Behavioral variation in pelvic phenotypes of brook stickleback, Culaea inconstans, in response to predation by northern pike, Esox lucius

Synopsis

Populations of Culaea inconstans, from Alberta and Saskatchewan, Canada exhibit phenotypic variation in expression of the pelvic skeleton and associated spines, from complete presence (with) through intermediate forms to complete absence (without). Such variation influences predation by Esox lucius which prefer the least spiny prey. Behavioral differences were investigated before and during pike predation. These differences may be associated either with the phenotype (with, without) or size of the stickleback (small, medium, large). Univariate differences between the 12 possible groups in mean time spent in various behaviors were due primarily to size ( = age) effects and presence or absence of the predator. The groups also exhibited phenotypic differences in multivariate means (centroids) of these behaviors. The phenotypes differed in variation of these behaviors, both univariately and multivariately, and such variation resulted in inappropriate behavior being exhibited when a predator was present. These differences were in a direction to counterbalance morphological effects of spine absence, thus likely assist in the maintenance of the without phenotype in the population.