Dep. Theory of Evolution, Biological Faculty, M.V.Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119899, Russia

Abstract

Flowers of Chamaenerion angustifolium, Geranium palustre and G. pratense are visited by more than 100 insect species. For all plants the spectrum of visitors is similar. However the role of insects species in pollination is different and depends on the stamen and stigma length, flexibility of pedicle and feeding behaviour of insect inside flower. The possibility to take and to transport pollen grains usually increase with the size of insect. The nature of this correlation is determined by stamen and stigma length. Pollinators of G.palustre with short stamens and stigmas are smaller than those of Ch.angustifolium and G.pratense. On the other hand, more flexible pedicles of G.palustre prevent the flowers from visits of big insects. Three plants studied by the authors are not equally attractive for different insect groups. Dense inflorescence of Ch.angustifolium and G.pratense that usually are lifted under the grass are very attractive for foraging social insects (honey bee, bumblebee). Flies avoid long distance travelling and prefer single flowers located not far from each other. For instance G.palustre is more attractive for flies not for social bees. It is pollinated mainly by flies and solitary bees with average weight of 10-70 mg. The main pollinators of Ch.angustifolium and G.pratense are honey bees, bumblebees and wasps with average mass exceeding 70 mg.