Incipient speciation in the Chihuahuan Desert shrub Berberis trifoliolata under divergent climate scenarios

The discovery of biotic and ecological factors that influence genetic isolation in populations contributes to our understanding of speciation, one of the most important issues in evolutionary biology. In this paper, we ask whether differences in climate preferences are influencing genetic isolation in two assemblages of populations of Berberis trifoliolata Moric., the Northeastern and the Mexican Plateau groups. Agarito, as this species is known, is a remarkable shrub in the arid regions of North America and found mostly in the Chihuahuan Desert. Ecological niche modeling and two tests of niche evolution were carried out. The Ecological Niche Modeling suggests that the potential distribution of the Northeastern group does not predict that of the Mexican Plateau group, and nor does the latter predict the former. Tests of niche evolution indicate a divergent niche between these two groups. Among the most important climate factors detected in the multivariate niche evolution test are mean annual temperature and annual precipitation. We concluded that the two lineages exemplify an incipient speciation process.