In the floodplains of the Rhine River near the city of Mainz, two different rockcress species are intercrossing. This results in a mixed population with higher genetic diversity, where a kind of ‘super genotype’ consisting of a patchwork of the two populations could emerge, ensuring the survival of the two species. That is the result of a study reconstructing the evolutionary history of the rockcress population carried out by biologists Professor Dr Juliette de Meaux and Dr Hannes Dittberner at the University of Cologne together with Professor Dr Aurélien Tellier at the Technical University of Munich. The results of their research have been published in the article ‘Approximate Bayesian computation untangles signatures of contemporary and historical hybridization between two endangered species’ in the journal Molecular Biology and Evolution.
The scientists first studied the genetic characteristics of a remnant population of the endangered rockcress species Arabis nemorensis in the Rhine meadows near Riedstadt (Hesse), which grows in floodplains, but has almost disappeared due to agriculture and river management. ‘Our goal was to find out how diverse the species is genetically in order to assess the chances of restoring the lost populations,’ said Juliette de Meaux from the University of Cologne’s Institute of Plant Sciences. ‘In the process, we discovered that there is not only one species in this remaining population on the Rhine, but another closely related species, Arabis sagittata, which does not usually grow in river floodplains at all.’ The researchers also found out that the two species not only occur together locally, but that they are intercrossing. The resulting hybrid genetic diversity could actually ensure the survival the Arabis nemorensis population.
The UoC scientists reconstructed the history of the rockcress in cooperation with Aurélien Tellier in Munich using population models and machine learning methods, comparing the genetic characteristics of the plants that are growing today with the diversity expected under different models. They found evidence that the two rockcress species had already intercrossed in the distant past. However, over the past 10,000 years, no intercrossing took place. ‘The machine learning approach has also shown that there is only one place where the two rockcress species are mixing: the Rhine floodplains near Riedstadt. This population is growing on an area only as large as a few basketball courts. At this site, something unique might be about to evolve. We are now monitoring the developments very closely,’ de Meaux concluded, adding, ‘The ground for this work was actually paved by a team of ecologists around Professor Dr Norbert Hölzel, a colleague from the University of Münster, and I feel fortunate he introduced us to this fascinating ecosystem.’
Media Contact:
Professor Dr Juliette de Meaux
Institute of Plant Sciences
+49 221 470-8213
jdemeaux
uni-koeln.de
Press and Communications Team:
Mathias Martin
+49 221 470-1705
m.martinverw.uni-koeln.de
Publication:
https://academic.oup.com/mbe/advance-article/doi/10.1093/molbev/msac015/6516021