Mapping the Genetic Basis of Lateral Plate Reduction in Different Natural Populations of Threespine Sticklebacks

<p>Crossing a completely plated Japanese marine fish with a low-plated fish from Paxton Lake, British Columbia, produced a mixture of complete, partial, and low morph phenotypes in F2 progeny animals (Cross 1). In contrast, crossing a completely plated fish and a low-plated fish from an inland freshwater stream in Friant, California, produced only complete and low-plated progeny (Cross 2). Red dots show the geographic origins of the populations studied. Scale bars equal 1 cm. <i>AA</i>, <i>Aa</i>, and <i>aa</i> refer to genotypes at <i>Gac4174</i> (a microsatellite marker) near the major plate locus on LG 4. The genotype at <i>Gac4174</i> is missing in ten of the 360 F2s in Cross 1. All fish were stained with alizarin red to reveal bony structures.