Outcrossing rate and inbreeding depression in the perennial yellow bush lupine, Lupinus arboreus (Fabaceae)

Little is known about the breeding systems of perennial Lupinus species. We provide information about the breeding system of the perennial yellow bush lupine, Lupinus arboreus, specifically determining self-compatibility, out crossing rate, and level of inbreeding depression. Flowers are self-compati ble, but autonomous self-fertilization rarely occurs: thus selfed seed are a product of facilitated selfing. Based on four isozyme loci from 34 matern al progeny arrays of seeds we estimated an outcrossing rate of 0.78. Howeve r, when we accounted for differential maturation of selfed seeds, the outcr ossing rate at Fertilization was lower, similar to 0.64. Fitness and inbree ding depression of 11 selfed and outcrossed families were measured at four stages: seed maturation, seedling emergence, seedling survivorship, and gro wth at 12 wk. Cumulative inbreeding depression across all four life stages averaged 0.59, although variation existed between families fur the magnitud e of inbreeding depression. Inbreeding depression was not manifest uniforml y across all four life stages. Outcrossed flowers produced twice as many se eds as selfed flowers, but the mean performance of selfed and outcrossed pr ogeny was not different for emergence, seedling survivorship, and size at 1 2 wh. Counter to assumptions about this species, L. arboreus is both self-c ompatible and outcrosses similar to 78% of the time.