Genetic basis and fitness consequences of winglessness in the two-spot ladybird beetle, Adalia bipunctata

The genetic basis and fitness consequences of winglessness were investigated in the two-spot ladybird beetle, Adalia bipunctata. By breeding lines from a wingless individual found at The Uithof, Utrecht in The Netherlands, the wingless condition was confirmed to be under the control of a major allele, recessive to the wild type. Wingless individuals, on average, had a longer developmental period, a lower egg production and a shorter lifespan than the wild type with wings, suggesting that the expression of the wingless allele has functionally interrelated gene actions involving a wide range of fitness components. While the wingless allele influences various traits, significant among-family variation in the degree of winglessness suggests that its phenotypic expression is also dependent on the genetic background and modifier loci. Furthermore, there was a consistent pattern of correlation between the degree of winglessness and life history traits; the most extreme wingless individuals showed the lowest fitness while those with more fully developed wings tended to have the highest fitness. This correlation suggests that the modifier genes influence both wing formation and fitness components. The significance of such epistatic effects to the evolution of flightlessness in insects is discussed.