Taxonomia das linhagens de Rhinella diptycha (Cope, 1862) do nordeste brasileiro

Abstract

The genus Rhinella is widely distributed in almost all of the American continent, from southern Texas to southern South America, characterized by great morphological diversity and species richness, composed so far by 97 species. The genus is organized in eight groups of species, among which is the group of Rhinella marina, composed of eleven valid nominal species and with extensive history of taxonomic problems. Rhinella diptycha, included in the group R. marina, presents morphological and bioacoustic variation along its geographical distribution, which indicates the possibility of R. diptycha representing a species complex. Also, recently R. jimi, a species occurring in the Brazilian Northeast, Pará and Espírito Santo was synonymized with R. diptycha based on phenotypic criteria such as presence and distribution of macroglands, and a polytomy position of R. jimi with R. diptycha. However, the external morphology analysis used low sample universe of localities and specimens. This study has as main objective to study the taxonomy of R. diptycha lineages in the northeast of Brazil. Analyses of external morphology, linear (traditional) morphometry and acoustics of the populations of Rhinella diptycha were carried out using a hypothesis-building approach, and the unified concept of species was adopted. The results indicated that, acoustically, the populations from the Northeast differ from all other populations, and have acoustic substructure for populations of high-altitude areas, forming two distinct clusters among the populations of the northeast, while differ from others localities with predominance in the difference of dominant frequency, number of pulses and call duration. The linear morphometry also indicated the formation of two main groups, being a third one related to the Serra do Espinhaço in Bahia, intermediate to the other two. The external morphology and color of the external surfaces are generally of great similarity, except for the populations of Bolivia, although it is noted that there are differences in discrete continuous traits, such as the color (e.g. pattern of spots) and presence and/or distribution of granular macroglands. Characteristics that mediate reproductive isolation were prioritized in this study. Despite having great morphological similarity, which previously caused the synonymization of R. jimi to R. diptycha, we found in this study that the population samples of R. diptycha from northeastern Brazil, formerly identified as R. jimi, differ from the other samples analyzed in this study for South America as to the parameters of the advertisement call, discrete characteristics of morphology and morphometric analysis of adults; the results obtained were consistent with the results of phylogenomic data published in the literature. The discrimination mediated by bioacoustics indicated potential pre-zygotic reproductive isolation among the studied population samples that, added to the characteristics of external and colored morphology, readily allow the identification of the samples previously associated with R. jimi. Based on the results obtained, we propose the revalidation of Rhinella jimi, elevating it to the taxonomic status of valid species. Finally, as we noted the partial acoustic and morphological differentiation in mountainous environments, indicate the development of future studies for a better understanding of the evolutionary scenario in order to understand how the environment may be acting for a morphological diversification in R. diptycha along its geographical distribution.