Thanks for sharing this thread guys.
Thanks for sharing the knowledge.
I never thought of taxonomy as exciting before.
Chris
Chris Charles
0412 911 184
33deg 47'30"S
151deg10'09"E
On 26/11/2011, at 9:24 PM, Nikolas Haass wrote:
Thanks David,
I totally agree. Looks like there was some misunderstanding of each
others comments...
The lurida story is indeed very interesting!
Cheers,
Nikolas
----------------
Nikolas Haass
Sydney, NSW
________________________________
From: David James <>
To: Nikolas Haass <>; Mike Honeyman
<>; ""
<>; "" <birding-
>
Sent: Saturday, November 26, 2011 8:33 PM
Subject: Re: [Birding-Aus] Definition of a species
Hi Nikolas,
Give me a break please. I didn't advocate a strict hybridisation
rule to define species. I only said that a study of hybridisation
could resolve the species/subspecies question for the lurida
boobook owl in the Wet tropics rainforests of North Queensland. You
then corrected me by saying "You cannot use hybridisation as a
proof for subspecies versus species". You have since refined that
to say that hybridisation cannot be applied strictly because
'valid' species of gulls and species of ducks hybridise. I agree
with entirely that these species hybridise, only with the caveat
that 'valid species' is a human concept based as much on fashion as
on reality. But lets work back to my original point through your
example.
Gulls are colonial breeders that disperse widely and are as much
nomadic as migratory. Not so long ago in geological time they
started radiating and diverging. But now, due to global warming
(historical) and the industrial revolution these new forms are
exploding in population size, expanding their ranges, overcoming
the isolation barriers thatr had them diverging, and coming into
secondary contact (i.e. meeting again the populations they were
previously isolated from). So they hybridise, not surprisingly.
Taxonomists argue for a SPECIAL case that hybridisation is not
relevant to gulls at the moment. Fair enough, although they now
recognise certain species that inevitably, through hybridisation,
will not exist for too long. Its not extinction, its reverse
radiation.
lurida is entirely different and not part of this SPECIAL case. It
is an owl confined to the wet tropics rainforests. The species has
a tiny range (though large enough to support many endemic species)
and is surrounded on all sides (presently) by its nearest
ancestor. It is isolated from other boobooks only by rainforest
habitat. Other boobooks occur in the same latitude, longitude,
altitude, terrain and climate. If it does not interbreed with other
forms of boobook on its door step it is genetically isolated and a
full species by any definition. If it does hybridise, them we have
to consider how much and why.
I don't say this based on what molecular taxonomists write about
birds they've never seen or what cladistic compute programs
consider most probable. I have spent well over a hundred nights
spotlighting in NE Qld and I have seen lurida, ocellata/boobook,
presumed hybrids, and unidentified boobooks of a different
character altogether (possibly an undescribed taxon) on many
occasions.
David James,
Sydney
==============================
From: Nikolas Haass <>
To: David James <>; Mike Honeyman
<>; ""
<>; "" <birding-
>
Sent: Friday, 25 November 2011 11:23 PM
Subject: Re: [Birding-Aus] Definition of a species
Hi David,
If you use hybridization as a strict indicator to rule out two
species, then there should be only one or a few Anas, one or a few
Aythya, one ore a few Larus... I could endlessly continue this list
of genera containing accepted species that hybridize
naturally. ...and what about the famous "Swoose" (Mute Swan X
Greylag Goose)? Is Greylag Goose a subspecies of Mute Swan or vice
versa?
BTW I'd like to correct a little error: I never said that
hybridization ONLY occurs between "two species nowadays". I said
that hybridization ALSO occurs between "two species nowadays"
Cheers,
Nikolas
----------------
Nikolas Haass
Sydney, NSW
From: David James <>
To: Mike Honeyman <>;
"" <>; "birding-
" <>
Sent: Friday, November 25, 2011 6:31 PM
Subject: Re: [Birding-Aus] Definition of a species
Species definitions are indeed a can of worms that have been
discussed on B-A many times, so I do not want to go
there.
However, either I don't understand or don't agree with Nikolas and
Mike about hybridisation. A hybrid is simply the offspring of two
different forms. The parents can be individuals from two different
genera, species, subspecies (races), varieties, breeds or cultivars
(but not morphs). It is not within the domain (or interest) of
taxonomy to redefine "hybridisation" as something that only occurs
between "two species nowadays".
Of course hybridisation can and is used to indicate species
boundaries in ALL species concepts. It is a line of evidence. When
two forms are sympatric and it is known that they don't hybridise
everyone agrees that they are two species (like the 2 white-tailed
black-cockatoos). When they merge into each other through
hybridisation over a broad front then everyone agrees they are one
species (like green and yellow figbirds). In between there is lots
of grey and disagreement, but there is grey and disagreement in
everything to do with taxonomy. Taxonomists can still use
hybridisation as a line of evidence regardless of the species
concept they follow, even if few do. There are at least two big
problems with using hybridisation: 1) to understand it you need
data from lots of individuals across a wide area; and 2) it is not
applicable to allopatric species. Neither is justification to
dismiss it as irrelevant to the process of speciation.
A frequent trend in taxonomy these days is to compare the
percentage differences in the Cytochrome B gene. Isn't this just
looking for an indication of whether two forms continue to share
genes through the process of
hybridisation, or how long ago they stopped?
Lastly, nearly all existing checklists are predicated on lines of
evidence originally formed around concepts of speciation based on
levels of interbreeding (or the extrapolation of similar patterns
when direct evididence is lacking). Regardless of contemporary
opinions, hybridisation still defines the bird species painted in
the field guides.
David James,
Sydney
==============================
________________________________
From: Mike Honeyman <>
To: ;
Sent: Thursday, 24 November 2011 10:03 PM
Subject: Re: [Birding-Aus] Definition of a species
I hear the sound of a can of worms being opened!
Simon there are many definitions of species, to suit specific
'species concepts'. There are different species concepts that are
preferred for different phyla.
For birds the two most prevalent species concept are the Biological
Species Concept (BSC) after Mayr, and the Phylogenetic Species
Concept (PSC) after Cracraft.
BSC species = "groups of interbreeding populations reproductively
isolated from other such groups"
PSC species = "the smallest diagnosable cluster of organisms within
which there is a parental pattern of ancestry and descent"
Historically the BSC could use the ability to hybridise or not as
an indicator of species, but I think it's a while since anyone
thought that was a reliable indicator, as Nikolas has pointed out.
Re the owls. It is possible that the morphological differences are
a red herring - there could be an environmental 'switch' (e.g. the
climate / habitats that prevail in Tassie and NZ) that cause a
particular morphology that exists widely within the gene pool of
the population to prevail. This could be tested by moving Qld birds
to Tassie and see what they look like after a couple of
generations (I've not looked at any of the papers by the way, just
flying a theoretical kite!)
Cheers
mjh
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