Genomic Breakthrough Unveils Structural Basis of Stick Insect Camouflage.

In a significant advancement in evolutionary biology, researchers have identified that intricate chromosomal rearrangements are responsible for the adaptive color variations in Timema cristinae stick insects. Published in the April 18, 2025, issue of Science, the study highlights how large-scale structural changes in DNA contribute to the insects' camouflage abilities, offering them protection from predators.​

The research team, led by evolutionary biologist Zachariah Gompert of Utah State University, employed phased genome assembly techniques to analyze the genomes of these insects. This approach allowed them to separately assemble each chromosome copy, unveiling two distinct chromosomal rearrangements involving the inversion and relocation of millions of DNA bases. These rearrangements occurred independently in separate populations residing on different mountains near Santa Barbara, California.​

"Traditional sequencing methods often miss such large-scale mutations," Gompert explained. "By using phased genome assemblies, we've been able to directly observe how these complex rearrangements facilitate adaptation by enabling the insects to blend into different host plants."​

The study focused on Timema cristinae populations that have adapted to two distinct plant species in coastal chaparral habitats. One morph exhibits a green coloration, providing camouflage among California lilac leaves, while another displays a thin white stripe, making it nearly invisible against the needle-like leaves of the chamise shrub. These color patterns are closely linked to the presence or absence of the identified chromosomal rearrangements.​

Contributing authors include Patrik Nosil from the French National Center for Scientific Research (CNRS), alongside scientists from the University of Notre Dame, the University of Nevada, Reno, and The Institute of Cancer Research in the United Kingdom. The research received support from the National Science Foundation and the European Research Council.​

The findings challenge the traditional view that adaptive evolution primarily results from numerous small mutations. Instead, they suggest that significant structural variations in the genome can have profound effects on an organism's phenotype, particularly in traits critical for survival such as camouflage.​

"These large mutations, despite their size, are often overlooked with standard DNA sequencing approaches," Gompert noted. "Our study indicates that structural variation may be a common and influential factor in evolution, rather than a rare occurrence."​

This research underscores the importance of advanced genomic technologies in uncovering the complexities of evolutionary processes. By illuminating the role of chromosomal rearrangements in adaptive traits, it opens new avenues for understanding how organisms evolve in response to their environments.

Source:https://www.sciencedaily.com/releases/2025/04/250418235500.html

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