Preenchendo lacunas: um olhar para os pequenos mamíferos amazônicos

Abstract

Although the Amazon is one of the most biodiverse areas in the world, information about its richness is still incipient, namely species distribution and boundaries, phylogenetic relationships and biogeographic patterns. Among mammals, small non-volant mammals are particularly poorly known, including basic knowledge of number and distribution of species. This thesis aims to narrow this gap, referred as Linnean and Wallacean shortfall. To do so we collected and examined specimens from poorly known regions in the Amazon, with the goal to conduct studies on systematics and distributional patterns of small mammals, especially marsupials. Our analyses relied on classical morphometric and morphological tools, as well as molecular data. The first chapter investigate the genetic diversity of the slender mouse opossums of the Marmosopos pinheroi complex, that includes Marmosops marina - a species recently described on morphological basis. Our goal was to test whether the proposed taxonomic arrangement for this species complex was sustained with the addition of molecular data and the use of species delimitation analyzes, and to propose a model for the diversification of this species in the Tapajós River region. We concluded that he diversity of the species complex to which M. marina belongs is underestimated by its morphology. The scenario with three species is the most parsimonious based on molecular data, although the four and five species scenarios cannot be discarded. Also, we identified that the emergence of the taxon probably took place at the Pliocene and that the Tapajós river acts as an effective barrier to gene flow between the analyzed populations and, consequently, plays an important role on distribution patterns of this group. In the second chapter, we analyze the morphology of M. marina, trying to elucidate how it varies in the specific region of Tapajós. We were not successful in finding robust morphological characters to distinguish the lineages across riverbanks identified in the previous chapter, thus sustaining the cohesion of the species. However, some characters have shown some degree of variation, departing to some extent from the original description of M. marina. The third chapter is based on a mammal survey and its richness account in an area close to the drain of the Madeira River and the metropolitan region of Manaus. We noticed that the observed richness of mammals in this paper was underestimated, registering three possible new taxa and reporting the increase of the distribution for two different species. In the fourth chapter, we analyzed and identified a set of specimens that were collected prior to the flooding of the Belo Monte dam area in the Xingú River. One of the analyzed specimens belong to Marmosa lepida, a poorly known and seldomly trapped marsupial. More efforts, including faunal inventories and systematic studies, are still badly needed to achieve a reasonable understanding of the diversity and the process underlying the emergence and the distribution of one of most distinctive groups that the Amazonia is home to.