Taxonomy and Cladistics (split from Whipsnade news thread)

[Javan Rhino]

These scientific names change far too much

The idea of them of course is to avoid confusion when discussing a species where there are several common names and language barriers, but everybody uses different synonyms of scientific names anyway and nobody can agree on the taxonomy, so it sort of defeats the point .

I had no idea that Broghammerus reticulatus was a reticulated python. A very quick search (phone data limits browsing), gives me the impression it is a monotypic genus, so the genus itself is surely new(ish)? Considering there are more than a few 'reticulated' species, it doesn't seem particularly obvious that this is then a reticulated python the first time you hear the scientific name, potentially causing confusion when somebody is under the impression the species is Python reticulatus. Still, it doesn't look like we need to remember Broghammerus anyway, as the species is also known as Malayopython, which looks to be the most up-to-date?

Apologies for the rant, and we should really keep on the topic of whipsnade, and you'd think I'd have something better to do on Christmas Eve, but the best present would be to see an animal placed in a genus/(sub)-family and stay there

 

[Maguari]

These scientific names change far too much

The idea of them of course is to avoid confusion when discussing a species where there are several common names and language barriers, but everybody uses different synonyms of scientific names anyway and nobody can agree on the taxonomy, so it sort of defeats the point .

I had no idea that Broghammerus reticulatus was a reticulated python. A very quick search (phone data limits browsing), gives me the impression it is a monotypic genus, so the genus itself is surely new(ish)? Considering there are more than a few 'reticulated' species, it doesn't seem particularly obvious that this is then a reticulated python, the first time you here the scientific name, potentially causing confusion when somebody is under the impression the species is Python reticulatus. Still, it doesn't look like we need to remember Broghammerus anyway, as the species is also known as Malayopython, which looks to be the most up-to-date?

But even one thing that changes from time-to-time is easier than hundreds of different common names in different languages.

In this case, the name changed from Python reticulatus because it became clear that reticulatus (and timoriensis) weren't part of the same clade as the other Python species - see the phylogeny here, for example: http://img268.imageshack.us/img268/5441/phylogenyofthepythons.png

Easiest way to think of a clade is a branch you could snip off (in one snip) without taking anything else, or leaving something you think ought to be part of your clade. As you can't 'snip' all the traditional Python species off the tree without taking non-Python species with them, the genus was paraphyletic and so the names were not reflecting the current understanding of the evolutionary history. Move reticulatus and timoriensis to their own genus, and both your new genus and the remainder of Python are now good clades - and as well as identifying your species, the names now tell the evolutionary history and allegiances more accurately as well.


And the fact that it changes with understanding is what makes science a) science and b) exciting.



For the record, Malayopython differ from Python physically as follows: (source: Malayopython reticulatus | The Reptile Database )

A genus of pythonine snakes, of large to gigantic size (adult total length reportedly to 10 m). Differentiated from Python (s.s.) by having the supralabial thermoreceptive pits less well defined than the infralabial pits (converse arrangement in Python); by infralabial pits set in a longitudinal groove defined ventrally by a longitudinal fold; colour pattern of the suborbital supralabial region similar to the rest of the supralabials, compared with Python, in which there is a dark suborbital patch; elongate medial anterior process of the ectopterygoid, which extends much further anteriorly than the lateral anterior process, compared with subequal processes in Python (excluding P. curtus); and by hemipenial morphology (McDowell et al., 1975); not known for timoriensis).

 

[Javan Rhino]

But even one thing that changes from time-to-time is easier than hundreds of different common names in different languages.

In this case, the name changed from Python reticulatus because it became clear that reticulatus (and timoriensis) weren't part of the same clade as the other Python species - see the phylogeny here, for example: http://img268.imageshack.us/img268/5441/phylogenyofthepythons.png

Easiest way to think of a clade is a branch you could snip off (in one snip) without taking anything else, or leaving something you think ought to be part of your clade. As you can't 'snip' all the traditional Python species off the tree without taking non-Python species with them, the genus was paraphyletic and so the names were not reflecting the current understanding of the evolutionary history. Move reticulatus and timoriensis to their own genus, and both your new genus and the remainder of Python are now good clades - and as well as identifying your species, the names now tell the evolutionary history and allegiances more accurately as well.


And the fact that it changes with understanding is what makes science a) science and b) exciting.



For the record, Malayopython differ from Python physically as follows: (source: Malayopython reticulatus | The Reptile Database )

So sort of like saying you can't keep snow leopard in Uncia because you'd need to take tiger with it? Ie, snow leopard and tiger form 1 Clade, and lion, leopard and jaguar form another? Or is that just a genus thing? Can 2 species from the same Clade be in different genus'?

Clades are a concept I've never really picked up on, but it seems to me it is a stage of splitting/grouping somewhere between subfamily and genus, similar to tribe (again, another one I don't get). I've always used the following breakdown:

Class > order > family > subfamily > genus > species > subspecies

(Also, agree that the odd change here and there is still less confusing than common names can be)

 

[TeaLovingDave]

Can 2 species from the same Clade be in different genus'?

Clades are a concept I've never really picked up on, but it seems to me it is a stage of splitting/grouping somewhere between subfamily and genus, similar to tribe (again, another one I don't get). I've always used the following breakdown:

Class > order > family > subfamily > genus > species > subspecies

Certainly two species in different genera can be in a single clade, as long as *all* species in said genera are in said clade - clades do not denote a particular taxonomic rank; rather they denote a monophyletic group. As such, any of the ranks you list above can be termed as clades as long as they are monophyletic.

For instance, the traditional class "Reptilia" is not a clade, as it is polyphyletic due to excluding birds. However the modern "Sauropsida" is a monophyletic clade, excluding as it does the synapsid line and hence mammals, and including as it does all birds.

To give an example fitting your question, Pan paniscus and Homo sapiens are members of a single clade - the subfamily Homininae, which encompasses Pan, Gorilla, Homo and certain extinct genera, but excludes Pongo.

 

[Maguari]

Clades are a concept I've never really picked up on, but it seems to me it is a stage of splitting/grouping somewhere between subfamily and genus, similar to tribe (again, another one I don't get). I've always used the following breakdown:

Class > order > family > subfamily > genus > species > subspecies

(Also, agree that the odd change here and there is still less confusing than common names can be)

Clades are not part of that hierarchy - it's simply a term for a cluster of taxa or individuals that represent a distinct lineage, and a way of understanding if a name we are using represents the evolutionary history.

Clades are easiest to think of in terms of trees - any branch you could cut off in one go without taking anything else is a clade - there's a useful diagram here: http://uedata.berkeley.edu//media/2/23342_evo_resources_resource_image_260_original.gif

Generally speaking, all of those taxonomic levels ought to represent good clades if they've been applied well. 'Classes' Aves, Mammalia and Amphibia are all solid clades (although it's questionable if Aves ought to be a Class) - Reptilia is not, because the birds (as TLD points out) would sit within the group - you couldn't cut reptiles out in one go and be left with just what we call reptiles as you'd have to take the birds with them.

We are well off-topic now - maybe TLD should use his mod powers to split this off somewhere more suitable!

 

[TeaLovingDave]

We are well off-topic now - maybe TLD should use his mod powers to split this off somewhere more suitable!

As, indeed, I have now done.

 

[wally war eagle]

taxonomists perpetuate their existence and profession through cladistics.

 

[Dassie rat]

Many years ago, New Guinea echidnas were divided into 3 species - the Bruijn's echidna (Zaglossus bruijni), Barton's echidna (Z. bartoni) and Bubu echidna (Z. bubuensis). Supposedly, London Zoo had the Bruijn's species, which had 3-4 toes on each forefoot, while the other two species had 5. I reckoned that the species had been misidentified and I spent quite a long time waiting for an echidna to lift up its front paw, so I could count the toes. I counted 5, which indicated that it was probably a Barton's echidna, as the Bubu species was known from only one or so specimens and is now no longer recognised as a species. I am glad that I have been vindicated, as the species kept at London Zoo has been classified as Z. bartoni. Some time later, I found that I was not the only person t count the toes on the echidna's front foot, but I'm glad I did.

 

[bongorob]

Broghammerus is now invalid, a genus proposed by Hoser and no longer accepted.

 

[Maguari]

taxonomists perpetuate their existence and profession through cladistics.

And pharmacologists 'perpetuate' themselves by trialling new drugs. (And traffic wardens 'perpetuate' themselves by looking for illegally parked cars!)

I either don't get your point, or you have a strange prejudice against taxonomists - members of a scientific field looking for new ways to examine their topic should not really be contentious! You wouldn't expect pharmacologists to just turn up to work one day and decide finding new drugs was just too confusing for everyone so they should just leave it there, would you?