Flores Martínez, Alejandro , Manzanero Medina, Gladys Isabel , Mandujano, Maria .
Population dynamics of an endangered endemic rupiculous cactus.
We studied the demography of two populations of Mammillaria huitzilopochtli an endemic species of Cactaceae inhabiting cliffs in the semiarid TehuacÃ¡n-CuicatlÃ¡n region of Mexico. Censuses were conducted over a five year period in different populations established at two contrasting management scenarios: a disturbed site (PDS) subject to extraction of materials for highway construction, and a well-preserved site (PPS). Our aim was to determine how management scenarios affected demographic parameters and life history components, and to assess the demographic performance of the species under simulated scenarios that could be useful for management. Five annual size-based and a mean transition matrices of each population were constructed to estimate population growth rates, population structure and reproductive values. Perturbation analyses were also used to assess the effect of changes of seedling and adult survival and individual growth on the finite rate of population increase. The population in PDS showed lower population growth rates than those at PCS. The elasticity values were highest for matrix entries corresponding to plants remaining in the same category (stasis) in the disturbed site, in contrast to the conserved site where elasticities were more related to growth than stasis. All simulations suggested population decline in PDS while population decline was only detected in PCS with decreasing seed survival. Population growth rates, elasticity and reproductive values showed between year variations, the variation is partially due to disturbance and its effect on reproduction and survival. This species is susceptible to disturbance, and the most important life history attributes is seedling survival which is limited by the highly restrictive habitat conditions found in cliffs. Our data suggest that the species in disturbed habitats have an increased risk of local extinction than those living on relatively less disturbed habitats. The conservation of Mammillaria huitzilopochtli mainly relies on the protection of its habitat.
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1 - Centro Interdisciplinario de Investigación para el Desarrollo Integral, Hornos 1003, Santa Cruz Xoxocotlán, Oaxaca, 71230, México
2 - Instituto de Ecología, UNAM, Ecologa de la Biodiversidad, Universidad Nacional Autónoma de México, Apdo. Postal 70-275, México D. F., México D. F., 04510, México
Population Viability Analysis (PVA)
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM