Filogeografia em lagartos no baixo Tocantins, Ilha do Marajó e Sul do Amapá

Abstract

Filogeographical studies have helped to clarify the spatial and temporal context of the diversification of organisms from Amazonian, which can be directly compared with specific geological scenarios. This study aims to contribute with the reconstitution of the recent history of low Tocantins/Marajó Island from a philogeographical analysis of Gonatodes humeralis and Kentropyx calcarata. The questions to be answered are whether there is a distinction among the population of the southern Amapá, Marajó Island, and each side of the Tocantins river, and how these populations interrelate one each other. In addition, this work also aims to assess the usefulness of the gene cytochrome oxidase I as a marker for studies of lizard populations. Data from 49 specimens of G. humeralis and 32 of K. calcarata from 14 localities in southern Amapá, low Tocantins, Marajó Island, and of an external population of the focal area of study, in the city of Itaituba, Pará, were analyzed. The molecular studies were based on mitochondrial gene cytochrome oxidase I. The levels of genetic variability were calculated: diversity of nucleotides (π) and diversity of haplotypes (h), the genetic differentiation through the analysis of molecular variance (AMOVA) and the estimates of Fst for pairs of populations and distribution of the differences between pairs of sequences. It was used a statistical test to detect possible R2 events of recent demographic expansion. The phylogenetic relations between populations were evaluated by the construction of non-rooted trees using the methods of maximum parsimony (MP) and maximum likelihood (MV). The results show that although the COI has been rarely used for this purpose, the observed variation in sequences of populations of G. humeralis and K. calcarata indicates that it is a useful marker for Phylogeographic analysis. The five populations of both species studied here, are genetically structured. This indicates a low or, more probably, inexistent gene flow among them. The observed Phylogeographic relations, although more certainly to G. humeralis than K. calcarata, indicates that significant changes have occurred in relatively recent times in the drainage system in the low Tocantins river and Marajo island. This is due strong indications, obtained in this study, that in recent past there was more movement, active or passive, of the species between regions of Marajo and west of the Tocantins river that would have been the most directly affected by these changes.