Format: ORAL

Graham Pyke, Zong-Xin Ren & Nickolas Waser

Determining how floral nectar attributes have evolved and continue to evolve is important and necessary for understanding, managing, conserving and manipulating plant biology. However, there are several pitfalls that can and do arise along this path. One pitfall is the assumption, often implicit, that plants evolve nectar attributes to benefit their animal pollinators, rather than themselves. Instead, floral nectar should be viewed as an evolutionarily stable strategy with fitness outcomes clearly identified for both plant nectar production and pollinator behaviour. To suggest that pollinators preferentially visit or revisit individual plants on the basis of their nectar attributes is similarly problematic because pollinators are generally unable to assess nectar attributes of a flower (volume, concentration, composition) without probing it and removing its nectar and unlikely to remember and preferentially revisit or avoid particular plants based on encountered nectar. Another pitfall is to argue, also often implicitly, that a plant population or species has certain nectar attributes because these attributes benefit the population or species rather than an individual plant. There are also problems with attempts to measure what has been termed ‘phenotypic selection’ by observing correlations across individual plants between some measure of plant reproductive fitness (e.g., seed set) and various phenotypic traits, possibly including nectar attributes. In addition, measurements of ‘phenotypic selection’ sometimes omit consideration of male function reproduction which should be half the story. A final pitfall may arise when attempts are made to determine the nature and extent of natural selection in relation to nectar attributes through experimental manipulation because such experiments may not leave everything else unchanged. Determining how floral nectar attributes evolve will therefore require a carefully developed approach with much care given to avoiding the pitfalls described above. However, this may not be easy, especially given how easy it is for these pitfalls to arise.