Delimitação e diversidade genética de espécies de Physalaemus Fitzinger, 1826 (Anura: Leptodactylidae) associadas à Caatinga, nordeste do Brasil

Abstract

The leptodactylid genus Physalaemus Fitzinger, 1826 currently houses 49 species, arranged in two large clades: P. signifer and P. cuvieri. The P. cuvieri species group includes ten species: P. albifrons, P. albonotatus, P. centralis, P. cuqui, P. cuvieri, P. ephippifer, P. erikae, P. fischeri, P. kroyeri and P. atim. They are small to medium-sized species, measuring 1.5 to 4 centimeters and are morphologically conserved, which makes it difficult to delimit species within the group. Thus, they are mainly identified based on acoustic characters. They are widely distributed in South America, occurring in all biomes on the diagonal of open formations. Driven by advances in molecular techniques, recent studies have revealed a high genetic diversity and the existence of cryptic lineages not described in the P. cuvieri species group. However, studies about species delimitation using genetic data are still scarce for Physalaemus, especially for species that occur along the Caatinga, in northeastern Brazil, where only a few localities have been sampled to date. Even so, the few locations sampled harbor highly structured lineages. Five species of the P. cuvieri species group are recognized in Northeastern Brazil: P. albifrons, P. centralis, P. kroyeri, P. cuvieri and P. erikae (the only one that has no record of distribution in the Caatinga). In addition to these, P. cicada is also widely distributed in the Caatinga and for this reason is included in the present study, even though it is not part of the group of species in question. In this context, given the high genetic diversity previously described for the P. cuvieri species group, the recognition of regionally well-structured cryptic lineages and the scarcity of data for Northeastern Brazil, the present study seeks to generate genetic data for the species of Physalaemus that are distributed in the Caatinga, aiming to fill sampling gaps in the region and for this we: 1) expanded the sampling of the Brazilian northeast, with a main focus on the Caatinga, adding locations not sampled in previous studies, 2) we analyzed the evolutionary lineages of the Northeastern Brazil and 3) we used species delimitation methods based on mitochondrial DNA sequences from a single locus. Our results recovered two lineages of P. albifrons, one widely distributed in the Caatinga and the other with a restricted distribution in the extreme south of the biome. Two lineages of P. cuvieri were recovered occurring in the Caatinga, one restricted to Chapada Diamantina. Whereas Physalaemus ephippifer and lineage 1 of “P. cuvieri” were recovered as a single lineage. Everything that was considered P. cuvieri above the São Francisco River was recovering being genetically closer to P. ephippifer. Finally, two distinct lineages of Physalaemus cicada were recovered with 8% of genetic distance for the mitochondrial gene 16S. One of them has a restricted distribution in the Caatinga of southern Bahia (and in ecotone regions), whereas the other is distributed in the northern portion of the Caatinga, possibly being a new species. Thus, our results reinforce the idea that the species of the P. cuvieri species group are morphologically cryptic and shed light on other possible species complexes that may exhibit high levels of cryptic morphology, such as the two lineages of P. cicada and P. albifrons recovered. Thus, we reinforce the importance of integrative studies, which use genetic, morphological and acoustic data together, aiming at the taxonomic resolution of these taxa, which can help in future proposals for conservation strategies in the Caatinga.