What are ant taxonomists buzzing about this week?*
Well. A hot new paper by John LaPolla, SeÃ¡n Brady, and Steve Shattuck in Systematic Entomology has killed Paratrechina as we know it.Â
Nearly all those adorable, hairy little formicines we knew as Paratrechina- like the phantom sand ant and the rasberry crazy ant- have been pulled out and placed in a resurrected genus Nylanderia. All that remains of Paratrechina is but a single species, the fabled Black Crazy Ant Paratrechina longicornis. Which, incidentally, is the species in this blog's header photo.
Here's what happened. LaPolla et al sequenced 5 genes from 50 ants in Prenolepis, Paratrechina, Euprenolepis, and Pseudolasius. Turns out that when they ran the phylogenetic analyses, Paratrechina longicornis- the name-bearing species for the genus- just wasn't closely related to any of the other nominal Paratrechina.Â Look:
Simplified cladogram from LaPolla et al 2010, based on DNA sequence data from 5 loci and 50 specimens. Red indicates lineages included in the old Paratrechina.
If you follow the red, you'll see that Paratrechina longicornis is in fact closer to the genera Pseudolasius and Euprenolepis. Most of the other Paratrechina, those that had been placed at various times in the subgenera Paraparatrechina and Nylanderia, are independent lineages. Taxonomists had long recognized that the black crazy ant was structurally different, but the more precise geneaology was unknown until now.
With the tree in hand, LaPolla et al set about crafting a new taxonomy based on evolutionary relationships. That meant reviving Nylanderia and the unfortunately-named Paraparatrechina as full genera. As the authors made a thorough job of describing morphological traits that diagnose each lineage, this paper is one of the finest ant examples yet of a productive interplay between molecular phylogenetics and morphological taxonomy.
One unsolved problem is the matter of Prenolepis. A Caribbean species, P. albimaculata, does not group with the others. I'm not sure why the authors let this example of paraphyly stand, but presumably that lineage could be renamed something highly aggravating like Pseudoparaparatrechina, in keeping with the rest of the clade.
One last thing. I'd like to reproduce this lovely figure from the paper, a depiction of nomenclatural history:
Fig. 1 (from LaPolla et al 2010). Taxonomic changes at the generic level. Circles indicate establishment of genus; widely separated lines indicate status as a full genus, closely spaced lines indicate status as a subgenus, and joined lines indicate synonymy; squares indicate status proposed in this study.
It reminds me of this.
*Finally, someone is not afraid to ask the questions on everyone's mind.
Source: LaPolla, J.S., Brady, S.G., Shattuck, S.O. 2010. Phylogeny and taxonomy of the Prenolepis genus-group of ants (Hymenoptera: Formicidae). Systematic Entomology 35: 118-131.
It seems we were thinking along the same lines re: the nomenclature question. With Prenolepis now rendered paraphyletic, I have urged the authors not to fall prey to the temptation to call the new genus "Paraparaparatrechina"!
By the way, lovely to see all your Nylanderia images bunched together (as an artifact of relabeling?) at http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Paratrec…
Still wondering "What the heck?" about the yellow one in the acorn ... Maybe its molecules can tell us something
I'm really confused about why systematists would /ever/ allow a paraphyletic grouping to stand publication.
You should check out Cavalier-Smith's papers.
On the other hand, perhaps you may actually value your mental health/sanity. ^^
He's the master of resurrecting dead taxa as new paraphyletic groupings. It ranges from mildly annoying to absolutely infuriating sometimes. And since I'm just 'working on' (attempting to read) one of his papers at the moment:
"I did not say that they 'might not be monophyletic'. [...] I said they might be paraphyletic, which in the classical and proper nomenclature that I use is a form of monophyly." (Cavalier-Smith 2006 Biol Direct, response to reviewer#3 comment about Chlorobacteria)
Can anyone help me comprehend that statement? I thought monophyly is generally synonymous with holophyly? Otherwise, since the line between paraphyly and polyphyly can become somewhat blurred, especially when the traits of the common ancestor are determined strictly by phylogeny rather than other data, wouldn't this make 'monophyly' a rather useless term...?
On the other hand, paraphyletic groupings could be convenient in informal situations. It's easier to call something a 'protist' rather than 'a eukaryote that is not a fungus, plant or animal' or listing 'chromalveolates, rhizaria, excavates, amoebozoans, ichthyosporeans, choanoflagellates' etc. But that probably doesn't justify using 'protista' as a taxon, IMO.
Meh, that's why I'm not a taxonomist! =P
As an advocate for maximum ridiculousness in taxonomy, I for one am in favor of Paraparaparatechina! Maybe I can prevail upon Steve to this end.
I love that chronotaxonogram too-- were there originally author names associated with the date labels?
It's great when you find papers that use morphological and molecular means to support an evolutionary hypotheses. Always gives interesting answers.
The clade which Prenolepis albimaculata falls in to hasn't got huge support to support it's position there. Bayesian is low and no MP/ML values. I don't know how much you would want to read into the paraphyly, based on that?
Perhaps Paraparatrechnia and Prenolepis need further morphological work to ascertain monophyly? Always easier said than done!
Hi from Australia, btw!
First off, thank you Alex for the very kind words regarding our paper. As for Prenolepis, the question as to whether or not it is monophyletic or paraphyletic is still unclear. In the current paper we left it as is because the support for placing it with Paraparatrechina was weak (the weakest branch on the whole tree) and it is still possible that Prenolepis will be recovered monophyletic. We didn't want to create yet another genus unless absolutely necessary and only if we had strong phylogenetic support for so doing. The good news is we are working on this very problem right now. We have a nice data set of Prenolepis from around the world and should have an answer as for what is going on here very soon. So James, Paraparaparatrechina still has a chance!
Although Alex highlights the circuitry and disturbing Star Wars parallels (disturbing to me, at least) of our Fig. 1, I would like to point out that our Fig. 2 comprises four fantastic photographs generously provided by Alex. Thanks, and perhaps we'll be hitting you up soon for some more "Paraparaparatrechina" shots....