José Luis Copete
One of the passerines with a widest natural distribution in the planet is the Horned Lark (Eremophila alpestris) since it’s present in boreal and alpine habitats from five continents or subcontinents: Europe, North Africa, continental Asia, North America and South America. Its habitat requirements were a selective pressure to produce isolated populations, especially those inhabiting mountains. So, it was a case to test about its phylogeography and the resulting taxonomic implications.
Sergei Drovetski, who is working for the University of Tromsø, has been involved during recent years in analysis of the phylogeography of Holarctic species. These cases are especially convenient to be analyzed in the light of the new laboratory and computer techniques, to check whether there are separate species along the break between North America and Eurasia. He entered into the subject more than 10 years ago, studying the phylogeography of species like the Winter Wren (Troglodytes troglodytes), Pine Grosbeak (Pinicola enucleator), some grouse (Tetraonidae) and rosy-finches (genus Leucosticte), as well a first study about the Horned Lark, examining the mtDNA of one subspecies, strigata, present in British Columbia (SW Canada) and NW USA south to Oregon (Drovetski et al 2005 Streaked Horned Lark Eremophila alpestris strigata has distinct mitochondrial DNA. Conservation Genetics 6: 875–883).
Now he and colleagues expanded the range of taxa examined in the same species, sampling the birds from a very wide range, in North America, Eurasia and North Africa (Drovetski et al 2014 Limited phylogeographic signal in sex-linked and autosomal loci despite geographically, ecologically, and phenotypically concordant structure of mtDNA variation in the Holarctic avian genus Eremophila. PLoS ONE 9(1): e87570. doi:10.1371/journal.pone.0087570).
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They propose a multiple split of some of the taxa present in the Palearctic, and one for North America, where pending of further study they are conservative.
The suggested splits would therefore be:
elwesi, from S & E of Tibetan Plateau
atlas, from Atlas Mts in Morocco
penicillata, from E Turkey and Caucasus E to N & W Iran
brandti, from SE European Russia (lower R Volga) and N Transcaspia E to W Manchuria, S to N Turkmenistan, Tien Shan and Mongolia
flava, from N Eurasia E to NE Russia (Anadyrland), S to S Norway, L Baikal and NW Amurland
and finally alpestris, for the whole of North America, pending further study, since in that continent there are around 30 different subspecies described, depending of the authorities.
Moreover, their results suggest paraphyly between Horned (alpestris) and Temminck’s (bilopha), confirming the traditional separation as two species in the birdguides.
It’s expected, probably, that more species will be proposed as the study continues as there are many subspecies described for mountains of south USA and Mexico, not to mention the most isolated population in the Sierra de Santa Marta (peregrina) and nearest mountains, in NW Colombia, far away from any other subspecies.