As the pace of global change increases, understanding how new interactions arise and how established interactions disappear is exceedingly important. On group of interactions that is of ecological and economic importance are mutualisms. Often mutualisms are facultative and comprised of multiple partners that come and go over time. Here we present work exploring the impact of having multiple partners in facultative mutualistic interactions. In coffee agroecosystems, the green coffee scale, Coccus viridis has a number of mutualistic ant partners, which makes it a good model system to study the impact of multiple mutualists partners. In this project, we measured C. viridis fitness when being tended by only the ant Azteca sericeasur, only the ant Brachymyrmex spp, by multiple ants, and by no ants. To do this, we located coffee plants with C. viridis tended by Azteca (n=5), Brachymyrmex (n=13), other ants (Solenopsis spp, Pheidole spp, Crematogaster spp, etc) (n=13) and not tended by any ants (n=13), and monitored them for fourth weeks. On each plant, we recorded the number of healthy and damaged C.viridis in addition to data on the community of natural enemies associated with C.viridis
Results/Conclusions
Over the course of our four week survey we found that plants with any ant group maintained higher proportions of health scales than plants with no ants at all, suggesting that ants are generally providing benefit to populations of the C. viridis. We also found that plants solely dominated by Azteca and Brachymyrmex did not have any significant differences in terms of the proportion of health the C.viridis on a plant. Interestingly plants that had an ephemeral mixture of various ant species kept a higher proportion of healthy C.viridis than Brachymyrmex. This finding suggests that there is possibly a complementary effect of having multiple mutualistic partners through time. We also investigated potential interactions that ant species may have with the community of natural enemies associated with C. viridis. We found no differences in abundance of syrphid fly larvae, ladybird beetle adults and larvae, and parasitism rates across the different ant groups. Interestingly we did find that the predatory fungi of the C. viridis, L. lecanii, is more abundant on plants dominated by Azteca. Overall our results suggest that the identity of a mutualistic partner can have important impacts on the dynamics and long-term persistence of a mutualism. Additionally we have shown that different mutualists may offer different types of benefits.