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Mutualistic traits can confer a selective advantage in a simple consumer-resource feedback model.
Golubski, Antonio*,1, 1 University of Illinois at Chicago, Chicago, IL
ABSTRACT- A central question regarding mutualisms remains what prevents "cheaters", which reap mutualistic benefits but provide nothing in return, from enjoying a selective advantage. Consumer-resource feedback models are developed here that simulate two competing consumers; the more mutualistic consumer gains less from a given resource patch but has a greater positive impact on future resource availability, and the less mutualistic consumer benefits the resource less but gains more from any given patch. Consumers disperse inoculum (and win patches next time step) in the proportions with which they obtain resources, and die at the end of each time step. In spatially explicit simulations, the more mutualistic consumer can exclude its competitor; spatially implicit versions of the model show that local dispersal is required for this outcome. These results show that in principle a mutualist can gain a selective advantage by sacrificing its ability to acquire resources in order to stimulate future resource production. This mechanism parallels those suggested to promote prudent predation or intermediate parasite virulence, but, as shown here, can operate without consumers having net negative effects on the resource or displaying any particular behaviors such as defending resource patches or abandoning patches with low resource abundance. Further, neither partner fidelity nor partner choice was explicity included. The effects of consumers were also integrated over several patches to explore the significance of co-infection of a host by multiple consumer types and the significance of non-additive effects of multiple consumers; the results suggest that added benefit of multiple partners can allow consumer coexistence. These models broaden the mechanisms by which and conditions under which mutualistic traits might be expected to be advantageous.
Key words: consumer-resource feedback, feeding restraint, mutualism, co-infection