INBREEDING DEPRESSION IN THE GYNODIOECIOUS SHRUB HEBE SUBALPINA (SCROPHULARIACEAE)

Inbreeding depression caused by self-fertilisation was examined in the gynodioecious shrub Hebe subalpina under two planting regimens, non-c ompetitive and competitive. We found differences among families in the magnitude of inbreeding depression, ranging from 0.31 to 0.63. On ave rage, outcrossed progeny grew nearly twice as large as selfed progeny, and the coefficients of variation (CVs) for dry mass were lower for o utcrossed progeny than selfed progeny within the non-competitive regim en. Planting regime had a highly significant effect on dry mass, such that plants grown in the competitive regimen were an order of magnitud e smaller than those in the non-competitive regimen, and they also had higher CVs. However, planting regimen did not significantly affect th e magnitude of inbreeding depression. Our results suggest that intrins ic differences exist in the growth rate of selfed and outcrossed indiv iduals, and that inbreeding depression helps to maintain females at a high frequency in the population. We suggest that among-family variati on in the magnitude of inbreeding depression is likely in gynodioeciou s species because of differences in inbreeding caused by gender.