Abstract
Winglessness in the two-spot ladybird beetle Adalia bipunctata (L.) is determined by a single locus with the wingless allele recessive to the winged wildtype allele. The expression of the wingless trait is highly variable, with individuals missing a vari- able part of elytra and flight wings; the elytra and wings appear to be truncated rather than miniature in form. The degree of wing- lessness is partly determined genetically. Here we report on the phenotypic plasticity of the degree of winglessness. The environmental effect on elytron length relative to maximal elytron length in wingless phenotypes was studied by rearing offspring of single pair crosses of this form at a low (19°C) or high (29°C) temperature. Offspring reared at 19°C showed relatively longer elytra than those reared at 29°C.
Highlights
Winglessness has evolved many times in insects in response to a change in ecological conditions, for example on high mountains or in caves (Roff, 1990)
Families each show a similar trend across temperatures, with individuals reared at 19°C having longer elytra than those reared at 29°C, and two families show highly significant heterogeneity chi-square values (Table 1)
Our results show an effect of temperature on the relative elytron size in wingless A. bipunctata
Summary
Winglessness has evolved many times in insects in response to a change in ecological conditions, for example on high mountains or in caves (Roff, 1990). In contrast to many other insects whose reduced wings resemble miniature normal wings (Darlington, 1936), both reduced elytra and flight wings of wingless A. bipunctata seem to be truncated Marples et al (1993) showed for an individual found near Utrecht in The Netherlands that the presence of the wingless character is controlled by a recessive allele at a single locus. The wingless trait shows variable levels of phenotypic expression, resulting in a variable degree of winglessness (DWL), with wingless individuals missing all or a variable part of elytra and flight wings. The presence of the trait is controlled by one gene but the expression of the trait is probably controlled by more genes (i.e modifier loci), resulting in a variable degree of winglessness
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