The significance of the invasive crucifer species Bunias orientalis (Brassicaceae) as a nectar source for central European insects

Abstract

The Turkish warty cabbage (or Russian old man) Bunias orientalis (Linnaeus 1753) is an extremely succcesful invasive plant species, which has firmly established itself in many central European habitats, and is rapidly expanding. For the first time, the nectar production and pollinators of this plant species are described, in order to predict its value as a food source for native insects. In addition, this study aims to predict possible competitive interactions with native plants in the context of pollination. It was found that nectar production per flower in B orientalis is relatively low. However, because of the extremely high number of flowers per plant and per area, this plant is a valuable food source for energetically demanding visitors such as bumble bees and honeybees. These are the most common visitors to B orientalis, even though classical pollination syndromes would categorise this flower as fly-pollinated. Since B orientalis is an attractive nectar source, it is conceivable that there is a negative impact of its presence on the fitness of native species, simply by depressing visitation frequencies to other species.