High rates of gene flow by pollen and seed in oak populations across Europe.
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.
BIOGECO, UMR1202, INRA, Cestas, France ; BIOGECO, UMR1202, University of Bordeaux, Talence, France.
Sophie
S
Gerber
UR 1052, INRA, Montfavet, France.
Joël
J
Chadœuf
Biodiversity and Conservation Biology, WSL Swiss Federal Research Institute, Birmensdorf, Switzerland.
Felix
F
Gugerli
Department of Ecology and Genetics, EBC, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Martin
M
Lascoux
Alterra, Wageningen UR, Wageningen, The Netherlands.
Joukje
J
Buiteveld
Forest Research, Northern Research Station, Roslin, Midlothian, Scotland, United Kingdom.
Joan
J
Cottrell
Biodiversity and Conservation Biology, WSL Swiss Federal Research Institute, Birmensdorf, Switzerland.
Aikaterini
A
Dounavi
Institute for Plant Protection, CNR, Sesto Fiorentino (Firenze), Italy.
Silvia
S
Fineschi
Forest Research, Northern Research Station, Roslin, Midlothian, Scotland, United Kingdom.
Laura L
LL
Forrest
Department of Ecology and Genetics, EBC, Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
Johan
J
Fogelqvist
NEIKER-Tecnalia, Vitoria-Gasteiz, Spain.
Pablo G
PG
Goicoechea
Forest & Landscape, University of Copenhagen, Copenhagen, Denmark.
Jan Svejgaard
JS
Jensen
Institute for Plant Protection, CNR, Sesto Fiorentino (Firenze), Italy ; Forest & Landscape, University of Copenhagen, Copenhagen, Denmark.
Daniela
D
Salvini
Institute of Biosciences and Bioresources, CNR, Sesto Fiorentino (Firenze), Italy.
Giovanni G
GG
Vendramin
BIOGECO, UMR1202, INRA, Cestas, France ; BIOGECO, UMR1202, University of Bordeaux, Talence, France.
Antoine
A
Kremer
D005060:Europe; D051456:Gene Flow / Q000235:genetics*; D006824:Hybridization, Genetic; D011058:Pollen / Q000235:genetics*; D029963:Quercus / Q000235:genetics*; D012098:Reproduction; D036226:Seedlings / Q000235:genetics; D012639:Seeds / Q000235:genetics*; D014197:Trees / Q000235:genetics