Extinction revisitedby Rebecca Priestley
A new species or an old one getting re-established? New genetic techniques are providing some answers.
A buller’s mollymawk lands heavily on the water and bobs up and down on the waves. Nearby, mother and baby sea lions bask on red sun-drenched rocks above slow-moving kelp. Less charmingly, a black-backed gull pecks a floating dead gull, spilling red guts over its grey and white feathers.
On board the MV Monarch at the end of the Otago Peninsula, I am wrapped in a down jacket, with my binoculars at the ready. Finally, we see what we’re here for. A northern royal albatross approaches, struggling to gain enough altitude to fly over the Taiaroa Head lighthouse. After several circuits, it lowers its big airbrake feet and lands next to an enormous fluffy chick. Through the binoculars, I can see the chick snapping its beak. The adult albatross will often return with as much as a kilogram of oily squid to regurgitate for its hungry chick.
The diverse wildlife around Otago Peninsula – other resident species include yellow-eyed and blue penguins, shags, terns, herons and dolphins – can seem a wonderful example of an intact coastal ecosystem. But new genetic techniques are telling a different story.
Recent research by Jon Waters, zoology professor at the University of Otago and a member of the Allan Wilson Centre for Molecular Ecology and Evolution, has revealed that several of these populations and species are new to the region – recent arrivals from the subantarctic islands or Australia.
Forty years ago, there were no sea lions on the peninsula. Although sea lions once lived all around the New Zealand coast, most were eliminated in the centuries after Polynesian settlers arrived. The few that survived around Southland and Stewart Island were dealt to by European sealers. “But in the 1980s, one tagged individual from the Auckland Islands turned up on Otago Peninsula and had her young there,” says Waters.
There is now a small population breeding on the peninsula. “It was interpreted as a long-lost native returning. There was an assumption that the subantarctic population was a reflection of what used to be around the mainland.” But Waters’s PhD student Catherine Collins is analysing genetic data from modern sea lions, all of subantarctic origin, against subfossil sea lions from middens and sand dunes around New Zealand, and it’s becoming “clear that what we have now is distinct from what used to be here”.
It’s a similar story for the yellow-eyed penguin. The species that’s often called the world’s rarest penguin – there are about 4000 left – is mostly limited to small colonies on the south coast of the Otago Peninsula and on Stewart, Campbell and Auckland islands. “This was assumed to be a species that was hanging on, that somehow survived human arrival.” But genetic analysis from midden bones shows that when humans arrived, a native endemic species was wiped out. “What we have here now is a subantarctic species.”
This time it’s not just the genetics telling the story. “The prehistoric bones look distinctly different from those of the birds we have today.” Other researchers in Waters’s group are studying Otago’s little blue penguins, which, surprisingly, are genetically connected not to North Island little blue penguins but to an Australian species.
“Our big underlying theme for this work is that extinction gives a new opportunity,” says Waters. “If there’s a vacant niche and the conditions are right, a new species can get a foothold. Things disperse all the time. We know from stray penguins like Happy Feet that things can haul out a long way from where they normally live, but if they land in a place that suits them, and there’s nothing else already filling the niche, then there’s a real chance they’ll thrive.”
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