The Spiders of the Churince Region, Cuatro Ciénegas Basin: A Comparison with Other Desert Areas of North America

Abstract

In this study we compare the arachnofauna of the region known as Churince, in the Cuatro Ciénegas Basin (CCB), with the spider communities found in other localities of the North American deserts. We also compare the communities found in the main vegetation types of study site. The spiders of North American deserts were grouped according to biogeographical regions. The only exception was White Sands, which is part of the northern Trans-Pecos subregion of the Chihuahuan Desert (CD) and is an area of gypsum dunes (calcium sulphate). This unique substrate almost certainly determines the species that can be present in the area and suggests that, in addition to biogeographical patterns, local conditions may have a strong influence as filters for the species present in a particular site. Our study site (Churince) had the lowest number of species shared with the other CD sites. The Basin is located in the southern part of the CD in the Mapimí subregion and is the southernmost of all. This partially explains the differences in composition. Furthermore, the CCB probably has more species of spiders than any other of the North American desert regions. The variety of vegetation types within a relatively small area partly explains this since few species are shared among vegetation types. The CCB has a particularly high richness of wandering species of Lycosidae and Gnaphosidae. The latter is typical of the Nearctic North American deserts, but wolf spiders (Lycosidae) are frecuently found in wet environments. The family also includes a number of “supertramp” species which colonize areas after natural or anthropogenic perturbations. The climate of the CCB shows extreme variations, but, more importantly, Churince has been subject to human-induced perturbations that have increased in recent years. Although this can explain the high number of wolf spiders, it also has had a negative influence on the abundance and number of other spider families.