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SUMMARY:The evolutionary history of baleen whales in an Antarctic context 
 - Jennifer Jackson (British Antarctic Survey)
DTSTART:20101005T100000Z
DTEND:20101005T110000Z
UID:TALK25923@talks.cam.ac.uk
CONTACT:Christian Franzke
DESCRIPTION:Baleen whales (Cetacea: Mysticeti) are the largest animals tha
 t have ever lived and have an Antarctic history stretching back into the l
 ate Eocene. To develop an improved estimation of substitution rate and spe
 cies\ndivergence times for the mysticetes\, we implemented a relaxed-clock
  phylogenetic approach using three fossil calibration dates: the divergenc
 e between odontocetes and mysticetes \;34 million years ago (Ma)\,\nbetwee
 n the balaenids and balaenopterids \;28 Ma\, and the time to most recent c
 ommon ancestor within the Balaenopteridae \;12 Ma. Data examined included 
 seven mitochondrial genomes\, a large number of\nmitochondrial control reg
 ion sequences and nine nuclear introns representing five species of whales
 \, within which multiple species-specific alleles were sequenced to accoun
 t for within-species diversity (1-15 for\neach locus). The total data set 
 represents 1.65 Mbp of mitogenome and nuclear genomic sequence. We also re
 viewed the available evidence for phylogenetic relationships among species
  from all published studies.\nThe estimated substitution rate for the hump
 back whale control region (3.9%/million years\, My) was slow relative to o
 ther mammal species with similar generation times (e.g.\, human-chimp mean
  rate 20%/My). The\nnuclear and mitogenome substitution rate estimates for
  baleen whales were roughly consistent with an 8- to 10-fold slowing due t
 o a combination of large body size and long generation times. Surprisingly
 \, despite the\nlarge data set of nuclear intron sequences\, there was wea
 k and conflicting support for multiple alternate hypotheses concerning the
  phylogenetic relationships of balaenopterid (rorqual) whales. This result
  is reflected\nin all other publications reviewed\, spanning over 40 genet
 ic loci\, and suggesting that interspecies introgressions (hybridization) 
 or a rapid radiation during the Miocene has obscured species relationships
  in the nuclear\ngenome. The fossil record of baleen species diversificati
 ons has been strongly correlated with changes in fossil diatom diversity a
 nd isotopic oxygen levels over time\; since nearly all baleen whale specie
 s are still\nstrongly associated with the polar regions\, the balaenopteri
 d radiation is discussed in the context of Antarctic environmental changes
  in the Miocene\n
LOCATION:British Antarctic Survey\, Room 330B
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