Historical Temperature Stability and Environmental Drivers Shape Patterns of Phylogenetic Diversity in Cactaceae

Abstract

Aim We aim to investigate the environmental drivers shaping macroecological patterns of phylogenetic structure in plants, using the cactus family (Cactaceae) as a model group. Major Taxa and Location Cactus family (Cactaceae), comprising 1892 species, distributed across the American continent (approximately 42 million km 2 ). Methods We compiled a robust dataset of 435,694 occurrence records and estimated two complementary metrics of phylogenetic structure: the standardised effect size of mean phylogenetic distance (ses.MPD, reflecting deep/basal lineages) and mean nearest taxon distance (ses.MNTD, reflecting recent/tip lineages). We also assessed the effects of climatic, topographic, and soil‐related variables on phylogenetic structure metrics at regional and continental scale. Results Phylogenetic structure in cacti is shaped by complex spatial interactions among environmental drivers varying across scales. Northern Mesoamerica—including central and northern Mexico and the southwestern United States—showed the highest ses.MPD but some of the lowest ses.MNTD values. This indicates that these regions harbour deeply divergent lineages while local communities remain composed of closely related species. Other regions, such as high‐elevation areas in South America, also showed high ses.MPD and ses.MNTD, indicating both deep and recent phylogenetic divergence. ses.MPD and ses.MNTD responded differently to environmental gradients, indicating that basal and tip lineages are influenced by different factors. Historical temperature stability (calculated as the temperature delta between the last glacial maximum and the present) was the strongest predictor of phylogenetic structure, mainly on a regional scale. Solar radiation and elevation, at the continental scale, also contributed to these patterns, indicating that topographic complexity and climatic drives recent phylogenetic divergence. Main Conclusions Cactus phylogenetic diversity is primarily driven by historical temperature stability but results from the combined influence of multiple environmental drivers acting across scales. These scale‐dependent effects reveal that cactus communities reflect both contemporary conditions and long‐term evolutionary constraints. Given the link between PD, ecosystem functioning, and conservation value, high‐PD regions, especially those with stable climates and heterogeneous topography, should be prioritized for conservation.

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