Mitochondrial phylogeographic structure of the white-browed piculet (Sasia ochracea):: cryptic genetic differentiation and endemism in Indochina

Aim Our understanding of the geographic patterns of gene flow between populations of birds in the Indo-Malayan faunal region is surprisingly poor compared with that in other parts of the world. A thorough knowledge of general patterns of phylogeographic structure is, however, of utmost importance for conservation purposes. Species with poor dispersal capabilities could serve as indicators of endemism and genetic isolation in the Indochinese subregion. From their morphology (tiny size, short tail, short and rounded wings), piculets of the genus Sasia are inferred to have poor dispersal capabilities, and thus form a suitable focal species. This study analysed the pattern of genetic variation within the White-browed Piculet (Sasia ochracea). Location Southeast Asia, north of the Isthmus of Kra. Methods We sampled 43 individuals throughout the breeding range of S. ochracea. DNA was extracted both from fresh tissues (n = 15) and from toe pads from ancient museum skins (n = 28). We amplified a 801-bp fragment of the mitochondrial ND2 gene to reconstruct the phylogeographic history of the White-browed Piculet. The sequence data were analysed using Bayesian inference, statistical parsimony, and population genetics methods (analysis of molecular variance, mismatch distributions). We estimated the amount of ongoing gene flow between populations using the coalescent-based method implemented in MDIV. Results The analysis of molecular variance indicated that the current taxonomy does not adequately reflect the amount of genetic variation within S. ochracea, as the great majority of genetic variation was nested within the nominal subspecies, which is distributed from Nepal to southern Vietnam. Bayesian inference analyses and haplotype networks suggested the occurrence of five main lineages that are strongly correlated with geography. Our coalescent-based analyses indicated a very limited amount of ongoing gene flow between these five lineages. Our dating analyses suggested that the genetic structuring probably occurred during the last 400,000 years. Main conclusions Our analyses revealed that S. ochracea is composed of at least five lineages: south Vietnam (South Annam and 'Cochinchina'), India and Nepal, Myanmar and India, the remainder of Indochina, and probably southern Myanmar (Tenasserim). We strongly recommend that studies aiming to understand the phylogeographic structure within Indo-Malayan species sample these areas.