Multiple gene evidence for expansion of extant penguins out of Antarctica due to global cooling

Author:

Baker Allan J12,Pereira Sergio Luiz1,Haddrath Oliver P1,Edge Kerri-Anne3

Affiliation:

1. Department of Natural History, Centre for Biodiversity and Conservation Biology, Royal Ontario MuseumToronto, ON, Canada M5S 2C6

2. Department of Zoology, University of TorontoToronto, ON, Canada M5S 1AI

3. Department of Zoology, University of OtagoPO Box 56, Dunedin, New Zealand

Abstract

Classic problems in historical biogeography are where did penguins originate, and why are such mobile birds restricted to the Southern Hemisphere? Competing hypotheses posit they arose in tropical–warm temperate waters, species-diverse cool temperate regions, or in Gondwanaland ∼100 mya when it was further north. To test these hypotheses we constructed a strongly supported phylogeny of extant penguins from 5851 bp of mitochondrial and nuclear DNA. Using Bayesian inference of ancestral areas we show that an Antarctic origin of extant taxa is highly likely, and that more derived taxa occur in lower latitudes. Molecular dating estimated penguins originated about 71 million years ago in Gondwanaland when it was further south and cooler. Moreover, extant taxa are inferred to have originated in the Eocene, coincident with the extinction of the larger-bodied fossil taxa as global climate cooled. We hypothesize that, as Antarctica became ice-encrusted, modern penguins expanded via the circumpolar current to oceanic islands within the Antarctic Convergence, and later to the southern continents. Thus, global cooling has had a major impact on penguin evolution, as it has on vertebrates generally. Penguins only reached cooler tropical waters in the Galapagos about 4 mya, and have not crossed the equatorial thermal barrier.

Publisher

The Royal Society

Subject

General Agricultural and Biological Sciences,General Environmental Science,General Immunology and Microbiology,General Biochemistry, Genetics and Molecular Biology,General Medicine

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