Stronger genetic differentiation among within-population genetic groups than among populations in Scots pine: new insights into within-population population genetic structuring in a long-lived woody plant

Abstract

Abstract We investigated the presence of spatial genetic groups within forest tree populations and determined if the genetic divergence among these groups is greater than that between populations using Pinus sylvestris as a model species. We genotyped 890 adult trees of Scots pine in six natural populations in Lithuania at 11 nuclear microsatellite loci. We used a Bayesian clustering to identify the within-population genetic groups within each of the six populations. We calculated the differentiation indexes among the genetic groups within each population and among the six populations by ignoring the genetic groups. The clustering revealed 2 to 6 distinct genetic groups of varying size as the most likely genetic structures within populations. The genetic differentiation indexes among the genetic groups within populations were nearly 10-fold greater (FST = 0.012–0.070) than those between the populations (FST =0.003). We conclude on a markedly stronger structuring of genetic variation within populations than between populations of Scots pine in large forest tracts of northerly Europe. Such genetic structures serve as a contributing factor to large within population genetic diversity in northerly conifers. We assume that within population mating in Scots pine is not completely random but rather is stratified into genetic clusters.