Conservation genomics of the oriental magpie-robin (Copsychus saularis)

Abstract

The Oriental Magpie-robin (Copsychus saularis) is one of the most commonly traded songbird species in Southeast Asia. The seven currently recognized subspecies differ morphologically, primarily in the plumage patterns. The nominate form is white-bellied, while three subspecies are black-bellied: adamsi, pluto in Eastern Borneo and amoenus in East Java and Bali. Although the species as a whole is listed as Least Concern by the IUCN, populations including the three black-bellied subspecies are experiencing rapid decline due to rampant trapping for the pet trade. Concern exists that the threatened black-bellied subspecies might merit recognition as a taxonomically distinct unit, thereby warranting treatment as a separate conservation unit, a hypothesis that was previously rejected for adamsi and pluto in Borneo. The taxonomic distinctiveness of the third black-bellied subspecies amoenus which occurs in Java and Bali, however, has so far not been investigated. Accordingly, in the first study presented in this thesis, I tested the hypothesis that subspecies amoenus is taxonomically distinct from the other two black-bellied subspecies that occur in Borneo. I combined newly sequenced mitochondrial DNA and ddRADseq data with those previously obtained by other studies. I then conducted phylogenetic and population genomic analyses. I found strong population structure between amoenus and other populations from mainland Asia and Borneo. Several lines of evidence also suggest that amoenus does not form a monophyletic group with Bornean black-bellied subspecies. The findings of this chapter are in support of the hypothesis that amoenus is a taxonomically distinct unit that should warrant its own conservation measures given the rarity of this subspecies in its range. Impacts of the cagebird trade are not constrained to source populations but also may affect populations in regions which import traded organisms. Despite being locally common in Hong Kong, thousands of magpie-robins from Southeast Asian countries are imported annually for sale in the market, predominantly indicated to be imported from Singapore. Release and escape of these magpie-robins into Hong Kong wild have been suspected. In the second chapter of this thesis, I tested the hypothesis that Hong Kong Oriental Magpie-robins have received gene flow from populations outside of Hong Kong. ddRADseq data revealed strong differentiation between subspecies musicus in Singapore and subspecies saularis in China and Hong Kong. However, I found very low levels of genetic contribution from Singaporean musicsus in not only Hong Kong individuals but also individuals from China. The evidence from this chapter did not support the hypothesis that there is gene flow into Hong Kong population of the magpie-robin from outside Hong Kong. This could reflect inadequate sampling of source populations or limited ability of released bird to interbreed with local individuals.