Design of a molecular assay to differentiate ‘white’ from ‘common’ threespine stickleback (Gasterosteus aculeatus) ecotypes

Abstract

The ‘White’ Threespine Stickleback is a form of stickleback endemic to Nova Scotia, Canada, which exists sympatrically with the ‘common’ marine Threespine Stickleback. These fish differ in both morphology and behaviour. White stickleback change colour to an iridescent white during the breeding season rather than blue like the commons. Common males also care for eggs while they are in their nests whereas white males remove eggs from their nests and disperse them throughout the surrounding algae. Aside from male breeding colouration there are no known morphological traits that clearly differentiate white from common ecotypes. Therefore, an effective identification method is necessary to classify females, juvenile males, and mature males outside of the breeding season to study the mechanisms underlying adaptive divergence in colouration and parental care. White and common stickleback do form genetically distinct groups and in this thesis I attempted to develop a molecular assay to identify the fish by using previously identified regions of the stickleback genome with high differentiation between the two ecotypes. I designed primer sets to amplify microsatellite markers from these ‘outlier’ regions and analyzed allele frequencies of three loci with a discriminant analysis of principal components. I found that the use of only three markers was insufficient to differentiate the ecotypes, so the addition of other markers will be needed to design a successful assay.