Geographic variation in shape and size of anuran tadpoles: Interpopulation comparisons in Scinax fuscovarius (Anura, Hylidae)

Abstract

Among anuran species with biphasic life cycle, the occurrence of intraspecific larval morphotypes has been related to variations in developmental time, diet, geographical variation, or response to predators. Here, we evaluated the external morphological variation of larvae among three populations, located more than 270 km apart, of the anuran hylid Scinax fuscovarius by linear and geometric methods, to elucidate the presence of geographically different morphs. Comparisons targeted development, growth, and external morphology. Studied populations exhibited differences in reproductive seasonality, growth rate, timing of development, shape, and size. Shape and size comparisons revealed two well-differentiated morphs, one of them shared by the two closest populations. Morphological differences evidenced a smaller and depressed form of the entire body plan in the most distant population, which showed continuous reproduction throughout the rainy season and under more unpredictable conditions. We interpret the occurrence of the two different larval morphs in S. fuscovarius as a by-product of local geographical conditions, and discuss on possible associations with biotic and abiotic factors cues.