Abstract

One of the central goals of evolutionary genetics is to understand how organisms adapt to environmental heterogeneity. A promising approach towards this end is to investigate systematic, gradual phenotypic and genotypic changes along environmental (e.g. climatic) gradients, so-called clines, which are thought to be driven by spatially varying selection. Over the past 7 years we have been using next-generation sequencing, population genetics and laboratory assays to identify and characterize candidate genes and polymorphisms that might contribute to variation in fitness-related (life-history) traits among populations of the vinegar fly, Drosophila melanogaster, situated along a latitudinal cline spanning the North American east coast. Our genomic and phenotypic analyses suggest that spatially varying selection is pervasive and acts on numerous loci and pathways, with many candidates implicated in the physiological regulation of life-history, for example in the insulin / insulin-like growth factor signaling pathway, and exhibiting parallel differentiation along the parallel cline along the Australian east coast. In my talk, I will focus on our recent work on two clinal polymorphisms, namely a large chromosomal inversion polymorphism that harbors an excess of clinal SNPs and a clinally varying allele in the insulin signaling transcription factor foxo. In both cases we have experimental evidence that these polymorphisms make a causative contribution to the observed phenotypic clines of several fitness components.