Scientists at UCSD’s Scripps Institution of Oceanography have discovered that a genetic mutation is likely responsible for the creation of weak “hybrid” offspring that results when species of marine crustaceans called copepods diverge and then reconnect.

Hybrids, which are produced when a species that has separated and gone through genetic mutations while apart reconnects and interbreeds to create offspring, often exhibit symptoms of weak evolutionary fitness such as lower fertility levels, slower development and higher levels of mortality.

The new research described by Christopher Ellison and Ronald Burton of the Scripps Institution of Oceanography is published in this week’s online edition of the Proceedings of the National Academy of Sciences.

Ellison and Burton have been studying copepods of the species Tigriopus californicus for the past several years by breeding specimens from different locations and observing the hybrid specimens in their environments during high and low tides. They found that certain genes that usually allow copepods to manage the stress caused by rapid change in salinity levels during tide were not activated in the hybrids, leading to low surivorship.

“When the incompatibility [of genes in hybridized populates] affects something as central as cellular energy production, as in Tigriopus, it is not surprising that hybrids show slower growth and reduced reproduction and survivorship,” said Burton, a professor in the Marine Biology Research Division at Scripps. “In addition to informing us about evolutionary processes, this research has important implications for a variety of biomedical and agricultural practices, such as stem cell production and cloning of domestic animals.”