Significant levels of self-fertilization in natural populations of tamarack

The mating system in five northern Ontario populations of tamarack (Larix laricina (Du Roi) K. Koch) was investigated using five allozyme marker loci (Aat3, G6p, Mdh3, Pgi2, and 6pg2). The mean multilocus outcrossing rate was 0.729, lower than estimates reported for most other conifers. The one population with a much higher stand density than the others had the highest outcrossing rate (0.908). Significant heterozygote deficiencies, relative to Hardy – Weinberg expectations, were observed at most loci in all five embryo populations. In contrast, there appeared to be few cases of heterozygote deficiencies in the adult populations, indicating that many inbred seedlings do not survive to the adult stage.