Background Historically the babblers have been assigned to the family Timaliidae but several recent studies have attempted to rest the taxonomy of this diverse passerine assemblage on a more firm evolutionary footing. The result has been a major rearrangement of the group. A well-supported and comprehensive phylogeny for this widespread avian group is an important part of testing evolutionary and biogeographic hypotheses, especially in Asia where the babblers are a key component of many forest ecosystems. However, the genus Liocichla is poorly represented in these prior studies of babbler systematics.
Methods We used a multilocus molecular genetic approach to generate a phylogenetic hypothesis for all five currently recognized species in the avian genus Liocichla. Multilocus DNA sequence data was used to construct individual gene trees using maximum likelihood and species trees were estimated from gene trees using Bayesian analyses. Divergence dates were obtained using a molecular clock approach.
Results Molecular data estimate a probable window of time for the origin for the Liocichla from the mid to late Miocene, between 5.55 and 12.87 Ma. Despite plumage similarities between the insular Taiwan endemic, L. steerii, and the continental L. bugunorum and L. omeiensis, molecular data suggest that L. steerii is the sister taxon to all continental Liocichla. The continental Liocichla are comprised of two lineages; a lineage containing L. omeiensis and L. bugunorum and a lineage comprised of L. phoenicea and L. ripponi. The comparatively early divergence of L. steerii within the Liocichla may be illusory due to extinct and therefore unsampled lineages. L. ripponi and L. phoenicea are parapatric with a Pleistocene split (0.07-1.88 Ma) occurring between an Eastern Himalayan L. phoenicea and a Northern Indochina distributed L. ripponi. L. bugunorum and L. omeiensis underwent a similar split between the Eastern Himalaya (L. bugunorum) and Central China (L. omeiensis) divided by the Hengduan Mountains.
Conclusions This study supports an origin of the Liocichla occurring sometime prior to the Miocene-Pliocene boundary, a period of significant climatic upheaval in Asia. The biogeographical patterns within the Liocichla mirror those of other birds in the region and allude to common geological and climatic drivers of avian diversification in Asia.
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