Little Auk Alle alle
Little Auk has been treated as a polytypic species based on size differences between the population on Franz Josef Land (A. a. polaris) and other populations (A. a. alle) (Vaurie 1965, Cramp 1985). Body size is indeed significantly larger in A. a. polaris than in A. a. alle (Stempniewicz et al. 1996, Wojczulanis-Jakubas et al. 2011, 2015). At the time of the original description of A. a. polaris, overlap of measurements between polaris and other populations was believed to be minimal (Stenhouse 1930), but this was based on a sample of only five male, two female, and three unsexed A. a. polaris. These subspecies are now known to overlap substantially in size (Vaurie 1965, Wojczulanis-Jakubas et al. 2015). In both wing length and head–bill length, fewer than 50% of A. a. polaris fall outside the range of A. a. alle (Wojczulanis-Jakubas et al. 2015: Fig. 2). Thus, A. a. polaris and A. a. alle do not meet the 75% rule for subspecies (Amadon 1949).
Recent studies suggest that size varies clinally from west to east, with the smallest birds found in Greenland and Jan Mayen, medium-sized birds on Svalbard, and the largest individuals (A. a. polaris) on Franz Josef Land (Wojczulanis-Jakubas et al. 2011, 2015). This pattern may reflect physiological adaptation. The Little Auks of Franz Josef Land breed in the lowest air temperature and apparently overwinter at higher latitudes than other populations (Wojczulanis-Jakubas et al. 2011).
No geographic differentiation has been detected in mitochondrial control region sequences or in microsatellites (Wojczulanis-Jakubas et al. 2014, 2015). Based on DNA data, it has been concluded that Little Auk forms a single Evolutionarily Significant Unit (Wojczulanis-Jakubas et al. 2015).
In conclusion, there is no evidence that Little Auk consists of more than a single population lineage and recognition of the subspecies A. a. polaris is not warranted. Little Auk is best regarded as a monotypic species.
Amadon, D. 1949. The seventy-five per cent rule for subspecies. Condor 51: 250–258.
Cramp, S. (ed.) 1985. The Birds of the Western Palearctic. Vol. 4. Oxford University Press, Oxford.
Stempniewicz, L., Skakuj, M. & Iliszko, L. 1996. The Little Auk Alle alle polaris of Franz Josef Land: a comparison with Svalbard Alle a. alle populations. Polar Res. 15: 1–10
Stenhouse, J.H. 1930. The Little Auk (Alle alle polaris Sub-Sp. nov.) of Franz Josef Land. Scott. Nat. 182: 47–49.
Vaurie, C. 1965. The Birds of the Palearctic Fauna. Non-Passeriformes. Witherby, London.
Wojczulanis-Jakubas, K., Jakubas, D., Welcker, J., Harding, A.M.A., Karnovsky, N.J., Kidawa, D., Steen, H., Stempniewicz, L. & Camphuysen, C.J. 2011. Body size variation of a high-Arctic seabird: the dovekie (Alle alle). Polar Biol. 34: 847–854.
Wojczulanis-Jakubas, K., Kilikowska, A., Fort, J., Gavrilo, M., Jakubas, D. & Friesen, V. 2015. No evidence of divergence at neutral genetic markers between the two morphologically different subspecies of the most numerous Arctic seabird. Ibis 157: 787–797.
Wojczulanis-Jakubas, K., Kilikowska, A., Harding, A.M., Jakubas, D., Karnovsky, N.J., Steen, H., Strøm, H., Welcker, J., Gavrilo, M., Lifjeld, J.T. & Johnsen, A. 2014. Weak population genetic differentiation in the most numerous Arctic seabird, the Little Auk. Polar Biol. 37: 621–630.
