Zachariah Gompert, an evolutionary geneticist at Utah State University, asserts that genetic variation serves as the ultimate fuel for evolution. However, natural selection and random genetic drift depleted that fuel reservoir over centuries.
Scientists are still debating whether or not genetic variation can persist over time. Gompert and associates from the College of Montpellier in France, the Unified Realm’s John Innes Center, the Public Independent College of México, Querétaro; the College of Nevada, Reno; and, what’s more, the College of Notre Dame, distribute their examination of this inquiry in the June 12, 2023, online release of the Procedures of the Public Foundation of Sciences.
Gompert, an associate professor in the USU Department of Biology and the USU Ecology Center, says, “We examined how you maintain genetic variation in a species and how such variation impacts adaptation.”
The team looked into stick insects (Timema) that eat a wide range of plants for the study.
“There are over a dozen Timema species in western North America, and they’re generalists that can eat a wide variety of plants. However, one species, Timema knulli, feeds and thrives on Redwood trees, which are one of the only plants that other Timema species can’t thrive on as well or at all.”
Geneticist Zachariah Gompert.
According to Gompert, “There are more than a dozen species of Timema in western North America, and they are generalists that can eat many different kinds of plants.” However, one animal variety, Timema knulli, takes care of and flourishes with redwood trees, which is one of the main plants that other Timema species can’t blossom with either by any stretch of the imagination.”
T. knulli appears to have this ability due to a chromosomal inversion, or change in the genome’s structure. According to Gompert, a chromosomal inversion occurs when two breaks in the chromosome are followed by a 180-degree turn of the segment and reinsertion at the original breakpoints, in contrast to a gene mutation, which is a change in the DNA sequence.
“With a reversal, huge lumps — for this situation, 30 million DNA bases — of the chromosome get flipped in reverse,” he says.
The team also found that T. knulli has an ancient inversion.
“We think it happened around 7.5 years ago,” Gompert says. “The cool thing is that T. Knulli populations still have both alleles, one for feeding on and flourishing on redwoods as a host plant and the other for increasing survival on the ancestral host plant, a flowering plant, and may be especially advantageous in the heterozygous form.
According to him, the persistence of the new and ancestral chromosomal variants, or polymorphism, which may give the organisms a leg up in a changing world by allowing for ongoing evolution and adaptation, is facilitated by environmental heterogeneity and gene exchange among migrating populations of stick insects.
According to Gompert, “the complexity of evolutionary processes affecting this inversion provides resilience against the loss of genetic variation and may foster long-term survival.” Rather than being a disadvantage, this inversion is advantageous.
More information: Nosil, Patrik et al, Complex evolutionary processes maintain an ancient chromosomal inversion, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2300673120
