High Rates of Gene Flow by Pollen and Seed in Oak Populations across Europe

Abstract

Gene flow is a key factor in the evolution of species, influencing effective population size, hybridisation and local adaptation. We analysed local gene flow in eight stands of white oak (mostly Quercus petraea and Q. robur, but also Q. pubescens and Q. faginea) distributed across Europe.Adult trees within a given area in each stand were exhaustively sampled (range [239, 754], mean 423), mapped, and acorns were collected ([17,147], 51) from several mother trees ([3], [47], 23). Seedlings ([65,387], 178) were harvested and geo-referenced in six of the eight stands. Genetic information was obtained from screening distinct molecular markers spread across the genome, genotyping each tree, acorn or seedling. All samples were thus genotyped at 5–8 nuclear microsatellite loci. Fathers/parents were assigned to acorns and seedlings using likelihood methods. Mating success of male and female parents, pollen and seed dispersal curves, and also hybridisation rates were estimated in each stand and compared on a continental scale.On average, the percentage of the wind-borne pollen from outside the stand was 60%, with large variation among stands (21–88%). Mean seed immigration into the stand was 40%, a high value for oaks that are generally considered to have limited seed dispersal. However, this estimate varied greatly among stands (20–66%). Gene flow was mostly intraspecific, with large variation, as some trees and stands showed particularly high rates of hybridisation.Our results show that mating success was unevenly distributed among trees. The high levels of gene flow suggest that geographically remote oak stands are unlikely to be genetically isolated, questioning the static definition of gene reserves and seed stands.

Morphological and Molecular Differentiation in Populations of Persian Oak (Quercus Brantii Lindl.) in Southwestern Iran

“…They do not generally show separate and specified genetic foundations (Kittelson et al, 2009). Moreover, gene flow is a key factor in species evolution that affects the hybridization and local adaptation (Gerber et al, 2014). Factors such as forest fragmentation, rapid climate change and interference of humans effect genetic diversity of the population in forest trees that are long-lived (Birchenko, 2008).…”

Size advantage for male function and size‐dependent sex allocation inAmbrosia artemisiifolia, a wind‐pollinated plant

“…This finding agrees with a general pattern of pollen dispersal in wind‐pollinated plants (Gerber et al., 2014; Levin & Kerster, 1974; Oddou‐Muratorio, Klein, & Austerlitz, 2005). This fat‐tailed distribution may be due to the position effect that a higher release point allows more horizontal movement and also the aerodynamic property that wind speed and turbulent flow are greater at a higher position where horizontal movement of pollen is favored (Burd & Allen, 1988).…”

Potential Population Genetic Consequences of Habitat Fragmentation in Central European Forest Trees and Associated Understorey Species—An Introductory Survey

“…Because most segregating molecular variants used in population genetics are selectively neutral (e.g., [23], pp. [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], population genetic diversity and differentiation for neutral markers are not prone to be modified by selection compared to adaptive genes (e.g., [24]). Genome-wide diversity and differentiation, nevertheless, may be affected in case of selection against inbred genotypes in a population which declines in size.…”