OFFSPRING FITNESS AND PARENTAL EFFECTS AS A FUNCTION OF INBREEDING INEPILOBIUM-ANGUSTIFOLIUM (ONAGRACEAE)

The fitness of plant offspring is determined not only by their nuclear genotype but also by non-nuclear contributions and provisioning by pa rents (parental effects). Nuclear and parental effects on the producti on and germination of offspring were estimated for self-, full-sibling and outbred pollinations in a diallel crossing design involving eight plants of Epilobium angustifolium. Seed-set and germination were sign ificantly higher in offspring derived from outbred pollinations than f rom self-pollinations. Full-sib pollinations had intermediate seed-set and germination but were not statistically different from self-pollin ations. The average nuclear contribution to offspring fitness was not significantly different among plants; however, variation in mean seed- set and germination percentage among particular parent combinations, w hich was attributable to nuclear effects, was highly significant. Pare ntal effects accounted for a significant portion of the variation in s eed-set and germination among the eight parent plants. Of these effect s, 50 per cent were maternal and 50 per cent were paternal. There was no interaction between parental effects and offspring nuclear genotype s. These results suggest that, although parental effects do influence seed number and germination, parents do not differentially provision i nbred and outbred offspring, and therefore differences in fitness betw een inbred and outbred offspring can be attributed to their nuclear ge notypes.