Whole-genome sequencing splits the gentoo penguin into four species

Gentoo penguins on Kerguelen look like gentoo penguins anywhere: the same white underside and black back, separated from their relatives by only subtle differences in body size and vocalizations ^[4]. Biologists call that a cryptic species, one that closely resembles its relatives while being genetically distinct ^[5]. The islands, known in French as the Desolation Islands, lie nearly 2,000 miles from any permanently inhabited landmass ^[11]. Many of the seventeen other penguin species also breed on islands that are difficult for researchers to reach and study ^[21].

The four-species result comes from whole genomes of 64 birds sampled at 10 breeding colonies ^[12], an average of about 6.4 genomes per colony ^[22]. That is a thin sample per site for a question about where one population ends and another begins. But it is the first gentoo study to cover nearly the entire geographic range of the birds ^[12], and the sequences were paired with comparisons of coloration, calls, breeding schedules, diet and feeding behavior ^[13]. Earlier authors had proposed as many as six subspecies without reaching agreement ^[14].

"There's probably no species of penguin where the taxonomy has been more debated than the gentoo penguin," said Rauri Bowie, a professor of integrative biology at UC Berkeley and a curator in its Museum of Vertebrate Zoology ^[15].

Splitting one species into four leaves the same number of penguins alive and changes the denominators: the same birds are now divided among four units, each with a smaller range and a smaller total than the taxon they were counted in before ^[24]. Three of the four live in the sub-Antarctic ^[23], the band of widely separated islands north of Antarctica under the jurisdiction of Chile, South Africa, France, the Netherlands, Australia and New Zealand ^[19]. Two of the newly defined species besides the Kerguelen birds could also be vulnerable as warming reshapes those regions ^[8]. The release does not describe the warming scenario behind the habitat projections, or how suitable habitat was defined.

Juliana Vianna of Andres Bello National University in Santiago, one of the paper's senior authors ^[20], located the risk geographically. "In Antarctica, of course, other species, not the gentoo, are threatened by climate change," she said ^[16]. "But the gentoo is of most concern in the sub-Antarctic region" ^[17]. She added: "It's very important that conservation institutions in all the different countries involved recognize and take appropriate action to save these three gentoo penguin species" ^[18].