Temporal analysis of breeding structure in jack pine (Pinusbanksiana Lamb.)

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Abstract
Outcrossing rates for 10 pollination years were estimated for a natural stand of jack pine using allozymic markers at the Mdh-2 and 6-pgd-1 loci. Outcrossing rate estimates showed a general increase with time since pollination. Population fixation index values for the progeny decrease with time since pollination, showing an increasing proportion of heterozygous progeny. These increases parallel those observed for jack pine, lodgepole pine, and alpine ash by other investigators, suggesting selection against inbred progeny may be occurring during the retention of the seed in the serotinous cones. Evaluation of the selection hypothesis by regression of the proportion of heterozygous progeny and of seed germination on year of pollination showed significant linear decreases in germination over a 10-year period for only one of eight trees. This was not accompanied by an increase in the proportion of heterozygous progeny. Apparent deviations from normal Mendelian segregation were noted at the Mdh-2 locus in two trees.