Aim The oriental magpie-robin (Copsychus saularis) of South and Southeast Asia is a phenotypically variable species that appears to be closely related to two endemic species of the western Indian Ocean: the Madagascar magpie-robin (Copsychus albospecularis) and the Seychelles magpie-robin (Copsychus sechellarum). This unusual distribution led us to examine evolutionary relationships in magpie-robins, and also the taxonomic significance of their plumage variation, via a molecular phylogenetic and population genetic analysis of C. saularis and C. albospecularis.
Location Southern Asia from Nepal across Indochina to southern China, and the Indian Ocean from Madagascar to the Greater Sunda and Philippine islands.
Methods We sequenced 1695 nucleotides of mitochondrial DNA comprising the complete second subunit of the nicotinamide adenine dinucleotide dehydrogenase (ND2) gene and 654 bases of the cytochrome c oxidase subunit I (COI) region in 51 individuals of eight C. saularis subspecies, 10 individuals of C. albospecularis (one subspecies) and single individuals of two other Copsychus species as outgroups. The data were analysed phylogenetically, with maximum likelihood, Bayesian, relaxed clock and parsimony methods, and geographically for patterns of genetic diversity.
Results Phylogenetic analysis indicated that C. albospecularis lies within the nominal C. saularis, making C. saularis polyphyletic. Malagasy and non-Philippine Asian populations form a monophyletic group that is sister to a clade of Philippine populations. Within non-Philippine Asian populations, two groups are evident: black-bellied birds in the eastern Greater Sunda islands and white-bellied birds in the western Sundas and on mainland Asia.
Main conclusions The phylogeny of magpie-robins suggests a novel pattern of dispersal and differentiation in the Old World. Ancestral magpie-robins appear to have spread widely among islands of the Indian Ocean in the Pliocene, probably aided by their affinity for coastal habitats. Populations subsequently became isolated in island groups, notably the Philippines, Madagascar and the Greater Sundas, leading to speciation in all three areas. Isolation in the Philippines may have been aided by competitive exclusion of C. saularis from Palawan by a congener, the white-vented shama (Copsychus niger). In the Greater Sundas, white-bellied populations appear to have invaded Borneo and Java recently, where they hybridize with resident black-bellied birds.