Evolution is powered by genetic variety, according to Utah State University evolutionary biologist Zachariah Gompert. Natural selection and genetic drift diminish that fuel reserve over ages.
Scientists wonder how genetic variety may last. In the June 12, 2023, online edition of the Proceedings of the National Academy of Sciences, Gompert and colleagues from Montpellier University in France, the John Innes Centre in the UK, the National Autonomous University of México, Querétaro, the University of Nevada, Reno, and Notre Dame University investigate this question.
Gompert earned a 2019 National Science Foundation CAREER Award and European project Council funding for the project.
“We examined how you maintain genetic variation in a species and how such variation impacts adaptation,” says Gompert, associate professor in USU’s Department of Biology and the Ecology Center.
The scientists studied stick insects (genus Timema) which eat several plants.
“There are more than a dozen Timema species in western North America and they’re generalists that can eat many types of plants,” Gompert explains. “But one species, Timema knulli, feeds and thrives on Redwood trees, one of the only plants that other Timema species can’t thrive on as well or at all.”
A chromosomal inversion may give T. knulli this capacity. Gompert states a chromosomal inversion happens when two breaks in the chromosome are followed by a 180-degree rotation of the segment and reinsertion at the breakpoints, unlike a gene mutation, which changes the DNA sequence.
He believes an inversion flips 30 million DNA bases of the chromosome.
The scientists found an old inversion in T. knulli.
Gompert estimates 7.5 million years. “And the cool thing is, T. Knulli populations still carry both versions of the alleles—the one for feeding and thriving on Redwoods as a host plant, and the original one that increases survival on the ancestral host plant—a flowering plant—and may be especially favorable in the heterozygous form.”
He claims environmental heterogeneity and gene exchange among migratory stick insects maintain new and ancestral chromosomal variations or polymorphism, which may help the creatures adapt to a changing world.
“Rather than being a detriment, the complexity of evolutionary processes affecting this inversion provides resilience against the loss of genetic variation and may foster long-term survival,” Gompert adds.