LATERAL PLATE MORPH GENETICS REVISITED - EVIDENCE FOR A 4TH MORPH IN 3-SPINED STICKLEBACKS

The view that four (not three) lateral plate morphs exist in the three -spined stickleback Gasterosteus aculeatus is supported in this paper. The morphs are: trachura (= completely plated), semiarmata (= partial ly plated), leiura (= low plated), and leiura-with-keel (= low-plated- with-keel). 2. Two one-locus and four two-locus models of lateral plat e morph inheritance are identified and reviewed. A new genetic model f or a two-locus system comprising one major gene with three alleles and one dominance modifier gene with two alleles is advocated. 3. Predict ions of different models are explicitly examined using the existent da ta. 4. Results of 10 new crosses that distinguished the form leiura-wi th-keel are presented. The segregation ratios obtained are best explai ned by the new model. 5. Adaptive value of plate morph differentiation is not clear. Different aspects of selection on the morphs are discus sed.