FITNESS CONSEQUENCES OF MATERNAL AND NONMATERNAL COMPONENTS OF INBREEDING IN THE GYNODIOECIOUS PHACELIA-DUBIA

I assessed the relationship between the level of inbreeding, F, and fi tness, and the effects of nonmaternal and maternal components of inbre eding on fitness in Phacelia dubia. I conducted two generations of con trolled crosses and tested the performance of the F-2 progeny in field and artificial conditions covering the whole life cycle. Inbreeding s ignificantly decreased the individual contribution of seeds to the nex t generation in the field, but this decrease apparently is not enough to explain the maintenance of gynodioecy. The inbred progeny contribut es significantly to the population genetic structure of P. dubia. Fitn ess estimates and fitness components tended to decrease, usually monot onically, with F. However, nonmonotonic relationships were found in ma le fitness components and, in some families, in fitness estimates, see d production per fruit, and establishment. Most of the inbreeding depr ession takes place at the level of seed establishment in the field, bu t, in artificial conditions the effects of inbreeding were similar at fecundity and establishment. I studied maternal and nonmaternal compon ents of inbreeding by testing the effects of the relatedness of matern al grandparents and parents on the performance of the progeny. Both co mponents affected fitness. Inbreeding depression was conditioned by th e level of inbreeding of the maternal plant, but this interaction vari ed at different fitness components. Also, the magnitude and even the d irection of the relationship between fitness and F changed as a result of the combined effects of maternal and nonmaternal components of inb reeding. Such interactions can render convex or concave fitness functi ons, giving in the latter case the appearance of a false purging. Mate rnal effects of inbreeding can result from several processes: maternal investment perhaps with serial adjustments during seed development, p urging of recessive deleterious genes, and nucleocytoplasmic interacti ons. These results illustrate the importance of maternal effects of in breeding, and the complex effects of inbreeding on fitness. A full und erstanding of the fitness consequences of inbreeding and, therefore, t heir potential implications in the evolution of breeding systems, shou ld take into account male and female components as well as transgenera tional effects in the context of the particular environment in which f itness is evaluated.