Ecological function and adaptive significance of staminodes in Delphinium caeruleum Jacq. ex Camb

We analyzed changes in the number of visiting insects, pollen quantity and quality, herbivore eating rate, and fruit and seed set ratios after removal of staminodes in a Delphinium caeruleum Jacq. ex Camb population to explore their ecological function and adaptive significance. Results showed that number of visits was significantly reduced after artificial removal of the staminodes, and pollen number and vitality were significantly reduced by rain and solar radiation. Compared with natural conditions, removing the staminodes also significantly reduced the fruit and seed set ratios, but had no significant effect on the herbivore eating rate. These findings indicate that the staminode is an important organ for D. caeruleum to attract pollinators and can improve reproductive fitness by limiting rain and solar radiation damage, but cannot prevent herbivores from eating the internal flower organs. Thus, the staminode may have important adaptive significance for D. caeruleum to cope with unfavorable environmental conditions.