Drivers of phylogenetic diversity and Cactaceae species richness in the American continent

Abstract

Biological diversity is not uniformly distributed across the planet but follows heterogeneous spatial patterns influenced by geographic, climatic, and historical factors. Understanding the relationship between species richness patterns and phylogenetic diversity, as well as how these patterns vary at different spatial scales, is crucial for conservation efforts. Using structural equation models, we investigated the direct and indirect effects (mediated by species richness) of climate, topography, and soil on the phylogenetic diversity of cacti distributed across the American continent. We found that cacti richness was a significant predictor of phylogenetic diversity. Temperature, precipitation, and solar radiation, along with topography and soil composition, positively influenced species richness and, indirectly, increased the phylogenetic diversity of cacti. Our results highlight the necessity and importance of considering multiple environmental predictors and different scales of drivers' effects to improve understanding of their impact on diversity patterns, aiming to optimize conservation strategies.