Genetic basis of extremely slow development in a population of Tribolium confusum

Abstract

An extremely slow developing form of Tribolium confusum is described. The slow phenotype is caused by an autosomal recessive mutation, sl (slow). Expression of this allele on growth rate was not significantly altered by diet, although a pleiotropic effect on survival was diet dependent. The allele has become fixed in a laboratory population, producing a phenotypic shift in developmental time of 7.1 standard deviations. Pupal weight is reduced in homozygotes by about 15%. Allele frequency data suggest that fixation of the sl allele may have been the result of selection and not genetic drift. The mutation is discussed in relation to models of phenotypic evolution.Key words: Tribolium, phenotypic evolution, slow development.