A new model of lateral plate morph inheritance in the threespine stickleback,Gasterosteus aculeatus

Abstract

The threespine stickleback,Gasterosteus aculeatus, is polymorphic for the arrangement of lateral bony plates. It is confirmed in this paper that four morphs (not three) should be distinguished in this species: low plated, low plated with a keel, partially plated and completely plated. A new model is proposed to explain the inheritance of these morphs which involves one major gene with three alleles displaying a dominance hierarchy withA (completely plated) dominant toa (low plated) which is dominant toa k (low plated with keel). The dominance of theA allele is modified to semidominance by a dominant alleleC at a second locus. This scheme explains all the results of relevant breeding experiments published so far. Field data also fulfill predictions derived from this model.

Genetics of Lateral Plate and Gillraker Phenotypes in a Rapidly Evolving Population of Threespine Stickleback

“…Two C × C crosses (26 and 27) produced all three morphs, which is predicted only by Avise's model, and two other crosses (13 and 16) produced segregation ratios that differed significantly from expectations based on every model except Avise's. Zuiganov's (1983) and Bańbura's (1994) models performed relatively well, providing an adequate fit for 19 of the 23 crosses evaluated. Hagen & Gilbertson's (1973a) model performed poorly, providing a fit for only 13 of the 23 crosses, and Münzing's (1959) model performed the worst, providing an adequate fit for only the 11 L × L crosses.…”

“…Both populations are trimorphic but have strongly bimodal LP number distributions that are dominated by completes and lows with partials occurring at low frequencies (about 5% in Friant and usually about 10% in Loberg; Bell et al, 2004). Although Avise's (1976) model is older than Ziuganov's (1983) and Bańbura's (1994) models, the latter two models are basically straightforward extensions of Münzing's (1959) one locus model with incomplete dominance, in which the dominance relations for the major plate locus A/a (or A/a/a k in Bańbura's model) are modified by a second 2 allele locus C/c. Although Ziuganov and Bańbura's models were a major improvement over existing models (including Avise's two-locus model) in some respects (Bańbura & Bakker, 1995), they do not account for the production of individuals of all three morphs from the C × C crosses obtained in our study, whereas Avise's model could.…”

The Genetic Architecture of Parallel Armor Plate Reduction in Threespine Sticklebacks

“…In one of these models, both major loci contribute equally to plate phenotype, and the total number of A and B alleles determines whether fish develop as complete (three or more A or B alleles), partial (two A or B alleles), or low-plated fish (one or less A or B allele) (Hagen and Gilbertson 1973b). Additional models have proposed either epistatic interactions between a single major locus and one modifier locus, or the presence of more than two alternative alleles at the major locus to account for variant results in some populations (Ziuganov 1983; Banbura 1994). All of these models were proposed before the development of genomewide genetic markers for sticklebacks (Peichel et al 2001) and have never been tested by linkage mapping.…”

The Darwinian sticklebackGasterosteus aculeatus: a history of evolutionary studies*

“…Subsequent breeding studies confirmed the genetic control of plate morphs. Different Mendelian models have been proposed (Hagen & Gilbertson, 1973), Avise (1976), Ziuganov (1983) and Banbura (1994). The evidence suggested the presence of a major locus determining plate morph, but whose effects were influenced by modifier genes.…”

“…In the low morph (leiurus), only thoracic plates are present, with up to 14 plates, but the abdomen and caudal region are unarmoured. Occasionally, low morph individuals with a caudal keel have been described (Ziuganov, 1983; Banbura, 1994). In some resident populations, individuals may lack lateral plates.…”