Offspring performance in Oxalis acetosella, a cleistogamous perennial herb

Seed weight, seed germination, seedling survival, and juvenile/adult fitnes s in chasmogamously (CH) and cleistogamously (CL) derived offspring of Oxal is acetosella were compared during three growing seasons, to test hypothese s of fitness differences between the offspring types accounting for the mai ntenance of cleistogamy. In plots at three field sites, CH and CL seeds ori ginating from all sites were sown to compare the performance of offspring g rowing in their habitat of origin and offspring growing in new habitats. Se eds were also sown in pots in a common garden, to test for effects of sibli ng competition. Ct seeds had significantly lower germination than CH seeds in the field, possibly because of lower mean seed weight due to later flowe ring. Since the outcrossing rate in the CH flowers of O. acetosella is not known, it is uncertain whether the lower CL germination is a consequence of inbreeding depression. CH seeds had higher germination if sown at their ho me sites than at new sites, white for CL seeds this made no difference; thi s contradicts the local adaptation hypothesis for cleistogamy. No other fit ness differences were found between the offspring types, and the findings d id not support the sibling competition or local adaptation hypotheses. We s uggest that the maintenance of the dimorphic reproductive system in O. acet osella is not explained by offspring characteristics, but rather by the two flowering phases complementing each other in maximizing annual seed produc tion in the face of environmental variability. It is, therefore, important to include temporal and spatial variation in studies of reproductive strate gies.