Implications of the Last Glacial Maximum on the Genetic Diversity of Six Co-Distributed Taxa in the Baja California Peninsula

Aim

During the Last Glacial Maximum, the temperature in the Baja California Peninsula decreased and the precipitation increased compared to present climatic conditions. These changes influenced the geographic distribution and the demographic processes of plants and animals. This article aims to determine how Pleistocene and current climate impacted the geographic distribution and the genetic diversity patterns of six species co-distributed in the Baja California Peninsula.

Location

Northwest Mexico.

Taxon

A group of six species with desert affinities, two cacti (Pachycereus pringlei and Stenocereus gummosus), one spider (Pardosa sierra), one reptile (Dipsosaurus dorsalis) and two birds (Melanerpes uropygialis and Basilinna xantusii).

Methods

Meta-analysis of published microsatellite data was carried out for the previously mentioned species. Hierarchical generalised additive models (HGAMs) were used to assess the relationship between genetic diversity values and six abiotic predictors (latitude, elevation, current climate, habitat suitability, climatic stability and habitat suitability stability from the Last Glacial Maximum to the present). The change in the distribution range from the Last Glacial Maximum to the present was found using potential distribution models (PDMs).

Results

HGAMs revealed that M. uropygialis showed a significant relationship between genetic diversity and climatic stability, while the genetic diversity of D. dorsalis responded to the current climate. The genetic diversity of M. uropygialis and P. pringlei was affected by habitat suitability change while in B. xantusii, genetic diversity changed with current habitat suitability. According to potential distribution models, four areas of northwest Mexico functioned as a refuge during the Last Glacial Maximum: the south of the peninsula, the region between the western tip of the Vizcaíno peninsula and Cedros Island, the upper Gulf of California and the coasts of Sonora. However, only the spatial patterns of predicted genetic diversity of M. uropygialis coincide with the location of Pleistocene refugia.

Main Conclusions

No evidence was found of a concerted response of species to climate change during the Pleistocene, only one species showed evidence of discrete Pleistocene refugia and climatic stability and habitat suitability are not always conducive to higher genetic diversity values.