A new study, led by the British Antarctic Survey and the University of Bristol, provides the first evidence that a controversial evolutionary process may be responsible for lanternfish becoming one of the most diverse families of fish in the deep sea.
Lanternfish are small, bioluminescent – meaning they give off light – fish, present in every ocean around the world. They live between the surface and 1000 m deep in the so-called “twilight zone”, and in the Southern Ocean they are a major consumer of krill – small, shrimp-like creatures – and are an important food source for king penguins and elephant seals.
There are about 250 species of lanternfish in the oceans, but scientists don’t know how this group of fish has become so diverse.
Typically, new species arise after a population has become geographically isolated, such as by a mountain range or waterway. However, the ocean is huge and unchanging over large areas, and many marine animals can move freely over great distances. By studying lantern fish, researchers hope to understand more about diversity in the ocean.
Researchers brought together historical data, created maps of lanternfish distribution and analyzed genetic information to help them understand more about how species diversify in the open ocean.
Using more than 60,000 historical records, the scientists created distribution maps for 161 species. They found that many lanternfish species have a global distribution — meaning they are found in oceans around the world — while others are confined to small areas with specific ocean conditions.
The scientists then reconstructed the evolutionary relationship between 175 species of lanternfish, using about 1,000 DNA sequences. Combining these relationships with the distribution maps, the researchers found that closely related species are more likely to overlap in their distribution, compared to species that are more closely related. This means that geographic isolation is unlikely to have caused species diversification.
dr. Jen Freer, a marine ecologist with British Antarctic Survey and lead author of the study, said: “This is a really exciting and important finding, as it is the first global evidence to support the idea of speciation without strict geographic isolation for these fish. This research helps us understand more about how species have diversified in the open ocean on a global scale, and also shows that there is much more to learn about the evolution of these fish.”
Prof. dr. Martin Genner of the University of Bristol, co-author of the study, said: “Lanternfish are one of the most diverse and ecologically important groups of marine fish. This study shows that the ancestral species of lanternfish are divided into multiple species with overlapping layers. “Seeing how the vast species diversity in the sea could have evolved without geographical barriers that divide populations. This idea remains a controversial biological process, so the insights lanternfish provide are extremely valuable to our understanding of evolution.”
The study is published in Global Ecology and Biogeography. Future research is now needed to look closely at the possible factors that allowed sister species to split up.
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Jennifer J. Freer et al, Global phylogeography of hyperdiverse lanternfish indicates sympatric speciation in the deep sea, Global Ecology and Biogeography (2022). DOI: 10.1111/b.13586
Quote: Study hints on how fish evolved in the twilight zone (2022, September 29) retrieved September 29, 2022 from https://phys.org/news/2022-09-hints-fishes-twilight-zone-evolved.html
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