Hidden diversity of Aegla (Decapoda, Anomura) in a priority area for conservation

Abstract

Aegla is a genus of freshwater anomuran crabs encompassing 94 described species occurring in meridional South America. Brazil harbours the greatest diversity of species, mainly in its southern region, which becomes a priority area for Aegla conservation due to high species richness and phylogenetic diversity, elevated endemism and threats to the Atlantic Forest. Here, we assessed Aegla richness and distribution in this priority area and tested the hypothesis of crypticism in the region's species. Sampling sites were distributed inside and in the surroundings of five protected areas, covering the major distribution range of several species described for southern Brazil. We applied three species delimitation methods to COI mitochondrial gene data, coupled with phylogenetic and morphological analyses. By integrating species delimitation based on the COI data and traditional taxonomy, we uncovered a high proportion of hidden diversity among Aegla in our study area and identified ten known species besides impressive 17 new putative species. Of these, eight are possible new taxonomic units that do not conform to any known species, and nine are divided into three cryptic groups: Aegla jarai complex, Aegla franciscana complex and Aegla camargoi complex. Most of these species have a narrow spatial distribution, making them highly vulnerable to habitat degradation. Despite the real richness of the genus still being largely unknown, the high diversity revealed here makes our study area the richest known region regarding the number of Aegla species within its distribution, making this area even more worthy for conservation efforts.