REPRODUCTIVE ALLOCATION AND THE FITNESS CONSEQUENCES OF SELFING IN 2 SYMPATRIC SPECIES OF EPILOBIUM (ONAGRACEAE) WITH CONTRASTING MATING SYSTEMS

Selfing has evolved repeatedly in outcrossing taxa, and theory predict s that an increase in the level of self-fertilization should occur in concert with changes in reproductive allocation and the magnitude of i nbreeding depression. Here we characterize the mating system of two sy mpatric congeners, Epilobium ciliatum and E. angustifolium, and compar e the taxa for 1) reproductive allocation patterns and 2) the fitness consequences of self-fertilization. For E. ciliatum, autogamy rates we re high, pollinator visitation was low, and electrophoresis revealed n o genetic variation at 11 putative isozyme loci. For E. angustifolium, autogamy rates were low, pollinator visitation was relatively high, a nd electrophoresis generated an outcrossing rate estimate of t = 0.64 (SE = 0.08). The pollen/ovule ratio was ten times higher for E. angust ifolium than for E. ciliatum, due to a decline in pollen production in the selfing species. The proportion of total flower biomass allocated to female function was significantly greater in E. ciliatum, while th at allocated to male function and attractive structures was greater in E. angustifolium. We quantified the fitness consequences of selfing a t three life stages: seed number, percent germination, and mature biom ass. Relative performance (RP) measures indicated less inbreeding depr ession for E. ciliatum than for E. angustifolium at all stages; differ ences in RP between the species were significant for seed number and c umulative total, but not for germination or biomass. RP was correlated among life history stages for only one comparison, suggesting that th e genetic basis of inbreeding depression differs among life history st ages. Variation among maternal parents for RP was significant at almos t all stages in both species, with the exception of seed number in E. ciliatum. The striking variation among maternal parents in E. angustif olium, ranging from strong inbreeding depression to strong outbreeding depression, may reflect both variation in the history of inbreeding a nd the long-distance migration of individuals from different populatio ns.