Sterility of Top Flowers Does Not Increase Fertility in the Grape Hyacinth Muscari armeniacum (Asparagaceae)

Premise of research. The functional significance of sterile flowers represents an interesting topic in floral biology and evolution. Sterile flowers have been hypothesized to attract pollinators, increasing plant fitness. Additionally, there may be postpollination effects through resource allocation from sterile to fertile flowers, also aiding in reproduction. I tested these two hypotheses in the grape hyacinth Muscari armeniacum, in which sterile flowers are inconspicuous, few, and small, located at the apex of a racemose inflorescence. Methodology. I carried out field experiments in which sterile flowers were left intact or removed early (beginning of flowering) or late (end of flowering) and recorded insect visitation and fruit and seed production. Pivotal results. The presence of sterile flowers did not increase insect attraction or the number of visited flowers. Flower position within inflorescences showed a significant association with fruiting not related to the presence or closeness to sterile flowers. Reproductive success was considerably low and not affected by early or late removal of sterile flowers, and seed output was not influenced by flower position. There was a significant negative effect of the number of flowers per inflorescence on fruit set. Conclusions. No evidence was found for either Darwin’s hypothesis that sterile flowers promote attraction or the hypothesis that there are postpollination effects through resource allocation from sterile to fertile flowers for reproduction. The findings suggest that top sterile flowers could be vestigial features.