Cook Inlet Belugas

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Cook Inlet Belugas

• ESA petition
• The Cook Inlet population of beluga whales is a
  small, geographically isolated and genetically
  differentiated population facing the imminent
  threat of extinction.
• Alaska Chapter of The Wildlife Society
• The Cook Inlet population of beluga whales is
  small, geographically isolated from all other
  beluga populations in Alaska, and genetically
  distinct.
• Marine Mammal Committee, ASM
• This small group of whales is geographically and
  genetically isolated from all other beluga
  populations.
  

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Cook Inlet Belugas

• NMFS AFSC Quarterly Report, December 2000
• Beluga whales (Delphinapterus leucas) that
  inhabit Cook Inlet, Alaska, form a small,
  isolated stock that is geographically and
  genetically segregated from the other four stocks
  of belugas found in Alaskan waters. Genetic
  evidence indicates that beluga whales in Cook
  Inlet have not mixed with other beluga stocks for
  thousands of years.
• Arctic Science Journeys
• Beluga whales in Alaska's Cook Inlet near
  Anchorage are thought to be genetically unique
  among the 50,000 belugas that live in waters off
  Alaska.

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Terms

• Genetically isolated
• no gene flow
• geographic barriers
• Genetically distinct
• probabilistic difference in genetic characters
• must define the level of analysis
• Genetically unique
• genetic characters that unambiguously identify
  membership in a population or other group

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Original report

• OCorry-Crowe et al. 1997. Phlyogeography,
  population structure and dispersal patterns of
  the beluga whale Delphinapterus leucas in the
  western Nearctic revealed by mitochondrial DNA.
  Molecular Ecology 6955-970.
• Alaskan populations
• mtDNA

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Findings

• 5 populations examined
• 29 haplotypes found
• 5 found in Cook Inlet
• all CI haplotypes shared with at least one other
  population
  
• all populations had at least one haplotype in
  common with CI
  
• differed in frequency only

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Findings

• significant genetic structure among Alaskan
  populations
  
• all populations differed significantly from all
  others
  
• Cook Inlet is the most genetically distinct of
  all geographical subpopulations with respect to
  mtDNA, an indication perhaps that the Alaska
  Peninsula may indeed be an effective barrier to
  genetic exchange or that drift in this small
  population offsets any homogenizing effects of
  gene flow.

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ABC Brown Bears

• mtDNA (Talbot and Shields 1996)
• distinct and ancient lineage
• found nowhere else
• represented earliest entry of bears into North
  America
  
• differed from bears on SE mainland
• nuclear microsatellites (Paetkau et al 1998)
• evidence of gene flow between ABC and mainland
• male-mediated
• ancient DNA (Leonard et al. 2000)
• all 3 lineages were present in eastern Beringia
  35,000 years ago
  
• indicated that there were no separate entries

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Closer to Home

• Brown Gladden, et al. 1999. Population structure
  of North American beluga whales (Delphinapterus
  leucas) based on nuclear DNA microsatellite
  variation and contrasted with the population
  structure revealed by mitochondrial DNA
  variation. Molecular Ecology 8347-363.
• populations from Norton Sound to St Lawrence
  River
  
• found differences among populations

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Take-home Message

• mtDNA
• likely to exhibit structure across populations
• female philopatry
• Nuclear loci
• more likely to show total amount of gene flow

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Implications for Cook Inlet Belugas

• They may be genetically distinct
• nuclear loci necessary for determination
• mtDNA data are informative
• no female immigration
• population growth must come from within

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Conservation Units

• Management Unit
• demography is determined by internal processes
• natality
• mortality
• NOT immigration
• all populations can be assigned to MUs
• Evolutionarily Significant Unit
• important component of the evolutionary legacy of
  a species
  
• not all populations need to be included in ESUs

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