PARENT SESSION
Poster Session 36: Genetics / Population Ecology
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Ecological implications of spatial and temporal variation for sustainable harvesting of Thrinax radiata , an endangered palm.

Calvo-Irabien, Luz Maria^*,1, Ceballos-Gonzalez, Gerardo¹, Mondragon, Demetria², ¹ Centro de Investigacion Cientifica de Yucatan, A. C., Merida, Yucatan, Mexico² Centro Interdisciplinario de Investigacion para el Desarrollo Integral y Regional, Oaxaca, Oaxaca, Mexico

ABSTRACT- Thrinax radiata a palm traditionally used by the Mayans is officially listed as an endangered species in Mexico. Recently, adults are extensively used and persistence of natural populations is threatened by overexploitation and habitat loss. As part of a management plan, a sustainable harvest model was developed based on data from a five year demographic study in community-owned forests. Demographic population viability analysis was used to evaluate the effect of different harvesting regimes. Survivorship, growth and reproduction patterns were obtained from three populations in NW Quintana Roo. Transition probabilities were estimated and using Lefkovitch matrices population finite growth rate (),as well as sensitivity and elasticity matrices were calculated. Temporal and spatial variation in population dynamics were incorporated into the model to calculate the stochastic values of and the quasi extinction probability. To estimate sustainable harvest intensities we simulated the quasi extinction probabilities for a 50 year period substracting different percentages of adult individuals. Our matrix model predicts that overall, actual population sizes will increase (= 1.022 + 0.001) with a zero probability of extinction in the next 50 years. Annual variation in demographic patterns was considerable, with a low seed production during dry years. Particular lambda values varied from 0.976 to 1.16, changes in survival and growth of juvenile and adult categories strongly affected lambda. Although changes in fecundity had a smaller impact on lambda, sensitivity and elasticity for the adult category were particularly high during low seed production years. Our results suggest that limitations to harvest of adult individuals of Thrinax radiata are principally due to slow individual growth and highly variable fecundities.

Key words: yucatan peninsula, matrix model, demography, extinction