Abstract
A classical notion in evolutionary biology is that ecological specialisation is a hazardous dead-end street. In this view, if the ecological conditions change, specialists cannot cope and are therefore faced with extinction. A recent theory by P.A. Aigner, challenges this notion in the context of pollination biology. The provocative idea is that a plant can display striking specialisation to a less efficient pollinator, provided that such specialisation does not interfere with the benefits conferred by more efficient pollinators. In other words, plants may be 'cryptic generalists', while their phenotype seems to match predictions of adaptation to a particular pollinator type. We found an ideal model system to study this hypothesis. The Canary Islands contain a unique guild of endemic plant species with orange-red flowers, which appear to be specialised to bird pollination. Yet there are no (more) specialised flower-visiting birds in the Canary Islands. Can extant plant species be specialised to extinct pollinators? Some workers have suspected that these flowers are pollinated by unspecialised birds, but quantitative data are absent. Could these flowers have been pollinated mostly by bees or other insect pollinators, ever since their avian pollinators became extinct in the Pliocene? The unique history of these plants offers a rare opportunity to test Aigner's hypothesis in a new framework: is it possible to retain ecological specialisation (to bird pollinators) without sacrificing the advantages of being a generalist (i.e. being pollinated by a broader spectrum of visitors)? To tackle this question, we propose a quantitative approach to identify the relative values of different pollinators for these flowers.
United Kingdom