Pectoral fins and paternal quality in sticklebacks

Sexual selection through female mate choice exerts a strong selection press ure on males' sexual traits, particularly when direct benefits are involved . In species with male parental care, one would expect sexual selection to favour paternal quality, for instance through selection on morphological st ructures which promote quality. We experimentally studied the influence of pectoral fins on paternal quality in male three-spined sticklebacks (Gaster osteus aculeatus L.). After reductions of fin area to different degrees, si milar-sized males had to perform a complete reproductive cycle in enclosure s in the field. The collected data on fanning behaviour and egg development showed that a reduction in pectoral fin size affected paternal quality pro bably through an increased beat frequency of the pectorals. Thus, pectoral fins can potentially signal paternal quality to choosy females.