Myrmecos

A suspicious similarity

Posted by Alex Wild on April 28, 2010
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Yesterday, Antweb posted its first images of Anomalomyrma workers, and I’ve been staring at them ever since.

This is a strange ant indeed, a member of the ancient subfamily Leptanillinae that is potentially a sister lineage to the remaining extant ants. It’s ostensibly a subterranean predator in the forests of tropical Asia, but beyond that little is known. The number of times Anomalomyrma has been collected can probably be counted on my fingers.

Here’s a pic:

i-28c2fa8dfb295077387eb0790413b821-anomalomyrma.jpg

Call me crazy, but the shape of this thing puts me in mind of another ant oddity: Martialis heureka:

i-dd89c5861ea908dad8fbbf8cec89cde7-martialis1.jpg

Martialis was discovered in the Amazonian rainforest a couple years ago to much fanfare, as preliminary genetic work placed it as the sister to remaining ants. Consider the following similarities to Anomalomyrma, though:

  1. The configuration of muscular forelegs and wimpy mid- and hind-legs. While ant fore femora are often a bit more developed than their serial homologs, the extent of the difference is more severe in both Martialis and Anomalomyrma than in other ants.
  2. The broad attachment of abdominal segment 3 (the post-petiole) to abdominal segment 4 (the “gaster”).
  3. The relatively long mandibles. More developed in Martialis than Anomalomyrma, but still longer than in most ants.

Add in that both ants are eyeless in the worker caste and have long, predatory stingers and that’s… well, I don’t know what that is. But it’s intriguing. Either the two ants are more closely related than we’d thought (Anomalomyrma DNA sequence has not yet been published, although other Leptanillines show no obvious genetic ties to Martialis), or they’ve developed a remarkable convergence.

Because of similarities in body proportion and structure, you can bet that the species share a number of biomechanical properties. The way they hold captured prey and use the sting, in particular, must be nearly identical. These ants may well be playing the same game, ecologically, mirrored across continents in the Amazon and in southeast Asia.

Unfortunately, dead specimens are all we have to go on. The rarity of both ants may doom us to decades of ignorance before someone finds live colonies for study. Assuming the forests can hold on that long, of course.

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Comments

  1. #1 TEO
    April 28, 2010

    I bet it’s just convergence. Is the Martialis specimen lacking most of the antennae? If so, what’s the leght compared to Anomalomyrma?

  2. #2 Joshua King
    April 28, 2010

    Pfft. C’mon Alex. Ecology, biology, morphology, natural history? All of those things are entirely uninteresting, unfundable, and irrelevant to what is scientifically important. It’s only their DNA sequences and phylogenetics that matter. Oh, and climate change.

  3. #3 Roberto Keller
    April 28, 2010

    If you want my honest opinion… screw it, here it goes whether you want it or not: both taxa are just very derived Amblyoponines. How are we going to deal with the large sequence divergence between ants and non-ants and among those early formicine splits? I have no clue.

  4. #4 Alex Wild
    April 28, 2010

    TEO- Yes, Martialis is missing some antennal segments on the near side of the specimen. The overall lengths look similar between the two species, but the relative lengths of the scape (the long 1st segment) and the funniculus are different.

    Josh- I wouldn’t be quite so harsh. In the absence of any chance of direct ecological or behavioral observations, phylogenetics at least allows the placement of mystery species in a predictive framework. That shouldn’t be the be-all and end-all of it, but when all you’ve got is dead ants on pins you do what you can.

    Roberto- count me among those who won’t be surprised to see your amblyoponine hypothesis borne out once more data are forthcoming. From what I understand, the AToL group hasn’t ruled that scenario out, either.

  5. #5 AnthonyK
    April 28, 2010

    Hi Alex,
    Came to your site off of (as they say) Pharyngula – I think Mymecos is a beautiful place and that you are an exceptional photographer, and no doubt all-round good guy. Keep on keeping on.
    I’ll be back
    AnthonyK

  6. #6 FormicidaeFantasy
    April 29, 2010

    I am an amateur ant taxonomist (and I’m probably being indulging by even saying that!) but these two ants seems to have very distinct characteristics that seem to possible override their similarities.
    — While the forelegs are obviously distinctly different from the mid- and hind-legs in both ants, the difference seems far greater with the legs of Anomalomyrma
    — The shape of the pronotum seems to be both way larger and far more bulbous in Anomalomyrma, as well as the fact that the front face of the pronotum is markedly broader than that of Martialis.
    — The separation of the petiole from the postpetiole is distinctly different between the two.
    — Anomalomyrma seems to be generally more rugose than Martialis, although that could just be angle.
    — It seems to me that while the lengths are similar, the “body proportions” aren’t really. Besides the things already mentioned, the pronotum when compared with the mesosoma seems larger and in a different position in Anomalomyrma than is seen in Martialis. In fact, most things about the thorax seem to differ between the two species.

    As I said, I am new at this, so I am perfectly willing to be told I’m way off with these comments! I’m interested in taxonomy and would like to get better at it!

  7. #7 Alex Wild
    April 29, 2010

    FF- This is the problem with discussing similarities and differences. These concepts are all relative, so discussing this is a bit like arguing whether the glass is half full or half empty. I don’t disagree with your characterization of these ants.

    However, I started from an assumption that the worker of Anomalomyrma would look something more like the other leptanillines. For instance, like Protanilla

    From this perspective, Anomalomyrma has converged on a more Martialis-like habitus than I would have expected.