Flower-visiting preferences of bumble bees (Apidae: Bombus spp.) in grasslands of the Velyka Dobron' Game Reserve (Transcarpathia, Ukraine)

Frequency of flower visitations of six bumble bee (Bombus) species was surveyed in Transcarpathia (Ukraine). hi four areas of the Game Reserve of Nagydobrony and surroundings five-five sampling quadrates were designated. The frequency of flower visitations of 16 dominant plant species (7 spp. in Fabaceae, 3 spp. in Asteraceae, 3 spp. in Lamiaceae, and 3 species from other families) were registered in four repetitions in mid-summer. The most frequent large bumble bee species, B. terrestris, exploited the widest spectrum of flower sources, with insignificant preference for Lotus corniculatus, Prunella vulgaris and Lythrum salicaria. The flower visitation of B. lapidarius was characterised by the high frequency of L. salicaria and Medicago sativa. The small bumble bee species, B. pascuorum, B. sylvarum and B. humilis, also showed significantly different preferences. Generally, the three most frequently visited plant species belonged to Fabaceae, followed by Symphytum officinale (Boraginaceae). We did not observe any significant difference between large vs. small bumble bees, either concerning the nectar source families or in length and shape of the visited flower corollas. Significant influence of flower colours, both as they are experienced by bumble bees (blue, bluish-green) and according to the visible colours (purple), was found on the flower visitation by nearly all bumble bee species. Since practically all species have shown somewhat different preferences for nectar sources, we could not observe any genuine communities of bumble bees; however, accidental feeding assemblages can exist based on high preferences of species in Fabaceae.