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Uniform phenotype conceals double colonization by reed-warblers of a remote Pacific archipelago


  • Alice Cibois,

    Corresponding author
    1. Natural History Museum of Geneva, Department of Mammalogy and Ornithology, CP 6434, 1211 Geneva 6, Switzerland
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  • Jean-Claude Thibault,

    1. Parc naturel régional de Corse, rue Major Lambroschini, BP 417, F-20184 Ajaccio, Corsica
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  • Eric Pasquet

    1. Muséum National d'Histoire Naturelle, Département Systématique et Evolution, FRE 2695 Origine, Structure et Evolution de la Biodiversité, 55 rue Buffon, and Service de Systématique Moléculaire, IFR 101-CNRS, 43 rue Cuvier, F-75005 Paris, France
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*Alice Cibois, Natural History Museum of Geneva, Department of Mammalogy and Ornithology, CP 6434, 1211 Geneva 6, Switzerland.


Aim  Remote oceanic islands often provide good illustrations of adaptive radiations, but phylogenetic studies have also demonstrated unexpected multiple colonization events for a given archipelago. In this study we investigate the relationships among endemic populations of the Marquesas reed-warbler, Acrocephalus mendanae Tristram, 1883, which have colonized nearly all islands of this remote Polynesian archipelago, and which exhibit a very uniform plumage pattern. We study the phylogeny and morphology of all subspecies in the Marquesas, providing an examination of the position of the Marquesas lineages in relation to reed-warblers distributed across multiple Polynesian archipelagos.

Location  This study focused on all the main islands of the Marquesas archipelago, along with samples from other Polynesian archipelagos (Society, Tuamotu, Austral, Cook, Kiribati) and Australia.

Methods  We used mitochondrial DNA markers (cytochrome b and ND2 genes) to develop a phylogeny of the main eastern Polynesian taxa. All subspecies for the Marquesas were investigated, including multiple individuals per island. Phylogenetic analyses using maximum-likelihood and Bayesian approaches were employed to infer relationships among A. mendanae populations and between the main Polynesian archipelagos. Morphometric analyses based on 110 specimens from museum collections were performed on external characters to investigate the differences between islands, and these results were compared to the phylogeny.

Results  Our data indicate that the Marquesas reed-warbler is in fact a polyphyletic taxon including two independent lineages: the northern Marquesas reed-warbler, closely related to the Tuamotu reed-warbler, and the southern Marquesas reed-warbler, sister taxon to that endemic to the Kiribati. Analyses of morphological characters show that the size and shape features of the Marquesas reed-warblers exhibit high plasticity linked to adaptation to ecological factors, particularly habitat richness (the diversity of vegetation structure that provides suitable resources and habitat for reed-warblers, simplified here as the number of indigenous plant species).

Main conclusions  Our results suggest that reed-warblers have successfully colonized the Marquesas archipelago, one of the most remote groups of islands in the Pacific Ocean, at least twice. Both events occurred more or less simultaneously at ca. 0.6 Ma, and are more recent than the islands' formation. We outline the taxonomic consequences of our phylogeny and discuss the supertramp strategy of reed-warblers in the Pacific.