Inbreeding depression affects fertilization success and survival but not breeding coloration in threespine sticklebacks

Abstract

Summary Inbreeding depression is a well-studied phenomenon which has been demonstrated in many animal and plant species. In fishes, most studies focus on species of commercial interest. Sticklebacks often colonize new habitats by starting with a small founder population which, thus, suffers a high risk of inbreeding. However, little is known about the degree of inbreeding depression of sticklebacks’ life-history traits like fertilization success or hatching and survival rate. Furthermore, there is a general lack of knowledge about the impact of inbreeding on sexually selected traits like males’ breeding coloration. In our study, one generation of inbreeding by brother–sister mating of wild-caught, anadromous sticklebacks significantly lowered the fertilization and hatching success of eggs. This effect was intensified by a second generation of inbreeding. Furthermore, fewer inbred individuals reached and survived the reproductive phase than outbred ones. However, surviving inbred and outbred males did not differ significantly in the intensity of red throat or blue eye coloration. Our data indicate that even one generation of inbreeding leads to a loss of fitness in threespine sticklebacks.