Print PageOenothera suffulta subsp. suffulta (hereafter, suffulta) and O. suffulta subsp. nealleyi (hereafter, nealleyi) are sister taxa in the plant family Onagraceae. Suffulta extends across Oklahoma and Texas, whereas nealleyi is confined to the central Panhandle of West Texas. Comparisons between these subspecies can help us understand the role of reproductive systems in the evolution of flowering plants. We hypothesize that floral traits and pollination systems correlate with the geographical distributions of the plants.
We monitored flower sizes and scents in the greenhouse, conducted pollinator observations in the field, and analyzed pollen load of captured insects. Pistils collected both day and night were used to determine the amount of pollen deposited by particular pollinator groups, and to determine breeding systems. Nealleyi has statistically larger flowers and stronger scents than suffulta. Our results show that nealleyi is visited by more species of insects; pollinators to nealleyi are in general more effective. Observations using fluorescence microscopy indicate that both species are self-incompatible and rely on night pollination by moths. Suffulta is pollen limited but nealleyi is not. Also, nealleyi receives additional morning pollination by bees, which serves as a form of reproductive assurance.
Results/Conclusions
Our study confirms our hypothesis and suggests that if a flowering plant has more restricted geographical locations as nealleyi does, its floral traits and reproductive system may change to adapt for more pollinator species with possibly higher efficiency. This ensures greater pollination success. However, further study is needed to determine the causal relationship between reproductive biology and geographical ranges.
