250 years of hybridization between two biennial herb species without speciation

In 1759, Linnaeus convinced his followers that plants could hybridize by crossing flowers in the daisy family and producing intermediate offspring. These hybrids, between Tragopogon pratensis and T. porrifolius, exist naturally today in London, UK, to all appearances the same. In a new study published in AoB PLANTS, Matthews et al. found that most of the London hybrids are in their first generation, though the authors provide chromosomal evidence that one is a little older. These hybrids do not seem to have given rise to a new species, even though both parents have produced new hybrid species in the last century when crossed with T. dubius. Understanding why hybrids often do not speciate, despite repeated opportunities, would enhance our understanding of both the evolutionary process and risk assessments of invasive species.