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The Laptev Sea walrus Odobenus rosmarus laptevi: an enigma revisited

Lindqvist, Charlotte; Bachmann, Lutz; Andersen, Liselotte W.; Born, Erik W.; Arnason, Ulfur LU ; Kovacs, Kit M.; Lydersen, Christian; Abramov, Alexei V. and Wiig, Oystein (2009) In Zoologica Scripta 38(2). p.113-127
Abstract
The walrus (Odobenus rosmarus) is in some current systematic schemes divided into three subspecies: O. r. rosmarus in the North Atlantic, O. r. divergens in the North Pacific and O. r. laptevi in the Laptev Sea. These three subspecies have been described as differing in body size, but the taxonomic status of O. r. laptevi is disputed. The current study applies molecular and morphometric methods to assess the taxonomic status of O. r. laptevi and to analyse the systematic and phylogeographic relationships between the three purported walrus subspecies. Tusk length and tusk circumference were measured from the few skulls available of O. r. laptevi, and the obtained values were within the ranges reported for Pacific walruses. Thus,... (More)
The walrus (Odobenus rosmarus) is in some current systematic schemes divided into three subspecies: O. r. rosmarus in the North Atlantic, O. r. divergens in the North Pacific and O. r. laptevi in the Laptev Sea. These three subspecies have been described as differing in body size, but the taxonomic status of O. r. laptevi is disputed. The current study applies molecular and morphometric methods to assess the taxonomic status of O. r. laptevi and to analyse the systematic and phylogeographic relationships between the three purported walrus subspecies. Tusk length and tusk circumference were measured from the few skulls available of O. r. laptevi, and the obtained values were within the ranges reported for Pacific walruses. Thus, morphologically, subspecies status for O. r. laptevi is not supported according to the Amadon Mayr '75% rule'. Phylogenetic analyses and haplotype networks based on mitochondrial nucleotide sequence data of NADH dehydrogenase 1, 16S rRNA, cytochrome oxidase I and the D-loop of the control region of the historic O. r. laptevi bone material and contemporary O. r. rosmarus and O. r. divergens showed that the Laptev Sea walrus groups with individuals from the North Pacific. Thus, the mitochondrial sequence data do not support the recognition of three walrus subspecies as reciprocally monophyletic evolutionary units with independent evolutionary histories. Only O. r. rosmarus and O. r. divergens meet this criterion with the present sampling. Accordingly, we recommend that Odobenus r. laptevi be abandoned and the Laptev walrus instead be recognized as the westernmost population of the Pacific walrus, Odobenus r. divergens. However, further research is recommended to assess whether the Laptev walrus could be considered as a significant unit in terms of conservation and management, since it is unique in several ecological parameters. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Zoologica Scripta
volume
38
issue
2
pages
113 - 127
publisher
Wiley-Blackwell
external identifiers
  • wos:000263522800001
  • scopus:61349159188
ISSN
0300-3256
DOI
10.1111/j.1463-6409.2008.00364.x
language
English
LU publication?
yes
id
a7dc3d49-557c-4db0-b3dc-e8e67f86c0a6 (old id 1372021)
date added to LUP
2009-05-08 17:13:13
date last changed
2017-09-24 04:02:53
@article{a7dc3d49-557c-4db0-b3dc-e8e67f86c0a6,
  abstract     = {The walrus (Odobenus rosmarus) is in some current systematic schemes divided into three subspecies: O. r. rosmarus in the North Atlantic, O. r. divergens in the North Pacific and O. r. laptevi in the Laptev Sea. These three subspecies have been described as differing in body size, but the taxonomic status of O. r. laptevi is disputed. The current study applies molecular and morphometric methods to assess the taxonomic status of O. r. laptevi and to analyse the systematic and phylogeographic relationships between the three purported walrus subspecies. Tusk length and tusk circumference were measured from the few skulls available of O. r. laptevi, and the obtained values were within the ranges reported for Pacific walruses. Thus, morphologically, subspecies status for O. r. laptevi is not supported according to the Amadon Mayr '75% rule'. Phylogenetic analyses and haplotype networks based on mitochondrial nucleotide sequence data of NADH dehydrogenase 1, 16S rRNA, cytochrome oxidase I and the D-loop of the control region of the historic O. r. laptevi bone material and contemporary O. r. rosmarus and O. r. divergens showed that the Laptev Sea walrus groups with individuals from the North Pacific. Thus, the mitochondrial sequence data do not support the recognition of three walrus subspecies as reciprocally monophyletic evolutionary units with independent evolutionary histories. Only O. r. rosmarus and O. r. divergens meet this criterion with the present sampling. Accordingly, we recommend that Odobenus r. laptevi be abandoned and the Laptev walrus instead be recognized as the westernmost population of the Pacific walrus, Odobenus r. divergens. However, further research is recommended to assess whether the Laptev walrus could be considered as a significant unit in terms of conservation and management, since it is unique in several ecological parameters.},
  author       = {Lindqvist, Charlotte and Bachmann, Lutz and Andersen, Liselotte W. and Born, Erik W. and Arnason, Ulfur and Kovacs, Kit M. and Lydersen, Christian and Abramov, Alexei V. and Wiig, Oystein},
  issn         = {0300-3256},
  language     = {eng},
  number       = {2},
  pages        = {113--127},
  publisher    = {Wiley-Blackwell},
  series       = {Zoologica Scripta},
  title        = {The Laptev Sea walrus Odobenus rosmarus laptevi: an enigma revisited},
  url          = {http://dx.doi.org/10.1111/j.1463-6409.2008.00364.x},
  volume       = {38},
  year         = {2009},
}