Multifunctional Roles of Extrafloral Nectaries in Shaping Plant-Insect Interactions.

Understanding the net outcomes of ecological interactions by examining the costs and benefits of organism associations is central to ecology. The mutualistic relationship between ants and plants mediated by extrafloral nectaries (EFNs) has long been viewed as protective, with ants defending plants from herbivores in exchange for nectar. However, alternative hypotheses, like the ant-distraction and flower-distraction, highlight the multifunctionality of EFNs. The flower-distraction hypothesis proposes that EFNs evolved to divert ants from flowers, reducing ant impact on pollination. Recent studies reveal that EFN interactions with ants are highly context-dependent, shaped by factors such as EFN location and ant behavior. Although EFNs often occur on vegetative tissues, they are sometimes located near flowers, raising the possibility that they serve both protective and distracting roles. This duality challenges the notion that EFNs can be categorized exclusively by location or function. Instead, their ecological roles likely shift in space and time, depending on plant growth form, pollination system, and interacting species. We propose moving beyond a dichotomous framework toward a nuanced perspective that embraces a potential continuum of functionalities. Considering multiple ecological and evolutionary factors will enhance understanding of EFN evolution, plant-animal interactions, and ecosystem dynamics.