The evolution of mutualism between alpheid shrimp and gobiid fishes: a balance between benefits and costs

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Issue Date
1-Aug-12
Authors
Lyons, Patrick
Publisher
The Graduate School, Stony Brook University: Stony Brook, NY.
Keywords
Abstract
I describe several assays designed to examine how costs and benefits interact in the development of mutualisms between species. A mutualism occurs between alpheid shrimp and gobiid fishes. These shrimp have poor vision but good burrowing ability. Individual shrimp share their burrows with a goby that, with good vision but no burrowing ability, acts as a watch-out warning shrimp when predators approach. In the Caribbean, a single species, Nes longus, which has been described as a mutualist, follows these behaviors. Others, such as Ctenogobius saepepallens, casually use shrimp burrows, rarely warn shrimp of danger, and are better described as commensalists. I found that N. longus more effectively avoids predators while using shrimp burrows than C. saepepallens. Thus, tight mutualism with shrimp is advantageous, especially in areas where shrimp burrows are abundant. I have quantified several behaviors that likely allow N. longus to use burrows more effectively. Why then would C. saepepallens not evolve such behaviors and become a strict mutualist if strict mutualism is advantageous? For gobies, there is likely a cost associated with mutualism with shrimp. To warn shrimp, gobies must remain at a burrow entrances and restrict foraging to that small area. I found that on the same restricted diet, C. saepepallens lost more weight than N. longus. Thus, C. saepepallens may be constrained to a casual association with shrimp due to foraging requirements. This story indicates that strict mutualism may evolve infrequently because few species can overcome the inherent costs of mutualism.
Description
106 pg.
DOI