Last Glacial Maximum's Effect on Kelp Genetics

Kelp genes reveal effects of subantarctic sea ice during the Last Glacial Maximum

1. Ceridwen I. Fraser1,
2. Raisa Nikula,
3. Hamish G. Spencer and
4. Jonathan M. Waters

-Author Affiliations

1.
Allan Wilson Centre for Molecular Ecology and Evolution, Department of Zoology, University of Otago, 340 Great King Street, Dunedin 9016, New Zealand

1.

Edited by Gary R. Carvalho, University of Wales, Bangor, Great Britain, and accepted by the Editorial Board December 23, 2008 (received for review October 23, 2008)

Abstract

The end of the Last Glacial Maximum (LGM) dramatically reshaped temperate ecosystems, with many species moving poleward as temperatures rose and ice receded. Whereas reinvading terrestrial taxa tracked melting glaciers, marine biota recolonized ocean habitats freed by retreating sea ice. The extent of sea ice in the Southern Hemisphere during the LGM has, however, yet to be fully resolved, with most palaeogeographic studies suggesting only minimal or patchy ice cover in subantarctic waters. Here, through population genetic analyses of the widespread Southern Bull Kelp (Durvillaea antarctica), we present evidence for persistent ice scour affecting subantarctic islands during the LGM. Using mitochondrial and chloroplast genetic markers (COI; rbcL) to genetically characterize some 300 kelp samples from 45 Southern Ocean localities, we reveal a remarkable pattern of recent recolonization in the subantarctic. Specifically, in contrast to the marked phylogeographic structure observed across coastal New Zealand and Chile (10- to 100-km scales), subantarctic samples show striking genetic homogeneity over vast distances (10,000-km scales), with a single widespread haplotype observed for each marker. From these results, we suggest that sea ice expanded further and ice scour during the LGM impacted shallow-water subantarctic marine ecosystems more extensively than previously suggested.

First, since it's my drum to beat lately, repeat after me: the world is not in a stable state.

Secondly, this makes for interesting thoughts on the extent of the southern hemisphere's ice during that last LGM.