[Taxacom] Does the species name have to change when it moves genus?

[brpatric at dwu.edu]

Hello Rod et al.,
 
I leave my computer for a few hours and 30+ emails about this.  Wow!  :-)
 
As I understand Rod's original query, you seem to be asking why we ever change a species name?  In other words, why does the entire binomial change.  Why the genus may change has been a main topic, and I will get to that in a few sentences.  However, it seems that you are also asking why the specific epithet changes when a species might be moved to a new genus, correct?  My understanding is that it does NOT change unless the new combination results in homonymy within the genus.  As I understand it, the specific epithet of the moved species is indeed subject to change to avoid homonymy.  
 
I don't think that name precedent counts for this (there are experts here who can confirm/correct this), so even if the moved species was described 100 years (or 100 days) before the genus+specific epithet combination already existing within the genus, the "older" species does not get precedence.  Okay-- please let me know if this is incorrect!  I have not looked in the handbook at this specifically...
 
Now, why does the genus name change?  Remember that the nomenclature is a hypothesis of evolutionary relationships.  Thus, species within a genus are (theoretically) sister species and are more closely related (evolutionarily speaking) to each other than to species in a different genus.  If a species is placed in one genus and is later hypothesized to be in a different genus, then it should indeed be moved and the name should reflect this change.  Why?  Because were this name change not made, the already (sometimes) murky evolutionary relationships would become impossible to decode!  The nomenclature provides a scaffolding upon which evolutionary hypotheses are built.  Thus, not changing names, particularly for species that have undergone several name changes, would be FAR worse than trying to keep track of synonyms.
 
Why would this be worse?  I'll use spiders as an example (that's my focal group, so I'll stick with what I know).  The genus Lycosa (Araneae: Lycosidae) does not occur in North America.  It was determined that the American species previously assigned to Lycosa were a different, new genus (Hogna, later broken into Hogna and Rabidosa).  This more accurately reflected the hypothesized evolutionary relationships between all of the species of Lycosa, Hogna, and Rabidosa.  
 
However, some species didn't just get moved to Hogna.  Rather, some were bounced all over and landed in different genera after going through at least these two.  To make a long story short, to not have changed names would have been complete nonsense to a more modern arachnologist who tries to study Lycosa.  Imagine the trouble they would have trying to get only Lycosa and ending up trying to track down American species because the name never changes.  It wouldn't make any sense!  The names MUST change to reflect the evolutionary relationships (at least our current hypothesis of those relationships).
 
If this didn't happen, then nomenclature would be chaos (far more than it seems to currently be in chaos).  Sure, I suppose, it would be fine for the end user only, but even then think of writing a key to a genus when the members are (by name) in several genera because the names were never changed!  But this isn't about convenience for the end user-- this is about evolutionary hypotheses!  A taxonomist systematically establishes hypotheses of evolutionary relatedness, and the nomenclature should reflect this.  Even Linnaeus understood this and tried to group species within genera based on the commonality of characters.  As evolutionary theory advanced, so did taxonomy and it's use of nomenclature to better reflect evolutionary relatedness.
 
I guess, to distill all of this, I would say that nomenclature is a reflection of our hypotheses of evolutionary relatedness.  That is the crux of how species are named, and how they are placed in genera, assigned raised to (or lowered from) species rank, how genera are assigned to families, etc...
 
Hope this helps!
 
Best regards, Brian
 
-----------------------------------------------------------------
L. Brian Patrick, Ph.D.
Assistant Professor of Biology and Chair
Department of Biological Sciences
Dakota Wesleyan University
1200 W. University Ave
Mitchell, SD  57301

________________________________

From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Roderic Page
Sent: Mon 6/18/12 1:18 PM
To: taxacom
Subject: [Taxacom] Does the species name have to change when it moves genus?



OK, I know this is what we do, but my question is "why do we do this?"

As names change over time it becomes a major challenge to find everything published about a taxon. Some groups, such as frogs, are especially prone to name changes as their classification is unstable. Frogs have a pretty good online database detailing name changes, but most animal groups lack this, leaving people like me floundering around trying to make sense of multiple names why may or may not be for the same thing.

It seems to me that names should be unique and stable. We don't change the name of a species called "africanus" if we discover that the specimen locality was actually from Australia, nor do we change the name "maximus" if we subsequently discover a bigger species. But we do if we move it to a new genus. Why?

Presumably it's because we like the idea of being able to interpret the name - two members of the same genus are presumably more closely related to each other than to a species in a different genus. But demonstrably that is often untrue (otherwise we wouldn't have all the name changes due to moving species to different genera), and we've learnt not to interpret the name literally when inferring any biological attributes, so why the desire to have the name match some current notion of classification? Why not simply accept that we can't infer relationships from the name?

It seems to be that if we simply stopped trying to make names reflect classification, at a stroke we'd remove perhaps the primary cause of nomenclatural instability. For example, the recent case of Drosophila melanogaster would be a non-issue. It's "Drosophila melanogaster" regardles sof whether it's nested in the part of the fly tree that includes Sophophora. The relationships of the taxon would have no bearing on its name.

Discuss.

---------------------------------------------------------
Roderic Page
Professor of Taxonomy
Institute of Biodiversity, Animal Health and Comparative Medicine
College of Medical, Veterinary and Life Sciences
Graham Kerr Building
University of Glasgow
Glasgow G12 8QQ, UK

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