Hybridization patterns and morphological variation in Quercus welshii

Abstract

Hybridization is common among plant species with weak reproductive barriers and overlapping geographic ranges. It can increase genetic and phenotypic variation in plant species, which is especially important for endemic species with restricted distributions. Species of the genus Quercus, commonly known as oaks, are particularly prone to hybridization and are good examples of how a group of interbreeding species can maintain gene flow while remaining taxonomically distinct. Since hybrid individuals tend to display characteristics that are intermediate of their parent species, our study aims to investigate how the proportion of genetic purity affects the degree of expression of morphological traits. Using Bayesian clustering (STRUCTURE), we assessed genetic admixture in our focal species, Quercus welshii, with four sympatric species (Q. gambelii, Q. turbinella, Q. grisea, and Q. arizonica). We then examined the correlation between admixture proportion in Q. welshii populations and their geographic distance from the nearest population of a potential hybridizing species. Additionally, generalized linear models were used to investigate the relationship between proportion of admixture and leaf trait variation. We found substantial hybridization between Q. welshii populations and other species in close proximity. Our analysis also supported the hypothesis that our populations would be more likely to hybridize as the geographic distance to other known hybridizing species decreased. Finally, our results indicated that admixture proportion in Q. welshii populations influences population mean leaf traits rather than their coefficient of variation. This study is the first step in better understanding how hybridization affects the genetic and morphological variation within populations, which is of special concern when creating conservation programs for species with limited distributions. However, whether these morphological changes confer an adaptive advantage is unclear and should be investigated further.Plant Biology, Ecology and Evolutio