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

Twenty-seven crosses were used to study the genetics of rapidly evolving traits in a recently founded population of threespine stickleback in Loberg Lake, Alaska. Lateral plate morph segregation ratios were inconsistent with all published models of lateral plate morph genetics except Avise’s (1976) general two-locus model. Incompatibility of the results of our plate morph crosses with those of most previous studies suggests that the genetic architecture underlying lateral plate morphs differs among populations or is more complex than presently recognized. Segregation ratios for lateral plate morphs indicate that consistently low frequencies of partial morphs observed in the Loberg Lake population at least partly reflect genetic architecture. Gillraker number and probably low morph lateral plate number are highly heritable and correlated with each other. Lateral plate asymmetry was high but not significantly heritable. Low and complete morph lateral plate number do not appear to be genetically correlated, indicating a significant element of independent genetic control.