Association pattenrn and plant community of Echinomastus unguispinus a rare cactus from northern México

Background/Question/Methods The status of endangered species relies on a basic framework of information that can be used to evaluate their conservation status and propose management plans. Echinomastus unguispinus is a globose cactus distributed in the northern states of the Chihuahuan Desert, Mexico. Even though it is considered endangered by the Mexican red species list, there is currently no basic ecological information that can be used to assess its true status. In this study, we describe the distribution, association pattern (nurse-protegé relationship) and plant community to determine a preliminary conservation status of Echinomastus unguispinus. Fieldwork was conducted in the Mapimi Biosphere reserve (MBR) in the Southern Chihuahuan Desert Mexico. We set up twelve 20 by 30 transects at five locations were populations of E unguispinus were located. The transects were used as grids in which individual plants were measured and located in x y coordinates. We determined distribution patterns of individuals and created vegetation to determine the tendency of association with nurse plants. We correlated Shannon's diversity index of the plant community with population density of Echinomastus unguispinus. Results/Conclusions We found that the species tends to have a random distribution (IH= 0.4696), however, 63% of the individuals were associated with a nurse plant, and a positive relationship existed between Shannon's diversity index and the population density of Echinomastus unguispinus. Even though individuals appear to be associated to nurse plants, the random distribution pattern suggests that it may not be restricted to the identity of the nurse plant. The fact that a positive correlation exists between the diversity of the plant community and the density of E. unguispinus tells us that the conservation of this rare species will largely depend on the conservation of its habitat.