How do birders want species-definition to be determined? Via Morphology, assortative breeding, or DNA analysis? (1 Viewer)

[DMW]

Given that logic it maybe best to lump all 'jaegers' too as these are routinely misidentified on seawatches (and even when sat on reservoirs inland), then you can just tick 'Jaeger' or 'Small Skua'. One problem with this taxonomic concept is the historical geneflow between Pomarine and the 'Catharacta' group. However given that all these species are hard to identify and given ongoing geneflow it would probably be best to lump all species of larger skuas and smaller jaegers together as a single species.

You miss the point. I'm not just talking about diagnosibility in the field, although as far as I am aware there is no reliable way to sperate Desertas and Fea's. We can readily identify many sub-species - lots of Yellow Wags for example.
The idea I'm floating is that from a listing perspective, it might make sense to re-lump certain taxa and treat them once again as sub-species. Many taxonomic decisions are arbitrary and inconsistent, and there is an undeniable bias in taxonomy towards splitting, so I'm not sure what is objectionable about creating a list that takes a more conservative approach and is useful for birders.

 

[Farnboro John]

And “Gull”, and “Duck” and...😉

No no no, split every diagnosable plumage of every species of gull, not to mention every Mallard variation from wild type to topknot, "Dipper duck" and Aylesbury!

John

 

[Welsh Peregrine]

How about gulls into those with sensible names (eg Little Gull) and those without (where do we start?)?

 

[Mysticete]

You miss the point. I'm not just talking about diagnosibility in the field, although as far as I am aware there is no reliable way to sperate Desertas and Fea's. We can readily identify many sub-species - lots of Yellow Wags for example.
The idea I'm floating is that from a listing perspective, it might make sense to re-lump certain taxa and treat them once again as sub-species. Many taxonomic decisions are arbitrary and inconsistent, and there is an undeniable bias in taxonomy towards splitting, so I'm not sure what is objectionable about creating a list that takes a more conservative approach and is useful for birders.

As mentioned, species exist in science outside of listing concerns, and honestly hobby listing purposes is certainly the least considered and important implication of taxonomic changes. It's find if you want to create a "field identifiable form" checklist, fine, but you shouldn't consider them species.

 

[ZanderII]

You miss the point. I'm not just talking about diagnosibility in the field, although as far as I am aware there is no reliable way to sperate Desertas and Fea's. We can readily identify many sub-species - lots of Yellow Wags for example.
The idea I'm floating is that from a listing perspective, it might make sense to re-lump certain taxa and treat them once again as sub-species. Many taxonomic decisions are arbitrary and inconsistent, and there is an undeniable bias in taxonomy towards splitting, so I'm not sure what is objectionable about creating a list that takes a more conservative approach and is useful for birders.

I don't miss the point - you wanted to lump Zino's which is field identifiable in #15. Desertas has yet to be split by all authorities and may yet prove to be field identifiable. I can't ID various vizmig passerines but that doesn't mean we need to lump them - if you feel upset by seawatch views of seabirds then get on a pelagic.

 

[ZanderII]

The idea I'm floating is that from a listing perspective, it might make sense to re-lump certain taxa and treat them once again as sub-species. Many taxonomic decisions are arbitrary and inconsistent

Examples that upset you that are widely-accepted at the species level?

 

[DMW]

I don't miss the point - you wanted to lump Zino's which is field identifiable in #15. Desertas has yet to be split by all authorities and may yet prove to be field identifiable. I can't ID various vizmig passerines but that doesn't mean we need to lump them - if you feel upset by seawatch views of seabirds then get on a pelagic.

You clearly do miss the point, and making condescending comments about not being able to ID every bird you see doesn't really add anything useful to the discussion. I might just as well say that if I can identify any individual bird in the field, like the partially albino Blackbird in my garden, then it must be a valid species.

I'm well aware that Zino's Petrel can be identified in the field under optimal conditions, and so can 3-4 taxa of Brent Geese, far more easily.

The fact is that we are seeing ever-increasingly small distinctions being used to promote sub-species to species level.

 

[DMW]

As mentioned, species exist in science outside of listing concerns, and honestly hobby listing purposes is certainly the least considered and important implication of taxonomic changes. It's find if you want to create a "field identifiable form" checklist, fine, but you shouldn't consider them species.

So give me an objective example of how species "exist in science". I don't even know what that means. "Science" can't even arrive at a unified position on what a species actually is, yet somehow can objectively tell me that X is a good species, but Y is only a sub-species.
As for hobby listing, I'd say it's generally much more important than you seem to think. Birding is a significant industry now, and people spend large sums of money based on what is on lists they follow. There are islands in remote places that now get birding bucks purely on the back of a newly-elevated species. Who else gives a damn about obscure birds in obscure parts of the world?

 

[Mysticete]

So give me an objective example of how species "exist in science". I don't even know what that means. "Science" can't even arrive at a unified position on what a species actually is, yet somehow can objectively tell me that X is a good species, but Y is only a sub-species.
As for hobby listing, I'd say it's generally much more important than you seem to think. Birding is a significant industry now, and people spend large sums of money based on what is on lists they follow. There are islands in remote places that now get birding bucks purely on the back of a newly-elevated species. Who else gives a damn about obscure birds in obscure parts of the world?

You are mixing up competing ideas over species (Phylogenetic vs Biological) and species criteria with the concept of species itself.

Species are used in all the following ways: defining conservation priorities and conservation related regulations, hunting regulations, import/export laws, scientific inventory, both of reserves as well as of museum specimens and zoo animals, precision in all sorts of scientific and not so scientific communication, defining study parameters for scientific research, faunal comparisons at both a regional and temporal scale, etc.

Listing is an incredibly trivial use compared to that.

I should also point out: "Field-Identifiable forms" is basically just the morphological species concept, something that was pretty much abandoned a century ago by neontologists for being even more arbitrary than existing definitions, and being poorly integrated with evolution in general. The only area its used is really paleontology, because morphology is all we have to work with (and even there it causes issues, like the recent Tyrannosaur taxonomic controversy).

 

[Xenospiza]

Recently, there was a study which showed that the differences between Arctic, Common and Lesser Redpoll were all caused by the inversion and subsequent different expression of one part of the DNA.
In the article and on Birdforum, this was lauded as a reason to lump these species. In the Netherlands, this was lauded as proof that their status as species was correct, as e.g. Hooded and Carrion Crow differ in a similar way.
Now who is right? Note that I can actually recognise all these taxa!

 

[wolfbirder]

Recently, there was a study which showed that the differences between Arctic, Common and Lesser Redpoll were all caused by the inversion and subsequent different expression of one part of the DNA.
In the article and on Birdforum, this was lauded as a reason to lump these species. In the Netherlands, this was lauded as proof that their status as species was correct, as e.g. Hooded and Carrion Crow differ in a similar way.
Now who is right? Note that I can actually recognise all these taxa!

This emphasises my OP perfectly. If you want Redpolls to remain split ( I certainly do) you are accused of merely wanting to increase list size. It’s not that, but they are mostly identifiable in the field and more importantly, they seem to recognise each other as different breeds.

 

[ZanderII]

Recently, there was a study which showed that the differences between Arctic, Common and Lesser Redpoll were all caused by the inversion and subsequent different expression of one part of the DNA.
In the article and on Birdforum, this was lauded as a reason to lump these species. In the Netherlands, this was lauded as proof that their status as species was correct, as e.g. Hooded and Carrion Crow differ in a similar way.
Now who is right? Note that I can actually recognise all these taxa!

There is a relatively narrow and stable hybrid zone between the crows but massive genetic admixture between redpolls. Who said they were similar in NL?

 

[ZanderII]

This emphasises my OP perfectly. If you want Redpolls to remain split ( I certainly do) you are accused of merely wanting to increase list size. It’s not that, but they are mostly identifiable in the field and more importantly, they seem to recognise each other as different breeds.

Have a read of New research: Redpoll species are all one they aren't recognising each other which is why there is geneflow.

 

[ZanderII]

You clearly do miss the point, and making condescending comments about not being able to ID every bird you see doesn't really add anything useful to the discussion. I might just as well say that if I can identify any individual bird in the field, like the partially albino Blackbird in my garden, then it must be a valid species.

I'm well aware that Zino's Petrel can be identified in the field under optimal conditions, and so can 3-4 taxa of Brent Geese, far more easily.

The fact is that we are seeing ever-increasingly small distinctions being used to promote sub-species to species level.

Not really. Its like saying let's lump the Arctic Warbler complex or even the treecreepers as they are hard to ID - despite being field identifiable at times. What other examples apart from the Pterodromas upset you?

 

[Xenospiza]

There is a relatively narrow and stable hybrid zone between the crows but massive genetic admixture between xbills. Who said they were similar in NL?

I looked up the corrrect wording about the similarity to the crow case here [Peter de Knijf: The genetic difference is similar because the difference between the two crows is caused by a single inversion].
George Sangster defends keeping the redpolls separate here [e.g. by saying that the study does not prove that there is no assortive mating]. If you're interested in a translation that goes beyond google translate, let me know.

 

[ZanderII]

I looked up the corrrect wording about the similarity to the crow case here [Peter de Knijf: The genetic difference is similar because the difference between the two crows is caused by a single inversion].
George Sangster defends keeping the redpolls separate here [e.g. by saying that the study does not prove that there is no assortive mating]. If you're interested in a translation that goes beyond google translate, let me know.

Thanks Xenospiza.

From de Knijff 2014's explainer of the Science paper

One particular 1.95-Mb segment, on the avian chromosome 18, showed clear genetic differentiation between carrion crow and hooded crow individuals. This region encompassed 81 of all 83 fixed differences [of 8.4 million single-nucleotide polymorphisms (SNPs) in total] between the two taxa. In this region, a complex pattern of inversions was discovered among carrion crows when compared to hooded crows. RNA-sequencing and gene expression analyses revealed underexpression, among hooded crows, of several genes in this region that are involved in the regulation of pigmentation, visual perception, and hormonal balance. Elsewhere in the crow genome, a number of smaller speciation islands were also found to harbor genes underlying these traits, which were also underexpressed in hooded crows. In this way, Poelstra et al. present a unique case of speciation whereby, despite substantial gene flow (especially from hooded crows into German carrion crows), phenotypic divergence likely caused by assortative mating and sexual selection is maintained by genetic variation in less than 1% of the genome.

and from Funk et al. 2021

Understanding the effects of the redpoll supergene, and the forces responsible for its maintenance, is difficult. In the absence of selection (imposed by the environment, or through mate choice), the supergene would function as a single locus with one of the haplotypes eventually becoming fixed or lost due to drift12. Even with some selection, high levels of migration (between inversion genotypes) would swamp out any loci contributing to local adaptation. The persistence of the redpoll supergene is therefore likely dependent on both selection and migration. One scenario that is supported by field data is that the supergene remains balanced through assortative mating. Redpolls often mate assortatively46, but, intermediates and mixed pairs have also been observed from multiple localities37,47. Thus, the strictness of assortative mating may vary depending on the locality or may relax during irruptive population years47. Relaxation of mate choice and mixed pairings would produce the intermediate number of inversion heterozygotes seen in our data, and ultimately maintain the supergene as a stable polymorphism. However, this scenario alone does not provide an explanation for the maintenance of latitudinal differences between ecotypes. Furthermore, no hybrid zone has ever been documented in redpolls, which would be expected under a strict assortative mating scenario. While regions of hybridization have been suggested in places like Iceland, where high color variation exists48,49, previous genetic studies have not recovered support for this hypothesis50.

However from de Knijff 2014

Armed with this new very detailed genetic information, it is clear that none of the currently formulated species concepts fully apply to these two crow taxa (unless one is willing relax some stringency in the various definitions). Indeed, the genomes of German carrion crows are much more similar to those of hooded crows than to Spanish carrion crows. Put simply, apart from the few carrion crow type “speciation islands,” German carrion crows could be considered to represent hooded crows with a black (carrion crow) phenotype.

 

[cajanuma]

Are their many birds that fall into this category? About the only ones I can think of are some seabirds like storm petrels or prions. Even then I have seen folks argue identification based on things such as molt patterns and so on.

Even in these cases, though, most of these seabirds have distinctive vocalizations. They could confidently be identified to species in the dark at their breeding colonies, but only become unidentifiable at sea (which happens to be 99% of birders encounter them).

 

[wolfbirder]

Have a read of New research: Redpoll species are all one they aren't recognising each other which is why there is geneflow.

I can't see where it says they are not involved in assortative breeding?

I like this response by a birder called Ryan O'Donnell, who makes salient points about the DNA Redpoll situation: -

"As the paper cites, Hoary and Common Redpolls have been shown to differ in physiology, timing of migration, nest habitats, diets, vocalizations, and behaviour (in addition to the sometimes tricky morphological differences). If you look carefully at the results in that paper, the genetic differences even between the redpolls (collectively) and the linnets are not consistent - redpolls and linnets share some mitochondrial haplotypes and also cluster together in a "STRUCTURE" analysis of microsatellite allele frequencies. In other analyses in this paper, Common and Hoary Redpolls did differ significantly: for example, in the AMOVA tests these two taxa differed at p=0.0086 (traditionally any value less than 0.05 is considered a significant difference). These results are completely consistent with two valid, biologically meaningful species that have recently diverged from one another. The paper itself represents this situation honestly, and says that "molecular data alone should not be used for designating species status and we acknowledge that there might have been missed the relevant genetic markers to distinguish gene pools." I'm afraid your summary here oversimplifies things and ignores the (quite likely) possibility of incomplete lineage sorting. This misleads people like Jane who read this and conclude that Hoary and Common Redpolls are not good species. But that is not what the data say, and not what the authors say.

In your response to David Sibley, you said, "We birders have long espoused genetics to split species, so why can't we accept the idea that things might go the other way sometimes as well?"" This also misrepresents what genetics can and can't tell us about species, because the case for splitting based on genetics is not symmetric. If genetics tell you that two groups of birds do not interbreed, and have not interbreed for millenia, then that is a good case for them being separate species. But if genetics (especially neutral markers like those used in this study) do not show a difference, there might still be one. If physiology, behaviour, morphology, vocalizations, and studies of mate choice show that two species are different, then genetics might not be necessary. And in fact, genes can be shared by two species. An excellent example is Polar Bears and Brown Bears: they are clearly morphologically, ecologically, and behaviourally different species, yet they are polyphyletic according to mitochondrial DNA. Closer to home, phylogenetically speaking, Gadwalls and Eurasian Wigeon share mitochondrial haplotypes - would you argue that they are the same species, as you have for Common and Hoary Redpolls?"

My understanding was that Lesser Redpoll and Common Redpoll do not form mixed pairs where they breed sympatrically (Lifjeld and Bjerke 1996 for example). Has this been contradicted?

 

[Mysticete]

IIRC, there is a redpoll thread in the taxonomy subforum...might be better to take up this debate there, since I am sure some of these points have been raised there.

 

[dantheman]

Interestingly the title of this thread is titled 'How do birders want species-definition to be determined?'

Given the options as a birder I'm happy for a range of the suggested methods to apply, depending on the group in question; no one method makes total sense if imposed overall. That's being pragmatic? (After all individual of 'species' know what they generally (but will hybridise if pushed to and able to) - whether by factors we can easily determine or not).

(Appreciate that promoting subspecies to species level can have positive connotations for conservation, but there has to be a rationale for it - with human population increase, development and climate change it will increasingly become a losing battle perhaps?*)

Birders in the field, and even the general public do have a deal of importance in conservation and maintaining population/diversity etc - it's a balance of both imo. If people don't care about, or even know about it can become a bit irrelevant ...

*(Conflict of ideas, or context of the question here perhaps - are we talking about what species I would hope to encounter in the UK, rarities or otherwise, or are we talking about worldwide and tropical/subtropical species I will never encounter?)