Ancient Sex Chromosomes Defy Expectations in Lizard Evolution
A new study challenges the long-held view that sex determination systems are unstable in reptiles. Researchers tested sex chromosome homology in 35 additional species of iguanas and anoles (Pleurodonta) using quantitative PCR to compare gene dosage. The findings confirm that these lineages have conserved the same XX/XY sex chromosomes for over 90 million years, since the group’s origin. This remarkable stability, also observed in a separate family with chromosomes over 25 million years old, suggests strong evolutionary constraints against change, even in ectothermic vertebrates previously thought prone to frequent sex chromosome turnover.
Why it might matter to you: This research provides a robust counterexample to the paradigm of labile sex determination, offering a concrete case study for models of chromosome evolution and selective pressure. For your work in evolutionary biology, it underscores the importance of genomic conservation in some lineages, which can refine predictions about speciation and reproductive isolation. Understanding the mechanisms behind this stability could inform broader theories on the evolutionary arms race and the genetic architecture underlying long-term adaptation.
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