Marine scientists have discovered that what was once thought to be a single sea slug species is actually at least 75 distinct species that were shaped over millions of years by repeated Antarctic glacial cycles.
Dr Paige Maroni and Dr Nerida Wilson, from The University of Western Australia's School of Biological Sciences and Oceans Institute, led the study published in Molecular Phylogenetics and Evolution, which reveals hidden biodiversity in one of Earth's most extreme and least understood marine environments.
"Antarctica is often perceived as biologically sparse, but discoveries like this reveal it contains extraordinary hidden diversity," Dr Wilson said.
"Advanced genomic techniques show that what appeared to be a single species is actually a complex system of many distinct evolutionary lineages.
"This type of work demonstrates the value of museum collection specimens – as the identity of these physical specimens change, we are able to update our understanding of broader biodiversity patterns."
Earlier genetic work suggested the Antarctic nudibranch Doris kerguelenensis represented about 59 hidden species.
Using large-scale genomic analysis across 130 specimens, researchers now estimate there may be at least 75 distinct species within what was once considered a single Antarctic sea slug species.
"By generating this universal set of genetic markers, we have created a resource that will help standardise future data collection for future comparative studies," Dr Maroni said.
Nudibranch only crawl along the seafloor as an adult and the evolution of the species is likely to have occurred over many glacial cycles.
"Over millions of years, Antarctic marine life has repeatedly been fragmented, displaced and reconnected as massive ice sheets advanced and retreated across the continental shelf," Dr Maroni said.
"These glacial cycles appear to have acted like an evolutionary engine driving the formation of entirely new species."
The findings provide a framework for understanding how climate-driven environmental change shapes biodiversity over evolutionary timescales.
"The results matter not only for reconstructing Antarctica's past but also for predicting how marine ecosystems may respond to rapid climate change in the future," Dr Maroni said
Dr Wilson is a partner investigator at Securing Antarctica's Environmental Future, an impact research program delivering science in, from and about Antarctica and the Southern Ocean.
