Marine Biology

, Volume 156, Issue 2, pp 107–115 | Cite as

Population structure of the planktonic copepod Calanus pacificus in the North Pacific Ocean

  • Mikelle L. NuwerEmail author
  • Bruce W. Frost
  • E. Virginia Armbrust
Original Paper


The pelagic copepod Calanus pacificus ranges nearly continuously across temperate-boreal regions of the North Pacific Ocean and is currently divided into three subspecies—C. pacificus oceanicus, C. pacificus californicus, C. pacificus pacificus—based on subtle morphological differences and geographic location. The relation between geography and genetic differentiation was examined for 398 C. pacificus individuals sampled from six widely distributed locations across the North Pacific, including an open ocean site and coastal sites on both sides of the North Pacific basin. For each individual copepod, the DNA sequence was determined for a 421-bp region of the mitochondrial coxI gene (mtCOI). A total of sixty-three different mtCOI sequences, or haplotypes, were detected, with a sequence divergence between haplotypes of 0.2–3.1%. The number and distribution of haplotypes varied with sampling location; 12 haplotypes were distributed across multiple sampling locations, and 51 occurred at only one location. Five genetically distinct populations were detected based on FST values. Haplotype minimum spanning networks, nucleotide divergence and FST values indicated that individuals from coastal sites in the North Pacific Ocean were more closely related to each other than to individuals from the open ocean site at Station P. These results provide genetic support for the designation of two subspecies—a coastal subspecies that consists of what is currently referred to as C. p. pacificus and C. p. californicus and an open ocean subspecies C. p. oceanicus. This work also indicates that planktonic copepods with potentially high dispersal capacity can develop genetically structured populations in the absence of obvious geographic barriers between proximate locales within an ocean basin.


Open Ocean North Pacific Ocean Unique Haplotype Shared Haplotype Planktonic Copepod 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



We thank B. Peterson, M. Galbraith, R. Goldblatt, E. Goetze, K. Kuma, J. J. Pierson, and A. Yamaguchi for collecting plankton samples used in the present study. Many thanks to A. Bucklin for scientific advice and encouragement. This manuscript has benefitted from the comments of two anonymous reviewers.


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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • Mikelle L. Nuwer
    • 1
    Email author
  • Bruce W. Frost
    • 1
  • E. Virginia Armbrust
    • 1
  1. 1.School of OceanographyUniversity of WashingtonSeattleUSA

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