Mating system analysis in Pinus leucodermis Ant.: detection of self-fertilization in natural populations

Abstract

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 self ing. 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.

Non-random mating in a Secale cereale L. (rye) population

“…(1989). This also occurs in other species (Farris & Mitton, 1984;Morgante et al, 1991). Thus, genotype frequencies between generations of adult plants can be more similar than between adult plants and their seedling progenies depending upon the genetically and/or environmentally variable outcrossing rate.…”

Selfing and sibship structure in a two-cohort stand of maritime pine (Pinus pinaster Ait.) using nuclear SSR markers

“…However, a certain level of biparental inbreeding is common as shown by differences between the multilocus estimate of outcrossing and the average of the single-locus estimate using progeny arrays (e.g. Pinus sylvestris [10], Pinus attenuata [11], Pinus washoensis [30], Pinus contorta [31], Pinus leucodermis [32]). Low genetic relatedness within a stand is usually caused by selection due to strong inbreeding depression or extensive gene flow [17].…”

Selection against inbreds in early life-cycle phases in Pinus leucodermis Ant.

“…It has been demonstrated in a previous study (Morgante et at., 1991) that Pinus leucodermis Ant., a conifer with a discontinuous and restricted distribution in southern Europe, is characterized by much higher levels of self-fertilization than those usually found in conifers and that the partial selling results in positive fixation indices in the dormant embryo (zygote) stage, but not in the adult parental trees. The present study was therefore undertaken to determine the stage of elimination of inbreds in seedlings of this species.…”

“…Selfing rates of 28 and 18 per cent (s = 1 -tm) were estimated for the 1985 seed cohort in La Spina and Pollinello populations, respectively (Table 1) (Morgante et a!., 1991) (Franklin, 1970), this relation was not obvious in our samples under the adopted experimental conditions.…”