Did Pheidole supermajors come before majors?

With all the recent attention devoted to Pheidole‘s apparently latent ability to produce supermajor workers at the drop of a hormone, now is an opportune time to mention Pheidole fimbriata.

Pheidole fimbriata major. Or is it supermajor? (Image: April Nobile/antweb.org)

Pheidole fimbriata is, according to Corrie Moreau’s research, the single sister species to the remaining 1000+ in the genus. That is, the first thing to happen when Pheidole first head-butted itself into the world some 60 million years ago was that the fimbriata lineage split from the others. Oddly, while the main lineage branched into a diversity insane enough to give taxonomists headaches, the fimbriata lineage contains but a single giant and rather strange Neotropical species*.

This lumbering ant is important. Pheidole fimbriata provides an independent window backwards through time in which to infer how supermajors emerged. Rajakumar et al did not include P. fimbriata in their study, as the logistics of South American research can be difficult, but surely this species is now worth a look.

On the surface, P. fimbriata is a typical Pheidole in that it has, like most of its congeners, just two size classes of worker. It is dimorphic, not trimorphic, and no one thought to include this ant among the supermajor-producing species.

But just look at it. The relative head size is massive compared to most Pheidole. It’s much more like the supermajor of Pheidole rhea than a typical major.

If P. fimbriata turns out with further developmental work to really be a supermajor, I can see a pair of interesting possibilities. First, perhaps the original Pheidole caste structure was dimorphic supermajor/minor. Under this scenario, the major caste as we know it may actually be the more recent innovation. Second, perhaps the Ur-Pheidole was like P. rhea, trimophic, but the fimbriata lineage somehow lost the major caste, leaving it with just supermajors and minors.

This is all just speculation, of course. But someone really ought to start looking at the biology of P. fimbriata. It’s an amazing ant.

I'm almost embarrassed to post this photo. It's from before I started learning about photography. Still, it's one of the few live photographs of P. fimbriata in the field. (San Lorenzo, Paraguay, 2002).

*Incidentally, P. fimbriata was one of the more common Pheidole where I was living in Paraguay. They appeared most frequently at night, running in dense columns through my lawn not unlike army ants.

12 thoughts on “Did Pheidole supermajors come before majors?”

  1. The photo looks like one of mine. Truly embarassing. 🙂

    So what is it with ants evolving (super-)majors then losing them in some lineages? Solenopsis, Carebara, Camponotus, Pheidole, possibly others . . .

  2. Pingback: Juvenil-Hormon bei Pheidole - Ameisenforum.de

  3. I <3 fimbriata! In Ecuador their ecology seemed quite unique as well – they were the only Pheidole species to forage primarily at night and the only one I observed to cover baits with a layer of dirt, then plant majors at the entrances to their tiny dirt castles as the minors slowly removed the food. This one is definitely unique!

  4. From my (limited) understanding, it seems that the terms, major and supermajor, are quite loosely defined. I have not yet come across a solid piece of writing that fully distinguishes the two.

  5. Hey Alex!

    I’m an undergrad working toward antstuff over at the University of Georgia. I don’t know whether or how you’d check comments on old articles, but I’ve been thinking about this since you posted it. Has any further information come to light?

    1. Wow, you don’t happen to be one of this year’s Goldwater Scholars? Awesome job! As a freshman who has similar interests it’s nice to know there are people out there who also want to do similar things with their lives. Anyway, sorry for creeping. XD

Leave a Reply