Genetics of plate morphology in an unusual population of threespine sticklebacks (Gasterosteus aculeatus)

Abstract

A collection of Gasterosteus aculeatus from a single locality (Friant) in Madera County, California, contains individuals with low and high lateral plate morphology, and very few intermediates. Electrophoretic evidence on protein similarities at 15 genetic loci is compatible with the thesis that members of these two morphs belong to a single interbreeding population. This thesis is also supported by broods from laboratory crosses between morphs, which segregate for low and high plate counts. Laboratory crosses between Friant fish and those from geographically isolated populations often yield some progeny with intermediate plate counts. The demonstration of significantly different patterns of plate development in intralocality versus interlocality crosses evidences a contrasting genetic basis for plate determination in different populations of sticklebacks.

Parallel genetic basis for repeated evolution of armor loss in Alaskan threespine stickleback populations

“…All families showed similar ratios that were not statistically different from 3:1 (see Table 2, which is published as supporting information on the PNAS web site), indicating a Mendelian basis for much of the armor loss. Our findings of a simple 3:1 Mendelian ratio match only one other study of lateral plate morphs, in which Avise (17) hypothesized the evolution of modifier loci that stabilized the dominance relationship. Alternatively, in young lacustrine stickleback populations, such as in Alaska, the ''ground state'' for the morph locus may be complete dominance.…”

“…Researchers have long been interested in these armor structures (17)(18)(19)(20), and have recently begun to use molecular genetic tools to study stickleback development (21)(22)(23)(24). We have built on existing stickleback work by examining the genetic basis of independent armor loss in three freshwater populations in south-central Alaska ( Fig.…”

LATERAL PLATE POLYMORPHISM AND ONTOGENY OF THE COMPLETE PLATE MORPH OF THREESPINE STICKLEBACKS (GASTEROSTEUS ACULEATUS)

“…Lateral plate morph genetics have not been analyzed in any population considered in this study, but crosses have been performed using other populations (Miinzing, 1959;Hagen and Gilbertson, 1973;Avise, 1976). Generally, there appear to be alternative alleles at one or two loci which specify the complete and low morphs and which in the heterozygous condition may produce the partial morpho However, dominance of the complete morph (Avise, 1976) and partial dominance of the complete and low morphs to the partial morph (Hagen and Gilbertson, 1973) occur in some populations.…”

“…Lateral plate morph genetics have not been analyzed in any population considered in this study, but crosses have been performed using other populations (Miinzing, 1959;Hagen and Gilbertson, 1973;Avise, 1976). Generally, there appear to be alternative alleles at one or two loci which specify the complete and low morphs and which in the heterozygous condition may produce the partial morpho However, dominance of the complete morph (Avise, 1976) and partial dominance of the complete and low morphs to the partial morph (Hagen and Gilbertson, 1973) occur in some populations. It appears that the plate morph genes regulate the rate of lateral plate ossification: complete morphs result from alleles specifying rapid plate ossification, low morphs from alleles specifying slow ossification and partial morphs from interactions among alleles which result in an intermediate rate of lateral plate ossification.…”

“…The low morph has only the abdominal row. Lateral plate morphs represent a true polymorphism in that phenotypes are distributed among three discontinuous classes and have a genetic basis (Miinzing, 1959;Hagen and Gilbertson, 1973;Avise, 1976). All three morphs occur throughout much of the range, including numerous islands that were defaunated by Pleistocene glaciation or oceanic islands such as Iceland (Saemundsson, 1926;Bell and Williams, unpu bI.…”