Original Article

Heredity (2007) 99, 432–442; doi:10.1038/sj.hdy.6801021; published online 4 July 2007

Patterns of genic diversity and structure in a species undergoing rapid chromosomal radiation: an allozyme analysis of house mice from the Madeira archipelago

J Britton-Davidian1, J Catalan1, J Lopez1, G Ganem1, A C Nunes2, M G Ramalhinho3, J C Auffray1, J B Searle4 and M L Mathias2

  1. 1Institut des Sciences de l'Evolution (UM2, CNRS), Laboratoire Génétique et Environnement, CC65, Université Montpellier II, Montpellier, France
  2. 2Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Bloco C2, Campo Grande, Lisboa, Portugal
  3. 3Centro de Biologia Ambiental, Departamento Zoológico e Anthropológico do MNHN, Universidade de Lisboa, Rua da Escola Politécnica, Lisboa, Portugal
  4. 4Department of Biology, University of York, York, UK

Correspondence: Dr J Britton-Davidian, Institut des Sciences de l'Evolution, UMR 5554, Laboratoire Génétique et Environnement, CC65, Université Montpellier II, 34095 Montpellier Cedex 5, France. E-mail: britton@isem.univ-montp2.fr

Received 23 October 2006; Revised 19 May 2007; Accepted 29 May 2007; Published online 4 July 2007.

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Abstract

The chromosomal radiation of the house mouse in the island of Madeira most likely involved a human-mediated colonization event followed by within-island geographical isolation and recurrent episodes of genetic drift. The genetic signature of such processes was assessed by an allozyme analysis of the chromosomal races from Madeira. No trace of a decrease in diversity was observed suggesting the possibility of large founder or bottleneck sizes, multiple introductions and/or a high post-colonization expansion rate. The Madeira populations were more closely related to those of Portugal than to other continental regions, in agreement with the documented human colonization of the island. Such a Portuguese origin contrasts with a study indicating a north European source of the mitochondrial haplotypes present in the Madeira mice. This apparent discrepancy may be resolved if not one but two colonization events took place, an initial north European introduction followed by a later one from Portugal. Asymmetrical reproduction between these mice would have resulted in a maternal north European signature with a nuclear Portuguese genome. The extensive chromosomal divergence of the races in Madeira is expected to contribute to their genic divergence. However, there was no significant correlation between chromosomal and allozyme distances. This low apparent chromosomal impact on genic differentiation may be related to the short time since the onset of karyotypic divergence, as the strength of the chromosomal barrier will become significant only at later stages.

Keywords:

house mouse, Madeira, radiation, island, allozymes, Robertsonian fusions