Associations of enzymic and chromosomal polymorphisms in the seaweed fly, Coelopa frigida

Abstract

SUMMARYPopulations of the seaweed fly Coelopa frigida are polymorphic at three loci determining the enzymes peptidase-1 (Pep-i), alcohol dehydrogenase (Adh) and larval esterase-2 (Es-2). Alleles at these loci have been shown by others to be non-randomly associated with each other. In the present paper we report non-random associations between the Adh and Es-2 loci and inversions on chromosome I. The two common alleles Adh-B and D are in strong linkage disequilibrium with the a and /3 inversions, but the Adh-A and C alleles are not so. The X and Y alleles at the Es-2 locus show weak, but still significant, associations with the inversions. We consider possible linkage relationships of the loci on the chromosomal arrangements, and discuss the hypothesis that they constitute part of a coadapted gene complex whose members code for functionally related enzymes.

Female mating preference for large size in Coelopa frigida (seaweed fly)

“…One such character is adult size. The phenotypic variation in adult size is very much greater in males than females (Butlin et al, 1982a,b;Day et a!., 1982), and it is the largest males that consistently exhibit the lowest survival from egg to adult (Collins, 1978;Butlin et al, 1982aButlin et al, , 1984Butlin & Day, 1989). A very much weaker candidate to be the preferred character is the genotype at the Adh locus, which was used by Engelhard et al (1989) andFoster (1989) to study male mating success.…”

“…A very much weaker candidate to be the preferred character is the genotype at the Adh locus, which was used by Engelhard et al (1989) andFoster (1989) to study male mating success. While they obtained evidence for disassortative mating with respect to this locus, they interpreted their results in terms of the chromosome I inversion system with which Ad/i is strongly associated (Day et al 1982). As the chromosome I inversion system is very large, comprising approximately 10 per cent of the entire genome (Aziz, 1975;Day et a!., 1982), it is difficult to distinguish between the effects of size, the Adh locus and the inversion system.…”

“…While they obtained evidence for disassortative mating with respect to this locus, they interpreted their results in terms of the chromosome I inversion system with which Ad/i is strongly associated (Day et al 1982). As the chromosome I inversion system is very large, comprising approximately 10 per cent of the entire genome (Aziz, 1975;Day et a!., 1982), it is difficult to distinguish between the effects of size, the Adh locus and the inversion system. There is known to be strong linkage disequilibrium associated with this inversion system (Collins, 1978;Day et a!., 1982Day et a!., , 1983, no recombination in heterokaryotypes or in males (Day et a!., 1982), and strong heterokaryotypic advantage (Butlin et al, 1982b).…”

“…As the chromosome I inversion system is very large, comprising approximately 10 per cent of the entire genome (Aziz, 1975;Day et a!., 1982), it is difficult to distinguish between the effects of size, the Adh locus and the inversion system. There is known to be strong linkage disequilibrium associated with this inversion system (Collins, 1978;Day et a!., 1982Day et a!., , 1983, no recombination in heterokaryotypes or in males (Day et a!., 1982), and strong heterokaryotypic advantage (Butlin et al, 1982b). Under these circumstances there would seem to be the ideal situation for the operation of a viability indicator system.…”

Genetic differences in mating success and female choice in seaweed flies (Coelopa frigida)

“…This chromosomal rearrangement, which involves over 10 per cent of the genome (Aziz, 1975;Day et a!., 1982), has profound influences on the flies' biology. The two alternative forms (a and /3) are associated with differences in development time (Day et a!., 1980), adult size (Butlin et al, 1982b), adult longevity (Butlin and Day.…”