Bees of the Victorian Alps: network structure and interactions of introduced species.
Bees are considered the most important plant pollinators in many ecosystems, yet little is known about pollination of native plants by bees in many Australian ecosystems including the alpine region. Here we consider bee pollination in this region by constructing a bee visitation network and investigating the degree of specialism and network 'nestedness', which are related to the robustness of the network to perturbations. Bees and flowers were collected and observed from 10 sites across the Bogong High Plains/Mt Hotham region in Victoria. Low nestedness and a low degree of specialism were detected, consistent with patterns in other alpine regions. Twenty-one native and one non-indigenous bee species were observed visiting 46 of the 67 flower species recorded. The introduced Apis mellifera had a large floral overlap with native bees, which may reduce fecundity of native bees through competition. The introduced plant, Hypochaeris radicata (Asteraceae), had the largest and most sustained coverage of any flower and had the most visitations and bee species of any flower. The network developed in this study is a first step in understanding pollination patterns in the alpine/subalpine region and serves as a baseline for future comparisons.