Diverse drivers of contemporary species shifts in the California flora
The differential responses of plant species to global warming are of great interest and grave concern for scientists and conservationists. We used 665234 georeferenced herbaria records to estimate geographic and climatic shifts over the past century in 4426 plant taxa from a wide range of bioclimatic life zones, functional types, and phylogeographic origins. Species distributions were estimated from the Bayesian posterior distribution of parameters defining the relative abundance of specimens of a target species along an environmental gradient, contingent on the sampling distribution of all specimens collected along the gradient, in the geographic locality of the target species.
Here we show that the distributions of species with high dispersal ability (small seeded) and that are successful in novel environments (exotic species) have shifted upward significantly, enough to maintain their thermal ranges. Endemic species have also shifted upslope, but not enough to maintain their thermal envelopes. Land use change had a large impact on the modeled species shifts, in particular by shaping the sampling distributions of specimens in regions that are currently human-impacted. These findings help explain differential observations in plant range shifts, highlighting those most vulnerable to warming.