Genetic variation in natural and nursery populations of Styrax magnus (Styracaceae) for the restoration of humid mountain forests in southern Mexico

Humid mountain forests (HMF) in Mexico have been heavily degraded by anthropogenic activities. A key conservation strategy consists of propagating HMF species in forest nurseries for subsequent repopulation in degraded areas. We evaluated genetic diversity in three natural populations (Huitepec, Bazom, and Mitziton) and one nursery population of Styrax magnus Lundell (Styracaceae) in Chiapas, Mexico. We expected a lower genetic diversity in the nursery than in wild populations. Styrax magnus is restricted to the Mexican state of Chiapas, close to the border with Guatemala and is likely to be at risk of extinction due to habitat loss and its low establishment rate. We used ten enzyme loci to determine genetic diversity. Genetic structure was examined by calculating genetic differentiation (Fst) and Nei’s genetic distances (Nei, Am Nat 106:283–292, 1972), in addition a Bayesian analysis was performed. The populations examined showed a moderate (He = 0.31) average genetic diversity. Bazom was the most distant and genetically differentiated population and showed the lowest genetic diversity (He = 0.21). Mitziton was the most diverse population (He = 0.40), whereas the nursery population showed an intermediate diversity (He = 0.30). We found a high level of total genetic differentiation (Fst = 0.48, P < 0.001), suggesting a limited gene flow between the populations studied. Our results suggest that propagation in the nursery promotes an intermediate level of genetic diversity (He) relative to wild populations, likely because the nursery population was made up by random seed collection from several sites. The genetic monitoring of introduced populations is highly recommended for an in-depth assessment of the success of actions aiming to conserve and restore HMF in Chiapas.