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

Abstract

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.

A review of the recent advances in the systematics of the avian superfamily Sylvioidea

“…Thibault, 1984;Dickinson, 2003), whereas some authors suggested splitting this species into three, mainly because of wide geographical separation: A. caffer s.s. on the Society Islands, A. atyphus on Tuamotu, and A. mendanae in the Marquesas (Pratt et al, 1987;BirdLife International, 2000;Cibois et al, 2011a, b). Using mitochondrial sequence data, Cibois et al (2007) showed that A. mendanae formed two independent lineages, which they proposed be treated as specifically distinct: A. percernis (closely related to A. atyphus) and A. mendanae s.s. (sister to A. aequinoctialis). In a later study, Cibois et al (2008) analyzed mitochondrial DNA from extinct Acrocephalus taxa from different Society Islands, and concluded that A. caffer s.l.…”

Biogeography of the fauna of French Polynesia: diversification within and between a series of hot spot archipelagos

“…For example, reed warblers have colonized nearly all the islands of the Marquesas and look remarkably similar across the islands. However, molecular data indicate that the Marquesas reed warbler includes two independent lineages: the northern Marquesas reed warbler, closely related to the Tuamotu reed warbler, and the southern Marquesas reed warbler, sister to that of Kiribati (Cibois et al 2007). Both colonizations occurred ca 0.6 Ma, more recently than the formation of the islands, and suggest that the bird is a 'supertramp', colonizing remote islands easily and repeatedly.…”

Type Specimens of Birds in The American Museum of Natural History. Part 7. Passeriformes: Sylviidae, Muscicapidae, Platysteiridae, Maluridae, Acanthizidae, Monarchidae, Rhipiduridae, and Petroicidae

“…AMNH 195478, 195479, 195486, 195491, and 195494 are not now in AMNH and may have been exchanged with other institutions, although the catalog was not so marked. Recent mtDNA studies by Cibois et al (2007) indicated that Acrocephalus populations in the Marquesas are polyphyletic. Their proposed classification included populations from the southern Marquesas in the species A. mendanae; Cibois et al (2008) extended their study to include Acrocephalus populations in the Society Islands.…”

“…Dickinson (2003: 585) listed aquilonis as a subspecies of A. caffer and referenced other treatments. Recent mtDNA studies by Cibois et al (2007) showed that populations from the northern Marquesas comprised an independent lineage; their proposed classification included aquilonis from Eiao in the species A. percernis.…”

“…Dickinson (2003: 585) listed postremus as a subspecies of A. caffer and referenced other treatments. Recent mtDNA studies by Cibois et al (2007) …”