New insights into the systematics of the enigmatic P olynesian sandpipers A echmorhynchus parvirostris and P rosobonia leucoptera

With only a single extant representative, endemic to the T uamotu A rchipelago, the P olynesian sandpipers ( A echmorhynchus and P rosobonia ) may have had a larger distribution in E astern P olynesia in the past, with four endemic taxa. Although these aberrant sandpipers' membership to the S colocapidae has been well supported, finding their closest living taxa has proved difficult and the phylogenetic relationships of these taxa have remained unresolved. We present the first molecular analysis of the P olynesian sandpipers, including sampling of the only known specimen of the extinct P rosobonia leucoptera , collected in 1773. Based on mitochondrial and nuclear gene sequence data, the phylogenetic analyses demonstrate that the P olynesian sandpipers were sister taxa and belonged to the clade that included the other sandpipers ( C alidris and allies) and turnstones ( A renaria ), although without a close relative among extant genera. Divergence time estimates suggested that the lineage leading to P rosobonia diverged from the other extant sandpipers during the O ligocene and that either the Line Islands or the T uamotu A rchipelago were probably the first archipelagos colonized by the P rosobonia lineage. On the basis of these results, we suggest that A echmorhynchus parvirostris and P rosobonia leucoptera be regarded as related species within the same genus, and thus that the senior name P rosobonia be used for both taxa.