Multi-dimensional biodiversity hotspots and the future of taxonomic, ecological, and phylogenetic diversity: a case study of North American rodents

Aim: We investigate geographic patterns across taxonomic, ecological, and phylogenetic diversity to test for spatial (in)congruency and identify aggregate diversity hotspots in relation to present land-use and future climate. Simulating extinctions of imperiled species, we demonstrate where losses across diversity dimensions and geography are predicted.

Location: North America

Time period: Present-day, future

Major taxa studied: Rodentia

Methods: Using geographic range maps for rodent species, we quantified spatial patterns for eleven dimensions of diversity: taxonomic (species, range-weighted), ecological (body size, diet, habitat), phylogenetic (mean, variance, and nearest-neighbor patristic distances, phylogenetic distance, genus-to-species ratio) and phyloendemism. We tested for correlations across dimensions and used spatial residual analyses to illustrate regions of pronounced diversity. We aggregated diversity hotspots in relation to land-use and climate-change predictions and recalculated metrics following extinctions of IUCN-listed imperiled species.

Results: Topographically-complex western North America hosts high diversity across multiple dimensions: phyloendemism and ecological diversity exceed predictions based on taxonomic richness and phylogenetic variance patterns indicate steep gradients in phylogenetic turnover. While an aggregate diversity hotspot emerges in the west, spatial incongruence exists across diversity dimensions at the continental scale. Notably, phylogenetic metrics are uncorrelated with ecological diversity. Diversity hotspots overlap with land-use and climate change, and extinctions predicted by IUCN status are unevenly distributed across space, phylogeny, or ecological groups.

Main conclusions: Comparison of taxonomic, ecological, and phylogenetic diversity patterns for North American rodents clearly shows the multifaceted nature of biodiversity. Testing for geographic patterns and (in)congruency across dimensions of diversity facilitates investigation into underlying ecological and evolutionary processes. The geographic scope of this analysis suggests that several explicit regional challenges face North American rodent fauna in the future. Simultaneous consideration of multidimensional biodiversity allows us to assess what critical functions or evolutionary history we might lose with future extinctions and maximize the potential of our conservation efforts.