Geographic distribution patterns of the genus Ariocarpus (Cactaceae) in Tamaulipas, Mexico

Abstract

The geographic distribution of the genus Ariocarpus in the State of Tamaulipas, Mexico was determined based on literature, herbarium vouchers, botanical gardens and several field trips in 1991 and 1992. Three species and two subspecies were detected: Ariocarpus agavoides, A. kotschoubeyanus, A. retusus subsp. retusus and A retusus subsp. trigonus. Ariocarpus agavoides is extremely restricted geographically, occupying an area less than 2 km²; the main factor responsible for its distribution is soil type, which has clay texture, low organic matter content and a slightly alkaline pH.Ariocarpus retusus subsp. trigonus has the largest distribution (all the arid and semiarid portions of the state) probably because of its tolerance to different ecological factors, such as vegetation, soil types, and its ability to survive even if nurse plants were removed.