Are Amazonia Rivers Biogeographic Barriers for Lizards? A Study on the Geographic Variation of the Spectacled Lizard Leposoma osvaldoi Avila-Pires (Squamata, Gymnophthalmidae)

Abstract With improvements in taxonomic resolution in recent years, the Amazon basin is increasingly recognized as containing restricted-range taxa and areas of endemism. For many of these taxa, rivers delimit their geographic distributions and separate sister species. Among most lizards the geographic pattern is not clear. We attempt to determine the existence of cryptic diversity in the Spectacled Lizard Leposoma osvaldoi by analyzing the geographic variation in its morphology. We specifically tested whether the Rio Madeira, Rio Purus, Rio Aripuana, and Rio Roosevelt delimit differentiated lizard forms. Using multivariate analysis, we detected that males of L. osvaldoi have larger heads than females but females have longer bodies. Large rivers, such as the Rio Purus and Rio Madeira, do not play a significant role in the geographic variation of L. osvaldoi. However, specimens from two localities on opposite banks of the upper Rio Aripuana occupy the lower and upper ranges of variation in L. osvaldoi and ...