Life history of Bicyclus anynana mutants: Can they serve as internal controls?

Correction for environmental effects in quantitative genetics experiments is often achieved by use of separate control populations. However, this method may not always correct accurately for environmental fluctuations in rearing conditions. A more suitable approach could be rearing mutants together with experimental groups, provided that these mutants are clearly distinguishable phenotypically and have similar life histories. We tested whether two mutants (yellow and Spotty) available for the tropical butterfly Bicyclus anynana could serve as such true internal controls. The yellow butterflies had lower survival and longer development time than the wild type animals they were reared with, whereas Spotty individuals were equivalent in those respects to their wild type counterparts. Moreover, heritability estimates for development time in the Spotty stock were mostly significantly different from zero and fell within the range found for wild type butterflies. Therefore, we conclude that a backcrossed stock homozygous for the Spotty mutant of B. anynana can reliably serve as an internal control in life-history studies and we discuss potential advantages of this method.