biogeography.pensoft.net
Biogeographic origins of the disjunct distribution of the chacoan Neotropical frog Pleurodema guayapae
Disjunct distributions, in which populations of a putative species are separated by large distances, represent an important, albeit poorly understood pattern in biogeography. Detailed study of these populations often reveals that they actually comprise more than one species resulting from prolonged restricted gene flow. The leptodactylid chacoan frog Pleurodema guayapae exhibits a striking disjunct distribution. Populations are well known to occur in north-central Argentina, whereas records from southern Bolivia are separated by ca. 820 km gap lacking confirmed records despite extensive surveys. In this study, we integrate molecular and paleoclimatic data to assess, 27 years after their discovery, whether the Bolivian populations are conspecific with Argentine populations and to explore the historical processes that shaped their current distribution. Despite the large geographical distance, our phylogenetic analyses based on two mitochondrial gene fragments revealed minimal divergence between Bolivian and Argentine populations, which do not form reciprocally monophyletic lineages. These results support the hypothesis that the Bolivian and Argentine populations are conspecific and present a true disjunct (i.e., bicentric) distribution resulting from recent range fragmentation rather than an ancient split. Paleoclimatic niche projections suggest a dynamic history of habitat connectivity and fragmentation. Suitable habitats were more continuous during the Last Glacial Maximum, became fragmented afterward, and then reconnected between ca. 8–13 ka; however, fragmentations during later climatic oscillations likely led to further range contractions and local extinctions that produced the current disjunct pattern observed in the species. Overall, our results support an intriguing case of conspecific disjunct distribution driven by historical climatic oscillations. Highlights We report a true disjunct distribution in amphibians. Molecular data confirm that Bolivian populations of Pleurodema guayapae are conspecific with Argentine populations. Pleurodema guayapae exhibits a true disjunct distribution, whose geographical clusters are separated by ca. 800 km. This disjunct distribution is best explained by climatic oscillations during the Last Glacial Maximum and Holocene.
