PubMed Health⌕ Search

Biomedical subjects

T H Day

Publications and source records attributed to T H Day.

15 recordsLinked to original sources
PubMed1995

Heritability of a sexually selected character expressed in both sexes.

Sexual selection is thought to be responsible for the evolution of exaggerated male characters and of female mate preferences. Evolutionary mechanisms driven by an advantage to the progeny are only effective if the preferred character has a large genetic component of variance; in most systems in which sexual selection operates, little is known of the relevant genetics. We have measured parent-offspring correlations, and report here that the preferred character (adult size) in seaweed flies has large additive genetic variance in males, but not in females. Virtually all the variance in male size is attributable to a chromosomal inversion system and, consequently, because this system is also a major determinant of larval viability, male size could be used by females as a reliable indicator of offspring survival.

Animals↗
PubMed1989

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

An association is described in seaweed flies, Coelopa frigida, between the genotype at the alcohol dehydrogenase (Adh) locus and mating success in pairwise mating trials. Significantly higher mating success was observed in females that carried the Adh-C allele, but no association was observed between Adh genotype and male mating success. There was heterogeneity in the success of different combinations of males and females, but only when the female lacked the C allele. Analyses of video recordings indicated that C-bearing females spent longer mounted by males and that they less frequently rejected males. Evidence is presented for mate discrimination by females not carrying a C allele. The significance of there being genetic differences in both mating success and in female discrimination are discussed in the context of previous results on mating behaviour in natural populations.

Alcohol Dehydrogenase↗
PubMed1982

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

Populations of seaweed fly Coelopa frigida are polymorphic at three loci determining the enzymes peptidase-1 (Pep-1), 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 alpha and beta 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.

Alcohol Oxidoreductases↗
PubMed1982

Genetic variation at the alcohol dehydrogenase locus in natural populations of the seaweed fly, Coelopa frigida.

Samples of the seaweed fly, Coelopa frigida, from six populations widely spaced around the English coast were collected during 1974-76 and again in 1979-80. Gene frequencies at the Alcohol dehydrogenase (Adh) locus were found not to vary significantly between sites, nor over the five year period of their study. Genotype distributions are compared with Hardy-Weinberg expectations and show consistent, mostly significant, differences. These results are interpreted in the light of an association between the Adh locus and a chromosomal inversion polymorphism. It is argued that the remarkable geographical uniformity must indicate the presence of strong selection, probably taking the form of heterokaryotypic advantage.

Alcohol Oxidoreductases↗
PubMed1980

Alcohol dehydrogenase polymorphism in the seaweed fly, Coelopa frigida.

Seaweed flies (Coelopa frigida) inhabit piles of decaying seaweed on the seashore. All populations so far studied have been found to be polymorphic at the alcohol dehydrogenase locus (Adh). This article reports an attempt to identify some of the forces of natural selection that may be maintaining this polymorphism First, the genetic determination of the rather complex isozyme system is described. Several inbred lines homozygous at the Adh locus were derived and the biochemical properties of their allozymes compared. Significant differences in both specific activities and thermal stabilities were found between ADH allozymes. A simple experiment is reported in which individuals with different Adh genotypes were cultured in competition with each other in the presence of elevated levels of ethanol. Although the presence of ethanol resulted in greater mortality, there is no evidence that it was selective with respect to the Adh genotypes. The possible relevance of these results to the maintenance of the Adh polymorphism is discussed.

Alcohol Oxidoreductases↗