The severe invasion of Sosnowsky’s hogweed Heracleum sosnowskyi favours European honeybees Apis mellifera over other pollinators

Abstract

Pollinators, such as the generalist European honeybee Apis mellifera, can attend flowering invasive plants. However, studies linking the characteristics of invasive plants with the occurrence of various pollinating insects are lacking. This study investigates whether and how areas invaded by Sosnowsky’s hogweed Heracleum sosnowskyi impact the abundance of A. mellifera and non-Apis pollinators, and the influence of invading species characteristics, as well as the distance to the nearest apiary on their co-occurrence. Pollinator surveys were conducted at 34 sites in southern Poland, each containing three study plots with varying invasion severity (uninvaded, less invaded, severely invaded). Honeybees were up to four and three times more abundant in severely invaded than uninvaded and less invaded plots, respectively. Hogweed flowering number attracted honeybees in severely invaded plots and non-Apis pollinators in less invaded ones. In severely invaded plots, the abundance of honeybees decreased when pollinated hogweed flowers became more frequent while the abundance of non-Apis pollinators increased. This study demonstrated that honeybees were highly attracted by the characteristics of invasive plant species reflecting severe invasion at the expense of other pollinators.