Male mate choice based upon female nuptial coloration in the brook stickleback, Culaea inconstans(Kirtland)

Abstract

Female brook sticklebacks develop distinct nuptial coloration following ovulation. When given a choice between a gravid, uncoloured, inter-spawning interval female and a gravid, nuptially coloured female, male brook sticklebacks from two Ontario populations (1) approached the nuptially coloured female first, (2) directed their first courtship pummel towards her, and (3) spent significantly more time with her than with the inter-spawning interval female. Males from Tooley Creek spent more of their time near the nuptially coloured female engaged in courtship behaviour and more of their time near the inter-spawning interval female engaged in aggressive behaviour. Males from Algonquin Park showed no difference in the intensity of courtship or aggression directed towards the two females. These results corroborate the hypothesis that female nuptial coloration plays a role in signalling courtship readiness in at least some gasterosteids. The hypothesis that males should become more discriminating in their choice of spawning partners as they increase their parental investment was tested by comparing male mate choice based upon female colour for males with no eggs, one clutch and two clutches. The results corroborated the hypothesis: compared to when they were eggless, males with two clutches (1) spent less time with the inter-spawning interval female, (2) spent more time with the nuptially coloured female, (3) spent a greater proportion of the time near the nuptially coloured female engaged in courtship behaviour, and (4) displayed a trend towards increasing levels of aggression directed towards the inter-spawning interval female with increasing parental investment.