DNA shows penguin evolution linked to island formation

Wednesday, 6 February 2019

New research has improved understanding of penguin evolution, revealing that the origin of many species is linked to island formation.

An international team of researchers from Australia – including the University of Adelaide – New Zealand, USA, UK, and China, analysed genetic data from all 20 living penguin species – plus several extinct species – and reconstructed the timescale for their evolution.

Published in the journal Molecular Biology and Evolution and led by the University of Otago in New Zealand, the researchers showed that new penguin species arose at the same time as the islands they breed on.

There are 20 living species of penguin, which range from the 45 kilogram emperor penguin to the 1.5 kilogram little penguin (known locally as fairy penguins). While penguins spend most of their lives at sea, they must all return to land to breed.

“The northern rockhopper penguin evolved at the same time as Gough Island emerged from the Atlantic Ocean,” says co-author Dr Kieren Mitchell, postdoctoral researcher at the University of Adelaide.

“This was the same for the royal penguin on Macquarie Island and the Galápagos penguin in the Galápagos Islands.

“We suspect this was caused by newly established breeding colonies becoming isolated, which after hundreds of thousands of years formed new species.

“And, while not necessarily linked directly to island formation, our results also provided additional evidence supporting previous studies that divided the little penguin into two distinct species: one breeding exclusively in New Zealand, and another breeding primarily in Australia, including the colonies on Granite Island and Kangaroo Island in South Australia, Phillip Island in Victoria or Bruny Island in Tasmania.”

Researchers at the University of Adelaide’s Australian Centre for Ancient DNA analysed DNA from prehistoric penguin bones found on the Chatham Islands east of New Zealand.

Surprisingly, ancient DNA from these bones revealed the existence of two previously unknown penguins: a new species of crested penguin (Eudyptes warhami) and a new dwarf subspecies of yellow-eyed penguin (Megadyptes antipodes richdalei).

“Finding the new yellow-eyed penguin was the biggest surprise,” says Dr Mitchell. “The bones were 10 to 20 percent smaller than the yellow-eyed penguin that currently lives in New Zealand, making it more like a rockhopper or macaroni penguin.”

Sadly, these new penguins became extinct when humans arrived in the Chatham Islands, highlighting the vulnerability of island ecosystems and the disruptive effects of new predators and competitors.

Their discovery, however, was key to confirming the link between island formation and penguin evolution: both extinct penguins originally arose following the emergence of the Chatham Islands 2–3 million years ago.

“From an evolutionary perspective, it’s fascinating to understand how and why species evolve,” says lead author Theresa Cole, PhD candidate from the University of Otago. “We were able to provide a comprehensive framework for exploring these questions about penguins, and demonstrated for the first time that islands may have played a key role in penguin evolution.”

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