Inbreeding Effects on Mating System Traits for Two Species of Lupinus (Leguminosae)

The consequences of inbreeding for reproductive traits were investigated for two closely related annual lupines that differ in their mating system. Lupinus bicolor (Leguminosae) is a primarily selling species while Lupinus nanus outcrosses at intermediate rates. A controlled crossing program was used for each species to produce selfed and outcrossed progeny. These progeny were then grown in a greenhouse and scored for the date of first flower, flower morphology, and autofertility. Selfed progeny of L. bicolor produced significantly smaller flowers but did not differ from outcrossed progeny for the remaining traits. Selfed progeny of L. nanus produced flowers that significantly differed in shape and had fewer ovules than the flowers of outcrossed progeny. Selfed progeny of L. nanus also had significantly lower rates of autofertility in comparison to outcrossed progeny. The significant effects of inbreeding on these mating system traits may indicate the presence of directional dominance at the loci underlying these characters. The consequences of these direct effects of inbreeding on reproductive traits for plants growing in natural populations may include nonadaptive changes in the outcrossing rate between generations.