Genetic structure of Platanus mexicana var. mexicana (Platanaceae) in southern Mexico.
Dulce María Galván-Hernández, Pablo Octavio-Aguilar, Oscar Carmona-Hernández, Hugo Asselin, José Armando Lozada-García.
Platanus mexicana is a typical species of the tropical cloud forest with a complex biogeographical history. High adaptive radiation and interspecific hybridization have been reported for this species, leading to high genetic variability and low differentiation. However, previous studies have shown that populations in the southern part of the species’ distribution in Mexico show different patterns. Therefore, this research aimed at characterizing the genetic structure of three Platanus mexicana populations in southern Mexico. The results revealed significant differences between the populations in Oaxaca, Veracruz and Chiapas (FST = 0.235 ± 0.08), whereas there was evidence of gene flow between the two northwestern populations (Nm = 1.5). Bayesian analysis of allele frequencies showed high selection pressure in Veracruz. Furthermore, the alleles that shifted away from the neutral model were overrepresented in Chiapas. The Oaxaca population had the highest genetic variability values (He = 0.25; P = 68.7), whereas the Chiapas population displayed the highest differentiation (Nei = 0.134). Considering the biogeographical history and topographic heterogeneity of the region, the results suggest three differentiation processes: presence of a climate refugium in Oaxaca, allopatry between Veracruz and Oaxaca, and vicariance in Chiapas.