Conspecific Pollen Loads on Insects fromPrunus fasciculata(Rosaceae) Female Flowers in Southern Nevada

Abstract

Desert almond, Prunus fasciculata (Rosaceae), is a Mojave Desert shrub that primarily produces male and female flowers on different plants. I investigated the plant's pollination by examining pollen loads on insects aspirated from female flowers on 3 dioecious shrubs, growing near male-flowering shrubs, at one locality in southern Nevada during March 2014. Pollen loads were analyzed on 9 species of Diptera in Bombyliidae, Syrphidae, Calliphoridae, and Tachinidae and 4 species of Hymenoptera in Andrenidae (all female Andrena). All but 4 of the 65 flies and 38 bees aspirated carried P. fasciculata pollen grains, recognized by their tricolpate shape in polar view and oblate shape in equatorial view. Two species of syrphid flies in Copestylum were frequently aspirated and carried high P. fasciculata pollen loads and moderate proportions of conspecific pollen. High conspecific pollen loads on the tachinid Chaetogaedia also indicated potential for pollinating P. fasciculata. Three of the 4 species of Andrena bees carried large amounts of P. fasciculata pollen. Conspecific pollen also comprised most of the pollen load on Andrena bees, suggesting high flower constancies to the plant. Pollinators of P. fasciculata would vary over the plant's range, and likely between years, because of the localized populations or narrow larval diets of many of the insects collected from flowers. The female desert almond shrubs examined in southern Nevada during 2014 appeared to be pollinated by a variety of native flies and bees, especially syrphid flies in Copestylum and andrenid bees in Andrena.