The Influence of Anthropogenic Disturbance on the Genetic Diversity of Ceratozamia fuscoviridis (Zamiaceae).

Determining the effects of disturbance on genetic variation of plant populations is an important step in establishing conservation strategies for the survival of natural populations. Disturbance reduces effective population size, leading to lower variation through genetic drift. However, a plant species' life cycle will influence the magnitude and speed of the response to disturbance. In this report, genetic structure and variability are evaluated for Ceratozamia fuscoviridis , a critically endangered, endemic, long-lived cycad from Mexico, at four sites with different levels of disturbance. Genetic analysis was performed using intersimple sequence repeat (ISSR) and simple sequence repeat (SSR) markers. Populations 1 and 3 were classified as conserved (disturbance index [DI] = 3.11 ± 1.117) and populations 2 and 4 as disturbed ( D I = 6.37 ± 1.414). Levels of genetic diversity according to ISSR markers ranged from 0.169 to 0.279 for expected heterozygosity (H E), and the informative index (I) ranged from 0.266 to 0.425. In general, the genetic diversity measure with ISSRs was greater in the conserved sites than in the disturbed ones. For the SSRs, H E ranged from 0.711 to 0.793, while I ranged from 1.391 to 1.621. Genetic structure shown with these markers does not correspond with geographic distance but does correspond with the conservation state of the populations. We found that there is a negative effect of perturbation on the genetic diversity of C. fuscoviridis. The loss of diversity can lead to various processes such as inbreeding and genetic drift that, in the long term, can culminate in local extinctions. We propose that studies should aim to evaluate the genetic diversity of juveniles, as it is possible that disturbances result in changes in the biology of the species that lead to divergences in the genetic diversity of adults and earlier stages. [ABSTRACT FROM AUTHOR]