Population structure and the mating system of white spruce

Abstract

Inheritance of allozymes of 12 polymorphic loci was demonstrated using haploid megagametophytic tissues of viable seed from a total of 47 white spruce trees in one stand. In general, allozymes segregated as expected in a 1:1 ratio. However, one allozyme of phosphoglucose isomerase (Pgi-2) did not segregate as expected. Significant deficiency in two different heterozygous combinations was observed. This result could be indicative of selection against the allozyme. The level of genetic variability in this stand of white spruce was similar to average levels of variation observed with many conifer species. Overall, an excess of heterozygotes was observed in the mature population. However, after 9 years of storage in a seedbank, no more than random selfing could be detected in the viable filial generation. Significant heterogeneity in allele frequency distribution of several loci was observed in the pollen pool in this stand. The calculated ratio of genetically effective males to females in this population was only 0.4. These results were interpreted as evidence for changes in the spatial genetic structure of the population, likely marking demes of related individuals, and restricted effective transmission distances of male gametes. Some implications for tree improvement programs are discussed.

Molecular and quantitative signatures of biparental inbreeding depression in the self-incompatible tree species Prunus avium

“…Seeds from one seed-tree (M3) even did not germinate. Loss of genetic diversity could be explained by a reduced fitness in seeds and seedlings leading to mortality, by instance through biparental inbreeding depression (Cheliak et al, 1985;Rajora et al, 2000;Hufford and Hamrick, 2003;Naito et al, 2005;Isagi et al, 2007;Duminil et al, 2009;Hasegawa et al, 2009). However, our data rather showed higher survival of offspring from related parents and fixation index showed excess of heterozygotes.…”

“…Loss of homozygote individuals seems indeed to be common in tree species (Cheliak et al, 1985;Hufford and Hamrick, 2003;Naito et al, 2005;Tamaki et al, 2009) and may result from very intensive competition for seedling establishment (Petit and Hampe, 2006) and heterozygote advantage (heterosis).…”

Genetic aspects of age dynamics of a natural Picea abies (L.) Karst. population in the Białowieża Primeval Forest, Poland

“…and Pinus sylvestris. A heterozygote surplus both in embryos (F = -0.066) and maternal plants (F = -0.074) was reported for Picea glauca (Moench) Voss in Ontario, Canada (Cheliak et al 1985). In a population of this species in Alberta, Canada, heterozygote deficiency was observed in adults (F = 0.039) and in embryos from two different seed crop years (F = 0.029-0.031) (King et al 1984).…”

Genetics of white pine and implications for management and conservation

“…The authors concluded that the even-aged, continuous stand conditions of Boreal white spruce, with accompanying high gene flow, would not favor development of genetically distinct neighborhoods. Cheliak et al (1985b) measured the mating system of a white spruce population near Whitney, Ontario from 9-year-old stored seed, and reported an average of 2% selfing, with near-random mating occurring in the stand. However, this estimate could have been biased due to mortality of heavily inbred seed as a result of selection against homozygotes during embryo development, storage and subsequent germination.…”