Asymmetry of post-F1 interspecific reproductive barriers among brown trout (Salmo trutta) and Atlantic salmon (Salmo salar)

Abstract F 1 hybrids of Atlantic salmon Salmo salar females and brown trout Salmo trutta males were backcrossed to four male salmon. Their offspring exhibited statistically significantly higher survival than offspring of F 1 hybrids of brown trout females backcrossed to three salmon. Some diploid progeny were observed in crosses between Atlantic salmon females and F 1 hybrid males, demonstrating that trout×salmon hybrid males can produce reduced gametes. Backcrosses of both hybrid types to brown trout failed. The results as a whole demonstrated that post-mating barriers were asymmetric between Atlantic salmon and brown trout, suggesting that the introgression of brown trout genes into Atlantic salmon gene pools is possible, but not the reverse.