Ethological isolation of plants 2. Odour selection by honeybees
Patrick H. Wells And Harrington Wells
The behaviour of honeybees (Apis mellifera) foraging in a patch of artificial flowers was studied experimentally with colour and odour as manipulated variables. Honeybees associated food with colour and/or odour and established individually constant foraging patterns. In a patch of colour-dimorphic flowers some bees were constant to yellow and some to blue flowers when all flowers provided clove-scented rewards. The colour-constancy of individual bees was not altered when the scent of all rewards was changed to peppermint. However, when the scent of only one colour morph was changed, some bees remained constant to colour, whereas others switched colour attachment and remained constant to odour. In a patch of uniformly coloured but odour-dimorphic flowers some bees were constant to peppermint scented and some were constant to cinnamon-scented flowers. A change in the colour of all flowers did not reduce the level of odour-constant foraging. Individual constancy to either colour or to odour can be sufficient to restrict gene flow between flower morphs. Whenever such individual constancy of pollinators occurs in nature, sympatric differentation of flower morphs is possible.