Date of Award


Document Type


Degree Name

Master of Science (MS) in Biology




"Background: Sensory bias models of the evolution of sexually selected traits predict that trait preferences evolve in a nonsexual context such as prey selection. Indicator models predict that sexually selected traits indicate mate condition. I investigated the potential for sensory exploitation and condition indication models to explain the evolution of what appears to be a recently evolved sexually selected trait. Question: Did red pelvic spine coloration in male Turnbull National Wildlife Refuge (TNWR) brook stickleback (Cu!aea inconstans) evolve to exploit a preexisting sensory bias for red prey, thus helping males draw females to the nest? Or, did it evolve as an intersexual signal indicating male condition to females? Methods: I recorded the frequency of red pelvic spine coloration in males versus females and breeding versus non-breeding males. I measured the condition factor of males with and without red coloration on their pelvic spines. I presented fish with a paired choice between a red versus an orange, yellow, green, blue, or purple bead, and recorded the proportion of bites at each color. I tested for sexual dimorphism in pelvic spines and made observations on their use by territorial males in comparison to dorsal spines. Results: Red coloration is significantly more common in males than females and in breeding than nonbreeding males. TNWR brook stickleback prefer red to other colors in a predation context. Males with strongly red pelvic spines have a significantly higher mean condition factor than those with plain spines. Pelvic spine size is similar in males and females. Males tend to extend their dorsal spines more often than their pelvic spines during agonistic encounters. Conclusions: Red pelvic spine coloration of TNWR brook stickleback is a secondary sexual character which may exploit a preexisting sensory bias for red prey while also indicating condition to females"--Document.


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