title: Ancient mitochondrial genome reveals unsuspected taxonomic affinity of the extinct Chatham duck (Pachyanas chathamica) and resolves divergence times for New Zealand and sub-Antarctic brown teals.
abstract: The Chatham duck (Pachyanas chathamica) represented one of just three modern bird genera endemic to the Chatham archipelago (situated ~850 km east of New Zealand) but became extinct soon after humans first settled the islands (c. 13th-15th centuries AD). The taxonomic affinity of the Chatham duck remains largely unresolved; previous studies have tentatively suggested placements within both Tadornini (shelducks) and Anatini (dabbling ducks). Herein, we sequence a partial mitochondrial genome (excluding the D-loop) from the Chatham duck and discover that it was a phenotypically-divergent species within the genus Anas (Anatini). This conclusion is further supported by a re-examination of osteological characters. Our molecular analyses convincingly demonstrate that the Chatham duck is the most basal member of a sub-clade comprising the New Zealand and sub-Antarctic brown teals (the brown teal [A. chlorotis], Auckland Island teal [A. aucklandica] and Campbell Island teal [A. nesiotis]). Molecular clock calculations based on an ingroup fossil calibration support a divergence between the Chatham duck and its sister-taxa that is consistent with the estimated time of emergence of the Chatham Islands. Additionally, we find that mtDNA divergence between the two sub-Antarctic teal species (A. aucklandica and A. nesiotis) significantly pre-dates the last few glacial cycles, raising interesting questions about the timing of their dispersal to these islands, and the recent phylogeographic history of brown teal lineages in the region.
authors.affiliation: Australian Centre for Ancient DNA, School of Earth and Environmental Sciences, University of Adelaide, North Terrace Campus, South Australia 5005, Australia. Electronic address: kieren.mitchell@adelaide.edu.au.
authors.forename: Kieren J
authors.initials: KJ
authors.lastname: Mitchell
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Wood
authors.forename: R Paul
authors.initials: RP
authors.lastname: Scofield
authors.forename: Bastien
authors.initials: B
authors.lastname: Llamas
authors.forename: Alan
authors.initials: A
authors.lastname: Cooper
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D004272:DNA, Mitochondrial / Q000235:genetics; D004372:Ducks / Q000145:classification / Q000235:genetics*; D005260:Female; D005580:Fossils; D054629:Genome, Mitochondrial; D006801:Humans; D062312:Islands; D009520:New Zealand; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial
keywords: Anas; Ancient DNA; Chatham Islands; Ducks; Extinct; Fossil