Geographic Variation in North American Ninespine Sticklebacks, Pungitius pungitius

Abstract

Ventral spine length and the number of lateral plates, dorsal spines, and gill rakers in Pungitius pungitius from 132 North American localities were compared. The number of lateral plates is consistently high in populations from tidal waters, and low in inland populations. Geographic variation in the number of dorsal spines and gill rakers suggest two allopatric forms of P. pungitius in North America. A Bering form ranges from Alaska along the arctic coasts of Canada, and a Mississippi form ranges from the Great Lakes to the Mackenzie River. Two glacial refugia are hypothesised to explain the origin and present distribution of these forms.