Historical and contemporary mating patterns in remnant populations of the forest tree Fraxinus excelsior L.
Genetic variation at microsatellite markers was used to quantify genetic structure and mating behavior in a severely fragmented population of the wind-pollinated, wind-dispersed temperate tree Fraxinus excelsior in a deforested catchment in Scotland. Remnants maintain high levels of genetic diversity, comparable with those reported for continuous populations in southeastern Europe, and show low interpopulation differentiation (E = 0.080), indicating that historical gene exchange has not been limited (Nm = 3.48). We estimated from seeds collected from all trees producing fruits in three of five remnants that F. excelsior is predominantly outcrossing (t(m) = 0.971 +/- 0.028). Use of a neighborhood model approach to describe the relative contribution of local and long-distance pollen dispersal indicates that pollen gene flow into each of the three remnants is extensive (46-95%) and pollen dispersal has two components. The first is very localized and restricted to tens of meters around the mother trees. The second is a long-distance component with dispersal occurring over several kilometers. Effective dispersal distances, accounting for the distance and directionality to mother trees of sampled pollen donors, average 328 m and are greater than values reported for a continuous population. These results suggest that the opening of the landscape facilitates airborne pollen movement and may alleviate the expected detrimental genetic effects of fragmentation.
Bacles
Cecile F E
CF
Institute of Evolutionary Biology, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, United Kingdom. cecile.bacles@edu.uq.au
Burczyk
Jaroslaw
J
Lowe
Andrew J
AJ
Ennos
Richard A
RA
D005075:Biological Evolution; D003710:Demography; D031661:Fraxinus / Q000235:genetics / Q000502:physiology*; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats / Q000235:genetics; D008954:Models, Biological; D011058:Pollen / Q000502:physiology; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology; D012606:Scotland; D012639:Seeds / Q000235:genetics