MATING SYSTEM-ANALYSIS IN PINUS-LEUCODERMIS ANT - DETECTION OF SELF-FERTILIZATION IN NATURAL-POPULATIONS

The mating system was analysed in two natural populations of Pinus leucodermis Ant., a narrow ranged and relic species. The amount of outcrossing was estimated by assaying four enzyme loci. An efficient multilocus model was used, which allows the joint estimation of outcrossing rate and pollen allele frequencies for individual trees. The estimated multilocus outcrossing rates were 0.765 and 0.840 in the two populations. Both regression of individual pollen allele frequencies on the additive value of the maternal genotypes and outcrossing rates estimated with the unique allele method revealed that these low outcrossing rate estimates were not merely determined by mating among relatives, but reflected significant levels of selfing. They are especially significant, if compared with those observed in other conifers, which are almost complete outbreeders. The estimated selfing rate may be an upper limit because it was obtained by analysing non-germinated seeds. The presence of such a selfing level in this species could have important implications for seed production, as it seems that strong selection acts against homozygotes derived from inbreeding between germination and the adult phase.