Roselyne Lumaret1, Roula Jabbour-Zahab. 1. UMR5175, Centre d'Ecologie Fonctionnelle et Evolutive, Centre National de la Recherche Scientifique, 1919 route de Mende, F-34293 Montpellier Cedex 05, France. roselyne.lumaret@cefe.cnrs.fr
Abstract
BACKGROUND AND AIMS: Quercus suber and Q. ilex are distantly related and their distributions partially overlap. They hybridize occasionally, but the complete replacement of Q. suber chloroplast DNA (cpDNA) by that of Q. ilex was identified in two specific geographical areas. The objective of this study was to determine whether the contrasting situation reflected current or recent geographical interspecies gene flow variation or was the result of ancient introgression. METHODS: cpDNA PCR-RFLPs (restriction fragment length polymorphisms) and variation at ten nuclear microsatellite loci were analysed in populations of each species, in 16 morphologically intermediate individuals and the progeny of several of them. Interspecies nuclear introgression was based on individual admixture rates using a Bayesian approach with no a priori species assignment, and on a maximum-likelihood (ML) method, using allele frequencies in the allopatric populations of each species as controls. Gene flow was compared specifically between populations located within and outside the specific areas. KEY RESULTS: High interspecies nuclear genetic differentiation was observed, with twice the number of alleles in Q. ilex than in Q. suber. According to Bayesian assignment, approx. 1 % of individuals had a high probability of being F(1) hybrids, and bidirectional nuclear introgression affected approx. 4 % of individuals in each species. Hybrid and introgressed individuals were identified predominantly in mixed stands and may have a recent origin. Higher proportions including allospecific genes recovered from past hybridization were obtained using the ML method. Similar rates of hybridization and of nuclear introgression, partially independent of cpDNA interspecies transfer suggestive of gene filtering, were obtained in the populations located within and outside the areas of complete cpDNA replacement. CONCLUSIONS: The results did not provide evidence for geographical variation in interspecies gene flow. In contrast, historical introgression is supported by palynological records and constitutes the more reliable origin of cpDNA replacement in specific regions.
BACKGROUND AND AIMS: Quercus suber and Q. ilex are distantly related and their distributions partially overlap. They hybridize occasionally, but the complete replacement of Q. suber chloroplast DNA (cpDNA) by that of Q. ilex was identified in two specific geographical areas. The objective of this study was to determine whether the contrasting situation reflected current or recent geographical interspecies gene flow variation or was the result of ancient introgression. METHODS: cpDNA PCR-RFLPs (restriction fragment length polymorphisms) and variation at ten nuclear microsatellite loci were analysed in populations of each species, in 16 morphologically intermediate individuals and the progeny of several of them. Interspecies nuclear introgression was based on individual admixture rates using a Bayesian approach with no a priori species assignment, and on a maximum-likelihood (ML) method, using allele frequencies in the allopatric populations of each species as controls. Gene flow was compared specifically between populations located within and outside the specific areas. KEY RESULTS: High interspecies nuclear genetic differentiation was observed, with twice the number of alleles in Q. ilex than in Q. suber. According to Bayesian assignment, approx. 1 % of individuals had a high probability of being F(1) hybrids, and bidirectional nuclear introgression affected approx. 4 % of individuals in each species. Hybrid and introgressed individuals were identified predominantly in mixed stands and may have a recent origin. Higher proportions including allospecific genes recovered from past hybridization were obtained using the ML method. Similar rates of hybridization and of nuclear introgression, partially independent of cpDNA interspecies transfer suggestive of gene filtering, were obtained in the populations located within and outside the areas of complete cpDNA replacement. CONCLUSIONS: The results did not provide evidence for geographical variation in interspecies gene flow. In contrast, historical introgression is supported by palynological records and constitutes the more reliable origin of cpDNA replacement in specific regions.
Authors: D Magri; S Fineschi; R Bellarosa; A Buonamici; F Sebastiani; B Schirone; M C Simeone; G G Vendramin Journal: Mol Ecol Date: 2007-11-11 Impact factor: 6.185
Authors: Filipe Sousa; Joana Costa; Carla Ribeiro; Marta Varandas; Francisco Pina-Martins; Fernanda Simões; José Matos; Maria Glushkova; Célia Miguel; Maria Manuela Veloso; Margarida Oliveira; Cândido Pinto Ricardo; Dora Batista; Octávio S Paulo Journal: PeerJ Date: 2022-06-16 Impact factor: 3.061