Interspecific gene flow in a multispecies oak hybrid zone in the Sierra Tarahumara of Mexico.
OBJECTIVE
Interspecific gene flow can occur in many combinations among species within the genus Quercus, but simultaneous hybridization among more than two species has been rarely analysed. The present study addresses the genetic structure and morphological variation in a triple hybrid zone formed by Q. hypoleucoides, Q. scytophylla and Q. sideroxyla in north-western Mexico.


METHODS
A total of 247 trees from ten reference and 13 presumed intermediate populations were characterized using leaf shape variation and geometric morphometrics, and seven nuclear microsatellites as genetic markers. Discriminant function analysis was performed for leaf shape variation, and estimates of genetic diversity and structure, and individual Bayesian genetic assignments were obtained.


RESULTS
Reference populations formed three completely distinct groups according to discriminant function analysis based on the morphological data, and showed low, but significant, genetic differentiation. Populations from the zone of contact contained individuals morphologically intermediate between pairs of species in different combinations, or even among the three species. The Bayesian admixture analysis found that three main genetic clusters best fitted the data, with good correspondence of reference populations of each species to one of the genetic clusters, but various degrees of admixture evidenced in populations from the contact area.


CONCLUSIONS
The three oak species have formed a complex hybrid zone that is geographically structured as a mosaic, and comprising a wide range of genotypes, including hybrids between different species pairs, backcrosses and probable triple hybrids.
Peñaloza-Ramírez
Juan Manuel
JM
Centro de Investigaciones en Ecosistemas, Universidad Nacional Autónoma de México (UNAM), Antigua Carretera a Pátzcuaro No. 8701, Col. Ex-Hacienda la Huerta, 58190 Morelia, Mexico. jpenaloza@oikos.unam.mx
González-Rodríguez
Antonio
A
Mendoza-Cuenca
Luis
L
Caron
Henri
H
Kremer
Antoine
A
Oyama
Ken
K
D001499:Bayes Theorem; D051456:Gene Flow; D017343:Genes, Plant; D006824:Hybridization, Genetic; D008800:Mexico; D018895:Microsatellite Repeats / Q000235:genetics; D018515:Plant Leaves; D029963:Quercus / Q000145:classification / Q000235:genetics*; D013045:Species Specificity