12.30 - 13.30
Using ant/plant symbioses to understand cooperation among species
Widespread in nature, mutualistic associations –cooperative interactions between unrelated species– are linked to major evolutionary transitions in life history, and are pivotal for ecosystem functioning. The evolution of mutualisms has long been a riddle: while they are thought to be prone to breakdown, some have persisted for millions of years. Theory predicts that mutualists frequently turn into parasites and exploit their partner. Whether or not cheating is an important selective force in mutualism is hotly debated. I use ant/plant symbioses to understand the evolution and stability of mutualisms.
Drawing on examples from my research, I show that non-reciprocating partners do not share evolutionary history with mutualists. Phylogenetically unrelated exploiters appear to be important players of mutualism stability. If cheating is not a major pathway to mutualism breakdown, then what is? Comparative studies have suggested that return to autonomy (mutualism dissolution) may be a common pathway to mutualism breakdown, but the ecological context of such breakdowns remains unclear.
Using a case study with 12 independent breakdowns, I show that niche shift to areas where partners are scarce appears to be a common pathway of mutualism breakdown, and this also relies on the level of dependency of the mutualism. This further highlights the need and difficulty for mutualists to re-associate at each generation. I present an example of how this risk can be mitigated, by presenting a novel ant/plant farming mutualism restricted to Fiji.