From finches in the Galápagos to honeycreepers in Hawaii, islands have played a key role in the evolution of new species. Now, an international team of scientists say the same holds true for penguins, even though these birds spend most of their life at sea.
About one third of living penguin species are endemic to geologically young islands that formed roughly in the last five million years. A research team led by evolutionary biologist Theresa Cole of the University of Otago, New Zealand, hypothesized that the formation of these islands could be a key driver of modern penguin diversification.
To test this theory, the team compared the mitochondrial genomes (mitogenomes) of all known living and recently extinct species of penguins. Analyzing how the mitogenomes of penguins changed from the fossil record to the present allowed the team to identify when and where new species emerged in penguin evolutionary history. Their data showed that penguins endemic to geologically young islands generally diverged into distinct species soon after the islands emerged above water, suggesting that islands offered the marine birds “new opportunities for isolation and speciation.”
The study not only shines a light on the role of islands in the adaptive radiation of penguins, but also suggests potential reasons for penguin species’ extinction. From genomic data from unidentified penguin bones in museums, the team discovered two recently extinct subspecies of the crested penguin, Eudyptes warhami, and of the yellow-eyed penguin, Megadyptes antipodes richdalei, both of which once lived on New Zealand’s Chatham Islands. The bones of these penguins were found in the kitchen waste of old human settlements, suggesting that these species were rendered extinct shortly after humans settled the Chatham Islands. Says Cole, “It really shows how vulnerable these ecosystems are.” (Molecular Biology and Evolution)