Effect of number of seed parents on the genetic diversity of artificially regenerated stands of holm oak

Artificial populations of holm oak (Quercus ilex L. s.l.) and their natural seed origin populations selected from Andalusia (Southern Spain) and Sicily (Southern Italy) were analysed with six nuclear microsatellite loci to explore the effect of seed collection methods. Low effective allele numbers (3.07-6.67) and extremely low effective populations sizes (35.4-102.9) were detected in both reforestation stands, probably due to an inappropriate forester seed collection strategy limited to a few mother trees. Analysis of simulated progenies showed that optimal sampling size to obtain seed collections genetically similar to the origin populations should range from 20 to 50 individuals, but could be different between the two regions, being higher in the more genetically diverse Andalusia.