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Scottish Crossbill (1 Viewer)

Well, I suppose technically, a particular species is constantly having to face a new or modified environment, which in turn affects its evolutionary process. If I remember correctly, then evolution was traditionally regarded as proceeding at a relatively constant, slow process, but our old friend Gould hypothesised that in fact this slow pace was occasionally interrupted by bouts of vastly increased evolutionary pace (I know that's not the best way of stating it!). However, even these "speeded up" phases still happened at a pace that was too slow for our perceptions.

I suppose we just have to make the best of our particular window of opportunity, and collect as much data as we can, and formulate theories accordingly. But you're right, it doesn't make it any less interesting.

Absolutely correct. I am not sure that Gould had the vision to realise that the PE theory could happen over even shorter elements of time, which is a shame because there is so much merit in the idea. Gould was mostly talking about the fossil record (with particular reference to the Burgess Shales and horse lineage amongst other examples) but though Gould's theory is relatively new (less than 30 years old), it was not realised at the time that we were developing the tools to examine this. In Gould's defence, he was often accused of arguing against Darwin's Linear Progression but the reality was, he never argued against this but offered a companion theory. Had he lived longer, he may have been able to see how his theory was gaining some ground albeit, from areas that he could not have guessed.

Ian
 
Geospiza Darwin's finches are a classical example that presents similarities with the crossbill case, as also noted in the recent Summers et al. paper posted here yesterday. They are classically treated as species under the BSC, which is presented by Summers et al. as an argument for treating the three Scottish Loxia types as distinct species. But there are other points of view... Bob Zink's discussion, published in Auk in 2002, is particularly interesting on this subject:
http://www.cbs.umn.edu/eeb/faculty/ZinkRobert/ANewPerspective.pdf

These are amazing cases, in which loose applications of the BSC can typically lead to more splitting than careful applications of the PSC - quite the opposite of the usual situation...

Laurent -


I agree with you here but only because we are still labouring under a Linnaean definition of species (at least to some people). It seems heresy to say this but I think we are rapidly approaching a time when we have to significantly revise our definition of speciation. I am not keen on splitting for the sake of it, especially if applied for birdwatching reasons on the sole grounds of physical appearance. Some of the gull splits are worrying, for example. However, I genuinely feel that our understanding of speciation projected against evolutionary theory has been over-simplified for too long. This means, we cannot possibly dismiss the Scottish crossbill on any level of technicalities simply because it has come to represent an important position in our understanding. In other words, the terminology is lagging behind the various threads of evidence and this along means we should look at protection.

Ian
 
Galapagos finches are still named species for convenience and as a sort of one-off leftover from the times when their genetics was unknown. I don't think you can use this as argument to turn crossbill races to species.

Interesting thought: Tens of conifer species exist, and some have significant geographical variation. As crossbills are supposed to quickly evolve bill shape tied to particular cone shape, we would expect very many races in Eurasia.

I wonder how many crossbill races exist - hundreds? And some races should smoothly change geographically and turn into others, reflecting conifer change.

Certainly, red crossbills I seen in Tibet sounded different.
 
I also have my own 'theories' as to the origins of Scotbill but these are just hypothetical, though I am examining what evidence I can. This (different) paper is much more controversial !!!!

Lindsay

Hi Lindsay,

As I mentioned elsewhere, this is one of the fundamental problems with any evolutionary theory in that we cannot observe it happening in real time. This is the main area that creationists have used to attack evolution given they will not be around to see their own theories disproved. Happily, the thread here has been much more fascinating with a lot of perfect valid items of discussion tabled. Jurek and Laurent have given me a lot to think about with their particular thoughts.

Ian
 
Galapagos finches are still named species for convenience and as a sort of one-off leftover from the times when their genetics was unknown. I don't think you can use this as argument to turn crossbill races to species.

Interesting thought: Tens of conifer species exist, and some have significant geographical variation. As crossbills are supposed to quickly evolve bill shape tied to particular cone shape, we would expect very many races in Eurasia.

I wonder how many crossbill races exist - hundreds? And some races should smoothly change geographically and turn into others, reflecting conifer change.

Certainly, red crossbills I seen in Tibet sounded different.


Hi Jurek,

You kinda read my mind on this one. The original Darwinian theory always assumed isolation of a race as the driving force and this is certainly compelling. Dare I say, Scottish crossbill is an island race (for convenience here) that may have been geographically separated from parrot and common crossbill in the past? Again, we cannot say whether the races (for convenience) developed in isolation or alongside each other because we are only seeing the here and now.

Ian
 
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A Parrot Crossbill, with a bill of 13.0+ mm, wing 108mm specialising on Scots Pine cones and a Common Crossbill with a bill of 10.0mm, wing 96mm specialising on Norway Spruce are the same 'species'

What is so strange? Look at other races. See e.g. migratory populations of different waders, ducks, cranes or passerines - differ in bill and wing length and dramatically differ in migration stategies but not always are even classified as subspecies.
 
What is so strange? Look at other races. See e.g. migratory populations of different waders, ducks, cranes or passerines - differ in bill and wing length and dramatically differ in migration stategies but not always are even classified as subspecies.

Do these other 'races' breed at different times of the year ? With Parrot and Common Crossbills their whole breeding strategy is sychronised to the availability of their preferred food Scots Pine and Norway Spruce respectively, which are available at very different times of the year. This also promotes positive assortative mating and inherited morphology (and presumably call structure). Their whole 'behaviour' is very different.

Lindsay
 
Lindsay,knowing by the hours and hours of work you put in with Scotbills,I agree with everything you say and people who have not even put a fraction of the time,that you have (in my opinion) dont really have an arguement.
 
I agree with you here but only because we are still labouring under a Linnaean definition of species (at least to some people). It seems heresy to say this but I think we are rapidly approaching a time when we have to significantly revise our definition of speciation. I am not keen on splitting for the sake of it, especially if applied for birdwatching reasons on the sole grounds of physical appearance. Some of the gull splits are worrying, for example. However, I genuinely feel that our understanding of speciation projected against evolutionary theory has been over-simplified for too long. This means, we cannot possibly dismiss the Scottish crossbill on any level of technicalities simply because it has come to represent an important position in our understanding. In other words, the terminology is lagging behind the various threads of evidence and this along means we should look at protection.

Ian

Is it not possible that this is where we can take a sociological perspective towards ourselves, and our research into evolutionary theory?

I am the last person to want to disparage in any way the work of anybody who conducts all this research (mainly because I'm deeply envious of their profession and their efforts!), but how far do we need to take speciation? Originally, this compartmentalising of the natural world has obviously proven of enormous benefit to science, and the advancement of understanding. But I think it's equally a comment on human nature that everything has to go into a box, and then depending on further research, certain species go into smaller boxes, or sometimes larger ones.

As a birder I'm delighted that Caspian Gull has been split and is recognised as a full species. It presents an enjoyable ID challenge and I'm glad I can tick it. But given the complexities of large white-headed gull taxonomy, and the views of some that the Herring/LBBG can be viewed as one "super-species", how does this split benefit Caspian Gull? The gulls don't care, they'll breed/interbreed and live however they see fit.

That was genuinely a question based on ignorance |=)|, so any answers would be greatly appreciated. I always want to know more!
 
But given the complexities of large white-headed gull taxonomy, and the views of some that the Herring/LBBG can be viewed as one "super-species", how does this split benefit Caspian Gull?

Of course the split does not benefit Caspian Gull, unless it suddenly becomes rare in the future and its recognition as an evolutionary unit of taxonomic importance will lead to conservation funds drifting in its direction. A highly unlikely scenario considering that large gulls generally do really well off the back of mankind.

I think you miss the point of the superspecies concept - taxonomic units that diverged from one another in isolation rather recently, and have subsequently remained largely or entirely geographically separated. There are many such examples.

he gulls don't care, they'll breed/interbreed and live however they see fit.

Obviously not true, if they hybridised freely then we wouldn't consider them to be species. The problem is this whole complex is very young and poorly genetically and phenotypically differentiated, thus reproductive isolation between some taxa is incomplete. Its a post-glacial thing, just look at Zonotrichia sparrows and Dendroica wood-warblers they are genetically very close (so close that you even get intergenic hybrids) yet no-one would question their specefic status....

Zander
 
Not sure if the last post (#53) was referenced in appeasement to myself but if it was I should make it clear I am not a 'professional' biologist (though I used to be) and neither do I have any affiliation with any organisation other than the BTO who issue my ringing permit. I do not get paid for what I do-thankfully. However, I like to think that my approach at least is thorough and is based on knowledge gained through experience in the field and not just by reading some papers or books.

I have said on other threads concerning Scotbill that I (and others !) deal in facts and evidence that have been 'collected' in the field. It is then our responsibility to 'report' these facts and the powers that be (BOU) can then determine the speciation of birds like Scottish Crossbill. They know much more about speciation than me, or are at least presumably applying consistent rules to such decisions. Bottom line, it is not 'my' problem !

I am not 'emotionally' attached to the 'idea' of a 'Scottish Crossbill', and certainly not for the principal purpose of political gain, whatever that may be.

Lindsay
 
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Obviously not true, if they hybridised freely then we wouldn't consider them to be species. The problem is this whole complex is very young and poorly genetically and phenotypically differentiated, thus reproductive isolation between some taxa is incomplete. Its a post-glacial thing, just look at Zonotrichia sparrows and Dendroica wood-warblers they are genetically very close (so close that you even get intergenic hybrids) yet no-one would question their specefic status....

Zander

Well, look at Thayers and Kumleins Gulls, and the debates that surround their species status. And don't Glaucous-winged Gulls hybridize freely within large parts of their breeding range?

We consider these birds species at the moment, but the situation is far from straightforward. However, if, as you suggest, this is a very young complex, then our knowledge of it's development will also be limited. We would have to follow it's evolutionary process "as it happens".

I'm afraid my knowledge of Zonotrichia sparrow and Dendroica wood warblers is pretty much zero, so I can't comment on that particular issue!
 
Not sure if the last post (#53) was referenced in appeasement to myself

Yeah, it was really! I'm sure you don't give two hoots as to my opinions on the merits of your research - I'm just some bloke at a PC - but even so, I think it's wrong to be dismissive about somebody whose knowledge is based on countless hours in the field, actually studying the subject that we're all discussing.
 
I tend to see BF contributions as discussion (thinking out loud, if you will) and this thread has certainly tended towards that direction. I would hope that no one here has been out to get a result in a debate scenario because we do not have enough information overall to do this. IMO, there are fair grounds for a massive review and overhaul of classification although I suspect it will not happen and we will be left with the awkward job of shoe-horning at times. This leaves the possibility of a growing acceptance of the concept of superspecies but this would be a compromise in many ways and dare I say, unacceptable to much of the world bird watching community.*

Ian

* I am partly against the superspecies concept because it is a gift for thos bl**dy creationists. ;)
 
Well, look at Thayers and Kumleins Gulls, and the debates that surround their species status. And don't Glaucous-winged Gulls hybridize freely within large parts of their breeding range?

We consider these birds species at the moment, but the situation is far from straightforward. However, if, as you suggest, this is a very young complex, then our knowledge of it's development will also be limited. We would have to follow it's evolutionary process "as it happens".

Ok, we are going from some sweeping generalisations on the taxonomoy of large white-headed gulls to two specific thorns in the side of taxonomists. Kumlien's Gull is most probably a hybrid swarm between Thayer's and Iceland Gulls which are themselves poorly differentiated. Western and Glaucous-winged Gulls exhibit a step cline - in this case a hybrid zone that settles on a marine ecotone. They may not be each others closest relatives yet show bounded hybrid superiority....
 
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