Genetic divergence and population demography of the Hainan endemic Black-throated Laughingthrush (Aves: Timaliidae, Garrulax chinensis monachus) and adjacent mainland subspecies

Geographic variation in the Black-throated Laughingthrush (Garrulax chinensis) is examined to infer the influence of Pleistocene glacial oscillations on the genetic diversity of its subspecies. Mitochondrial evidence suggests that the endemic Hainan Island taxon, G. c. monachus, is monophyletic, whereas its closest continental relatives, G. c. chinensis and G. c. lochmius, are not. Multilocus coalescent analysis based on two mitochondrial and two nuclear intron loci indicates inter-subspecific genetic differentiation during the Pleistocene and substantial post-divergence genetic introgression from G. c. chinensis into G. c. lochmius. In contrast, G. c. monachus experienced no post-divergence gene flow despite occasional land-bridge contact with its continental relatives, suggesting its isolation may have been imposed by ecology as well as geography. It is probably reproductively isolated and should be treated as a distinct species.

Highlights► The influence of Pleistocene glacial oscillations on the genetic diversity of Garrulax chinensis is discussed. ► The Hainan endemic taxon is monophyletic while its two adjacent mainland relatives are not. ► No post-divergence gene flow is detected between Hainanese and its close mainland relatives. ► There is a substantial post-divergence genetic introgression from Garrulax chinensis chinensis into Garrulax chinensis lochmius. ► Pleistocene glacial events maybe shape the genetic diversity of G. chinensis.