XVI International Botanical Congess

An ecological-genetic approach was used to explore the causes of extinction of Pinus strobus chiapensis from Mexico. Inbreeding is low and located mostly within populations. Our smallest population lies in the tropical forest of Chimalapas, were 55% of the trees were dead, and the rest (51 individuals) were old, probably due to environmental (lack of openings for recruitment)and intrinsic (low seed viability: 3%) factors. At El Rincón, this pine is wide-spread and one of the most important during secondary succession. A 4-year demographic study suggests that this population is near equilibrium. Heterozygosity is low. Thus, this population probably was originated from a small number of founders after human disturbance. Recurrent disturbance seems to be crucial.