Phylogeny, Distribution, and Biology of Pygmy Whitefish (Prosopium coulterii) in the Beringia Region (Chukotka)

Abstract

The pygmy whitefish Prosopium coulterii (C. H. Eigenmann & R. S. Eigenmann, 1892) is a freshwater fish with a highly disjunct distribution ranging from the middle part of North America to Chukotka. There is still no consensus regarding its phylogeny and dispersal history due to limited information from the Chukotkan part of the range. We investigated 22 lakes over Chukotka and found a much broader distribution than it was previously thought. Pygmy whitefish was found to be a common species in the lakes that belong to rivers draining into the Arctic. Cytochrome B, cytochrome oxidase subunit 1, and ATP synthase F0 subunit 6 mitochondrial sites were analyzed from 25 samples to reconstruct the phylogenetic history of pygmy whitefish. Two haplogroups belonging to the east and west Chukotkan ranges were identified; both groups are closely related to Alaskan pigmy whitefish and distant from the Cascadia-Mackenzie (Peace) populations. Combining the distribution patterns, phylogenetic network topology, and the contemporary knowledge on the glaciation history of the region, we suggest a possible colonization pathway over Beringia region and beyond it. The basic biological characteristics (fork length, number of gill rakers, and pyloric caeca, age structure, and feeding) are also presented to characterize the populations over the investigated range.