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Self-pollinating plant shows rapid loss of genetic variation

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Without bumblebees, a self-pollinating flowering plant lost significant genetic variation in just nine generations, an experimental study shows.

A group of “selfing” monkey flower plants lost 13% to 24% of their genetic variation compared to another group propagated by bumblebees. This loss could rob the plants of their ability to adapt to environmental challenges, according to the study published in the journal Evolution. With bee populations in decline, the findings point to serious problems for wild plants and crops that depend on these pollinators.

“We found that in a very short time there were major impacts on the genome of the plants when they had to adopt themselves,” said Jeremiah Busch, a Washington State University evolutionary biologist and lead author of the study.

Pollinators such as bees are important to biodiversity in their own right, Busch added, but the study indicates their decline will also have potentially devastating effects on plants, and soon.

“If pollinators are lost, it won’t just be a problem for the pollinators. Plant populations will lose genetic variation over tens of generations — not thousands, but dozens,” Busch said.

While scientists knew that adopting self-pollination could jeopardize the long-term survival of a plant species, they weren’t sure exactly how that worked genetically or how quickly.

Busch’s colleagues set up a controlled greenhouse experiment with yellow monkey flower plants, a common wildflower found in the western U.S., isolated a group of plants from their bumblebee pollinators. Initially, the non-bee plants produced few seeds, then they produced many as they adapted to self-pollination. The flowers also changed with their male and female reproductive parts, the tips of their stamens and pistils, coming closer together to allow for the transfer of pollen.

As the self-pollinating plants continued to reproduce, they lost genetic variation compared to a control group visited by bumblebees.

Adjustment is key to explaining these surprising declines, Busch said. In self-generating populations, a favored genotype will propagate if it has an advantage, but so will all the other mutations it carries simply because they are lucky enough to reside in that plant’s genome. This phenomenon of “genetic hitchhiking” is much less pronounced when bees visit plants, because offspring are a mix of their parents’ genetic variability.

“Strong inbreeding fundamentally changed the consequences of adaptation,” he said.

Future research should follow plants over a longer period of time to see if and when the loss of genetic variation leads to population collapse, Busch said.

“A really important next step is to see how quickly highly inbred groups will decrease their viability over time — to know how quickly those populations will die out,” he said. “We really need to understand the consequences of the loss of pollinators. It will be important for wild populations of plants and crops. Many crops depend on bees.”

Declining bee populations: a natural phenomenon or a warning?

More information:
Jeremiah W. Busch et al, Loss of pollinators causes rapid adaptive evolution of self-pollination and drastically reduces genome-wide genetic variability, Evolution (2022). DOI: 10.1111/evo.14572

Provided by Washington State University

Quote: Self-pollinating plant shows rapid loss of genetic variation (2022, August 10) retrieved on August 10, 2022 from https://phys.org/news/2022-08-self-pollinating-rapid-loss-genetic-variation.html

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