Plant-pollinator co-evolution: it's time to reconnect with Optimal Foraging Theory and Evolutionarily Stable Strategies

Pollination syndromes (correlations between floral and pollinator traits), have long interested ecologists, but remain inadequately explained. For example, plant species pollinated by relatively large animals cannot have evolved correspondingly high rates of nectar-energy production simply because such animals need relatively more energy; evolution does not work that way. The inverse correlation between pollinator body-size and nectar concentration is similarly difficult to explain.To remedy this, I propose that Optimal Foraging Theory (OFT) and the Evolutionarily Stable Strategy approach (ESS) be combined and applied to pollination syndromes. Both hypothesise that, through evolution, average biological fitness of individuals has been maximised. OFT predicts foraging consequences for pollinators varying in body size, and other attributes, allowing the ESS approach to be applied to co-adapted plant-pollinator traits. This should lead to predicted relationships between plants and their pollinators.The steps involved in this process are conceptually straightforward, but empirically difficult, which may explain why the approach has been very little pursued in the past. However such difficulties can be overcome, thus pointing to the future.We surely need to understand pollination systems, in order to conserve and manage them. It is therefore time to reconnect OFT and plant-pollinator co-evolution, within the general ESS approach, and hence increasing our understanding of pollination syndromes and other plant-pollinator relationships.