Microevolution and mega-icebergs in the Antarctic

doi:10.1073/pnas.0502281102

Microevolution and mega-icebergs in the Antarctic

^*Allan Wilson Centre for Molecular Ecology and Evolution, Institute of Molecular BioSciences, Massey University, Private Bag 102904, NSMC, Albany, Auckland, New Zealand; ^†Allan Wilson Centre for Molecular Ecology and Evolution, School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand; ^‡Point Reyes Bird Observatory Conservation Science, Stinson Beach, CA 94970; ^§H. T. Harvey and Associates, 3150 Almaden Expressway, Suite 145, San Jose, CA 95118; ^¶LandCare Research New Zealand Ltd., Private Bag 6, Nelson, New Zealand; and ^∥Dipartimento Scienze della Terra, Università di Pisa, and Consiglio Nazionale Ricerche, Institute of Geoscience and Earth Resources, Via Santa Maria 53, 56126 Pisa, Italy

Edited by Tomoko Ohta, National Institute of Genetics, Mishima, Japan, and approved September 21, 2005 (received for review March 20, 2005)

Abstract

Microevolution is regarded as changes in the frequencies of genes in populations over time. Ancient DNA technology now provides an opportunity to demonstrate evolution over a geological time frame and to possibly identify the causal factors in any such evolutionary event. Using nine nuclear microsatellite DNA loci, we genotyped an ancient population of Adélie penguins (Pygoscelis adeliae) aged ≈6,000 years B.P. Subfossil bones from this population were excavated by using an accurate stratigraphic method that allowed the identification of individuals even within the same layer. We compared the allele frequencies in the ancient population with those recorded from the modern population at the same site in Antarctica. We report significant changes in the frequencies of alleles between these two time points, hence demonstrating microevolutionary change. This study demonstrates a nuclear gene-frequency change over such a geological time frame. We discuss the possible causes of such a change, including the role of mutation, genetic drift, and the effects of gene mixing among different penguin populations. The latter is likely to be precipitated by mega-icebergs that act to promote migration among penguin colonies that typically show strong natal return.

Footnotes

↵ ** To whom correspondence should be addressed. E-mail: d.m.lambert{at}massey.ac.nz.
Author contributions: C.D.M., G.B., D.G.A., P.R.W., and D.M.L. designed research; L.D.S., G.B., D.G.A., P.R.W., G.D.H., and C.B. performed research; C.D.M., G.B., D.G.A., and D.M.L. contributed new reagents/analytic tools; L.D.S., G.B., D.G.A., G.D.H., C.B., and D.M.L. analyzed data; and L.D.S., C.D.M., G.B., D.G.A., P.R.W., and D.M.L. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.