PT - JOURNAL ARTICLE AU - M. E. James AU - H Arenas-Castro AU - J. S. Groh AU - J. Engelstädter AU - D. Ortiz-Barrientos TI - Highly replicated evolution of parapatric ecotypes AID - 10.1101/2020.02.05.936401 DP - 2020 Jan 01 TA - bioRxiv PG - 2020.02.05.936401 4099 - http://biorxiv.org/content/early/2020/02/07/2020.02.05.936401.short 4100 - http://biorxiv.org/content/early/2020/02/07/2020.02.05.936401.full AB - Parallel evolution of ecotypes occurs when selection independently drives the evolution of similar traits across similar environments. The multiple origin of ecotypes is often inferred on the basis of a phylogeny which clusters populations according to geographic location and not by the environment they occupy. In contrast, when ecotypes arise once, expand their range and colonise similar environments, their populations cluster by ecology and not geography. However, discriminating between these scenarios is difficult because gene flow upon secondary contact can create the appearance of multiple origins despite a true single origin history. Here, we convincingly demonstrate multiple origins within the Dune and Headland ecotypes of an Australian wildflower, Senecio lautus. We observed phylogenetic clustering by geography and strong genetic structure between populations. There was surprisingly little gene flow between parapatric ecotypes, which is not high enough to obscure a single origin history. Overall, our work highlights the importance of demonstrating that populations have arisen repeatedly and independently within studies of parallel evolution.