Evolution of color  polymorphism in the Hawaiian Happy face spider

The Hawaiian happy face spider Theridion grallator (Theridiidae) exhibits a spectacular array of color morphs, which can be plain either 'yellow' or 'patterned' (red, black or white patches differing in form and extent, on the yellow background). In Maui populations abdominal color is controlled by simple Mendelian alleles, with 'yellow' morphs recessive to all patterned morphs. The progeny always segregate for the parental color alleles in Mendelian ratios. Fundamental differences exist in the genetics underlying color polymorphism in different populations. For example, the polymorphism appears to be controlled at a single major locus on Maui, two on Hawaii; and there is no evidence of associations of any morphs with a particular sex on Maui, whereas on Hawaii island, 4 morphs are limited to a single sex. We are investigating the mechanisms whereby these differences have arisen during colonization of the different islands.  Selection appears to be operating to maintain similar frequencies of color alleles in different populations.  Hawaiian bird predators are the most likely selective agent capable of modifying their feeding effort according to the frequency of a morph. This work has been conducted in collaboration is Geoff Oxford, York University, England.

Happy face spiders

Genomics of Repeatedly Evolving Color Diversity in the Polymorphic Hawaiian Happy Face Spider

PIs: R Gillespie, M. Eisen, N. Patel, G. Oxford.

Postdoc P. Croucher, graduate student D. Cotoras,

A major challenge in evolutionary biology is to understand the molecular basis of diversification. Making the most of recent advances in comparative genomics, the research here focuses on the exuberantly patterned Hawaiian happy face spider which displays a visible and balanced genetic color polymorphism, and in which the mode of inheritance of the color polymorphism has changed between islands in the Hawaiian chain. Accordingly, despite similar sets and frequencies of color forms across islands, the diversity has arisen independently on different islands. The research will identify the genomic basis for the differences between islands, and hence the mechanism through which color diversity is recreated.  The project uses genome-wide sequence scanning, linkage mapping, and candidate genes. The research will provide insights into how diversity is created during evolutionary history, while allowing generation of the first body of genome sequence and data on expressed genes for any spider. The system of visible and genetically controlled color polymorphism in spiders also provides an ideal mechanism for teaching of complex concepts in genetics and molecular evolution and hence an understanding how evolution works. Parallel systems to that of the Hawaiian happy face spider occur elsewhere (including California), allowing the development of teaching tools using local spiders.

Funded by the National Science Foundation