Abstract
Each marine mussel which has been studied has a polymorphism for leucine aminopeptidase (LAP) loci. In each case, there is a deficit for all, or nearly all, classes of heterozygotes. The consistency of the results suggests that the loci constitute non-transient polymorphisms with heterozygous disadvantage. No satisfactory explanation of this situation has been available. Heterozygous deficits are also often found at other loci in mussels, particularly those encoding aminopeptidase (AP) enzymes. The present work was prompted by the theoretical investigations of Hastings (1982) which revealed the possibility that selective interactions with other loci might enable the maintenance of polymorphisms with marginal underdominance. Non-random associations between genotypes were sought in 10 loci (in four groups of enzymes with related functions) in Brachidontes rostratus and five loci (in two groups) in Xenostrobus pulex. Five of the 30 pairs of loci displayed significant genotypic associations. However, none of these comprised functionally-related enzymes. It remains possible that epistatic interactions may, in special circumstances, be involved in the maintenance of variation. But the process seems unlikely as a general explanation of genotypic frequencies of the LAP and AP polymorphisms of mussels.
Similar content being viewed by others
Article PDF
References
Adamkewicz, L, Taub, S R, and Wall, J R. 1984. Genetics of the clam Mercenaria mercenaria. I. Mendelian inheritance of allozyme variation. Biochem Genet, 22, 215–219.
Ahmad, M, and Hedrick, P W. 1985. Electrophoretic variation in the common mussel, Mytilus edulis: random association of alleles at different loci. Heredity, 55, 47–51.
Beaumont, A R, Beveridge, C M, and Budd, M D. 1983. Selection and heterozygosity within single families of the mussel Mytilus edulis (L.). Marine Biol Lett, 4, 151–161.
Colgan, D J. 1980. Theoretical and Practical Studies on Genetic Fitness Ph.D. Thesis, University of Melbourne, Melbourne.
Colgan, D J. 1981. Spatial and temporal variation in the genotypic frequencies of the mussel Brachidontes rostratus. Heredity, 46, 197–208.
Colgan, D J. 1984. The effects of linked loci on estimates of relative viability derived from pedigree analysis. Heredity, 53, 69–77.
Colgan, D J. 1986. Developmental changes in the isoenzymes controlling glycolysis in the acridine grasshopper, Caledia captiva. W Roux Arch Dev Biol 195, 197–201.
Foltz, D W. 1986. Null alleles as a possible cause of heterozygote deficiencies in the oyster Crassostrea virginica and other bivalves. Evolution, 40, 869–870.
Garthwaite, R. 1986. The Genetics of Californis populations of Guekensia demissa (Dillwyn) (Mollusca): further evidence on the selective importance of leucine aminopeptidase variation in salinity acclimation. Biol J Linn, Soc, 28, 343–358.
Gartner-Kepkay, K E, Dickie, L M, Freeman, K R, and Zouros, E. 1980. Genetic differences and environments of mussel populations in the Maritime provinces. Can J Fish Aquat Sci, 37, 775–782.
Harris, H, and Hopkinson, D A. 1977. Handbook of Enzyme Electrophoresis in Human Genetics North-Holland, Amsterdam.
Hastings, A. 1982. Unexpected behavior in two-locus genetic systems: an analysis of marginal underdominance at a stable equilibrium. Genetics, 102, 129–138.
Hilbish, T J. 1985. Demographic and temporal structure of an allele frequency cline in the mussel Mytilus edulis. Mar Biol, 86, 163–171.
Kartavtsev, Y F. 1978. Genetic variability of a bivalve mollusk, the mussel Crenomytilus grayanus. Soviet Genetics, 14, 186–190.
Koehn, R K, Milkman, R, and Mitton, J B. 1976. Population genetics of marine pelecypods. IV. Selection, migration and genetic differentiation in the blue mussel Mytilus edulis. Evolution, 30, 2–32.
Levinton, J S, and Suchanek, T H. 1978. Geographic variation, niche breadth and genetic differentiation at different geographic scales in the mussels Mytilus edulis and Mytilus californianus. Mar Biol, 49, 369–376.
Lewontin, R C. 1958. A general method for investigating the equilibrium of gene frequency in a population. Genetics, 43, 419–434.
Mallet, A L, Zouros, E, Gartner-Kepkay, K E, Freeman, K R, and Dickie, L M. 1985. Larval viability and heterozygote deficiency in populations of marine bivalves: evidence from pair matings of mussels. Mar Biol, 87, 165–172.
May, W L, and Macpherson, J H. 1958. An Illustrated Index ofTasmanian Shells, D. E. Wilkinson, Government Printer, Tasmania.
Mitton, J B, and Koehn, R K. 1973. Population genetics of marine pelecypods. III. Epistasis between functionally related isoenzymes of Mytilus edulis. Genetics, 73, 487–496.
Skibinski, D O F, Beardmore, J A, and Cross, T F. 1983. Aspects of the population genetics of Mytilus (Mytilidae; mollusca) in the British Isles, Biol J Linn Soc, 19, 137–183.
Sokal, R R, and Rohlf, F J. 1969. Biometry, W. H. Freeman, San Francisco.
Theisen, B F. 1978. Allozyme clines and evidence for strong selection in three loci in Mytilus edulis L. (Bivalvia) from Danish waters. Ophelia, 17, 135–142.
Young, J P W, Koehn, R K, and Arnheim, N. 1979. Biochemical characterization of “Lap”, a polymorphic aminopeptidase from the blue mussel Mytilus edulis. Bioch Genet, 17, 305–323.
Zouros, E, and Foltz, D W. 1984. Possible explanations of heterozygote deficiency in bivalve molluscs. Malacologia, 25, 583–591.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Colgan, D. Deficits of heterozygotes in relation to selective interactions between loci in the mussels Brachidontes rostratus and Xenostrobus pulex. Heredity 59, 355–362 (1987). https://doi.org/10.1038/hdy.1987.143
Received:
Issue date:
DOI: https://doi.org/10.1038/hdy.1987.143
This article is cited by
-
Population genetic instability and the phylogeography of the mussel Austromytilus rostratus (Dunker, 1857) (Bivalvia: Mytilidae)
Marine Biodiversity (2019)
-
Interspecific isozymic substitution is not random
Heredity (1992)
-
Heterozygote deficiency and population structure in the bivalve Ruditapes decussatus
Heredity (1991)
-
Genetic studies of laboratory-rearedMytilus edulis
Marine Biology (1990)
-
Genetic studies of laboratory reared Mytilus edulis.: II. Selection at the leucine amino peptidase (Lap) locus
Heredity (1989)
