Ecology and evolution of sympatric sticklebacks (Gasterosteus): mate choice and reproductive isolation in the Enos Lake species pair

Morphological, genetic, and ecological evidence indicates that two species of sticklebacks (Gasterosteus) coexist in Enos Lake, Vancouver Island. These species are referred to as benthics and limnetics (the names allude to their foraging behaviour and distribution within the lake). Field observations, mate choice experiments, and courtship experiments were conducted to determine if courtship behaviour contributes to reproductive isolation between these two species. Reproductive males and females of both species regularly encounter each other in nature and occasional heterospecific courtships occur. In laboratory mate choice experiments, males and females of both species selected only conspecific mates. In forced courtship experiments, behavioural differences between limnetics and benthics were more pronounced in the early phases of courtship than in the late phases of courtship. Some aspects of male courtship changed with the species of female courted; this suggests that males can distinguish the two type...