How do altitude and soil properties influence the taxonomic and phylogenetic structure and diversity of Brazilian páramo vegetation?

Abstract

Altitude and environmental variables such as edaphic properties are considered determinants of species distribution and community composition in mountain ecosystems. Here, we aimed to outline the effects of distinct mountain peaks, altitude and soil properties on community composition, species density, phylogenetic structure and diversity of angiosperm paramo communities from the Serra do Brigadeiro State Park, Minas Gerais, southeastern Brazil. For that, we identified all angiosperm species found in 300 plots (1 m × 1 m) from three mountain peaks, measured soil depth and analyzed soil fertility and texture in each plot. To reduce the number of soil variables and species composition, we computed principal coordinates based on soil properties and principal coordinates based on species-plot matrix for each plot. Furthermore, we computed the standard effect sizes of the mean phylogenetic pairwise distance and the mean nearest phylogenetic taxon distance for each plot to investigate differences in the degree of relatedness among coexisting species. We compared differences in response variables between peaks and modelled them in function of altitude and principle components of soil properties using mixed effect models. Species density and phylogenetic diversity differed between peaks, but, contrary to the previous findings, no relationships between species richness or phylogenetic diversity and altitude or soil properties were found, indicating that further investigations are necessary to understand the altitude-biodiversity relationship in Brazilian paramo vegetation. Community composition differed between peaks and depended on altitude, soil properties and interactions between them, indicating that upward shifting of bioclimatic conditions due to climate changes may alter communities of this ecosystem. Phylogenetic structure differed between peaks and was influenced by altitude and soil properties. As phylogenetic clustering increased with altitude, eventual upward movements of species in Brazilian paramo vegetation due to climate change may alter community composition and the degree of relatedness among coexisting species, increasing the risk of species from higher altitudes to disappear. Therefore, conservation priorities arise for higher landscape portions, where these high altitude species may find refuges.