Differences in male courtship in freshwater and marine sticklebacks (Gasterosteus aculeatus)

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Abstract
Earlier studies indicated that the freshwater and marine forms of threespine stickleback (G. aculeatus) in the Little Campbell River are genetically differentiated and that they do not mate randomly. The possible contribution of male courtship to this positive assortative mating was examined. Marine and freshwater sticklebacks were obtained from the Little Campbell River, southwestern British Columbia [Canada]. Males were allowed to build nests in large aquaria and court females. The following courtship behaviors were recorded: zigzag bouts per minute, bites per minute, fanning bouts per minute, glueing, creeping through and the males'' 1st response. Freshwater males zigzag more, bite less and glue more than marine males. The intensity of courtship in freshwater males depends on the form of female courted; marine males do not alter their courtship with different forms of females. Freshwater males typically zigzag on 1st contact with a female and marine males usually bite. This difference in male 1st response is independent of the type of female courted. Differences in male courtship provide a basis for positive assortative mating between the 2 forms of sticklebacks. Selection should favor a male 1st response that signals genotype.