The Endangered Species Dioon edule in the Sierra Madre Oriental in San Luis Potosí: Demography and Genetic Diversity

The distribution of the endangered species Dioon edule is in populations scattered throughout the Sierra Madre Oriental in San Luis Potosí, Mexico. Its habitat is tropical dry forests at lower elevations and oak forests at higher elevations, mainly disturbed by anthropic activities. We determined and analyzed nine populations' demographic structure and explored the genetic diversity of five using SSR markers. The population density averaged 2050 individuals ha-1 and have an aggregated distribution pattern. Differences in the plants' size among localities are due to site quality, based on their adaptation capacity and response to climate and soil traits. Most populations have the highest mortality in the early stages of life, with a low mortality rate for those who survive this bottleneck. Two populations have a relatively constant mortality rate, attributed to disturbance of the habitat. The populations show low genetic diversity and an excess of homozygotes. Their similarity is probably related to the formation of natural corridors favoring connectivity between populations. The deterioration and fragmentation of the habitat have severe effects on the populations' viability, like reducing gene flow, which has led to inbreeding and genetic drift.