Detecting adaptive divergence in a widespread aquatic plant using genetic markers under selection and genome scans

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The goal of this project is to identify genes under positive divergent selection as one strategy for studying molecular adaptation under natural conditions. The plant model is eelgrass (Zostera marina), a widespread marine angiosperm that has recently become a population genetic model species of coastal environments. Based on existing EST (expressed sequence tag)-libraries, I will establish gene-linked markers (SNPs ¿ single nucleotide polymorphisms; microsatellites) in order to compare genetic differentiation among replicated pairs of populations in contrasting habitat types, corresponding to divergent selection. A genome scan approach will identify outlier loci by formally rejecting neutral population genetic models that incorporate realistic scenarios of gene flow, mutation rates and drift. The advantages of gene-linked markers over anonymous ones for estimating selectively relevant genetic diversity will be assessed in re-examining established heterozygote-fitness correlations. Genes under divergent selection based on genome scans will be further characterized and sequenced in order to find additional evidence for molecular adaptation at the DNA sequence level.