No time. Too busy. Toy pelicans from Marwell Zoo. Accompanying thoughts from Dave Hone here; involves azhdarchids. Bye now, sorry for lack of substantive content.
did you catch the recently out there video of the orcas at seaworld ripping to shreds a poor pelican that landed in their tank midshow?
apparently they do it to any bird that lands in the tank. just usually the birds don't come while hundreds of ppl are watching. quite an interesting bit of behaviour as the whales kick into predatory pack mode and as a group work at dismembering the bird, and at the same time ignoring their trainers entirely!
Darren, I may guess the reason of your "no time" takes the root also in your new status of young father. My congratulations, by the way! I got the same status last... no, since February, 2008. And I may say only one thing: little children - little troubles, bigger children - bigger troubles. Accustom your daughter (BTW, I also have a daughter) to reading, my baby likes to watch pictures in encyclopedias.
So, possible, you hadn't seen this reference: http://www.sivatherium.h12.ru/library/Dixon_2/00_en.htm
I hope you'll like it. Now I prepare Russian translation and correct text of English version. The third his book (about man) is also in my plans. This year... possible...
I'm puzzled as to why pelicans are absent from the South American interior. Wetlands like the Pantanal would appear to be prime pelican habitat, yet South America's pelicans are exclusively coastal species.
I'm puzzled as to why pelicans are absent from the South American interior.
That's a good question. But I don't know if there's any good answer, apart from referring to the vagaries of evolutionary history.
And there are other similar cases where certain otherwise widespread bird groups are missing from entire continents, for no obvious reason. Why are cranes absent from South America? Why are lapwings absent from North America? Why are swans absent from Africa?
Sometimes the birds that are absent nowadays were present in the past, though. For example, there were swans in Africa in the Miocene (Louchart et al., 2005). So perhaps there were freshwater pelicans in South America too, once upon a time?
Reference:
Louchart, A., Vignaud, P., Likius, A., Mackaye, H.T. & Brunet, M. 2005. A new swan (Aves: Anatidae) in Africa, from the latest Miocene of Chad and Libya. Journal of Vertebrate Paleontology 25, 384-392.
Big waterbirds are generally stuff of cold climates and seasonal waters. In rainforests they are outcompeted/predated by fish and crocodiles. Pantanal itself is relatively new, few 1000's years ago it was a desert.
BTW - are any pterosaurs likely to dive using wings, like eg. auks, gannets and shearwaters?
Jerzy - that generalisation (that large waterbirds are out-competed in the tropics by fishes and crocodiles) might be partly true, but it isn't wholly accurate - look at shoebills, hammerkops, aquatic-feeding storks and anhingas. In fact, could the diverse giant anhingas of the Cenozoic be something to do with the absence of pelicans from tropical South America? Several giant extinct anhingas are known from the South American tropics: see the refs below.
As for wing-propelled diving in pterosaurs: no pterosaur has any of the adaptations we'd expect for this lifestyle, and most of the pterosaurs associated with marine life have peciliarities that rule this out further (e.g., rhamphorhynchids have very long tails, pteranodontians were generally gigantic). However, plunge-diving is not ruled out for pterosaurs. Having said all that, I don't think we'd have predicted from morphology that certain petrels can dive as deeply as they do, so there might still be room for doubt.
Refs - -
Alvarenga, H. M. F. & Guilherme, E. 2003. The anhingas (Aves: Anhingidae) from the Upper Tertiary (Miocene-Pliocene) of southwestern Amazonia. Journal of Vertebrate Paleontology 23, 614-621.
Noriega, J. I. 2001. Body mass estimation and locomotion of the Miocene pelecaniform form Macranhinga. Acta Palaeontologica Polonica 46, 247-260.
- . 2002. Additional material of Macranhinga paranensis (Aves: Pelecaniformes: Anhingidae) from the Upper Miocene Ituzaingó Formation of Entre Rios Province, Argentina. In Zhou, Z. & Zhang, F. (eds). Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution. Science Press (Beijing), pp. 51-61.
- . & Alvarenga, H. M. F. 2002. Phylogeny of the Tertiary giant anhingas (Pelecaniformes: Anhingidae) from South America. In Zhou, Z. & Zhang, F. (eds). Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution. Science Press (Beijing), pp. 41-49.
Jerzy: Pelicans would probably not mind living in a desert, as long as there is a large body of water (permanent or temporary) within comfortable flying distance. Think of the Australian pelican Pelecanus conspicillatus; on those rare occasions when heavy rainfall forms lakes in the interior of Australia, pelicans fly there to fish and to breed.
that generalisation (that large waterbirds are out-competed in the tropics by fishes and crocodiles) might be partly true, but it isn't wholly accurate - look at shoebills, hammerkops, aquatic-feeding storks and anhingas.
What Darren said. There are plenty of fish-eating tropical freshwater birds; cormorants, in particular, are common at rivers and lakes just about everywhere in the tropics.
Besides, it might be that waterbirds living in the temperate or boreal zones actually suffer as much from fish competition as their tropical relatives. There is a great number of studies on the question whether waterbirds (mostly anatids) and fish compete for food, and most of these studies tend to answer this in the affirmative. As for the question of predation, there is a fairly rich literature on the importance of fish (mostly pike Esox) predation on waterbirds (again, mostly anatids); these studies, too, tend to suggest that fish predation on temperate/boreal waterbirds is often non-trivial.
I just returned from Venezuelan Llanos and at least species diversity of waterbirds (swimming, not wading ones) is much smaller. Three species of ducks, hehehe. And no wonder, because edge of every lake has a line of caymans sunning.
About pterosaurs - I find it improbable that the large sub-group of fish-eating animals only skimmed the water surface, without plunge-diving, swimming and diving.
Jerzy - your competition hypothesis is interesting and I wonder if there is any published data that backs it up. As mentioned above (by Dartian and myself), at least in some parts of the world, tropical waterbirds are doing fine alongside their fish and crocodilian neighbours.
As for pterosaurs: to be frank (this is not meant to sound rude!), it does not matter what you personally find improbable. The fact is that pterosaurs just do not have the sorts of wing shapes, wing loadings, body shapes etc. we see in diving and swimming birds. Recent work has indicated that pterosaurs were more diverse ecologically than conventionally thought (e.g., Witton 2008), but.. nope, still no overlap with dedicated diving and swimming birds. It might be that the involvement of the hindlimb in the wing membrane prevented pterosaurs from adapting to such lifestyles: note that there are no swimming or diving bats either (though there are of course bats that gaff or grab prey from the water surface).
Ref - -
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B 28, 143-158.
I won't be surprised if predation and competition with fish and crocodilians is significant for some species of waterbirds in some areas. Locally, it's said that predation of chicks by snakehead (Channa spp.) might prevent certain waterbirds like lesser whistling duck (Dendrocygna javanica) and little grebe (Tachybaptus ruficollus) from establishing themselves in some of Singapore's wetland areas.
Yet I'm sure that this is not the only limiting factor. After all, in many African, Asian and Australian wetlands, we get storks, herons and egrets, ibis and spoonbills, pelicans, cormorants, anhingas, grebes, ducks, cranes, rails, finfoots and waders all living in close proximity to large predatory fish and crocodilians. Perhaps ducks, grebes and rails might be more vulnerable to predators, since their chicks swim around instead of growing up in a nest, but I'm sure there are specific habitat preferences or behaviours which limit the risk of predation.
Jerzy: Llanos has only 3 species of ducks? This site lists 6 resident and 1 migratory anatid. In any case, Anatidae as a whole would appear to be more diverse and abundant in temperate regions, but there are quite a number of species present in fish and crocodilian-rich waters of the tropics.
Besides, like so many other waterbirds, pelicans nest in colonies either in trees or on the ground, so predation by fish or crocodilians on the chicks isn't likely to be a significant reason why the family is excluded from South America.
Regarding specifically the idea that fishing/swimming birds are ecologically excluded by crocodilians through predation or competition... An interesting idea, to be sure, and it might contain some truth. But it certainly can't be the whole explanation.
The first map showed the global distribution of anhingas, and the second the global distribution of crocodilians. Judging by the map, the former donât exactly seem to be trying to avoid the latter...
(Sorry for the double post, but my post contained more than one link and I didnât want it to be caught by the spam filter.)
I saw only three Anseriformes species. I know there are more. Not many, considering that in Europe it is possible to see a dozen in one lake! It is really strange to notice that huge wetland is without geese, swans, gulls, with few terns and one species of cormorants and grebes.
What exists there is outcompeted to special niches. Neotropic cormorants live in very deep waters, whistling ducks - in very small, shallow floodlands.
I think competition may be mostly with fish, water turtles and aquatic mammals. When waterbody is permanent (does not dry out, does not freeze, is not separate from the large water systems) they can colonize it and thrive not worrying about supporting these huge flight muscles.
Distribution of eg. swans, diving ducks and mergansers suggests that.
About pterosaurs - look again! Maybe fossils can be re-interpreted to allow for swimming. Could pterosaurs paddle with half-closed wings, like alcids do?
About pterosaurs - look again! Maybe fossils can be re-interpreted to allow for swimming. Could pterosaurs paddle with half-closed wings, like alcids do?
All I can do is repeat the answer I gave above. Several researchers have looked at pterosaur ecomorphology very recently, and in fact I'm working on it at the moment. No, pterosaurs lack the wing and body shapes associated with diving, swimming etc. See above.
Sorry if this sounds condescending, but remember that scientific hypotheses are evidence-led: we do not formulate intuitively appealing ideas and then argue that they must be correct, even when evidence indicates otherwise! Or, if we do, we should not.
Something that I've been wondering about concerning pelican morphology...
As everyone knows, 'brown' pelicans (Pelecanus occidentalis & P. thagus) feed by plunge-diving whereas 'white' pelicans do not. How is this difference expressed in their respective morphology/anatomy*? Or, in other words, if pelicans were only known as fossils, could paleontologists tell that the feeding behaviours of 'brown' and 'white' peilcans were different?
* Apart, obviously, from their plumage colouration.
An interesting point which has actually been addressed in the pelican and pterosaur literature (Richardson 1943, Bennett 2001). There are no 'special' skeletal adaptations that make the brown pelicans different from all the others, but there is one subtle difference in soft tisse morphology: the nares are closed over by horny flaps in brown pelicans. That seems to be about it!
Counter-intuitively, brown pelicans have less of their volume occupied by subcutaneous air-sacs than do white pelicans: in the latter, Richardson (1943) reported air-sacs occupying 34-38% of inflated corpses, but 25.7% in a brown pelican. Richardson even speculated, based on this data, that white pelicans evolved from plunge-diving ancestors and that they had since elaborated on the pneumaticity because it then became useful 'in other ways'.
The lack of special plunge-diving adaptations in the brown pelican skeleton led Bennett to note that plunge-diving was indeed possible for pteranodontid pterosaurs. A previous objection to this idea has been that 'pterosaurs were too light', but - given recent work indicating that pterosaur masses have been substantially under-estimated (Witton 2008) - we can look at this anew.
Refs - -
Bennett, S. C. 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part II. Size and functional morphology. Palaeontographica Abteilung A 260, 113-153.
Richardson, F. 1943. Pneumaticity of the white pelican. The Condor 45, 37-38.
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B 28, 143-158.
I don't think that Richardson was necessarily saying that brown pelicans were the most primitive members of the group - rather, that plunge-diving was primitive. I doubt that this is true given that it isn't widespread in pelicans, nor is it primitive for any of the taxa considered close relatives of pelicans (shoebills, frigate birds etc.). I'm not aware of any species-level phylogenies for Pelecanidae: is anyone?
Hi Darren, for paleontologist its only intuition, but for ecologist its perfectly valid question.
Why large ecological niche is apparently left unoccupied? Why pterosaurs - as interpreted by now - didn't evolve swimming and diving ability, despite that this would be very useful for catching their primary prey, fish?
I agree with your osteological arguments, but keep an eye open for this possibility!
BTW - I read somewhere about pterosaur trackways containing only forefeet, interpreted as swimming beast touching the bottom only with arms.
Hi Jerzy - it occurred to me yesterday that you might be 'unhappy' with the lack of diving/swimming pterosaurs because you think it odd that this niche was going unexploited in the Mesozoic. While pterosaurs were not filling this role, note that there were diving birds during the Cretaceous (e.g., hesperornithines, Gansus and possibly loons). There were also lots more aquatic reptiles throughout the Mesozoic than there were in the Cenozic: in addition to crocodilians, there were several lineages of amphibious/aquatic sphenodontian in the Jurassic and Cretaceous, numerous swimming anguimorph lineages during the Cretaceous (aigialosaurs, dolichosaurs, mosasaurs), ichthyosaurs and sauropterygians throughout the Mesozoic (placodonts, pachypleurosaurs, nothosaurs, plesiosaurs), and then such things as hupehsuchians, thalattosaurs, choristoderes, helveticosaurs, and so on. It's conceivable that these animals slowed or constrained the evolution of aquatic habits in pterosaurs.
pterosaur trackways containing only forefeet, interpreted as swimming beast touching the bottom only with arms.
More likely undertracks, or tracks made on soil that was too hard for the hindfeet to make an impression -- the hands carried a lot more weight on a much smaller surface than the feet.
You must have been very unlucky on the Llanos. I saw 8 duck species there, five were common to abundant (Dendrocygna bicolor, viduata, autumnalis, Anas discors, Amazonetta brasiliensis) while Neochen jubata and Sarkidiornis melanotos were rather uncommon and Cairina moschata was downright rare.
However I agree that anatids are generally rather scarce in the tropics.
I looked around all my usual haunts for a phylogeny of Pelecanidae but no luck. Looks like they are one of the many groups that needs a good phylogenetic analysis. Anyone want to throw money my way? A quick search of genebank showed that 6 of the 8 extant members of the genus Pelecanus although there was no single gene that had been posted for all species. Maybe next time I'm bored I'll run a quit analysis on the better sampled genes and see what happens.
On the other hand there seems to be some interest in their feather mites, maybe that will push for a host phylogeny.
Will do, its spring break after all and what better way to spend it then running phylogenies. I'll try and get to it in the morning. As some that's addicted to PAUP and Mr.Bayes I'm not joking...
A quick search of genebank showed that 6 of the 8 extant members of the genus Pelecanus although there was no single gene that had been posted for all species. Maybe next time I'm bored I'll run a quit analysis on the better sampled genes and see what happens.
Why not run an analysis with all 6 species and all genes? Missing data don't bite.
No money on my side either, however. Grad student. :-|
David: there is more missing data then non-missing data. While missing data are fine if its a little bit here and there, or maybe a few taxa lacking a gene, this is abit more extreme that that. 38 genes or gene regions are only sequenced once, so including those would be pointless. Of the remaining 7 genes 4 of which are sampled across 3 taxa and the last 3 are sampled across 2 taxa. On the bright side only 1 species has no shared genes sequenced. Once I get the data aligned I'll try included all 7 genes with multiple taxa sequenced, but if that doesnt work I'll have to just use the 4 with the greatest taxa coverage.
Yeah I think it may work, there looks to be enough overlap to hopefully get a decently resolved tree. Working on the alignments right now. Picked an outgroup from the sister family in one analysis that had sequences from all but CO1. We'll see what happens. TNT if nothing else should be able to handle it
Ok so the phylogeny is posted on my blog (http://tacatanach.blogspot.com). The name of the post is "So what to systematists do for spring break?" Its based on 6 genes (almost 4,000bp).
that is soooo funny! i'd watch that movie.
did you catch the recently out there video of the orcas at seaworld ripping to shreds a poor pelican that landed in their tank midshow?
apparently they do it to any bird that lands in the tank. just usually the birds don't come while hundreds of ppl are watching. quite an interesting bit of behaviour as the whales kick into predatory pack mode and as a group work at dismembering the bird, and at the same time ignoring their trainers entirely!
i saw the video at http://swimatyourownrisk.com/2009/02/24/shamu-attacks-and-kills-pelican/
not sure if it has hit youtube yet.
Darren, I may guess the reason of your "no time" takes the root also in your new status of young father. My congratulations, by the way! I got the same status last... no, since February, 2008. And I may say only one thing: little children - little troubles, bigger children - bigger troubles. Accustom your daughter (BTW, I also have a daughter) to reading, my baby likes to watch pictures in encyclopedias.
So, possible, you hadn't seen this reference:
http://www.sivatherium.h12.ru/library/Dixon_2/00_en.htm
I hope you'll like it. Now I prepare Russian translation and correct text of English version. The third his book (about man) is also in my plans. This year... possible...
Just a random thought:
I'm puzzled as to why pelicans are absent from the South American interior. Wetlands like the Pantanal would appear to be prime pelican habitat, yet South America's pelicans are exclusively coastal species.
Hai-Ren:
That's a good question. But I don't know if there's any good answer, apart from referring to the vagaries of evolutionary history.
And there are other similar cases where certain otherwise widespread bird groups are missing from entire continents, for no obvious reason. Why are cranes absent from South America? Why are lapwings absent from North America? Why are swans absent from Africa?
Sometimes the birds that are absent nowadays were present in the past, though. For example, there were swans in Africa in the Miocene (Louchart et al., 2005). So perhaps there were freshwater pelicans in South America too, once upon a time?
Reference:
Louchart, A., Vignaud, P., Likius, A., Mackaye, H.T. & Brunet, M. 2005. A new swan (Aves: Anatidae) in Africa, from the latest Miocene of Chad and Libya. Journal of Vertebrate Paleontology 25, 384-392.
Big waterbirds are generally stuff of cold climates and seasonal waters. In rainforests they are outcompeted/predated by fish and crocodiles. Pantanal itself is relatively new, few 1000's years ago it was a desert.
BTW - are any pterosaurs likely to dive using wings, like eg. auks, gannets and shearwaters?
Jerzy - that generalisation (that large waterbirds are out-competed in the tropics by fishes and crocodiles) might be partly true, but it isn't wholly accurate - look at shoebills, hammerkops, aquatic-feeding storks and anhingas. In fact, could the diverse giant anhingas of the Cenozoic be something to do with the absence of pelicans from tropical South America? Several giant extinct anhingas are known from the South American tropics: see the refs below.
As for wing-propelled diving in pterosaurs: no pterosaur has any of the adaptations we'd expect for this lifestyle, and most of the pterosaurs associated with marine life have peciliarities that rule this out further (e.g., rhamphorhynchids have very long tails, pteranodontians were generally gigantic). However, plunge-diving is not ruled out for pterosaurs. Having said all that, I don't think we'd have predicted from morphology that certain petrels can dive as deeply as they do, so there might still be room for doubt.
Refs - -
Alvarenga, H. M. F. & Guilherme, E. 2003. The anhingas (Aves: Anhingidae) from the Upper Tertiary (Miocene-Pliocene) of southwestern Amazonia. Journal of Vertebrate Paleontology 23, 614-621.
Noriega, J. I. 2001. Body mass estimation and locomotion of the Miocene pelecaniform form Macranhinga. Acta Palaeontologica Polonica 46, 247-260.
- . 2002. Additional material of Macranhinga paranensis (Aves: Pelecaniformes: Anhingidae) from the Upper Miocene Ituzaingó Formation of Entre Rios Province, Argentina. In Zhou, Z. & Zhang, F. (eds). Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution. Science Press (Beijing), pp. 51-61.
- . & Alvarenga, H. M. F. 2002. Phylogeny of the Tertiary giant anhingas (Pelecaniformes: Anhingidae) from South America. In Zhou, Z. & Zhang, F. (eds). Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution. Science Press (Beijing), pp. 41-49.
Jerzy: Pelicans would probably not mind living in a desert, as long as there is a large body of water (permanent or temporary) within comfortable flying distance. Think of the Australian pelican Pelecanus conspicillatus; on those rare occasions when heavy rainfall forms lakes in the interior of Australia, pelicans fly there to fish and to breed.
What Darren said. There are plenty of fish-eating tropical freshwater birds; cormorants, in particular, are common at rivers and lakes just about everywhere in the tropics.
Besides, it might be that waterbirds living in the temperate or boreal zones actually suffer as much from fish competition as their tropical relatives. There is a great number of studies on the question whether waterbirds (mostly anatids) and fish compete for food, and most of these studies tend to answer this in the affirmative. As for the question of predation, there is a fairly rich literature on the importance of fish (mostly pike Esox) predation on waterbirds (again, mostly anatids); these studies, too, tend to suggest that fish predation on temperate/boreal waterbirds is often non-trivial.
I just returned from Venezuelan Llanos and at least species diversity of waterbirds (swimming, not wading ones) is much smaller. Three species of ducks, hehehe. And no wonder, because edge of every lake has a line of caymans sunning.
About pterosaurs - I find it improbable that the large sub-group of fish-eating animals only skimmed the water surface, without plunge-diving, swimming and diving.
Jerzy - your competition hypothesis is interesting and I wonder if there is any published data that backs it up. As mentioned above (by Dartian and myself), at least in some parts of the world, tropical waterbirds are doing fine alongside their fish and crocodilian neighbours.
As for pterosaurs: to be frank (this is not meant to sound rude!), it does not matter what you personally find improbable. The fact is that pterosaurs just do not have the sorts of wing shapes, wing loadings, body shapes etc. we see in diving and swimming birds. Recent work has indicated that pterosaurs were more diverse ecologically than conventionally thought (e.g., Witton 2008), but.. nope, still no overlap with dedicated diving and swimming birds. It might be that the involvement of the hindlimb in the wing membrane prevented pterosaurs from adapting to such lifestyles: note that there are no swimming or diving bats either (though there are of course bats that gaff or grab prey from the water surface).
Ref - -
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B 28, 143-158.
I won't be surprised if predation and competition with fish and crocodilians is significant for some species of waterbirds in some areas. Locally, it's said that predation of chicks by snakehead (Channa spp.) might prevent certain waterbirds like lesser whistling duck (Dendrocygna javanica) and little grebe (Tachybaptus ruficollus) from establishing themselves in some of Singapore's wetland areas.
Yet I'm sure that this is not the only limiting factor. After all, in many African, Asian and Australian wetlands, we get storks, herons and egrets, ibis and spoonbills, pelicans, cormorants, anhingas, grebes, ducks, cranes, rails, finfoots and waders all living in close proximity to large predatory fish and crocodilians. Perhaps ducks, grebes and rails might be more vulnerable to predators, since their chicks swim around instead of growing up in a nest, but I'm sure there are specific habitat preferences or behaviours which limit the risk of predation.
Jerzy: Llanos has only 3 species of ducks? This site lists 6 resident and 1 migratory anatid. In any case, Anatidae as a whole would appear to be more diverse and abundant in temperate regions, but there are quite a number of species present in fish and crocodilian-rich waters of the tropics.
Besides, like so many other waterbirds, pelicans nest in colonies either in trees or on the ground, so predation by fish or crocodilians on the chicks isn't likely to be a significant reason why the family is excluded from South America.
Regarding specifically the idea that fishing/swimming birds are ecologically excluded by crocodilians through predation or competition... An interesting idea, to be sure, and it might contain some truth. But it certainly can't be the whole explanation.
First, have a look at this map...
...and then compare it with this map.
The first map showed the global distribution of anhingas, and the second the global distribution of crocodilians. Judging by the map, the former donât exactly seem to be trying to avoid the latter...
(Sorry for the double post, but my post contained more than one link and I didnât want it to be caught by the spam filter.)
I saw only three Anseriformes species. I know there are more. Not many, considering that in Europe it is possible to see a dozen in one lake! It is really strange to notice that huge wetland is without geese, swans, gulls, with few terns and one species of cormorants and grebes.
What exists there is outcompeted to special niches. Neotropic cormorants live in very deep waters, whistling ducks - in very small, shallow floodlands.
I think competition may be mostly with fish, water turtles and aquatic mammals. When waterbody is permanent (does not dry out, does not freeze, is not separate from the large water systems) they can colonize it and thrive not worrying about supporting these huge flight muscles.
Distribution of eg. swans, diving ducks and mergansers suggests that.
About pterosaurs - look again! Maybe fossils can be re-interpreted to allow for swimming. Could pterosaurs paddle with half-closed wings, like alcids do?
Jerzy writes...
All I can do is repeat the answer I gave above. Several researchers have looked at pterosaur ecomorphology very recently, and in fact I'm working on it at the moment. No, pterosaurs lack the wing and body shapes associated with diving, swimming etc. See above.
Sorry if this sounds condescending, but remember that scientific hypotheses are evidence-led: we do not formulate intuitively appealing ideas and then argue that they must be correct, even when evidence indicates otherwise! Or, if we do, we should not.
Something that I've been wondering about concerning pelican morphology...
As everyone knows, 'brown' pelicans (Pelecanus occidentalis & P. thagus) feed by plunge-diving whereas 'white' pelicans do not. How is this difference expressed in their respective morphology/anatomy*? Or, in other words, if pelicans were only known as fossils, could paleontologists tell that the feeding behaviours of 'brown' and 'white' peilcans were different?
* Apart, obviously, from their plumage colouration.
An interesting point which has actually been addressed in the pelican and pterosaur literature (Richardson 1943, Bennett 2001). There are no 'special' skeletal adaptations that make the brown pelicans different from all the others, but there is one subtle difference in soft tisse morphology: the nares are closed over by horny flaps in brown pelicans. That seems to be about it!
Counter-intuitively, brown pelicans have less of their volume occupied by subcutaneous air-sacs than do white pelicans: in the latter, Richardson (1943) reported air-sacs occupying 34-38% of inflated corpses, but 25.7% in a brown pelican. Richardson even speculated, based on this data, that white pelicans evolved from plunge-diving ancestors and that they had since elaborated on the pneumaticity because it then became useful 'in other ways'.
The lack of special plunge-diving adaptations in the brown pelican skeleton led Bennett to note that plunge-diving was indeed possible for pteranodontid pterosaurs. A previous objection to this idea has been that 'pterosaurs were too light', but - given recent work indicating that pterosaur masses have been substantially under-estimated (Witton 2008) - we can look at this anew.
Refs - -
Bennett, S. C. 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part II. Size and functional morphology. Palaeontographica Abteilung A 260, 113-153.
Richardson, F. 1943. Pneumaticity of the white pelican. The Condor 45, 37-38.
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B 28, 143-158.
Thanks for the information, Darren! It leads me to a follow-up question though:
An intriguing idea... but are occidentalis and thagus the most basal pelicans?
I don't think that Richardson was necessarily saying that brown pelicans were the most primitive members of the group - rather, that plunge-diving was primitive. I doubt that this is true given that it isn't widespread in pelicans, nor is it primitive for any of the taxa considered close relatives of pelicans (shoebills, frigate birds etc.). I'm not aware of any species-level phylogenies for Pelecanidae: is anyone?
Hi Darren, for paleontologist its only intuition, but for ecologist its perfectly valid question.
Why large ecological niche is apparently left unoccupied? Why pterosaurs - as interpreted by now - didn't evolve swimming and diving ability, despite that this would be very useful for catching their primary prey, fish?
I agree with your osteological arguments, but keep an eye open for this possibility!
BTW - I read somewhere about pterosaur trackways containing only forefeet, interpreted as swimming beast touching the bottom only with arms.
Hi Jerzy - it occurred to me yesterday that you might be 'unhappy' with the lack of diving/swimming pterosaurs because you think it odd that this niche was going unexploited in the Mesozoic. While pterosaurs were not filling this role, note that there were diving birds during the Cretaceous (e.g., hesperornithines, Gansus and possibly loons). There were also lots more aquatic reptiles throughout the Mesozoic than there were in the Cenozic: in addition to crocodilians, there were several lineages of amphibious/aquatic sphenodontian in the Jurassic and Cretaceous, numerous swimming anguimorph lineages during the Cretaceous (aigialosaurs, dolichosaurs, mosasaurs), ichthyosaurs and sauropterygians throughout the Mesozoic (placodonts, pachypleurosaurs, nothosaurs, plesiosaurs), and then such things as hupehsuchians, thalattosaurs, choristoderes, helveticosaurs, and so on. It's conceivable that these animals slowed or constrained the evolution of aquatic habits in pterosaurs.
No, it's biomechanics, it's science.
More likely undertracks, or tracks made on soil that was too hard for the hindfeet to make an impression -- the hands carried a lot more weight on a much smaller surface than the feet.
Jerzy
You must have been very unlucky on the Llanos. I saw 8 duck species there, five were common to abundant (Dendrocygna bicolor, viduata, autumnalis, Anas discors, Amazonetta brasiliensis) while Neochen jubata and Sarkidiornis melanotos were rather uncommon and Cairina moschata was downright rare.
However I agree that anatids are generally rather scarce in the tropics.
I looked around all my usual haunts for a phylogeny of Pelecanidae but no luck. Looks like they are one of the many groups that needs a good phylogenetic analysis. Anyone want to throw money my way? A quick search of genebank showed that 6 of the 8 extant members of the genus Pelecanus although there was no single gene that had been posted for all species. Maybe next time I'm bored I'll run a quit analysis on the better sampled genes and see what happens.
On the other hand there seems to be some interest in their feather mites, maybe that will push for a host phylogeny.
Well, let us know if and when you get round to it. I'd love to throw money in your direction.. but, sorry, I'm running a bit short :)
Will do, its spring break after all and what better way to spend it then running phylogenies. I'll try and get to it in the morning. As some that's addicted to PAUP and Mr.Bayes I'm not joking...
Why not run an analysis with all 6 species and all genes? Missing data don't bite.
No money on my side either, however. Grad student. :-|
David: there is more missing data then non-missing data. While missing data are fine if its a little bit here and there, or maybe a few taxa lacking a gene, this is abit more extreme that that. 38 genes or gene regions are only sequenced once, so including those would be pointless. Of the remaining 7 genes 4 of which are sampled across 3 taxa and the last 3 are sampled across 2 taxa. On the bright side only 1 species has no shared genes sequenced. Once I get the data aligned I'll try included all 7 genes with multiple taxa sequenced, but if that doesnt work I'll have to just use the 4 with the greatest taxa coverage.
That could be enough, actually. But of course getting more sequences can only help.
Yeah I think it may work, there looks to be enough overlap to hopefully get a decently resolved tree. Working on the alignments right now. Picked an outgroup from the sister family in one analysis that had sequences from all but CO1. We'll see what happens. TNT if nothing else should be able to handle it
Any as always, more sequences would be nice :)
Ok so the phylogeny is posted on my blog (http://tacatanach.blogspot.com). The name of the post is "So what to systematists do for spring break?" Its based on 6 genes (almost 4,000bp).