Effects of invasive American signal crayfish (Pacifastacus leniusculus) on the reproductive behaviour of threespine stickleback (Gasterosteus aculeatus) sympatric species pairs

Abstract

Environmental change, including that caused directly or indirectly by invasive species, presents a major threat to the persistence of native freshwater biodiversity. The invasive American signal crayfish ( Pacifastacus leniusculus (Dana, 1852)) has recently been implicated in the collapse of a pair of threespine stickleback ( Gasterosteus aculeatus L., 1758) species in Enos Lake, British Columbia, through introgressive hybridization; yet there are few data describing potential interactions between crayfish and these recently evolved stickleback species. We conducted a behavioural study, using an intact sympatric G. aculeatus species pair from a nearby lake, to examine if and how interactions with P. leniusculus may influence the breeding behaviour of sticklebacks. We found that the reproductive behaviour of limnetic males was disrupted to a greater degree than that of benthic males, suggesting that crayfish may disproportionately impact limnetic male reproductive success and may have contributed to biased hybridization between the Enos Lake species pair. Our study illustrates how newly differentiated taxa may be especially susceptible to environmental perturbations, particularly those caused by invasive species.