What are ant taxonomists buzzing about this week?*
Well. A hot new paper by John LaPolla, Seán Brady, and Steve Shattuck in Systematic Entomology has killed Paratrechina as we know it. 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. Look:
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:
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.