Neo-Sex Chromosome Evolution in Treehoppers Despite Long-Term X Chromosome Conservation

Area of Science:

• Evolutionary biology
• Genomics
• Entomology

Background:

• Sex chromosomes evolve differently from autosomes, often leading to differentiation and heteromorphic systems.
• Heteromorphic sex chromosomes can be evolutionary traps, hindering system turnover.
• Chromosomal fusions with autosomes may offer a mechanism for refreshing old or degenerated sex chromosome systems.

Purpose of the Study:

• Investigate sex chromosome evolutionary dynamics in treehoppers (Membracidae).
• Analyze X chromosome conservation and variation across diverse treehopper species.
• Understand the role of chromosomal rearrangements in sex chromosome evolution.

Main Methods:

• Assembled a comprehensive reference genome for Umbonia crassicornis.
• Conducted comparative genomic analyses across 12 treehopper species.
• Compared the ancestral treehopper X chromosome with those in the broader Auchenorrhyncha clade.

Main Results:

• The X chromosome is largely conserved across treehopper species.
• Identified an X-autosome fusion in Calloconophora caliginosa, an exception to X conservation.
• Demonstrated X chromosome conservation across Auchenorrhyncha for over 300 million years.

Conclusions:

• Treehopper sex chromosomes exhibit remarkable long-term conservation.
• Chromosomal rearrangements, like X-autosome fusion, can occur and potentially impact sex chromosome evolution.
• Comparative genomics provides insights into the evolutionary trajectories of sex chromosomes.