Drawing lines between larks: How many species of Horned Lark are there?

A genetic study reveals four primary lineages. But are they also distinct species?

During my student-days in Belgium, I was asked to prepare the sports questions for a pub quiz. Being a proper ornithologist, I managed to sneak in a bird-related question: “Which bird species is mentioned in the Liverpool-anthem You’ll Never Walk Alone?” The answer is obvious:

When you walk through a storm
Hold your head up high
And don’t be afraid of the dark
At the end of a storm is a golden sky
And the sweet silver song of a lark

But which lark are the Liverpool-fans referring to? The lark-family Alaudidae contains numerous species. One specific genus of larks has a particularly complex taxonomic history. This genus – Eremophila – currently contains two species, but that might change…

Horned_lark

A Horned Lark in the snow © Tom Koerner | Wikimedia Commons

 

It’s complicated

In 1904, Bianchi reviewed the genus Eremophila (then known as Otocorys) and divided it into eight distinct species. Over the years, the number of Eremophilaspecies has declined and we are now left with two species: the Horned Lark (E. alpestris) and the Temmick’s Lark (E. bilopha). Both species are widely distributed: the Temmick’s Lark occurs in North Africa and the Middle East while the Horned Lark is found across the Holarctic. The widespread occurrence of the Horned Lark (it breeds on five continents!) and the variation in head patterns has led to a proliferation of subspecies: up to 42 have been proposed over the years.

The wide distribution and the considerable morphological variation suggest that there might be more than one species of Horned Lark. And indeed, based on several genetic markers, Sergei Drovetski and his colleagues proposed to divide the Horned Lark into six distinct species. Now, another study in the Journal of Ornithology – using new samples – took a closer look at the genus Eremophila. How many species did they recognize?

Temminck's_Lark

A Temminck’s Lark in Morocco © Francesco Veronesi | Wikimedia Commons

 

Four Lineages

Fatemeh Ghorbani and colleagues looked at two mitochondrial genes (cytb and ND2) for 46 samples. Phylogenetic analyses of these genes uncovered four primary lineages that originated about 3 million years ago. The exact relationships between these lineages are uncertain (they can probably be resolved with genomic data), making it difficult to pinpoint the origin of this genus. Nonetheless, the researchers propose to treat the four lineages as distinct species:

  1. Himalayan Horned Lark E. longirostris (comprising E. l. longirostrisE. l. deosaiensisE. l. elwesiE. l. khamensisE. l. przewalskiiE. l. argaleaE. l. teleschowi, and E. l. nigrifrons) from the Himalayas and Qinghai–Tibetan plateau
  2. Temminck’s Lark E. bilopha (monotypic), from North Africa to the Middle East
  3. Mountain Horned Lark E. penicillata (E. p. penicillataE. p. atlasE. p. albigulaE. p. balcanica, and E. p. bicornis) from northwest Africa and southeast Europe/southwest Asia
  4. Common Horned Lark E. alpestris sensu stricto (E. a. alpestris and many other American subspecies, E. a. flavaE. a. brandti) from the Northern Palearctic and North and northern South America
tree_larks

The species tree for the genus Eremophila points to four distinct lineages. From: Ghorbani et al. (2020) Journal of Ornithology

 

It’s still complicated

Interestingly, the morphological data and plumage patterns are not in line with the genetic data. Only the Temminck’s Lark (E. bilopha) and one subspecies of the Mountain Horned Lark (E. penicillata) could be confidently separated from the rest. This indicates that the evolutionary history of these larks has been shaped by substantial convergent evolution and perhaps interbreeding. Perhaps hybridization between different subspecies has led to the exchange of “head pattern genes”, similar to the situation in wagtails. Stay tuned for more interesting studies on larks!

PCA_larks

Morphological data could only discriminate he Temminck’s Lark (green circle on the right) and one subspecies of the Mountain Horned Lark (blue circle on the left) from the other taxa. From: Ghorbani et al. (2020) Journal of Ornithology 

 

References

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 One9(1).

Ghorbani, F., Aliabadian, M., Olsson, U., Donald, P. F., Khan, A. A., & Alström, P. (2019). Mitochondrial phylogeography of the genus Eremophila confirms underestimated species diversity in the Palearctic. Journal of Ornithology, 1-16.

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