Physiological consequences of hybridization: early generation backcrossing decreases performance in invasive bigheaded carps

Abstract

Hybridization can influence a range of characteristics and outcomes for an organism; however, relatively little is known about evolutionary consequences on nutritional performance. Information on hybrid nutritional performance would provide an understanding of how hybrids interact with their environment and insights into mechanisms affecting survival. Our goal was to test for relationships between hybridization and nutritional performance in invasive bigheaded carps (Hypophthalmichthys nobilis), silver carp (Hypophthalmichthys molitrix), and their hybrids in the Marseilles reach of the Illinois River, Illinois, USA. Silver carp showed better nutritional performance relative to bighead carp. Early generation bighead and silver carp hybrid groups were intermediate to both parental lines, thereby, reducing their nutritional performance, and advanced generation bighead and silver carp groups were nutritionally more similar to their respective parental species. Differences in gill raker morphology and feeding habits among bigheaded carps and their hybrids are plausible mechanisms explaining observed nutritional performance patterns. In addition to providing unique insights about how hybridization influences the nutritional performance of wild organisms relative to parentals, our findings may have management implications for bigheaded carps if interbreeding persists over time and reduced nutritional performance is further manifested by continued hybridization.