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

Submitted to: Journal of Pollination Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 21, 2011
Publication Date: June 20, 2011
Citation: Tepedino, V.J., Bowlin, W.R., Griswold, T.L. 2011. Diversity and pollination value of insects visiting the flowers of a rare buckwheat (Eriogonum pelinophilum: Polygonaceae) in disturbed and "natural" areas. Journal of Pollination Ecology. 4(8)57-67.

Interpretive Summary: West central Colorado is currently undergoing rapid change due to human population growth and the development it engenders. The area is home to several plants that occur nowhere else in the world, some of which are listed under the Endangered Species Act. This study reports on a threatened species of buckwheat, Eriogonum pelinophilum, the flowers of which must be visited by insects for seeds to be produced. The small, open, easily exploited flowers of this species are visited by numerous species of bees, wasps, flies and ants, all of which appear to be important pollinators in both undisturbed and disturbed sites. Almost all insect species visit the flowers primarily for nectar but also incidentally collected pollen on their bodies as they visit the flowers. The diversity of flower visitors at any site and the difference in flower visitors between sites makes it almost impossible for conservationists responsible for managing the well being of this species to plan for the health of necessary pollinator populations. Overall, habitat preservation both by federal and private entities is the most promising way to conserve this species and its insects go-betweens.

Technical Abstract: We compared flower-visitors of the endangered plant Eriogonum pelinophilum, at a largely undistributed (UN) and a smaller, highly disturbed and fragmented site (DI). We found no difference between the DI site and the UN site in: 1) flower visitation rate, or 2) species richness of E. pelinophilum flower-visitors; 3) species diversity of flower-visitors was higher at DI than at UN but 4) there was no difference between sites in equitability. We found significant differences 5) among 14 abundant bee species, 6) among eight abundant wasp species, and 7) among 12 abundant fly species in total E. pelinophilum pollen carried on the body; 8) both bee and wasp species tended to carry significantly more pollen on the ventral segments of the body where it would most readily effect pollination; 9) pollen on the body of fly species tended to be more equally distributed on ventral and dorsal body surfaces, compared to Hymenoptera groups, perhaps making them somewhat less valuable as pollinators of E. pelinophilum flowers; 10) a regression of total amount of pollen carried on flower-visitor bodies (dependent variable) with visitor length (independent variable) was highly significant and strongly suggests that the most effective pollinators of E. pelinophilum flowers are the largest visitors; 12) the most abundant flower-visitor, the small ant Formica obtusopilosa, carried 30% morepollen than predicted by its size; in limited trials, that pollen was found to be as viable as pollen collected from some freshly dehisced anthers; despite its size this very abundant ant is undoubtedly a very important pollinator. We end by relating our findings to the conservation of E. pelinophilum.