Distribution and diversity patterns of soil mites and other microarthropods in a Chihuahuan desert site

Abstract

This paper reports the results of a pilot survey of the patterns of distribution and species diversity of soil microarthropods from 12 different sites in a Chihuahuan Desert watershed in southern New Mexico. A total of 18 orders of arthropods was recorded from 49 samples, distributed across this watershed. Mites and Collembola predominated throughout. Mites were more abundant than Collembola in all sites except in Prosopis litter from the edge of a playa. At this site, collembolan density was estimated to be 24,460/m 2 . Four orders of mites occurred in the sites surveyed: Prostigmata, Cryptostigmata, Mesostigmata and Astigmata. The last-named group was so infrequent that it was not considered further. The Mesostigmata were numerous only in Atriplex litter. Prostigmata and Cryptostigmata were equally abundant at only two sites: the litter under Prosopis on the bajada site and the mineral soil under Fallugia. Elsewhere, Cryptostigmata tended to be more numerous than Prostigmata where the organic content of the substratum was high (> 30%) and vice versa. The highest total mite density occurred in the Juniperus litter (29, 486/m 2 ), the lowest in Larrea litter (8274/m 2 ). These estimates are considerably higher than those recorded from a Juniperus site in the more arid Mojave Desert, but they are much lower than densities considered typical of cool, moist temperate deciduous forests. The densities of Prostigmata and Mesostigmata compare favourably with those reported from sites with similar rainfall in Australia. Cryptostigmatid densities are much higher in the Chihuahuan sites, however. An Index of Diversity, calculated for the various groups of microarthropods at the 12 sites, was very variable, but values approximating to those reported for the microarthropod fauna of an English beech woodland were obtained for several sites. The equitability component of this species diversity provided a good indicator of the relative stability of the sites studied.