Variation in the genetic structure and reproductive biology of holm oak populations

Five polymorphic enzymatic loci were studied in 30 populations of Quercus ilex distributed from Crete to North Africa. A high within-population genetic diversity was found for each locus studied. Most of the alleles were common to all the populations, indicating that the holm oak corresponds to a single genetic entity. Observation of breeding system characteristics showed that the holm oak is monoecious, wind-pollinated, and likely to possess genetic autoincompatibility. Furthermore, studies of flowering phenology in a single population showed that the period of flowering varied notably among trees. An average of 29% of the trees showed inter-annual variation in flowering time. The male, female or vegetative investment also varied widely among trees from one year to another. This results in a diversification of pollen source received by a given tree each year, and also from one year to another.