Estrutura da taxocenose de lagartos em uma região de dunas no semiárido brasileiro: avaliando a influência de fatores históricos e ecológicos

Abstract

Studies on taxocene structure seek to understand the mechanisms responsible for species organization in natural environments. Aspects such as species richness and abundance, organism distribution, and resource use are important elements of this structure and have been the focus of ecological studies. We investigated the structure of a lizard taxocene in a dune area of the Brazilian semi-arid and analyzed the influence of ecological and historical factors on this structure. The study was conducted in the municipality of Casa Nova-BA, in the São Francisco River region. We quantified the trophic and morphological niche of the lizards in the community and subjected these data to a niche overlap analysis, revealing the degrees of overlap between each pair of species, as well as the overall taxocene overlap. We used the null model proposed by Geange (2011) to test whether resource use in the taxocene differed from what would be expected by chance. We submitted the proportions of each food item consumed by each species, as well as the mean of each morphological variable, to a phylogenetic principal component analysis (pPCA) to identify the influence of ecological and historical factors on the lizard community. The niche overlap analysis revealed the absence of trophic structure, indicating a low niche segregation among species. Additionally, a greater influence of ecological factors on lizard diet was observed. This, along with the considerable overlap values found between several species pairs, suggests that recent competition may be influencing the structure of the taxocene. The niche overlap results in the morphological dimension showed that the community is structured, with species being grouped. Eight out of ten morphological variables were responsible for niche partitioning, and the highest overlaps occurred among closely related species. The pPCA results for morphology indicated a greater influence of historical factors on the Casa Nova taxocene, highlighting a set of morphological attributes that separate lizards into distinct niche dimensions, allowing them to occupy and explore different microhabitats. This morphological pattern is similar to that found in other studies on lizard taxocenes in Neotropical regions and points to strong niche conservatism.