Factors affecting effective population size estimation in a seed orchard: a case study of Pinus sylvestris.

Effective population size as a parameter closely correlating with the genetic and genotypic diversity of the seed orchard output is an important indicator of seed orchard functioning. It is determined by the variation of male and female gametic contributions of parental genotypes (including those outside the seed orchard), influenced by the variation in male and female gamete production, reproductive phenology, pollen dispersal within seed orchard and other factors. The assessment of fertility and phenological variation requires labor and finances. We tested empirically what is the relative importance of these factors for effective population size (status number) estimation by gradual adding one-by-one in the order of labor requirements (female contribution, male contribution, reproductive phenology, pollen dispersal) in three Scots pine (Pinus sylvestris L.) seed orchards in central Slovakia. The study has shown that in old, fully fructificating seed orchards, effective number of clones is a satisfactory estimator of the effective population size, but the inclusion of female and male fertility variation improves the estimate of status number. On the other hand, phenological variation and spatially-dependent pollen dispersal do not considerably affect NS estimates and need not be assessed for practical purposes. In contrast, a young seed orchard proved to be unbalanced and phenologically not synchronized; consequently, effective number of clones was a poor estimator of the effective size and status number was affected by all factors (male + female fertility, phenology, spatial design)