Translator Disclaimer
1 April 2009 How to Prevent Cheating: A Digestive Specialization Ties Mutualistic Plant-Ants to Their Ant-Plant Partners
Author Affiliations +

Mutualisms often involve reciprocal adaptations of both partners. Acacia ant-plants defended by symbiotic Pseudomyrmex ant mutualists secrete sucrose-free extrafloral nectar, which is unattractive to generalists. We aimed to investigate whether this extrafloral nectar can also exclude exploiters, that is nondefending ant species. Mutualist workers discriminated against sucrose whereas exploiters and generalists with no affinity toward Acacia myrmecophytes preferred sucrose, because mutualist workers lacked the sucrose-cleaving enzyme invertase, which is present in workers of the other two groups. Sucrose uptake induced invertase activity in workers of parasites and generalists, but not mutualists, and in larvae of all species: the mutualists loose invertase during their ontogeny. This reduced metabolic capacity ties the mutualists to their plant hosts, but it does not completely prevent the mutualism from exploitation. We therefore investigated whether the exploiters studied here are cheaters (i.e., have evolved from former mutualists) or parasites (exploiters with no mutualistic ancestor). A molecular phytogeny demonstrates that the exploiter species did not evolve from former mutualists, and no evidence for cheaters was found. We conclude that being specialized to their partner can prevent mutualists from becoming cheaters, whereas other mechanisms are required to stabilize a mutualism against the exploitation by parasites.

© 2009 The Society for the Study of Evolution.
Stefanie Kautz, H. Thorsten Lumbsch, Philip S. Ward, and Martin Heil "How to Prevent Cheating: A Digestive Specialization Ties Mutualistic Plant-Ants to Their Ant-Plant Partners," Evolution 63(4), 839-853, (1 April 2009).
Received: 1 April 2008; Accepted: 1 November 2008; Published: 1 April 2009

This article is only available to subscribers.
It is not available for individual sale.

Get copyright permission
Back to Top