Extrafloral-floral nectar trade-offs or synergies in cotton (Gossypium)

Background/Question/Methods Species are simultaneously engaged in multiple species interactions, including multiple mutualisms. Because individuals have limited resources, constraints may arise that limit rewards produced to attract multiple mutualistic partners. For example, plants use carbon nectar resources to reward both ants that serve as body-guards against plant herbivores and pollinators that mediate plant sex. Much evidence exists demonstrating trade-offs for multiple antagonistic species interactions, such as an herbivore and a competitor. For example, induced defense against herbivores leads to decreased competitive ability in tobacco. However, we know little of the potential constraints species face when attracting multiple mutualist groups. Across individuals within a species, or across species within a clade, negative correlations among reward traits for different mutualist species would suggest the existence of evolutionary constraints on trait evolution. In contrast, traits could show patterns of multi-mutualist synergies, with positive correlations between rewards provided to different mutualists. Results/Conclusions We ask whether trade-offs or synergies exist for attracting and maintaining two types of mutualists, bodyguards and pollinators, in the cotton clade (Gossypium), including ~40 wild species. In addition, because species are not independent, we use phylogenetically independent contrasts to ask whether evolutionary history influences potential trade-offs or synergies. This research, which evaluates simultaneous engagment of multiple mutualist guilds, is a necessary step forward towards understanding the maintenance of multiple positive interactions. Indeed, most species not only engage with multiple antagonists, but multiple mutualists.