Owing to the reduction of population density and/or the environmental changes it induces, selective logging could affect the demography, reproductive biology and evolutionary potential of forest trees. This is particularly relevant in tropical forests where natural population densities can be low and isolated trees may be subject to outcross pollen limitation and/or produce low-quality selfed seeds that exhibit inbreeding depression. Comparing reproductive biology processes and genetic diversity of populations at different densities can provide indirect evidence of the potential impacts of logging. Here, we analysed patterns of genetic diversity, mating system and gene flow in three Central African populations of the self-compatible legume timber species Erythrophleum suaveolens with contrasting densities (0.11, 0.68 and 1.72 adults per ha). The comparison of inbreeding levels among cohorts suggests that selfing is detrimental as inbred individuals are eliminated between seedling and adult stages. Levels of genetic diversity, selfing rates (∼16%) and patterns of spatial genetic structure (Sp ∼0.006) were similar in all three populations. However, the extent of gene dispersal differed markedly among populations: the average distance of pollen dispersal increased with decreasing density (from 200 m in the high-density population to 1000 m in the low-density one). Overall, our results suggest that the reproductive biology and genetic diversity of the species are not affected by current logging practices. However, further investigations need to be conducted in low-density populations to evaluate (1) whether pollen limitation may reduce seed production and (2) the regeneration potential of the species.

Combining phenotypic and genetic characteristics in a genetic variation study is of paramount importance to effectively orient the selection of producers’ elite trees in a seed orchard. In total, 28 phenotypic characteristics and 16 microsatellite loci were used to analyze the clonal genetic variation, to characterize the genetic diversity, and to refine the genetic classifications of 110 Pinus koraiensis clones grown in the Naozhi orchard in northeastern China. All clones were significantly different in most traits. Most of the phenotypic characteristics showed great genetic variation among clones, while the genotypic differentiation was weak between the selection sites of clones. The SSR markers showed a relatively high level of genetic diversity (Na = 4.67 ± 0.43, Ne = 2.916 ± 0.18, I = 1.15 ± 0.07, Ho = 0.69 ± 0.04, He = 0.62 ± 0.02, and mean polymorphic information content (PIC) of 0.574), with higher heterozygosity as an indication of a lower probability of inbreeding events in the orchard. Despite weak correlation coefficients between dissimilarity matrices (r(A/B), range equal to 0.022, p-value < 0.001), the genetic and phenotypic classifications congruently subdivided all the clones into three major groups. The patterns of phenotypic trait variations and genetic diversity are valuable to effectively select materials in breeding programs of P. koraiensis.

Genetic parameters were evaluated for growth and cone characteristics (tree height, diameter at breast height, volume, cone number, thousand seeds weight and single cone seeds weight) on 86 half-sib families of Pinus koraiensis aged 31 years. Analyses of variance revealed significant differences (p < 0.001) in all growth and cone traits among families while no significant differences were detected among blocks and the interaction between blocks and families. The average family values for growth traits were 17.22 m, 8.67 cm and 0.43 m 3 for tree height, diameter at breast height and volume, respectively. The average cone number, thousand seeds weight and single cone seeds weight were 17.57, 748.91 g and 77.25 g, respectively. Genotypic additive variance and phenotypic variances ranged from 0.00009 to 3.820 and from 0.0005 to 23.066, while genotypic and phenotypic coefficients of variation ranged from 2.693% to 37.196% and 4.963% to 60.595%, respectively. Heritability at the individual and family level ranged from 0.152 to 0.215 and 0.611 to 0.862, respectively. Growth traits were significantly positively correlated with each other, but cone traits showed a weak correlation with growth traits. Based on 10% selection rate, nine families each were selected as elite materials in terms of high performance in volume and cone numbers, with 22.16% and 43.82% genetic gain in volume and cone number, respectively. These results provide beneficial information to select excellent families and establish orchards of P. koraiensis from improved seeds.

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