The Solidago virgaurea complex shows remarkable morphological and ecological diversity in Japan. Phylogeographic analysis suggested the multiple expansions from the Eurasian continent into the archipelago via land bridges, followed by lineage diversification within the island chain. Its genetic structure corresponds to the geography, but interestingly there is no concordance between genetic and ecotypic boundaries.
Sakaguchi et al. propose that the traits specific to the ecotypes are maintained by natural selection, or were very recently generated and have little effect on the genomes. This study shows that the goldenrod complex has a high ability to evolve, enabling rapid ecological diversification over a recent timeframe.