Genetics of Color Expression in the Spider Enoplognatha ovata (Araneae: Theridiidae) from Coastal Maine

Abstract

The theridiid spider Enoplognatha ovata exhibits a conspicuous color polymorphism of red and nonred phenotypes, the genetic control for which has been investigated through previous rearing studies in Europe. Among European populations, red phenotypes may develop early or late during ontogeny. Two genetic models have been proposed to explain the inheritance patterns observed to date. Hippa and Oksala (1979) hypothesize parallel series of autosomal color alleles at two loci that differ only in the code for when red pigments are deposited during development. Oxford (1983) postulates an autosomal locus for color linked to a regulatory locus that controls the timing of red pigment deposition. Both models propose dominance of red alleles. We raised spider broods collected from coastal Maine populations to determine if the patterns of inheritance and the timing of red pigment deposition conformed to either or both of these genetic models. We found that the pattern of inheritance and number of color phenotypes in the Maine populations were consistent with Oxford's (1983) model, although Hippa and Oksala's (1979) model could not be dismissed. In contrast to European populations of Enoplognatha ovata, red-pigmented spiderlings from Maine always deposited red pigments early in development. Thus our data suggest genetic differences between Maine and European E. ovata populations. The significance of these differences and the difficulty in evaluating genetic models for E. ovata by rearing spiders from distinct geographical regions are discussed.