The importance of native shrubs on the distribution and diversity of reptiles and amphibians in the central drylands of Southwestern USA.

Conservation and management of drylands is a global challenge. Key attributes of these ecosystems, such as dominant vegetation including shrubs, can provide a crucial mechanism to inform conservation strategies. The shrub species Ephedra californica and Larrea tridentata are common native shrub species within the deserts of California and frequently benefit other plant and animal species. Here, we tested the hypothesis that shrubs support reptile and amphibian communities through relative increases in available habitat, estimated through increasing shrub densities at the site level. Reported occurrence data from the Global Biodiversity Information Facility (GBIF) and high-resolution satellite images were used to test for local-to-regional patterns in reptile and amphibian distribution and diversity by shrub densities at sites. At 43 distinct sites, the relationship between shrub density and reported reptile and amphibian communities was also tested. A total of 71 reptile and amphibian species were reported regionally. Increases in shrub density across sites positively influenced the relative abundance and richness of reptiles and amphibians observed. Moreover, increasing shrub density also had a positive influence on species evenness. Aridity differences between sites did not significantly influence the relationship between shrub density and reptiles and amphibians suggesting that the relationship was robust. This study highlights the importance of foundational shrub species in supporting reptile and amphibian communities in arid and semi-arid regions. Large-scale patterns of biodiversity in deserts can be supported by positive plant-animal interactions including small islands of fertility and resources for animals in the context of a warming climate.