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Whatever happened to the species concept?? (1 Viewer)

Dimitris

Dimitris

Birdwatcher in Oz
During the past few years it seems that the number of splits have been increasing at a very high (ridiculous?) rate. And no I'm not talking about crypto species that are being proven via genetics (i.e no gene flow) to be distinct species. I'm talking about large gulls (LBBG complex), Yellow Wagtails, Carrion/Hooded(shouldn't these two be considered a failed speciation event?) Crow and the like that show considerable (i.e. not an occasional sterile hybrid) gene flow between populations.
So are we kicking ring species etc out the door? Can someone shed some light on what a 'modern' species is?

Cheers!

Dimitris
 
Dimitris,

The following is a useful short discussion summarising BOU's current policy:

Helbig et al 2002. Guidelines for assigning species rank. Ibis.
http://www.bou.org.uk/sppguidelines.pdf

Of course, there are many alternative opinions! But the multiple splitting of Yellow Wagtails is only implemented under the PSC (as followed by e.g. the Dutch Birding Association).

Richard
 
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Many thanks for that Richard. One has to wonder if we are overdoing it, at least the birds don't care...

Cheers!

Dimitris
 
Dimitris,
some of the examples you mention here have had entire threads devoted to them, try searching in this forum as well as in the id forum. I think even the biological species concept does allow for hybridization to take place, if there is a significant barrier to gene flow; the difficulty there is what is the definition of "significant", and how good are the data describing how effective the barrier is. Another can of worms is the populations that does not overlap in range, which the biological species concept and most other concepts can only handle by approximations.

Niels
 
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The biggest problem is that humans delight in "one size fits all" solutions whereas the rest of nature just gets on with it.

John
 
njlarsen said:
Dimitris,
some of the examples you mention here have had entire threads devoted to them, try searching in this forum as well as in the id forum. I think even the biological species concept does allow for hybridization to take place, if there is a significant barrier to gene flow; the difficulty there is what is the definition of "significant", and how good are the data describing how effective the barrier is. Another can of worms is the populations that does not overlap in range, which the biological species concept and most other concepts can only handle by approximations.

Niels
Click to expand...


Hello Niels,

Thanks for your answer, It does as long as the hybrids are infertile and as far as I know it is not used in plants. If it was we would only have 5 species of Eucalypt instead of 600 etc. At least the rest of living things don't care what we think...

Cheers!

Dimitris
 
Quote from Dr. Martin Collinson, British Birds 94(1):2-27, in the pages devoted to Biological species concept: "The 'high school' definition, that two animals belongs to the same species if they can interbreed and produce fertile young, is inaccurate: many birds which are not the same species can do this (e.g. Lesser Black-backed Gull Larus fuscus and Herring Gull L. Argentatus)". And a second quote, about ½ page later: "at least 10% of the Worlds bird species have been shown to hybridize with others in the wild, often producing fertile young (Grant & Grant 1992, 1997). Postzygotic maintenance of the biological species relies on the hybrid youngsters usually (there are exceptions) being at a selective disadvantage, being not so fertile as their parents or being less able to attract mates, such that hybrids are preferentially eliminated from the population. Hybrid zones are not uncommon, maintained by some balance between the production of hybrids by interbreeding and their subsequent poor viability or breeding performance (Barton and Hewitt 1985)".

All in all, Dr Collinson mentions about ten and details two species concepts in this review.

Cheers
Niels
 
njlarsen said:
Quote from Dr. Martin Collinson, British Birds 94(1):2-27, in the pages devoted to Biological species concept: "The 'high school' definition, that two animals belongs to the same species if they can interbreed and produce fertile young, is inaccurate: many birds which are not the same species can do this (e.g. Lesser Black-backed Gull Larus fuscus and Herring Gull L. Argentatus)". And a second quote, about ½ page later: "at least 10% of the Worlds bird species have been shown to hybridize with others in the wild, often producing fertile young (Grant & Grant 1992, 1997). Postzygotic maintenance of the biological species relies on the hybrid youngsters usually (there are exceptions) being at a selective disadvantage, being not so fertile as their parents or being less able to attract mates, such that hybrids are preferentially eliminated from the population. Hybrid zones are not uncommon, maintained by some balance between the production of hybrids by interbreeding and their subsequent poor viability or breeding performance (Barton and Hewitt 1985)".

All in all, Dr Collinson mentions about ten and details two species concepts in this review.

Cheers
Niels
Click to expand...


Most interesting Niels, though if there's extensive backrossing as a result of these hybrids I would still expect them to be the same species (as seems to be the case with many Yellow Wagtail races). I'll have to look that up in my uni library then (something to do in the midsemester break)

Cheers!

Dimitris
 
Dimitris said:
Most interesting Niels, though if there's extensive backrossing as a result of these hybrids I would still expect them to be the same species (as seems to be the case with many Yellow Wagtail races).
Click to expand...

Not necessarily - it's just because the traditional "high-school" biology, for simplicity, simply teach that different species cannot produce fertile hybrids rather than the actual, somewhat more complex, reproductively isolated (as also noted by Niels). There may be massive hybridization - even back-crossing - but as long as the hybrid-zone is relatively narrow, you can be fairly sure these hybrid individuals are "less fit", meaning that the two "original" species actually are reproductively isolated. I'll refrain from commenting on the crow example you mentioned, as it isn't a case I've spend any amount of time looking into (though I suspect the relatively narrow hybrid zone plays a role), but there are some real issues regarding the species-limits in herring/LBBG complex (not a ring-species, as previously believed). The traditional Yellow Wagtail is also problematic, as it isn't monophyletic (I'll add that BSC species can be paraphyletic, cf. speciation by peripheral isolates - but that's another discussion). Full papers on both these cases are available here (PDF):

Gull:
http://web-28.promotor.telia.se/app...900&File=Liebers+&+Helbig+Proc+R+Soc+2004.pdf

Wagtail:
http://www.cbs.umn.edu/eeb/faculty/ZinkRobert/Phylogeographic patterns in Motacilla.pdf
 
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Rasmus Boegh said:
(I'll add that BSC species aren't necessarily monophyletic, cf. speciation by peripheral isolates - but that's another discussion). Full papers on both these cases are available here (PDF)
Click to expand...

Sounds interesting, Rasmus. Can you elaborate or provide a source?
 
fugl said:
Sounds interesting, Rasmus.
Click to expand...

My mistake. My last post was evidently written too fast without re-reading it (as I usually do). What I meant to say is that under bsc, species can be paraphyletic, which is the logical consequence of species per peripheral isolates.
 
Gosh, I was surprised to see people discussing my 2000 paper here:
Collinson, M. (2001) Shifting Sands: taxonomic changes in the world of the field ornithologist. Brit Birds 94, 1-24.

Although I spent a lot of time on it, looking back, i think bits of it were a bit naive, or at least incomplete.

The Ibis paper (Helbig et al - linked above) is still widely used and cited (72 times at last count).

More recently, I did a DNA paper with Norman Maclean and Dick Newell
Maclean, N., Collinson, M. & Newell R. G. 2005. Taxonomy for birders: a beginner’s guide to DNA and species problems. Brit. Birds 98, 512-537.

that I think had been helpful.

I can provide pdfs of any of these for anyone interested.
 
Rasmus Boegh said:
Not necessarily - it's just because the traditional "high-school" biology, for simplicity, simply teach that different species cannot produce fertile hybrids rather than the actual, somewhat more complex, reproductively isolated (as also noted by Niels). There may be massive hybridization - even back-crossing - but as long as the hybrid-zone is relatively narrow, you can be fairly sure these hybrid individuals are "less fit", meaning that the two "original" species actually are reproductively isolated. I'll refrain from commenting on the crow example you mentioned, as it isn't a case I've spend any amount of time looking into (though I suspect the relatively narrow hybrid zone plays a role), but there are some real issues regarding the species-limits in herring/LBBG complex (not a ring-species, as previously believed). The traditional Yellow Wagtail is also problematic, as it isn't monophyletic (I'll add that BSC species can be paraphyletic, cf. speciation by peripheral isolates - but that's another discussion). Full papers on both these cases are available here (PDF):

Gull:
http://web-28.promotor.telia.se/app...900&File=Liebers+&+Helbig+Proc+R+Soc+2004.pdf

Wagtail:
http://www.cbs.umn.edu/eeb/faculty/ZinkRobert/Phylogeographic patterns in Motacilla.pdf
Click to expand...


Thank you so much Rasmus! and Doc Martin please pm me. I'm most deifnately interested!

Cheers!

Dimitris
 
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