Morphological Variability among Spawning Populations of Bering Cisco Coregonus laurettae
Bering Cisco Coregonus laurettae is an anadromous coregonine species known almost exclusively from northwestern North America and with only three documented spawning populations, all in Alaska. Previous studies of Bering Cisco phenotypic variation examined individuals collected primarily in coastal rearing habitats where population affiliation was not known. Here we compare meristic counts and morphometric ratios of pre-spawning adults among the three known populations: one each in the Yukon, Kuskokwim, and Susitna rivers in Alaska. We also compare meristic data with those previously reported for this species. Populations in the Yukon and Kuskokwim rivers were very similar, while the population in the Susitna River was significantly divergent for certain meristic counts and morphometric ratios. Our findings are consistent with recent genetic analyses that found the Susitna River population to be the most divergent of the three populations. While the Yukon and Kuskokwim river populations survived the Wisconsinan Ice Age in the Beringian Refugium, the Susitna River population colonized the drainage following ice retreat sometime in the last few thousand years. The population's divergence from the source population in the Yukon or Kuskokwim river could be due to a founder effect or adaptation to different environmental conditions.
Bering Cisco Coregonus laurettae is an anadromous North American coregonine species with a terminal mouth and non-pigmented ventral fins.
Samples were collected from pre-spawning Bering Cisco at or approaching the three known spawning areas located in main-stem reaches (shaded) of the Yukon, Kuskokwim, and Susitna rivers in Alaska. Documented marine distribution is indicated by shaded coastal areas in western and northern Alaska, northern Gulf of Alaska, and isolated occurrences on the Alaska Peninsula, Bristol Bay, and eastern Chukotsk Peninsula.
Scatterplot of the Bering Cisco meristic data scores from the first two principal components illustrating the relatively close intermingling of Yukon and Kuskokwim river samples compared to the distinct separation to the right of the Susitna River samples.
Scatterplot of Bering Cisco morphometric data scores from the first two principal components illustrating a central area of intersection with clear variation in centers of distribution among the Yukon (upper left), Kuskokwim (lower left), and Susitna (right) river samples.
Histograms of lower limb gill raker counts among Arctic and Bering Cisco collections presented by McPhail (1966), Bering Cisco from the Susitna River, and Bering Cisco from western Alaska, including the Yukon and Kuskokwim river sample groups pooled because they had equal means and distributions.
Histograms of the pooled lateral line scale counts from the three Bering Cisco sample groups in this study (A, n = 104, mean = 85.1) and Bering Cisco data presented by McPhail (1966; B, n = 33, mean = 85.2). Mean values are indicated with vertical lines.
Contributor Notes
Associate Editor: T. Grande.