Old Age Sex: A Parentage Study of Different Age Cohorts in a Native Veteran Pedunculate Oak (<i>Quercus Robur L.</i>) Woodland Using Microsatellite Markers

Abstract

To quantify levels of gene flow among and genetic variation within different age cohorts of pedunculate oak ( Quercus robur L.) in a semi-natural oak woodland, diversity and parentage studies were undertaken on a stand in Ballytobin, Co. Kilkenny, Ireland. Trees were categorised into four size classes seedlings, saplings, mature trees and veterans, and genetic differentiation was estimated for three microsatellite markers using AMOVA. Parentage was assessed using a likelihood assignment approach. Between nine and fourteen alleles were detected per locus (mean gene diversity, h, 0.8312). All samples from Ballytobin were heterozygous. AMOVA between age cohorts (veterans, mature, saplings and seedlings) estimated that only 2% of the variation was partitioned among age cohort and the mean FSt was low (0.015) but significant (P = 0.034). Parent-pair analysis revealed that out of 24 candidate trees, fifteen were assigned as parents to at least one offspring and, out of these, five were veteran. The average pollination distance was estimated at 47.8m with seven out of the twelve parent-pairs being within 50m of each other. The measured range of distances between trees indicated in the analysis as parents was between 22m and 150m. The highest values for number of parent/ offspring assignments were between 40m and 49m. Overall, veteran oak at the site were found to be reproductively successful and a low level of differentiation was found between age cohorts indicating that population genetic diversity has been maintained over time.