Patronus charm: a comparison of benefactor plants and climate mediation effects on diversity

Deserts are subject to significant anthropogenic pressure. The capacity to buffer against changes in the local environment and biodiversity are critical for ecosystem functioning. Foundation species can be a solution to rapidly assess ecological function and provide a simple nature-based solution to protect against continuing biodiversity losses. A foundation species is defined as a species that exerts and promotes a positive set of processes for the biotic network. Two different shrub species in the central drylands of California were used to assay a potential buffer for plant species richness and to examine the species-specificity of foundation facilitation. A five-year dataset in two distinct regions differing in aridity was used to test the hypothesis that the direct effects of foundation plants facilitate other plant species and buffer diversity losses to a changing climate. The predicted positive effects of both shrub species on species richness increased with increasing local temperatures sampled. Finally, projected temperature increases for the region in trained Bayesian models demonstrated that both shrub species can profoundly increase in their capacity to facilitate plant species richness. Colloquially, this positive ecological effect can be described as the patronus charm hypothesis because regardless of the form of the protector, shrub species provided a talisman against local loss of richness driven by temperature increases.