QUANTUM SHIFTS IN THE GENETIC-CONTROL OF A COLOR POLYMORPHISM IN THERIDION GRALLATOR (ARANEAE, THERIDIIDAE), THE HAWAIIAN HAPPY-FACE SPIDER

Theridion grallator, the Hawaiian happy-face spider, endemic to four i slands in the Hawaiian archipelago, exhibits an exuberant colour and p attern polymorphism involving both the carapace and opisthosoma (abdom en). Previous work has shown that on Maul (and probably on Moloka'i as well) all colour morphs act as if they are determined by alleles at o ne autosomal locus (although linked loci cannot be excluded) and all m orphs are expressed equally in males and females. Here we demonstrate that on Hawai'i, the youngest island, Yellow and Red front morphs seem to be controlled by a single allele, sex-limited in expression, such that females are Yellow and males Red front. Red blob and Red ring for m a similar pair of morphs, again apparently controlled by one allele, with Red blob confined to females, Red ring to males. Morphs Red fron t + back and Black ring are not sex-limited. Evidence from one brood i ndicates that two unlinked loci are involved in determining the colour polymorphism on Hawai'i. At least the sex-limitation of Yellow and Re d front is shown to be island-wide and suggests that the quantum shift s in the genetic control of the polymorphism among islands probably tr ace their origins to the founding event when T. grallator colonized Ha wai'i from Maul.