Knowledge status and trends in description of amphibian species in Brazil

Overcoming the Linnaean and Wallacean shortfalls is an urgent task for biologists. It has been estimated that only a small fraction of the biodiversity on Earth is known, while geographic ranges of already described species are poorly documented. We performed a systematic review and modeling on species descriptions of Brazilian amphibians to evaluate the taxonomic knowledge on this group, to estimate the number of new species that remain to be described, and to identify description trends and relevant information for guiding future studies. All descriptions made between 1758 and 2017 of amphibian species and anuran tadpoles in Brazil, the country with the richest amphibian fauna, were gathered and characterized (species, year of description, number of authors per article, and coordinates of the collecting site). We found 1,119 amphibian species reported occurring in Brazil. The number of descriptions of both amphibian species and anuran tadpoles, as well as the number of authors per article, has exponentially increased over time. Phylogenetic regression analysis revealed that species with smaller body length and distribution area were described later, and that these two species traits are also correlated. According to two predictive models and several scenarios, we estimated that at least 25% of the Brazilian amphibian species have not yet been described. Our findings highlight the maintenance of significant Linnaean and Wallacean shortfalls in the knowledge of Brazilian amphibian species, despite of the increasing research efforts. The northern (Amazon) and central region (Cerrado) of Brazil should be priority areas for herpetological research. Society and the scientific community must commit to a greater investment in biodiversity knowledge to improve conservation strategies before the described and undescribed species become extinct.