Genetic diversity and structure of Magnolia mexicana (Magnoliacea): A threatened species in eastern Mexico

This study analyzes the diversity and genetic structure of seven natural populations of Magnolia mexicana (Yoloxóchitl), an endangered and endemic species distributed in the Mexican Sierra Madre Oriental. The objective of the analysis is to generate basic information for the development of management and conservation programs for this species. The variation and genetic structure were estimated based on 12 SSR markers. The results indicate that the expected heterozygosity was 0.63±0.02 and the allelic richness was 1.21±0.05. The analysis of molecular variance (AMOVA) showed that variation between individuals explains 49 % of the total variation, and variation within individuals explains 36 %. The technical Neighbor joining and the ordination diagram of the canonical discriminant analysis show that the populations are made up of two genetic groups mostly. By contrast with the model Bayesian grouping (obtained with the STRUCTURE program) indicated the formation the six genetics groups. Recent bottleneck effects were observed in all localities, except in Duraznillo, El Cajón, and Zapotla. The relationship between genetic and geographic distances was not significant, which rules out a structure determined by isolation; the results suggest that the diversity and genetic structure of the species are affected by local factors such as habitat fragmentation, land use change, and excessive use of the flowers and fruits of M. mexicana by the inhabitants. Therefore, it is a priority to implement management and conservation programs to guarantee their survival.