The inheritance of female polymorphism in the damselfly ischnura (Rambur) (odonata: Coenagrionidae)

Abstract

The damselfly Ischnura graellsii has three female coloration patterns: the male-like coloured or androchromatypic (A) females, and two gynochromatypic females: infuscans (olive-green to brown females, I), and aurantiaca (orange to brown females, O). The inheritance of this polymorphism was studied by rearing the offspring of 33 laboratory crosses. Fourteen F1, eight F2 and eleven F3 crosses produced more than 2400 adults in laboratory conditions. Results of these crosses indicate: (1) the progeny of one female can consist of one, two or all phenotypes; (2) when two phenotypes occur the ratio is 1:1 or 3:1; and (3) when all phenotypes occur the ratio is 2:1:1 for A: I: O females. The simplest hypothesis to explain these results is that three alleles of one autosomal locus control this polymorphism. The androchromatypic allele (pa) is dominant over both gynochromatypic alleles, and infuscans (pi) over aurantiaca (po) (Dominance: pa>pi>po). Males possess all six possible genotypes but only one phenotype (pa). All matings were compatible with the hypothesis, and the presence of all genotypes was proved with the matings obtained. Hypotheses about the maintenance of female polymorphism in Ischnura damselflies so far studied are revised. © 1990 The Genetical Society of Great Britain.