Jimenez-Sierra, Cecilia L. , Mandujano, Maria , Eguiarte, Luis E. .
Population ecology of the barrel candy cactus Echinocactus platyacanthus Link et Otto (Cactaceae) in the desert of Tehuacan-Cuicatlan, Mexico.
We used matrix projection models to analyze the population dynamics of the barrel candy cactus E. platyacanthus, an endangered species native of Mexico. We studied 6 populations during 3 years (2 transitions). The populations are established in diverse plant communities and are subject to anthropic disturbance. Lefkovitch matrices were used to estimate the finite rate of population increase (l), reproductive value (v) and stable size structure (w). We estimated the elasticity and sensitivity of lambda to proportional changes in the vital rates on each year and site (12 projection matrices). A life table response experiment (LTRE) was done to measure the contribution of each demographic process, size-class, year and site towards lambda. These stage-structured populations were characterized by high seed production(mean = 171 seed/fruit), low rates of seedling recruitment, high seedling mortality (20%), low adult mortality (< 2.5%) and fertility increases markedly with plant size. Population structures are not in a stable stage distribution and the density vectors are dominated by seed (99%) and followed by the adult stages. Population growth rates (l) ranged from 0.90 to 1.001. Like other cacti, elasticity values are highest for survival (0.968), followed by growth (0.101) and by reproduction (0.0001). Analysis of the long-term population dynamics (l = 0.98 ± 0.098) indicated that small habitat changes would increase the risk of extinction in these populations.
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1 - Universidad Autonoma Metropolitana-I, Departamento de Biologia, Av. San Rafael Atlixco 186, Col. Vicentina, Iztapalapa, Mexico D. F., D. F., 09340, Mexico
2 - Universidad Nacional Autonoma de Mexico, Instituto de Ecologia, Ciudad Universitaria, A.P. 70-275, Mexico, D.F., 04510, Mexico
3 - Instituto De Ecología, Unam, Apartado Postal 70-275, C.U., CoyoacăˇN, Mă©Xico, D.F., C.P. 04510, Mexico
matrix population models.
Presentation Type: Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM