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NYT article on Killer Whale speciation (1 Viewer)
- Thread starter fugl
- Start date
Mysticete
Well-known member
Here is the abstract:
"Killer whales (Orcinus orca) currently comprise a single, cosmopolitan species with a diverse diet. However, studies over the last 30 years have revealed populations of sympatric "ecotypes" with discrete prey preferences, morphology and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. This low level of diversity is likely due to low mitochondrial mutation rates that are common to cetaceans. Using killer whales as a case study, we have developed a method to readily sequence, assemble, and analyze complete mitochondrial genomes from large numbers of samples to more accurately assess phylogeography and estimate divergence times. This represents an important tool for wildlife management, not only for killer whales but for many marine taxa. We used high-throughput sequencing to survey whole mitochondrial genome variation of 139 samples from the North Pacific, North Atlantic and southern oceans. Phylogenetic analysis indicated that each of the known ecotypes represents a strongly supported clade with divergence times ranging from approximately 150,000 to 700,000 years ago. We recommend that three named ecotypes be elevated to full species, and that the remaining types be recognized as subspecies pending additional data. Establishing appropriate taxonomic designations will greatly aid in understanding the ecological impacts and conservation needs of these important marine predators. We predict that phylogeographic mitogenomics will become an important tool for improved statistical phylogeography and more precise estimates of divergence times."
"Killer whales (Orcinus orca) currently comprise a single, cosmopolitan species with a diverse diet. However, studies over the last 30 years have revealed populations of sympatric "ecotypes" with discrete prey preferences, morphology and behaviors. Although these ecotypes avoid social interactions and are not known to interbreed, genetic studies to date have found extremely low levels of diversity in the mitochondrial control region, and few clear phylogeographic patterns worldwide. This low level of diversity is likely due to low mitochondrial mutation rates that are common to cetaceans. Using killer whales as a case study, we have developed a method to readily sequence, assemble, and analyze complete mitochondrial genomes from large numbers of samples to more accurately assess phylogeography and estimate divergence times. This represents an important tool for wildlife management, not only for killer whales but for many marine taxa. We used high-throughput sequencing to survey whole mitochondrial genome variation of 139 samples from the North Pacific, North Atlantic and southern oceans. Phylogenetic analysis indicated that each of the known ecotypes represents a strongly supported clade with divergence times ranging from approximately 150,000 to 700,000 years ago. We recommend that three named ecotypes be elevated to full species, and that the remaining types be recognized as subspecies pending additional data. Establishing appropriate taxonomic designations will greatly aid in understanding the ecological impacts and conservation needs of these important marine predators. We predict that phylogeographic mitogenomics will become an important tool for improved statistical phylogeography and more precise estimates of divergence times."
Mysticete
Well-known member
Incidently, I saw this presentation at the last Marine Mammals meeting, and was probably the best talk there.
as indicated, 3 species are at this point tentatively supported (there is no formal description of names, much to my frustration...arrrghh)
These include:
Transient Killer Whale, the earliest divergence, confined AFAWK to the North Pacific and possibly Antarctica. Incidently these species are sympatric with Pacific Residents, which mitochondrial DNA shows they diverged from 700,000 years ago.
The Antarctic Killer Whale, found in the southern Oceans. This may also be the form for in the tropics,as a sample from the Gulf of Mexico clusters here. Sampling in the tropics at this point is too poor to really be sure
And the, for lack of better name, Resident Killer Whale, which includes the North Pacific Resident and Offshore populations, as well as both presumed ecotypes in the North Atlantic.
as indicated, 3 species are at this point tentatively supported (there is no formal description of names, much to my frustration...arrrghh)
These include:
Transient Killer Whale, the earliest divergence, confined AFAWK to the North Pacific and possibly Antarctica. Incidently these species are sympatric with Pacific Residents, which mitochondrial DNA shows they diverged from 700,000 years ago.
The Antarctic Killer Whale, found in the southern Oceans. This may also be the form for in the tropics,as a sample from the Gulf of Mexico clusters here. Sampling in the tropics at this point is too poor to really be sure
And the, for lack of better name, Resident Killer Whale, which includes the North Pacific Resident and Offshore populations, as well as both presumed ecotypes in the North Atlantic.
lewis20126
Well-known member
Mysticete
Any linkages between these three species and the Type A, Type B and Type C outlined in Shirahai et al. (and elsewhere?). Is external appearance correleated with the behavioural and genetic factors?
[PS - I hope a good type series of all three species were collected!
]
cheers, alan
Any linkages between these three species and the Type A, Type B and Type C outlined in Shirahai et al. (and elsewhere?). Is external appearance correleated with the behavioural and genetic factors?
[PS - I hope a good type series of all three species were collected!
]cheers, alan
Fascinating stuff, raising all sorts of questions. I wonder how malleable the feeding practices of the different taxa are. Is there any evidence of hybridization between the various KW “species”, does anyone know? What about cross-fostering (very unlikely to happen in nature, I would imagine), any instances of this?
Mysticete
Well-known member
Lewis: Marine mammalogists don't need to collect specimens...that is what stranding networks are for....
I have the Hadoram Shirihai book at home, but my recollection is that the different A, B, C types are the antarctic morphs right? In which case all three of these would be lumped into one "Antarctic species" There is some evidence though that taxa referrable to the Transient form may occur in Antarctica as well.
Fugl: The NYT article I think overblows the feeding specialization. There is anectdotal and isotope evidence that suggests transients will take fish, and that the occasional resident will eat seals. They do to a certain degree specialize on different food sources, but carnivorous mammals as a rule are not that picky...
I am not if cross-fostering occurs in the wild, but I do now of a case where a Killer Whale was raised with Bottlenose dolphins. When it "grew" up, it had a fairly bizarre set of vocalizations which were a mix of bottlenose and typical killer whale, which suggests at least some of the vocal (cultural) differences are learned.
I have the Hadoram Shirihai book at home, but my recollection is that the different A, B, C types are the antarctic morphs right? In which case all three of these would be lumped into one "Antarctic species" There is some evidence though that taxa referrable to the Transient form may occur in Antarctica as well.
Fugl: The NYT article I think overblows the feeding specialization. There is anectdotal and isotope evidence that suggests transients will take fish, and that the occasional resident will eat seals. They do to a certain degree specialize on different food sources, but carnivorous mammals as a rule are not that picky...
I am not if cross-fostering occurs in the wild, but I do now of a case where a Killer Whale was raised with Bottlenose dolphins. When it "grew" up, it had a fairly bizarre set of vocalizations which were a mix of bottlenose and typical killer whale, which suggests at least some of the vocal (cultural) differences are learned.
Mysticete
Well-known member
Another point:
North Atlantic (and by default, Resident) would properly belong to Orcinus orca
.
Antarctic taxa would belong to Orcinus glacialis, which has holotype material associated with it, but might be lost
Hypothetically, Orcinus "rectipinna" could be used for the Transient population, but it is unclear what animal this refers to. It is from a North Pacific locality, but I am not certain if it's known whether this taxon refers to a Transient or Resident Whale
North Atlantic (and by default, Resident) would properly belong to Orcinus orca
.
Antarctic taxa would belong to Orcinus glacialis, which has holotype material associated with it, but might be lost
Hypothetically, Orcinus "rectipinna" could be used for the Transient population, but it is unclear what animal this refers to. It is from a North Pacific locality, but I am not certain if it's known whether this taxon refers to a Transient or Resident Whale
lewis20126
Well-known member
Yes, as far as I am aware but not sure whether (i) these (or other) morphs exist within all of the three species, or (ii) whether 1-2 of the species are monomorphic or even whether (iii) the cetacean and / or academic community recognises the three types/morphs! I saw some "Type B"s of f Macquarie in November I think.
cheers, alan
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lewis20126
Well-known member
M - noticed your other thread - does "rectipinna" lack a holotype or neotype? And, if this is the case, assuming no strandings are diagnosable as this form in the short term, what course of action would you recommend? Hypothetically speaking of course....
a
Mysticete
Well-known member
The different types of Antarctic whale are (A, B, C) are recognized by the marine mammal community (the original paper indicates the location on the tree by using those types) All form a monophyletic group, so your Macquarie animal would be referrable to the Orcina glacialis. Actually there is another older name for this animal, based only on records at sea.
rectipinna is based on a drawing and description...looking up the information in the wonderful Herskovitz 1966 catalog, it is defined by a significantly larger dorsal fin (a diagnostic character for transients). So it appears Orcinus rectipinna would be the appropriate existing name for transients at this moment
As for holotypes, a neotype might be useful for the transient and Antarctic form, but as previously mentioned this material would be in collections already. The clearest and best idea would be to use ancient DNA analysis on the proper specimens to link them. We will see if this is ever done..., although I suspect Morin et al are pursuing this avenue.
rectipinna is based on a drawing and description...looking up the information in the wonderful Herskovitz 1966 catalog, it is defined by a significantly larger dorsal fin (a diagnostic character for transients). So it appears Orcinus rectipinna would be the appropriate existing name for transients at this moment
As for holotypes, a neotype might be useful for the transient and Antarctic form, but as previously mentioned this material would be in collections already. The clearest and best idea would be to use ancient DNA analysis on the proper specimens to link them. We will see if this is ever done..., although I suspect Morin et al are pursuing this avenue.
rockfowl
Mark Andrews
Should have added this here, a few pics anyway - http://www.wildlifeextra.com/go/new...les are probably several different species#cr
