ABSTRACT
Historical processes that have interrupted gene flow between distinct evolutionary lineages have played a fundamental role in the evolution of the enormous diversity of species found in the Neotropical region. Numerous studies have discussed the role of geographic barriers and Pleistocene forest refugia in the diversification of the region's biodiversity. In the present study, we investigated the relative contribution of these different factors to the evolutionary history of Pithecopus nordestinus, a Neotropical tree frog, which is amply distributed in the Brazilian Atlantic Forest and adjacent areas of the Caatinga biome. We used an extensive sample and multilocus DNA sequences to provide an overview of the intraspecific genetic diversity of P. nordestinus, characterize historical diversification patterns, and identify possible phylogenetic splits. We tested different scenarios of diversification based on Pleistocene Refugia and river barrier models using approximate Bayesian computation (ABC) and ecological niche modeling (ENM). The phylogenetic approach indicate the occurrence of processes of phylogeographic divergence in both time and space, related to historical shifts in the course of the São Francisco River during Plio-Pleistocene period, resulting in two principal, highly divergent clades. The ABC model provided strong statistical support for this scenario, confirming the hypothesis that the São Francisco River acted as an effective geographical barrier during vicariant events in the evolutionary history of P. nordestinus. We believe that the climatic changes that occurred during the Pleistocene also played a secondary role in the genetic signatures identified, reinforcing the divergence of populations isolated by physical barriers. These findings reinforce the conclusion that the two models of diversification (geographic barriers and refugia) are not mutually exclusive in the Neotropical domain but may interact extensively during the diversification of species on a regional scale.
ABSTRACT
The Brazilian Atlantic Forest has long been considered a global biodiversity hotspot. In the last decade, the phylogeographic patterns of endemic taxa have been unraveling the biogeographic history of the biome. However, highly diverse invertebrate species have still been poorly studied. Sodreana harvestmen (Gonyleptidae) are distributed in most of the humid coastal forests in the southern portion of the Atlantic Forest, a region that has experienced complex topographic evolution and differing climatic conditions since the Early Cretaceous, which likely affected the geographic distribution and diversification of the group. In this study, we investigated the molecular phylogeny and phylogeography of Sodreana to clarify the species relationships and to make inferences about the historical biogeography of the southern Atlantic Forest. We applied coalescent-based phylogenetic analyses using one mitochondrial and three nuclear markers coupled with an ecological niche modeling approach to verify relationships among species, date the main divergence events in the genus, and make inferences concerning possible changes in the geographical distribution and population dynamics from the past. Our results supported the validity of most Sodreana species and suggested that Paleogene-Neogene geomorphologic processes such as the formation of rivers systems, uplift of mountain ranges and related environmental changes have profoundly affected the evolutionary history of Sodreana. The ecological niche models showed that the areas potentially occupied by the species were greatly reduced during Quaternary glacial periods but no recent lineage divergences or genetic bottlenecks were detected, suggesting that climatically stable micro-habitats could have helped maintain populations during drier periods. Our study highlights the importance of humidity-dependent and poor-dispersal taxa in understanding the effects of ancient geological and climate processes on the Atlantic Forest biota.
