Filogeografia comparativa e diversidade genética de espécies do gênero Hylaeamys (Rodentia: Sigmodontidae)

Abstract

Phylogeographic studies have helped clarify the spatial and temporal context of the diversification of Amazonian organisms. Given the current state of environmental degradation and the future impacts expected from the implementation of developmental plans proposed for the Amazon region, it is necessary to understand the evolutionary dynamics of the biota of the Amazon lowland forest. Therefore, the goal of this study was to provide information that increases the taxonomic and biological knowledge for the species of the genus Hylaeamys (H. megacephalus, H. yunganus and H. perenensis), which have predominantly Amazonian distribution, testing the existence of population structure for each species and if this structure is concordant with their geographical distribution. We used a total of 254 individuals sampled over 43 locations; 151 individuals of H. megacephalus from 35 localities, 80 individuals of H. perenensis from 14 localities and 23 individuals of H. yunganus from 8 localities. Molecular studies were based on the sequencing of 947 base pairs of the mitochondrial cytochrome b gene The phylogenetic relationships were assessed by the construction of trees by the method of maximum likelihood (ML) and genetic differentiation through analysis of molecular variance (AMOVA) and Fst estimates. For H. perenensis, AMOVA analysis performed to test the population structure considering the Jurua River as geographical barrier, revealed that most of the variance (96.15%) was within localities and only 3.85% (Fst = 0.03851, P = 0.00366) of the variation could be explained by differences between localities. Even considering an Nm = 12.48, Fst values were significant, indicating a moderate genetic structure. For H. yunganus, considering the low number of samples obtained, it was not possible to address the issue of the rivers as a barrier through a population-genetic analysis. Considering only the distribution of haplotypes, the results are similar to those reported by Patton and colleagues (2000), where the Juruá River is not a barrier to gene flow. For H. megacephalus, the ML tree topology revealed the presence of four structured, geographically distinct clades with high support and average genetic distance between them of 4.8%, ranging from 0.2% to 9.6%. In the work of Patton et al. (2000) and Costa (2003), the average values of genetic distances (5.3% and 8.7%, respectively) were similar to those found in this study (7% and 8%) for populations north and south Amazon River. In this scenario, the genetic diversity by H. megacephalus is consistent with the model of allopatric speciation, and the Amazon River acting as a geographical barrier to gene flow. The levels of genetic divergence, considering the values reported for rodents in the literature, do not allow completely to dismiss the possible existence of a complex of species in what is now recognized as H. megacephalus. However, to establish the taxonomic status of the four lineages recognized, it would be necessary to conduct additional analyses of morphological, ecological, and natural history data.