Genomics research provides insights into the recent hybrid origin of Oxford ragwort

This new study in the journal, Current Biology, describes a high-quality genome assembly for Oxford ragwort and presents some analyses resulting in new evolutionary insights.

Oxford ragwort may seem like a non-descript yellow-flowered urban weed in the UK, so much so, that Carl Linnaeus, the father of modern taxonomy, called it, Senecio squalidus, when he was sent herbarium samples to describe and was told how it grew in squalid areas of towns and cities.

However, it has a remarkable history tied to the UK. It is a new species, having formed from hybridization between two distinct ragwort species from Mount Etna and its surroundings in Sicily when they were brought here by botanists in the 17^th century. The hybrids eventually established in Oxford and spread to become the familiar urban plant it is today.

This special history means that “Oxford ragwort serves as a small, exceptional laboratory for studying hybridization and its role in the emergence of new species and the colonization of challenging environments” according to lead author Bruno Nevado, CE3C - Centre for Ecology, Evolution, and Environmental Changes, University of Lisbon. Oxford ragwort’s genome shows clear signals of this recent, rapid hybrid origin showing a mixture of long tracts of genome that seem to come from one parent or the other. Importantly, this reassortment of the genome is not random, with areas contributing to reproductive isolation and divergent selection between the parents being more likely to reassort and become fixed. These processes created a unique species with traits from both parents that could survive and spread in a new environment in the UK.

This humble species gives us valuable insights into rapid evolution in response to human perturbation with lessons about our wider influence on the natural world. This research involved collaboration between Dr Adrian Brennan, Biosciences Department Durham University, and researchers from the Universities of Lisbon, Oxford, Southampton, Bath, St Andrews, and the Wellcome Sanger Institute in Cambridge.

The paper can be found here: Genomic changes and stabilization following homoploid hybrid speciation of the Oxford ragwort Senecio squalidus - ScienceDirect

A longer press release (in Portuguese) about the study can be found here: https://www.ce3c.pt/media/news/do-monte-etna-a-conquista-do-reino-unido-genetica-revela-historia-natural-unica-e-resiliencia-impar-de-planta-hibrida

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Further Information:

• Find out about the Department of Biosciences at Durham University
• Learn more about the work of Dr Adrian Brennan here at Durham University .
• Our Department of Biosciences is a leading centre for this increasingly important area of study and is ranked 4th in the UK in The Guardian University Guide 2024. Feeling inspired? Visit our Biosciences webpages to learn more about our postgraduate and undergraduate programmes. 
• Durham University is a top 100 world university. In the QS World University Rankings 2024, we were ranked 78th globally.

Image credit: close-up of an Oxford Ragwort flower. John Baker