Inbreeding depression in Hydrophyllum appendiculatum: role of maternal effects, crowding, and parental mating history

Abstract

The amount of inbreeding depression detected was small during the first year of life but increased with age and had significant effects on adult size and reproductive traits. The lack of significant breeding depression during early growth is likely due to the overriding influence of maternal environmental effects on seed size and seedling growth, but as maternal effects decreased with age, the seedling's own genotype became a more important determinant of its fate. Selfed and outcrossed seedlings were grown alone or with other H. appendiculatum seedlings. No inbreeding depression was detected in the plants grown alone, but under competitive conditions, outcrossed seedlings were significantly larger than selfed seedlings by the end of the first growing season. The author examined the consequences of two successive generations of selfing on seed set and seed weight. Amount of inbreeding depression increased following the second generation of selfing. In the first generation, seed set and seed weight differed by <5% between selfed and outcrossed progeny. However, both traits were 15% greater for outcrossed plants after two generations. Since the alleles responsible for the reductions in these traits were not purged, the action of multiple loci with deleterious effects is suggested. -from Author