Evaluating the Hypothesis of Pleistocene Refugia for Mammals in the Cuatro Ciénegas Basin

Abstract

The Cuatro Cienegas Basin (CCB) in the state of Coahuila, Mexico, is a very diverse ecosystem with high endemism of flora and fauna. It is included in the Ramsar list of wetlands and considered as a priority area for conservation by the World Wildlife Fund (WWF). This site is located within the Chihuahuan Desert (CD) in an isolated area surrounded by the Sierra Madre Oriental and Sierra del Carmen. A previous study by Contreras-Balderas et al. (Southwest Nat 52:400–409, 2007) found 39 mammalian species occurring in the CCB Natural Protected Area, 30 of which are widespread. These authors concluded that there has been a long-term environmental stability in the area, based on archaeological records. In addition, the mammalian biota found is an admixture between the biotas from the Chihuahuan Biotic Province and the Tamaulipeca Province. Therefore, the aim of this study is to describe the biogeographic patterns of the mammals that occur in the CCB to determine whether this site was an important area of refuge during the Pleistocene’s climate pulses and to deepen our knowledge of the mammalian biota of the CCB. We obtained ecological niche models (ENMs) and projected them into past environmental conditions, Last Glacial Maximum (LGM) and Last Interglacial (LIG), to determine whether this area could have constituted a refuge area for mammalian species. A review of the phylogeographic studies on these species to determine whether or not the CCB could have been a Pleistocene refuge for mammalian species was also conducted. Accordingly, we expect that species that found refuge in the CCB will show high genetic variation in this area, while species that were not present in the area during the Pleistocene will show lower levels of genetic variation. According to our results, the CCB was an important area of refuge during Pleistocene climatic changes, specifically over the Sierra la Madera and Sierra San Marcos. Most mammalian species of the CCB are widespread. Results from past ENMs and phylogeographic analyses were consistent, except for five species of rodents, which did not conform to the expected patterns of genetic diversity and changes in their distribution. Most reviewed analyses failed to include an adequate sample size for Mexican populations. Therefore, conducting phylogeographic studies of these mammals in the CD is fundamental for understanding the dynamics that determined its biodiversity.