers successfully identified the taxonomic identity of specimens, also uncovering cryptic diversity in the amphibians of the Sahara-Sahel ecoregions. Amphibian richness in Mauritania increases southwards and it is mostly concentrated in areas under pressure due to habitat conversion, lacking legal protection. The combination of DNA barcoding with spatial modelling can be easily applied to any desert system to address pressing needs for research on biodiversity distribution.