A lot of zoos have very neat murals and other works of art. Over the weekend we visited Marwell here in Hampshire: it's our 'local' zoo and we go there a lot. I really like the 'march of the penguins' feature they have on the outside of the penguin pool. Here's Will, looking at each penguin species in turn...
While I've photographed this feature a few times before (I previously featured it here), this time round I did something new: I photographed each penguin figure individually. Here they are, squashed into a montage that destroys the sense of correct scaling present in the original.
Are these all the penguins of the world, as most visitors will assume? The small penguin at the far left of the march represents Eudyptula, but the populations of this taxon might represent two species, rather than one (E. minor, the Little blue or Fairy penguin, and E. albosignata, the White-flippered or Northern blue penguin). The Rockhopper Eudyptes chrysocome of tradition might also be more than one species: Banks et al. (2006) suggested that this species be split into the Western rockhopper E. chrysocome, Eastern rockhopper E. filholi, and Northern rockhopper E. moseleyi. These taxa (originally regarded as subspecies) are biogeographically distinct and diverged from one another during the Middle and Late Pleistocene (de Dinechin et al. 2009).
There are a few other interesting things to note. Megadyptes (the Yellow-eyed penguin) is close to Eudyptula in the 'march', presumably reflecting the fact that the two were previously thought to be close relatives. However, recent phylogenetic work indicates that Megadyptes is actually closer to Eudyptes, the crested penguins (Baker et al. 2006, Ksepka et al. 2006). The two Aptenodytes penguins are shown at the 'end' of the march because (I assume) they've usually been considered the 'most advanced' of penguins. However, recent studies have found Aptenodytes to be one of the most basal* 'genera' within crown-Spheniscidae, if not the most basal [below is the crown-penguin phylogeny recovered by Baker et al. (2006)].
* Some of you might recall John Harshman registering a brief complaint about the use of the term 'basal'. I see his point, but I can't find another way of describing the concept I'm referring to. 'Oldest diverging'?
There's never been much at Tet Zoo on penguins. But if you like them a lot be sure to check out Penguinology. I am reliably informed that another penguin-themed blog is due to make a splash soon.
Refs - -
Baker, A. J., Pereira, S. L., Haddrath, O. P. & Edge, K. A. 2006. Multiple gene evidence for expansion of extant penguins out of Antarctica due to global cooling. Proceedings of the Royal Society 273, 11-17.
Banks, J., Van Buren, A., Cherel, Y. & Whitfield, J. B. 2006. Genetic evidence for three species of rockhopper penguins, Eudyptes chrysocome. Polar Biology 30, 61-67.
de Dinechin, M., Ottvall, R., Quillfeldt, P. & Jouventin, P. 2009. Speciation chronology of rockhopper penguins inferred from molecular, geological and palaeoceanographic data. Journal of Biogeography 36, 693-702.
Ksepka, D. T., Bertelli, S. & Giannini, N. P. 2006. The phylogeny of the living and fossil Sphenisciformes (penguins). Cladistics 22, 412-441.
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But if the Aptenodytes species really are the most basal extant penguins, it is absolutely correct to visually illustrate that by placing them at the "end" of the line-up. It would be equally correct to put at the "beginning", of course. What would be wrong would be to put them anywhere in the middle (or to separate the king and the emperor penguin from each other).
What real penguins do they have at Marwell?
"They are/form the sister-group of/to all other penguins"?
A bit lengthy...
I do use "basal" for "furthest from the subclade I'm interested in at the moment". But here, you're not less interested in the other penguins than in Aptenodytes...
No, that won't do. Aptenodytes diverged at exactly the same time as its sister group.
I think the point you're trying to bring out here is that after that divergence, the Aptenodytes branch evolved in a straight line till the present (or at least that all sub-branches except one went extinct along the way), whereas the other branch from that divergency point when on to become bushy. If so then the best you can do is the phrasing that David suggested (and even that's not really right).
The extant sister-group to all other extant penguins :-)
Mike (comment 4) says...
Sure: if Aptenodytes really was first to diverge, then there's a divergence between Aptenodytes and 'all other crown-penguins'. But I was specifically talking about 'genera'. Here is the section of the article...
Yes, there's a penguin lineage which is equally as old as Aptenodytes, but there isn't another 'genus' that's equally as old (as all other 'genera' are part of that other lineage). Maybe the solution is to talk about lineages and not 'genera', and to avoid wordings like mine in the article. So, one might say that Aptenodytes represents one of the two oldest lineages within crown-penguins.
I've heard that penguins are the best birds (though I'm personally partial to herons and woodpeckers).
The "basal" problem is all caught up in concepts of clade rank. Aptenodytes might be the basal genus, but what's a genus? We divide Aptenodytes' sister group into multiple genera probably because there are more species than anyone wants to fit into a single genus. If you lumped all those species -- and why couldn't you? -- which genus would then be basal? "Basal" just means "depauperate compared to its sister group". There's also an implication -- and this is I think the pernicious bit -- that the "basal" group is somehow primitive. I think even the current discussion, among enlightened folk, has tinges of that implication. I do think it's worth avoiding the word "basal" because of its several false implications.
So what do we say instead? Well, what do we really mean? When you say Aptenodytes is basal, you do indeed mean, as David says, that it's the sister group of other penguins (which are, by implication, a more diverse group). So why not just say that? Or if you really like the word "basal", you could talk about the basal divergence rather than the basal clade, that divergence involving two groups of equal prospective merit or advancement, whatever that means.
I understand your retort to Harshman, but you aren't just using the word here to be terse, you're using it to refute claims that Aptenodytes is advanced; and I think _that_ is the heart of his complaint.
By the way, every single penguin species represents one of the two oldest lineages within crown penguins. Aptenodytes just happens to be on the lineage that has the least net branching (speciations minus extinctions). And that's really all you can say.
I'm going to snatch this opportunity to plug my blog, with a repost of my 2008 series of illustrations and descriptions of all of the extant sphenisciforms, including Eudyptes moseleyi and the white-flippered penguin.
http://subhumanfreak.blogspot.com/2010/03/penguins-everywhere.html
Is the concept we're trying to name the most evolutionary distinct lineage, chronologically? In this case, we do not care how the lineage became depauperate per se. (Whether it was because of extinction or the branch is just 'less vigorously evolving'). Just that it is.
Aren't we just saying "Wow Aptenodytes closest living cousins branched off in the Oligocene?! Neat!"
Don't we have a word for "diverged least in skeletal characters from the last common ancestor of all penguins"? 'Cause that's what we're talking about, right? There could be every degree of branching all over the tree, but only one extant gets the pewter for sticking most closely to tradition, eschewing innovation, for toughing it out with fewer namby-pamby "adaptations", for keeping more options open.
Nice-looking mural!
Sure: "primitive", more or less. However, we can't say from the tree whether any species is the most primitive, or whether that even means anything. (It's hardly necessary that any of these species is the most primitive -- some could be highly derived in pelvic characters but primitive in beak characters, or vice versa, etc.) "Basal" does seem to imply "primitive", but that's a spurious implication.
Hmm, I don't see anything wrong with saying "Aptenodytes is a basal clade among living penguins" or "is basal to all other living penguins"; used relatively like this, it's a topological term rather than an altitudinal one (Never say higher or lower - and don't presume they are implied when unsaid!). Of course if you were talking about a Paleocene fossil, 'basal' could be also legitimately be infused with connotations of morphological conservatism, primitiveness and potential ancestry. But I don't think it would necessarily be derogatory then, either.
When you say "Aptenodytes is a basal clade among living penguins", what do you mean by that? I'm not entirely sure you know. Unless you mean that it's the sister group of all other extant penguins, in which case why is Aptenodytes the basal clade, rather than all other extant penguins being the basal clade?
The distinction here may be that Aptenodytes represents the only living members of the lineage that diverged from all other living penguins.
There is no really easy way to say it, without invoking issues with "most conservative" and I find that they are unlikely to be representative of the initial stock, based on where spheniscids and allies diverge relative to other "procellariiform"-like birds. They may even be the most dynamically derived of all penguins, but are still the earliest diverging lineage from other living penguins.
If I were to invoke phylogenetic terminology here, and I know some readers object to this, I would say that Aptenodytes would then be the most stemward lineage of extant spheniscids relative to all non spheniscids.
Darren:
Historical footnote: Aptenodytes hasn't always been considered the most "advanced" of the penguins. One of the stated scientific aims of Robert Scott's Terra Nova Expedition to the Antarctic (1910-1913) was to secure emperor penguin embryos for study. The reason for this was that this species was believed by the expedition's chief zoologist, Edward A. Wilson, to be not only the most "primitive" penguin but possibly also the most primitive of all living birds. Wilson got the embryos he wanted in 1911, but their examination eventually failed to support his hypothesis about the primitiveness of the emperor penguin. (Wilson did not live to learn this; he perished in 1912 during Scott's ill-fated return journey from the South Pole.)
Evolution does not always go from less to more specialized. Today's alligators are secondary generalists, descended from a fairly long line of mollusk- and/or turtle-eaters; and all limbed vertebrates come from meter-long second-tier predators comparable to the modern arapaima.
Good idea.
The last few times I've gone back to Australia, I've noticed we no longer call it the Fairy Penguin, in the interests of political correctness. Now it's almost always the blue, or little blue, every time I've seen info on it.
Perhaps a better approach is to ask what "advanced" means here. If it means anything like "better" or "more changed from the LCA", then clearly it's not incompatible with being basal in a topological sense. Darren seem to be using it to mean something like "deeply nested among living forms", which has no obvious connection to everyday ideas about being advanced.
Darren: this might of interest -- an extremely rare mutant all-black king penguin:
http://news.nationalgeographic.com/news/2010/03/100316-antarctica-black…
"The most stemward lineage" just means "basal", and has the same problems as "basal". Why should the Aptenodytes lineage be considered more basal than any other lineage?
For that matter, what does "lineage" mean here? The word is ambiguous in biology. It most often means a series of ancestor-descendant populations. On a tree, that would mean some path of connected branches from some node to some descendant node. In that sense, there is actually no Aptenodytes lineage, there being two terminal nodes of that name.
The only thing that could possibly be termed uniquely basal (or most stemward) is the genus; it's the most basal genus. And talking about genera as if they mean something has its own problems. For one thing, that assumes a stem-based definition of all genera, so that Aptenodytes includes its own stem group, while no other genus includes the stem group of any other genus. Please note that no stem-Aptenodytes necessarily has any of the characters that diagnose the crown genus.
Talking about basal clades or most stemward clades communicates only one's prejudices about the proper ranks of clades, which we should all know are arbitrary.
And, as has been pointed out, even Darren has the evil meme basal = primitive, when he said "The two Aptenodytes penguins are shown at the 'end' of the march because (I assume) they've usually been considered the 'most advanced' of penguins. However, recent studies have found Aptenodytes to be one of the most basal 'genera' within crown-Spheniscidae, if not the most basal." It's hard to make sense of the "however" in any other way than to suppose that "basal" precludes "advanced".
And there's my case: "basal" is a snare and a delusion. (So is "stemward".) The only proper use of the term is in referring to divergences, as in "the basal divergence in penguins separates Aptenodytes from all other genera." Notice that no clade is basal, and no clad diverged first. A divergence involves two groups separating from each other.
End of rant. For now.
Yeah, I agree: I didn't mean to imply that Aptenodytes is 'primitive' when saying that it was basal (rather, I meant that it wasn't necessarily a recently evolved, cutting-edge novelty, as is typically assumed for 'advanced' or 'derived' taxa), but I see that this is indeed what most readers would think.
Using the 'right' language when discussing phylogenetics and evolution is a bit of a minefield... no matter what you say, someone always accuses you of typological thinking, of unjustified assumptions etc. Sigh... :)
Not quite the same thing. In general usage, 'little blue penguin' is the general common name for the species Eudyptula minor found in Australia and New Zealand, while 'fairy penguin' refers specifically to the Australian subspecies E. m. novaehollandiae.