Ruiz González, Sylvia Patricia , Golubov, Jordan , Mandujano, Maria .
Population dynamics and association of Echinomastus unguispinus, a rare threatened cactus from northern Mexico.
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. We describe the population dynamics and association pattern (nurse-protegÃ© relationship) of Echinomastus unguispinus and the plant community present in the study sites in the MapimÃ Biosphere Reserve. We set up twelve 20 by 30 m plots in which all plants were mapped and measured. Individuals of E. unguispinus were tagged and their reproductive structures counted. The volume of each E. unguispinus plant was then used to categorize individuals into size classes and population was analyzed using standard matrix population models. A Hopkins test was performed to determine whether these populations have a random, uniform or clumped distribution. We correlated plant diversity at each plot with density of E. unguispinus and determined the importance of nurse species on the size of protÃ©gÃ©. The population density of this species was 0.05 ind/m2, similar to other cacti, however it is highly restricted to small calcareous salty hills. We found a small proportion of individuals in the smaller and largest size, which suggests low recruitment in the former and high mortality in the latter. The population was found to be at numerical equilibrium. Only 34% of all individuals appeared to be associated with a nurse plant, and only significant for seven of the fifteen perennial species found. Individual density of E. unguispinus appears to be positively correlated with species diversity. The main threat of E. unguispinus populations is the highly restrictive habitat and slow growth rates.
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1 - Universidad Autonoma Metropolitana, El Hombre y Su Ambiente, Calz. del Hueso 1100, Col. Villa Quietud, Del. Coyoacan, Mexico D. F., DF, 04960, Mexico
2 - Ciudad Universitaria, UNAM, Circuito exterior s/n anexo al Jardín Botánico Exterior, Apartado Postal 70-275, México, D.F., 04510, Mexico
pattern of association
Presentation Type: Poster:Posters for Topics
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM