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hubie writes:

New research in Science is showing how the rise of modern agriculture has turned a North American native plant, common waterhemp, into a problematic agricultural weed:

An international team led by researchers at the University of British Columbia (UBC) compared 187 waterhemp samples from modern farms and neighbouring wetlands with more than 100 historical samples dating as far back as 1820 that had been stored in museums across North America. Much like the sequencing of ancient human and neanderthal remains has resolved key mysteries about human history, studying the plant's genetic makeup over the last two centuries allowed the researchers to watch evolution in action across changing environments.

"The genetic variants that help the plant do well in modern agricultural settings have risen to high frequencies remarkably quickly since agricultural intensification in the 1960s," said first author Dr. Julia Kreiner, a postdoctoral researcher in UBC's Department of Botany.

The researchers discovered hundreds of genes across the weed's genome that aid its success on farms, with mutations in genes related to drought tolerance, rapid growth and resistance to herbicides appearing frequently. "The types of changes we're imposing in agricultural environments are so strong that they have consequences in neighbouring habitats that we'd usually think were natural," said Dr. Kreiner.

[...] Common waterhemp is native to North America and was not always a problematic plant. Yet in recent years, the weed has become nearly impossible to eradicate from farms thanks to genetic adaptations including herbicide resistance.

[...] Agricultural practices have also reshaped where particular genetic variants are found across the landscape. Over the last 60 years, a weedy southwestern variety has made an increasing progression eastward across North America, spreading their genes into local populations as a result of their competitive edge in agricultural contexts.

Journal Reference:
Julia M. Kreiner, Sergio M. Latorre, Hernán A. Burbano, et al., Rapid weed adaptation and range expansion in response to agriculture over the past two centuries, Science, 378, 2022. DOI: https://doi.org/10.1126/science.abo7293

Original Submission