Hi Peter,
I don't understand either, but it is not a simple analysis like determining
sex, or whether one species is different to another. The key element is good
quality tissue to begin with. I think that means that contemporary samples are
needed, and that would also include the molecular "footprint" of the species
undoubted decline [if there is one showing in the molecules, we can assume that
this is likely] since roughly 1890 (perhaps before).
I'm familiar with one molecular study that compared Australian Zebra Finch
[Genome known!], with Lesser Sundas Zebra Finch (usually still considered one
species, which is fair). They compared about 30 Aust birds (sample specimens)
from several sites, with 12 birds from Lombok and Timor - Indonesia [tissue
specimens well preserved]. The study estimated that 9 individual Zebra finches
colonised the Lesser Sundas from Australia, that that occurred at an estimated
1.9 million yrs before present (95% interval: 1.2-2.8 million years); and that
the current Lesser Sunda population is around 18000-26000 birds; and the
Australian population at 1.3 million and 7 million (using different analyses).
These are only estimates [not necessarily "reality"], based on the analysis
with the many assumptions and limitations discussed.
I guess it does highlight the difficulties/complexities of such a study, even
with the best (or second best) known bird species on the planet.
Colin
> From:
> To: ; ;
> Date: Mon, 12 Aug 2013 11:39:17 +1000
> Subject: RE: [Birding-Aus] DNA confirms elusive Night Parrot found
>
> Thanks for all that, Colin. I don't understand how DNA analysis gives a
> population estimate. Is it to do with the number of ancestors each bird must
> have had in order to have that amount of variation in its DNA?
>
> And if you could get the necessary samples, would you know when that
> population estimate was valid for? I assume the estimate derived from, say,
> 20 samples collected 100 years ago would be no different to 20 collected
> today, yet the population is likely different today to 100 years ago. Even
> 100 years ago there might have been a tiny fraction of the population 200
> years ago.
>
> Peter Shute
>
> > -----Original Message-----
> > From:
> > On Behalf Of
> > colin trainor
> > Sent: Monday, 12 August 2013 10:06 AM
> > To: Ross Macfarlane (TPG);
> > Subject: [Birding-Aus] DNA confirms elusive Night Parrot found
>
> > Determining NParrot populations from bits of existing
> > specimens would be problematic (recognising their incredible
> > value and fact you don't want major
> > damage) ie. availability of tiny bits of dried
> > [non-preserved, and therefore with DNA increasingly degraded]
> > flesh from "footpads" or from within a feather - most likely
> > from specimens
> > >100 years old.
> >
> > Samples size - if you could get some fresh or well preserved
> > NParrot tissue or blood, you might get an estimate of
> > population number, but probably with very broad confidence
> > limits (e.g. with one bird - Result = 10,000 individuals,
> > made up 95% confidence limits = population is within the
> > range 100 to 20,000 birds), but with additional samples it
> > may get closer to reality, and narrower confidence limits.
> >
> > You might need say 3-5 samples to get an ?ok result, but need
> > more to refine it. Sample size would be critical is getting
> > an estimate close to "reality".
> >
> >
> >
> >
> >
> > > From:
> > > To: ;
> > > Subject: Re: [Birding-Aus] DNA confirms elusive Night Parrot found
> > > Date: Sun, 11 Aug 2013 11:48:08 +1000
> > >
> > > Colin, it's actually very feasible, in fact highly
> > important DNA has
> > > been extracted from early human fossils that are 100s or
> > thousands of
> > > years old, that has been used to build a picture of human
> > evolution.
> > > DNA extracted from frozen mammoth carcases in Siberia have
> > led to some
> > > researchers to propose reviving mammoth as a species (I truly hope
> > > this does not happen, but that's not a discussion for
> > here.) The same
> > > has been proposed for thylacines using DNA extracted from
> > preserved joeys in museums.
> > >
> > > In other words recovery of DNA from museum specimens is
> > > well-established science. It doesn't need to be a complete genome,
> > > just enough long fragments to distinguish night parrot from its
> > > closest relatives (presumably ground parrot and western ground
> > > parrot.)
> > >
> > > Also distinguishing between human and parrot DNA would be a very
> > > simple exercise - much more so than for ancient humans as
> > described above.
> > > Basically the scientists can look at a series of bands on a
> > screen and
> > > see which ones are human and which non-human, almost as
> > easily as they
> > > could distinguish a human and a bird footprint.
> > >
> > > -----Original Message-----
> > > From: colin trainor
> > > Sent: Saturday, August 10, 2013 7:15 PM
> > > To:
> > > Subject: [Birding-Aus] DNA confirms elusive Night Parrot found
> > >
> > > DNA - Most specimens (?all but 3 perhaps) collected before 1900, so
> > > not sure how useful it would be.
> > >
> > > I'm ignorant of molecular approaches, but this detailed type of
> > > analysis may not be possible on gnarly old specimens
> > (?better on blood
> > > and fresh tissue? - of which there is none)
> > >
> > > >>>>>>>>>>>>
> > >
> > > To:
> > >
> > >
> > >
> > >
> > >
> > >
> > > Subject:
> > >
> > > DNA confirms elusive Night Parrot found
> > >
> > >
> > >
> > >
> > > From:
> > >
> > > Andrew Hobbs <>
> > >
> > >
> > >
> > >
> > > Date:
> > >
> > > Sat, 10 Aug 2013 14:22:41 +0800
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > There are apparently 22 known specimens in various museums
> > around the
> > > world. I would think it quite possible to use DNA analysis
> > on those
> > > to make some estimates of population sizes etc. and their
> > relationship
> > > to the recent samples. I would be surprised if that is not already
> > > being done or at least considered.
> > > Cheers
> > >
> > > Andrew
> > >
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> >
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