Desvinculando as etapas da especiação: fatores geográficos levam a mudanças no sinal sexual de uma rãzinha-de-liteira por meio da variação do tamanho corporal

Abstract

Geographical and environmental distances influence the divergence of characters between biological populations, especially on a macro spatial scale, making it difficult to interpret the individual contribution of these predictor variables in the process of differentiation between populations. Anurans are excellent models for multi-character evolutionary studies, due to their low vagility and frequent territoriality, causing certain environmental changes to result in barriers that isolate populations. Accordingly, we propose to test the correlation of environmental and geographical distances with phenotypic and genotypic population characters in the absence of evident vicariant barriers using as a study model an Amazonian litter-frog. We tested the general hypothesis that geographic and environmental differentiations affect the variation in the morphometric, acoustic and genetic characters of Allobates sumtuosus along a latitudinal gradient at a fine spatial scale. All data sets with the exception of those involving genetic distance showed correlation. Controlling the effect of the different data sets, we observed that the geographical distance showed a greater number of correlations, with an explanatory force always greater than 60%. The geographical distance associated with the environmental distance likely shapes the acoustic characters of populations of A. sumtuosus by means of pressures on body size. This is because the climatic environmental gradient along the latitudinal gradient results in changes to the area-volume relationship of individuals, maximizing survival rate and resulting in larger body sizes at locations closer to the Equator. Consequently, the acoustic signals diverge due to variations in the organs involved in vocalization. Despite showing the presence of an intrapopulation genetic structure for this species, this structure was not associated with phenotypic variations. In summary, this study breaks down the stages of speciation in an Amazonian frog, demonstrating that environmental factors can lead to changes in the sexual signal of a litter-frog due to the variation in body size.