MELBOURNE, Sept. 6 (UPI) -- Many assume hybridization, the interbreeding of two species, always yields a better, stronger species. But that wasn't that case when Neanderthals and Homo sapiens interbred, and new research shows it's not the case among interbreeding weeds in Australia.
Australia once featured two similar-looking invasive weeds, American sea rocket, Cakile edentula, and European sea rocket, C. maritima -- both low-lying, shrub-like annuals with green foliage and small white and lilac flowers.
Despite interbreeding, European sea rocket dominated, and the American version is now mostly gone -- only a few of its genes remain in European sea rocket populations.
The episode recalls the interbreeding among humans and Neanderthals. Ultimately, Neanderthals died out, but modern humans continue to carry a few Neanderthal genes with them.
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The differences between American and European sea rocket are less obvious than those between Neanderthals and Homo sapiens, but a small difference makes all the difference.
"The European sea rocket can grow over winter, and because our winters aren't that bad, the plant can thrive," Roger Cousens, a biologist at the University of Melbourne, said in press release. "And when it starts to flower in summer, it gets bigger, so it has a head start."
Cousens and his colleagues built a model to better understand how European sea rocket's head start has allowed it to dominate. Their simulation revealed something interesting. The dominance of European sea rocket likely wouldn't have happened without the presence of American sea rocket, which arrived in Australia in the 1850s, roughly half a century before European sea rocket found its way Down Under.
"The European species needed multiple individuals of its own species in order to reproduce; if only one of them arrived, it would not have succeeded," Cousens explained. "But because the America one was here, it could use that as something to mate with."
Researchers published their novel findings this week in the journal PNAS.
"By doing computer modeling, what we've managed to do is show that not only can hybridization be really important, but it can be important in different ways than how people have guessed before," Cousens concluded.
Though European sea rocket is an invader, it has become naturalized along the coasts of most of Australia. Its presence isn't all bad, either. It provides nectar and food for butterflies, bees and parrots.
