Spots of high diversity of troglobites in Brazil: the challenge of measuring subterranean diversity

Subterranean ecosystems are among the most fragile and threatened worldwide. Among organisms living in the subterranean domain, source populations restricted to subterranean habitats are called troglobites, generally distinguished by sets of morphological, physiological, and ecological specializations. The singularities at both systemic (high dark and phylogenetic diversities) and species levels greatly contribute to regional and global biodiversity. However, good descriptive and interpretative knowledge about this diversity, which is important as a basis for effective conservation policies, is lacking especially for tropical areas. We describe and characterize Brazilian karst areas recognized as spots of high diversity of troglobites, highlighting particularly important cave systems. We considered not only taxonomic richness but also indicators of phylogenetic (e.g., presence of relictual taxa) and genetic diversities, the latter based on degree of specialization of individual species, i.e., accumulation of autapomorphies. For this, we used available literature and our own data, both published and unpublished. Only identifications validated by a taxonomist were considered, while all data based on parataxonomy were disregarded. We propose hypotheses based on models of origin of troglobites aiming to explain the differences between karst areas.