Study reveals island formation as one of the main drivers of penguin speciation – ScienceDaily



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Since Darwin first stepped on the Galapagos, evolutionary biologists have long known that the geographic isolation of the archipelago has helped to stimulate the formation of new species.

Now an international research team led by Theresa Cole of the University of Otago in New Zealand has found that the same holds true for penguins. They found the first convincing evidence that modern penguin diversity is driven by islands, despite spending most of their lives at sea.

"We propose that this pulse of diversification be linked to the emergence of islands, which has created new opportunities for isolation and speciation," Cole said.

Over the past 5 million years, during the Miocene period (particularly in the last 2 million years), the emergence of islands in the Southern Hemisphere has boosted several branches in the evolutionary tree of penguins, and has also boosted the most recent influence of man-made extinctions . of two species of penguins recently extinct from the Chatham Islands of New Zealand.

"Our findings suggest that these taxa were extirpated shortly after human settlement on the Chatham Islands," Cole said. "These discoveries, therefore, represent potentially important new examples of the man-made Holocene extinction in the Pacific."

"While our findings reinforce the islands' importance in biodiversity generation, they also underscore the role of humans as agents of biodiversity loss, especially through the extinction of endemic taxa in islands," Cole said. Because many of the bones were mediocre, our results provide direct evidence that our newly discovered extinct taxa have been hunted by humans. "

The publication appears in the online edition of the magazine Molecular Biology and Evolution.

About 20 species of modern penguins exist, from the penguin emperor of the Antarctic, the penguin Fiordland that inhabits the forest and the tropical penguin of Galápagos. A fossil record of more than 50 species can trace the history of penguins more than 60 million years ago – indicating that the diversity of penguins may have been much larger than today.

Using historical samples of skin and sub-fossils from natural history museums, along with blood samples, the researchers conducted the largest survey thus far, on all penguin taxa.

The team tested their island hypotheses using 41 near-complete mitochondrial genomes, representing all extant and extinct penguin taxa. They calibrated their mitogenomic evolution to make an evolutionary clock based on the fossil record.

"By using well-justified fossil calibrations, we have solved the timing and diversification mechanisms of modern penguins," Cole said.

They found that the two largest and most adapted penguins are brothers of all other living penguins. DNA evidence has also shown that species of genetically similar penguins may be in the early stages of diversification.

The study provides new insights and insights for the debate about the origins of penguin diversity. It will also help to better understand the role of islands as drivers of speciation for other animals and for marine life.

The new taxa were named Eudyptes warhami and Megadyptes antipodes richdalei after John Warham and Lance Richdale, pioneers of penguin biology.

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