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Sexual competition, choice helps protect species from extinction

When scientists forced monogamy on flour beetles, they were less able to cope with environmental stressors and genetic bottlenecking. Photo by University of East Anglia
When scientists forced monogamy on flour beetles, they were less able to cope with environmental stressors and genetic bottlenecking. Photo by University of East Anglia

June 19 (UPI) -- Forced monogamy leaves species more vulnerable to extinction from environmental and genetic stressors, according to a new study. Conversely, species allowed sexual competition and mate choice are more resilient.

For the research, published Friday in the journal Global Change Biology, scientists bred flour beetles under controlled lab conditions for more than a decade.

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Flour beetles reproduce quite rapidly, so scientists can study evolutionary processes over relatively short periods of time. They're also easy to culture and their productive processes are well documented in the scientific literature, researchers say.

When it was time for the beetles to mate, females in one group of beetles were given their choice of five males. Females in a second group weren't given a choice. Instead, they were forced to remain monogamous.

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"After the monogamous pairs or polyandrous groups had bred, we mixed back together all the offspring within a line (to avoid inbreeding)," lead researcher Matt Gage, biological scientists with the University of East Anglia, told UPI in an email.

"At the next generation, we then isolated males and females again and set them up to breed either monogamously or polyandrously again, and repeated this every generation for more than ten years and 95 adult generations," said Gage, a co-author on the study.

When scientists exposed the two lineages of beetles to environmental stressors, including food scarcity, prolonged heat and genetic bottle-necking, the monogamous group proved much more susceptible to extinction.

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"The results were clear that beetle populations coming from our monogamous histories ... were 'weak' when exposed to environmental or genetic stress," Gage said. "All our monogamous lines went extinct within 15 generations of the extinction vortex."

The beetles from the polyandrous sexual selection group were quite healthy, and capable of surviving stressors, the researchers reported.

"The study shows that sexual selection in the struggle to reproduce also strengthens 'naturally' selected abilities to cope with environmental and genetic stress," Gage said.

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The latest findings, could help scientists identify species vulnerable to reductions in mate choice and limited sexual competition.

If conservationists can help species maintain sufficient levels of sexual competition, the newly published study suggests these species will be better able to cope with climate change, habitat loss and genetic bottlenecks.

"The study shows that sexual selection in the struggle to reproduce also strengthens 'naturally' selected abilities to cope with environmental and genetic stress," Gage said. "If we let vulnerable populations fragment or get down to levels where normal mate choice and male-male competition cannot occur, we might reach an important tipping point for further decline to extinction if sexual selection cannot operate normally."

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