Evolutionary process behind live birth in lizards uncovered
Scientists studying one of nature's greatest reproductive innovations have discovered how some lizards evolved from laying eggs to giving birth to live young. The new research is the first to reveal the evolutionary process behind this important biological change and offers a unique insight into how other species—including mammals—may have evolved to give birth to live young millions of years ago.
Researchers at the University of Glasgow have uncovered the evolutionary process behind the development of live birth in lizards. The study, led by Dr. Hongxin Xie, reveals that this significant reproductive transformation occurred through the gradual accumulation of many small genetic changes over time, rather than a single large mutation.
This discovery provides a unique window into how other species, including mammals, may have evolved to give birth to live young. The researchers analyzed whole-genome sequences from lizards across the Eurasian common lizard's range, discovering that the transition to live birth resulted from natural selection acting on numerous regions across the genome.
These changes primarily occurred in regulatory DNA, which controls when and where genes are switched on during pregnancy, and were associated with increased gene expression in the uterus of pregnant live-bearing lizards. Despite continued gene flow between egg-laying and live-bearing lineages, the research team found that reproductive adaptations were maintained in lizards that had developed them, providing insight into how complex traits can persist in populations.
This study offers a clear reconstruction of how a complex evolutionary innovation can emerge through many small genetic changes over time.
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