Does the Genetic Diversity of Macuilillo,Oreopanax xalapensis(Araliaceae), Change Along Successional Gradients of the Montane Cloud Forest?

Abstract

Forest regeneration after human-induced or natural disturbances results in a sequential replacement of species, starting with colonizing of pioneer species that modifies the physical conditions of the environment, which later allows the establishment of mid- and late-successional species. Whether the forest succession implies a reduction of population size of tree species might be expected a less genetic diversity in populations inhabiting oldest succession stages. We aimed to study whether genetic diversity of Macuilillo, Oreopanax xalapensis (a understory tree), decreases in advanced age-classes and in late successional of montane cloud forest at Huitepec Ecological Reserve (Chiapas, Mexico). We counted individuals from three age classes: seedlings, saplings, and young reproductive individuals in nine plots along three successional stages (early-, middle-, and late-successional forests). Seven enzyme systems (SOD, AP, FUM, G6PDH, GOT, GPI, and G3PDH) were used to obtain common genetic diversity; Φ-statistics and a Bayesian model were used to infer population structure. At the early-successional stage, O. xalapensis had a bigger population size and significantly high numbers of seedlings. In general, among the successional stages, the genetic diversity of O. xalapensis was moderate to high ( He = 0.25–0.46); the saplings presented the highest expected genetic diversity ( He). Populations were genetically structured by age-classes but not by successional stages. The successional stages affected the demographic dynamics with a mild impact on the genetic structure across age-classes of O. xalapensis. The scenic and recreational conservation strategies implemented in this forest have effectively allowed for population development of O. xalapensis and provide some explanation of genetic diversity at early-succession stage.

Diversidad y enriquecimiento florístico con especies nativas de bosque mesófilo de montaña, en un bosque urbano de Chiapas, México

“…The genetic diversity of Oreopanax xalapensis in Los Altos de Chiapas has also been studied through enzymes, showing high genetic diversity and low genetic structuring at relatively small spatial scales (Ruiz-Montoya, Correa-Vera, Alfaro-González, Ramírez-Marcial, & Vallejo, 2011;Vera-Maloof, Ruiz-Montoya, & Ramírez-Marcial, 2019). Our results showed lower levels of genetic diversity than previously reported in Oreopanax xalapensis; possibly, the difference is due to the bias by sample size (low number of parent trees), so it is suggested to increase population genetics studies in native species of montane cloud forest trees.…”