Diversity and pollination value of insects visiting the flowers of a rare buckwheat (Eriogonum pelinophilum: Polygonaceae) in disturbed and "natural" areas

Abstract

We compared flower-visitors of the endangered plant Eriogonum pelinophilum, at relatively undisturbed and highly disturbed sites. We found no difference between sites in flower visitation rate or species richness of flower-visitors; species diversity of flower-visitors was higher at disturbed than at undisturbed sites but there was no difference in equitability. We found significant differences in total E. pelinophilum pollen carried on the body among 14 abundant bee species; eight abundant wasp species; and 12 abundant fly species. Both bee and wasp species carried significantly more pollen on the ventral compared to dorsal segments of the body; pollen on the body of fly species was more equally distributed across body surfaces. Total pollen carried on flower-visitor bodies was significantly related to visitor length, suggesting that larger visitors were more effective pollinators. Total Pollination Value, a measure combining both visitor abundance and body pollen was greater at the disturbed site than the undisturbed site, further suggesting that pollination in fragments of this rare species is not a major concern. We conclude that the high diversity of insect flower-visitors and the generalized nature of E. pelinophilum flowers make a special management programme to conserve pollinators unnecessary. Conservation of this buckwheat is best achieved by simple habitat preservation, together with a program to enlist private citizens to include buckwheat plants in their backyard gardens.

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