Korean Magpie - Systematics and Evolution

Systematics and Evolution

Recent research comparing 813 bp mtDNA sequences indicates that either all Pica magpies should be considered races of one species, or that P. p. sericea needs to be separated as a distinct species; it has been reproductively isolated for longer even than the Yellow-billed Magpie (P. nuttalli) of North America. Hence, pending more comprehensive studies, the species binomen is put into parentheses, indicating that this bird may or may not be considered distinct. The large magpies found from the eastern Himalayas region to southern China (Tibetan Magpie or Black-rumped Magpie, P. p. bottanensis) could belong to sericea if that is split off as a species. The relationships of P. p. leucoptera, found north of the arid lands of Mongolia, is yet to be determined, but the similar-looking subspecies from Kamchatka Krai and its surroundings (P. p. camtschatica) is the easternmost population of the "European" Magpie. Of particularly interest is also the population called P. p. jankowskii (which is often included in sericea); this taxon refers to the birds found north of Korea, towards the range of leucoptera. P. p. japonica from southern Japan is usually included in sericea today.

It seems that the Korean Magpie's evolution as a distinct lineage started considerably earlier than the Gelasian date of c.2 million years ago (Ma) indicated by a molecular clock analysis. The assumed divergence rate – 1.6% point mutations per Ma – is appropriate for a long-lived passerine, but hybridization – which as only mtDNA was used would be hard to detect – and the few specimens analyzed make the molecular clock estimate just an approximation. Meanwhile, the fossil record of North American magpies has a specimen – UCMP 43386, a left tarsometatarsus from Palo Duro Falls (Randall County, Texas) – which is probably from the Early Pleistocene Irvingtonian age, around 2-1 Ma. It shows the distinct features of a Black-billed Magpie (P. (p.) hudsonia), though it might be from a common ancestor of Black- and Yellow-billed Magpies. This was not used to calibrate the molecular clock analysis, but accounting for the phylogenetic hypothesis it appears more likely that the Korean Magpie's ancestors diverged from other Pica in the Early Pliocene already, perhaps 5-4.5 Ma, antedating the uplift of the Sierra Nevada which cut off most gene flow between the two North American populations. Residual gene flow between them (and between the two (or more?) Eurasian magpie lineages) until the onset of the Quaternary glaciation some 2.6-2 Ma may also have skewed the molecular clock results.

Like the other Pica magpies, the Korean Magpie is a member of the large radiation of mainly Holarctic corvids, which also includes the typical crows and ravens (Corvus) nutcrackers (Nucifraga) and Old World jays. The long tail might be plesiomorphic for this group, as it is also found in the tropical Asian magpies (Cissa and Urocissa) as well as in most of the very basal corvids, such as the treepies. The unique black-and-white color pattern of the "monochrome" magpies is an autapomorphy.