Old climatically-buffered infertile landscapes (OCBILs): more than harsh habitats, Atlantic Forest inselbergs can be drivers of evolutionary diversity

Abstract

Granite-gneiss rock outcrop inselbergs are ancient stable ecosystems with old, climatically-buffered infertile landscapes (OCBILs). Although inselbergs provide key ecosystem services, little is done for their conservation and, so far, a lot of their unknown evolutionary history has already been lost by human activities. Using a fine-scale approach, here we tested if habitat and environmental filtering (the inselberg’s harshness) affect the evolutionary diversity of an Atlantic Forest inselberg in Brazil. We recorded all trees with a diameter at breast height ≥ 5 cm in 20 plots in four habitat types (total sampled area of 0.8 hectares), from highest to lowest: island, hillside, foothill, and semideciduous forest (matrix). We also collected soil samples for chemical, textural and physical soil characterization. We fitted linear models to test the effects of soil and habitat on plot-level metrics of phylogenetic diversity and structure, lineage diversity, phylogenetic β-diversity, and evolutionary distinctiveness. We found that the upper inselberg habitats contain a distinct set of ancient, closely related, harsh-tolerant lineages, as well as a subset of lineages that persist under harsh conditions with a certain degree of water availability. The inferior inselberg habitats harbor higher lineage diversity than expected by chance. Soil strongly predicted evolutionary diversity. We concluded that soil depth, slope, nutrients and texture (environmental filtering) and habitat types and topography (habitat filtering) shape the evolutionary history contained in fine-scale inselberg habitats, which should encourage the conservation of these ancient ecosystems.