Horned Lark taxonomy: possible split into six species

A recent study suggested splitting the Horned Lark into six different species: one in the Nearctic and five in the Palearctic including the Moroccan endemic taxon (atlas).

The Horned Lark (Eremophila alpestris) is a widely distributed passerine across North America and Eurasia, with two isolated populations in the Atlas Mountains of Morocco and Colombia in South America. Several subspecies have been described in its huge range, however not all of them are equally recognized (i.e. synonyms). For example, ‘IOC World Bird List’ recognises forty-two (42) subspecies, while ‘Handbook of the Birds of the World Alive’ recognises only twenty-eight (28) subspecies.

The study

The new study by Drovetski et al. (2014) used samples from Europe, Asia, North America and Morocco. However, they didn’t include samples from some important areas like the isolated population in Colombia (subspecies peregrina), or from the Himalayas (subspecies longirostris, see below why it’s important).

In their analysis, the authors used both mitochondrial (one mtDNA gene) and nuclear DNA (one sex-linked intron and one autosomal intron) to elucidate the large scale phylogeographic patterns in the genus Eremophila.

Splitting or lumping?

The first main result is the paraphyly of the Horned Lark in respect to the Temminck’s Lark (Eremophila bilopha). The latter is already recognised as a distinct species, so here is also confirmed by genetic data (this result is well supported by both mtDNA and nuclear DNA).

This same result seen from a different angle: elwesi (Tibetan Horned Lark) is more divergent than all Eremophila taxa (including bilopha), this means the Horned Lark is a paraphyletic species. So, to have a monophyletic species a taxonomic revision of the genus Eremophila is needed: either lumping the Temminck’s Lark with the Horned Lark or splitting the Horned Lark. The first option should be discarded because Temminck’s Lark is already recognized as said above; moreover it’s different phenotypically and ecologically. So the solution is splitting the Horned Lark (at least elwesi or all the clades identified in the study, see below).

The mtDNA data identified six clades within the Horned Lark which the authors suggested should be treated as distinct species. The geography as well as the ecological and phenotypic data largely support the result of the mtDNA. However, nuclear loci provided poor support for the clades identified by mtDNA.

Taxonomic implications:

Here are the clades supported by the mtDAN which the authors suggested should be split:

• alpestris – American Horned Lark (North America).
• flava – Shore Lark (Northern Eurasia).
• brandti – Steppe Horned Lark (SE European Russia to W Mongolia and N China).
• atlas – Atlas Horned Lark (Atlas Mountains of Morocco). Moroccan Horned Lark is a better name because the Atlas Mountains are not entirely within Morocco.
• penicillata – Caucasian Horned Lark (E Turkey, Caucasus to N and W Iran).
• elwesi – Tibetan Horned Lark. (The Himalayan Horned Lark longirostris (not included in the analysis) should have priority if it belongs to this clade because it was described earlier than elwesi).

Reference:

Drovetski, S.V., Raković, M., Semenov, G., Fadeev, I.V. & Red’kin, Y.A. 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

Update:

In a paper published in Dutch Birding, Jan Hein van Steenis reviewed the taxonomy of the ‘horned larks’. After presenting the published genetic data, the author added the morphological element to the mix (after all, that’s what the birders see in the field). The paper is illustrated using several photos of different taxa.

van Steenis, J. H. 2014. Trends in systematics: Taxonomy of ‘horned larks’. Dutch Birding 36: 188-194.

Thanks to Lukasz for the comment below!