Another extant squamate ticked off the life list :)

I was thrilled and delighted to encounter this amazing beast at a recent meeting. It's another of those creatures that you might know well from the literature, but (you assume) are unlikely to ever see in the flesh. Yet here it is...

i-154da405d05f15668e2ed937262f8b95-super-cute-squamate-2-April-2010.jpg

Your challenge: tell us all what it is. As usual, this is dead easy... so long as you know the answer. And, to those people who have already seen the photos on my Facebook wall: you are not allowed to play.

i-344124c24d73d4dcecdd457ef96f5ab9-super-cute-squamate-April-2010.jpg

It's a good time to feature neat lizards, what with today's publication of the paper on the new Philippine monitor Varanus bitatawa (Welton et al. 2010). This large (2 m long) frugivorous species is closely related to the also frugivorous Gray's monitor V. olivaceus (a third Philippine species, V. mabitang, is also frugivorous and also recently discovered: it was named in 2001). Would love to talk more about V. bitatawa, but no time. Will aim to write at length about recently recognised monitor species at some stage.

Ref - -

Welton, L. J., Siler, C. D., Bennett, D., Diesmos, A., Duya, M. R., Dugay, R., Rico, E. L. B., Van Weerd, M. & Brown, R. M. 2010. A spectacular new Philippine monitor lizard reveals a hidden biogeographic boundary and a novel flagship species for conservation. Biology Letters doi: 10.1098/rsbl.2010.0119

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Gallotia simonyi?

Well, I can't tell what species that is, and if I can't, then nobody else can tell what it is either!

/Dunning-Kruger mode off.

My first impression was that it's some kind of teiid, but Gallotia is probably a better guess.

Regarding the title of this post, by the way... When you count 'lifers', you apparently include captive individuals, right? Do you also keep a separate list of tetrapod species you've seen in the wild (in the UK and/or anywhere in the world)?

When I was some years ago at Gran Canaria, I saw countless of this huge lizards (it´s Gallotia stehlini), and I couldn´t get enough of them up the last day of the holiday. Okay, they are not really spectacular in terms of colour, but they are just huge, and especially the males have enormous heads. The large males have bodies as big as those of rats, and at some places they have learnt to wait for tourists which feed them with fruits. Especially at such places they can be comparably numerous. You should still have some photos I sent you some years ago Darren.
Gallotia stehlini is already large, but it is really amazing that not that long ago there were monster lizards at the Canary islands which reached SVL of more than a half metre.

I did not know there were frugivorous monitor lizards! All the ones I'd heard of are carnivores. That's really cool.

(No clue what the thing in the picture is, beyond "a lizard".)

By William Miller (not verified) on 08 Apr 2010 #permalink

It's a Giant Tree Skink from the Solomon Islands

By gray Stanback (not verified) on 08 Apr 2010 #permalink

Yes, it's definately a skink, but I can't get any more specific than that. It's a big skink.

Random question: Has anyone done a critical evaluation of the genus Varanus? Seems like monitor = Varanus, which seems lazy to me.

Varanus certainly seems to have a lot of highly diverse species within it. I see Zach Miller has got to this point before me, but I have to ask: is it likely that this genus will get split up at some point?

When I saw it, my first reaction was to say, "That looks like some kind of giant skink."

Since I'm strictly an amateur fanboy, I must say I was thrilled to see real biologists in the comments saying the same thing. I'll be even happier if we're right!

It is definitely not a skink, and most certainly not a Solomon Islands Tree Skink ([i]Corucia zebrata[/i]). I'm thinking along the same lines as Sordes: [i]Gallotia stehlini[/i]. Definitely a lacertid of some sort.

As for [i]Varanus[/i], there have been single locus (mitochondrial) phylogenies published, but it isn't really that large of a genus, and there isn't very much variation in morphology, if you see a [i]Varanus[/i], you know its a [i]Varanus[/i]. I doubt the genus will be split up, although it has been divided into subgenera, some of which do provide useful groupings of related and ecologically similar species (e.g. the subgenus [i]Euprepiosaurus[/i] contains the mangrove monitors ([i]V. indicus[/i] species group) and the tree monitors ([i]V. prasinus[/i] species group).

Subgenera are cop-outs. If the mangrove monitors are all more closely related to each other than the other world's monitors, then just put them in their own genus.

Andy:

is it likely that this genus will get split up at some point?

No, or at least not in the near future, according to this highly respected authority.

Regarding subgenera of Varanus; many have indeed been proposed. IIRC, Robert Mertens (1942) erected about ten (on phenetic grounds). In light of our current knowledge, some of these - e.g., Odatria - apparently correspond to real clades, while others do not (Ast, 2001).

Peteykins:

I was thrilled to see real biologists in the comments saying the same thing.

Actually, most people here are saying that it's some species of Gallotia. If that's correct, the animal is a lacertid, not a skink.

References:

Ast, J.C. 2001. Mitochondrial DNA evidence and evolution in Varanoidea (Squamata). Cladistics 17, 211-226.

Mertens, R. 1942. Die Familie der Warane (Varanidae). Dritter Teil: Taxonomie. Abhandlungen der Senckenbergischen Naturforschenden Gesellschaft 466, 235â391.

Thanks for comments, and well done to all who identified the lizard as a Gallotia. More specifically, it's a G. stehlini (well done Markus - and, yes, I do remember your excellent photos, and I'm planning to use them at some stage). Gallotia is a lacertid, and (according to some phylogenies) seems to have diverged very early on in the history of this clade: it's outside of the group that includes all other lacertids, though Psammodromus might be its sister-taxon. There's a lot to say about the gallotias, so I'll be covering them at another time. The evolution of giantism and herbivory, the loss and rediscovery of various species, etc.

No, I don't keep a life list of lizards (comment 4), I was merely using this term to make a catchy title :) I don't keep lists of any kind as goes the creatures I've seen.

As for the splitting of Varanus: to reiterate what Dartian has already said (comment 14), it seems that varanid specialists are essentially happy with the idea that all crown-monitors (and this is a clade that now includes 70 or so species) can be included within the one 'genus'. I still think this is because of 'social inertia' [= 'it's what we've always done, so it's what we'll always do'], and there is evidently enough variation and diversification within this clade to warrant its splitting into more manageable chunks (note that some divergences within Varanus seem to have occurred prior to the Miocene). Some herpetologists argue that Varanus sensu lato is morphologically conservative, and that maintaining the 'one genus' approach therefore reflects diversity well... But is this really true? Many other clades that exhibit far less genetic and/or morphological diversity have been split up into separate 'genera', and many of the clades identified within Varanus sensu lato look pretty distinct to me.

e.g. the subgenus [i]Euprepiosaurus[/i] contains the mangrove monitors ([i]V. indicus[/i] species group) and the tree monitors ([i]V. prasinus[/i] species group

So... the full names of the type species of those species groups are Varanus (Euprepiosaurus) (indicus) indicus and Varanus (Euprepiosaurus) (prasinus) prasinus?

Reminds me of what Bufo and Rana were like before they were blown to smithereens from 2006 onwards.

Some herpetologists argue that Varanus sensu lato is morphologically conservative, and that maintaining the 'one genus' approach therefore reflects diversity well... But is this really true?

"True"? It's not even measurable. There's no science in such arguments either way.

By David MarjanoviÄ (not verified) on 09 Apr 2010 #permalink

Hey, I got Gallotia stehlini (and only read the comments after figuring it out). Just wanted to point that out, not that it matters.

Anyway, back to the important stuff: Varanus. Darren, can you list a few of the genera you're thinking of in that "Many other clades that exhibit far less genetic and/or morphological diversity have been split up into separate 'genera'"? In some cases, like Aspidoscelis being split from Cnemidophorus, and and Plestiodon being split from Eumeces, this is to preserve the monophyly of genera. In other cases, such as Bufo and Rana, there are some rather odd splits that Frost et al (2006) made, but many of their splits were to preserve the monophyly of genera, and the distinctiveness of clades they felt were sufficiently divergent to recogize as distinct genera (ignoring their methodological problems in resolving the phylogeny and assuming that their phylogeny is the true phylogeny). I would argue monophyly is the most important characteristic of genera, since any groupings above the species level are at least somewhat arbitrary / subjective. And as for "is this really true?" again, I and many other biologists would argue that species is the largest real / natural grouping, and any groupings above the species level are somewhat arbitrary and subjective. So I guess you could say there is no such thing as a 'true' generic arrangement, but that being said I think it is useful to have nomenclature above the species level that identifies monophyletic clades that are, at least in somewhat, distinctive.

Darren:

I don't keep lists of any kind as goes the creatures I've seen.

Aw, man, keeping such lists is half the fun.

Eric wrote:

Darren, can you list a few of the genera you're thinking of in that "Many other clades that exhibit far less genetic and/or morphological diversity have been split up into separate 'genera'"?

I would put all members of Felidae in this camp. Felids are as diverse, or less than Varanidae, yet have been split into multiple genera and even subfamilies.

I think Darren is on the right track regarding the reasoning behind keeping all Varanids in Varanus. For whatever reason, herpetology seems to attract lumpers (as exemplified by the grotesquely swollen Anolis genus). I also agree that excessive lumping tends to downplay diversity within a group.

Eric also wrote:

I and many other biologists would argue that species is the largest real / natural grouping, and any groupings above the species level are somewhat arbitrary and subjective.

Ah, but species by what definition? Biological species concept? Phylogenetic species concept? Ecological species concept? Typological species concept?

I would argue that species definition is no less arbitrary than genus, or family. It is just that that the criteria we use (something along the lines of a distinct genotypic/phenotypic pool) seem more concrete than the more nebulous criteria of higher level classifications. In the end though, they are still arbitrary distinctions made up so it is easier for the human mind to grasp.

The way I currently view it, defining species is like modeling electrons. In reality, electrons should be modeled as fuzzy clouds of probability, but that's too hard to grasp (and hella hard to model), so we arbitrarily make them "points" in an orbit around protons and neutrons. Species seem to work in a similar way. We can see distinctiveness in populations, but between horizontal gene transfer (or chromosome transfer in some plants), and ring species, that distinctiveness gets fuzzier as the resolution increases.

Different groups seem to have different traditions on what is a genus; birds and mammals tend to have tiny genera, insects and plants (Euphorbia - 2000+ species which look nothing alike) often have huge ones.

@17 Eric: >>I would argue monophyly is the most important characteristic of genera, since any groupings above the species level are at least somewhat arbitrary / subjective.

I would agree with the latter (though I don't think this is a bad thing!) but not the former. Certainly monophyly is important, but I think *usefulness* is the most important feature, and I think in some cases paraphyletic genera are justifiable (I can't think of any specific cases off the top of my head, but I can imagine situations where I think that would be the desirable option). Fundamentally, genera need to be useful tools for remembering what an organism is ("oh, it's Empidonax, it's going to be a small, drab, oliveish-colored New World flycatcher") before anything else.

By William Miller (not verified) on 09 Apr 2010 #permalink

The example I used to point to where a paraphyletic genus 'made sense' was Australopithecus, as a phylogenetically unresolved mess of 'upright apes' basal to Homo and closer than Pan. It's not such a good example anymore since Ardipithecus and several other slices have been taken out of it, but (partly because palaeoanthropologists can't get both feet on the running board of the Phylogenetics bus) it's still in use as a 'grade' genus (e.g. Berger et al., this week). When enough fossils have been found the phylogeny will be better resolved and a stable monophyletic binominal system will be possible. Maybe next week.

Berger, L.R. et al. 2010. Australopithecus sediba: a new species of Homo-like australopith from South Africa. Science 328: 195-204.

By John Scanlon, FCD (not verified) on 09 Apr 2010 #permalink

The way I currently view it, defining species is like modeling electrons.

The way I view it, it's just word salad. Many species concepts describe something interesting that exists in nature -- but there's no reason to pretend they describe the same thing. The species concepts have nothing in common except the word "species".

Maybe there should be separate nomenclatures for different species concepts. Impractical, but no more confusing than reality itself. "Things should be made as simple as possible, but not any simpler" (Albert Einstein).

Different groups seem to have different traditions on what is a genus; birds and mammals tend to have tiny genera, insects and plants (Euphorbia - 2000+ species which look nothing alike) often have huge ones.

This is exacerbated by the fact that the ICZN allows only two ranks between genus and species (the subgenus and the "group of species"). If you want to name three nested clades (of more than one species each) inside a genus, you either can't and have to arbitrarily pick two of them, or you have to split the genus. The ICBN lacks such restrictions, and botanists talk about sections and subsections (within subgenera) all the time.

Drosophila as currently used groups at least 1,450 species in its many subgenera. It's going to be split. Get used to Sophophora melanogaster.

Fundamentally, genera need to be useful tools for remembering what an organism is ("oh, it's Empidonax, it's going to be a small, drab, oliveish-colored New World flycatcher") before anything else.

Nothing makes sense in biology except in the light of evolution (Dobzhansky).

Nothing makes sense in evolution without a good phylogeny (G. C. Gould & B. MacFadden).

You can't make sense of phylogeny if you can't talk about it, and paraphyletic taxa are actively misleading in this respect, unless maybe if their paraphyly is somehow marked in the name itself, and even then they'd prevent overlapping clades from being named.

palaeoanthropologists can't get both feet on the running board of the Phylogenetics bus

"The closer you get to humans, the worse the science gets."

By David MarjanoviÄ (not verified) on 10 Apr 2010 #permalink

I would put all members of Felidae in this camp. Felids are as diverse, or less than Varanidae, yet have been split into multiple genera and even subfamilies.

As a herpetologist, I can't really comment much on other groups such as felids. But I will say that I agree with what William said in that I don't think that genera, families, etc. of all groups are equal. That is a genus of bird isn't the same as a genus of squamate. This is probably largely due to the arbitrariness of groupings above the species level.

Ah, but species by what definition? Biological species concept? Phylogenetic species concept? Ecological species concept? Typological species concept?

The way I think of species concepts is much the same as what de Keiroz has called the 'unified species concept' and has discussed in numerous publications: criteria used in various species concepts, such as reciprocal monophyly, phenotypic differences, reproductive isolation, etc, arise more as a consequence of speciation. As lineages diverge into independently evolving metapopulation lineages, these differences arise and these criteria are met, but it is more that they are independently evolving that makes them species, not necessarily that they meet (or fail to meet) these criteria that makes them distinct species or not.
But yes, although a natural and extremely important grouping, species are extremely complex entities that are in practice far from straightforward to explain or even identify (particularly in some cases like ring species as you mention).

I think *usefulness* is the most important feature, and I think in some cases paraphyletic genera are justifiable

But 'usefulness' depends on what questions you are interested in. Usefulness from an ecological perspective isn't necessarily the same as usefulness from an evolutionary perspective. Take the Sand Skink (Plestiodon (formerly Neoseps) reynoldsii) for example. It was long considered a distinct monotypic genus due to being very morphologically and ecologically distinct (a limbless sand-swimming skink), but some recent phylogenetic work has shown it is embedded in a clade with most the rest of the North American skinks (Brandley et al. 2005, Smith 2005), and it was placed in the genus Plestiodon with the rest of these skinks to maintain the monophyly of Plestiodon (failure to due so would result in the paraphyly of Plestiodon with respect to the Sand Skink, reynoldsii). From an evolutionary perspective, this makes perfect sense and is very interesting and useful: it maintains the monophyly of the genus Plestiodon, and it is interesting to consider this one lineage of limbless sand-swimming skink within this larger clade of fully-limbed, fully-digitated skinks. But from a natural history or ecological perspective, you could argue that it is very different from all of its relatives, and is unique among North American skinks in being a limbless sand-swimmer, and thus from this perspective perhaps it is more useful to consider the Sand Skink as a distinct genus.
Consider also Atheris (formerly Adenorhinos) barbouri. This is a small, terrestrial species that eats mainly small, soft-bodied invertebrate prey such as slugs and earthworms. Recent phylogenetic work (Lenk at al. 2001) found this species to be embedded within Atheris, the African bush vipers, a group of arboreal snakes that typically prey on vertebrates such as frogs, lizards, and small mammals and birds. From an ecological perspective, it may be more useful to maintain barbouri as a distinct genus, since it is so morphologically and ecologically different from all Atheris species. But from an evolutionary perspective, it is, like the sand skink, interesting to think of this small terrestrial viper that eats slugs to have evolved from this clade of arboreal vertebrate eating vipers, and as such may be more useful to maintain the monophyly of Atheris and classify barbouri as a member of this genus.
So basically, I would argue against "usefulness" as the most important feature because what generic (or higher) groupings are most useful depend strongly on your perspective. As an evolutionary biologist, I think it is more useful to maintain monophyly of higher-level groupings, as these higher level groupings will then be informative on the evolutionary history of the lineages, but I can see ecologists or natural historians being more interested in groupings that reflect the morphology or ecology of the organisms.

I'd also agree with what David said in that

You can't make sense of phylogeny if you can't talk about it, and paraphyletic taxa are actively misleading in this respect,

Brandley MC, Schmitz A, Reeder TW. 2005. Partitioned Bayesian analyses, partition choice, and the phylogenetic relationships of Scincid lizards. Systematic Biology. 54(3): 373-390.

Lenk P, Kalyabina S, Wink W, Jogera U. 2001. Evolutionary Relationships among the True Vipers (Reptilia: Viperidae) Inferred from Mitochondrial DNA Sequences. Molecular Phylogenetics and Evolution. 19(1): 94-104.

Smith, HM. 2005. Plestiodon: a Replacement Name for Most Members of the Genus Eumeces in North America. Journal of Kansas Herpetology. Number 14.

That is a genus of bird isn't the same as a genus of squamate.

Importantly, a genus of bird isn't the same as another genus of bird either!

By David MarjanoviÄ (not verified) on 12 Apr 2010 #permalink

Some genera are more equal than others.

By Sven DiMilo (not verified) on 12 Apr 2010 #permalink

Darren:

Psammodromus might be its sister-taxon

That view is supported by Cox et al. (in press). They also suggest that the ancestors of the extant Gallotia have lived on the Canary Islands since the Miocene (with the initial colonisation taking place 17-20 MYA).

Reference:

Cox, S.C., Carranza, S. & Brown, R.P. In press. Divergence times and colonization of the Canary Islands by Gallotia lizards. Molecular Phylogenetics and Evolution, doi:10.1016/j.ympev.2010.03.020