Breeding System in Limnanthes alba: Several Alternative Measures

Seven populations of Limnanthes alba were described for their rates of outbreeding, amount of genetic variability, and response to enforced selfing in terms of inbreeding depression. Outcrossing rates, estimated by using two genetic marker loci, varied between 43 and 97%. Heterozygosity level was found to be in the range of 12 and 27 percent, whereas percent polymorphic loci varied twofold (between 29 and 57%) among populations. Inbreeding depression was found to be significant in four of seven populations for number of flowers per plant, plant height, and seed set per flower. There was no association between observed patterns of inbreeding response and predictions from the genetic variation parameters, so that variations in outbreeding rates and consequences need a detailed quantitative verification. In populations showing no inbreeding depression, autofertility seemed to increase with inbreeding (presumably accompanied by natural selection) and to be under genetic control. This is relevant to the hypothesis on the origin of inbreeders under conditions lacking pollinators, e.g., colonization of marginal areas.