Investigations of pollinators species diversity in boreal forests in Lithuania

Abstract

Pollination of flowers by animals, which involves a significant fraction of invertebrate animals, is believed to play a crucial role in generating and sustaining the biodiversity of terrestrial ecosystems. Domesticated pollinators contribute a lot less than wild pollinators. While there are few definitive studies, all estimates put wild pollinators as pollinating most insect pollinated outdoor crops and wildflowers, some studies put wild pollinators at over 90%. We studied the impact of forest clear cuts on pollinator visitation to flowers of common vascular plant species from Vaccinio-myrtillosa forest understory. We selected Ericaceae shrubs Calluna vulgaris L., Vaccinium myrtillus L. and V. vitis-idaea L., which are indicator species of North European conifer forest understory. To record insect activities, we used digital video cameras, which is a standard procedure in many similar studies. For each plot, we completed at least 12 rounds of observations on both clear cut and mature stands. The highest visit frequency (4.9 ±2.7) and most diversified pollinator assemblage were recorded for C. vulgaris. This included social bees (A. mellifera and Bombus sp.), solitary bees (Andrena sp.), ants, sphecid and true wasps, ichneumonids, butterflies (Polygonia c-album; Nymphalidae), and flies from the family Calliphoridae and Syrphidae. Our transect walks revealed that flowers of both Vaccinium species were visited mostly by social bees (Bombus sp.), solitary bees (Andrena sp.), wasps (Vespidae), and also by hoverflies (Syrphidae). We recorded visits of ants (Formicidae). Ants are an important element of boreal forest ecosystems, and some authors suggest that potentially they could be important in pollination of species with easily accessible flowers producing little nectar and occurring in high local densities.