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.