How Should Taxonomists Name Your Favorite Ants?

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Are these two Temnothorax, or one Temnothorax and one Protomognathus?
Are these two Temnothorax species, or one Temnothorax and one Protomognathus?

Last year, a team of Antweb-affiliated myrmecologists published an evolutionary study concluding, among many results, that a slate of socially parasitic genera had evolved from within their host genera. The names of parasitic genera were subsequently sunk. Inclusion of derived groups in their parent genera has been standard practice for decades as a way to keep names consistent with ancestry.

But a number of myrmecologists do not approve of their favorite ants losing their names, and struck back with a strongly worded opinion in Insectes Sociaux this week:

We contend that banning all paraphyletic groups while simultaneously executing binominal Linnaean nomenclature results in a taxonomy going off the rails.

The dissenting authors make a lengthy argument about information content, evolution, and practicality, but the logic distills to, “the sunk genera look different, and we feel it more useful that the difference is reflected in a unique name.” If this argument looks familiar, it is the same case put forth by Ernst Mayr’s “Evolutionary Taxonomy” school in the 1960s and 70s. This was not a winning argument. Most biologists found disagreements about trait differences subjective compared to the relatively clarity of ancestry, and taxonomists today generally agree that recognizing paraphyletic groups is more confusing than the alternatives.

I have little personal experience with the genera in question. From my perspective as an outsider, I had to look up Epimyrma in Bolton’s catalogue to figure out what kind of an ant it was. Formicine? Myrmicine? Had I known it was basically a parasitic Temnothorax, I’d have been that much ahead of the game. Monophyly is information; paraphyly less so. But utility is a question of perspective and context, I suppose, and I can empathize with those who regularly work with these ants. Treating these distinct species as congeners may be as awkward as attending a party where everyone is named Jayden.

Still, given the volumes of vituperative ink spilled a half-century ago in the cladism wars, and the weight of the pro-monophyly consensus among all biologists, I suspect this renegade group of ant scientists will be fighting an uphill battle.

Disclosure: I eclosed as a myrmecologist from Phil Ward’s lab, so of course I am not without my allegiances.

Sources: Seifert, B. et al 2016. Banning paraphylies and executing Linnaean taxonomy is discordant and reduces the evolutionary and semantic information content of biological nomenclature. Insectes Sociaux doi: 10.1007/s00040-016-0467-1

Ward, P.S. et al 2015. The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae). Systematic Entomology, 40: 61–81. doi: 10.1111/syen.12090

34 thoughts on “How Should Taxonomists Name Your Favorite Ants?”

  1. There was once an ant named Teleutomyrmex schneideri, very distinctive and easely recognized. This ant became in 2014 Tetramorium inquilinum, not Tetramorium schneideri because that is another species… Maybe in a few years it will be known as Myrmica saasfeei, yes, inquilinum is already used for an ant in the Myrmicinae… and if we go back to the classification of Linnaeus it can become Formica saasfeei, yes all ants are related… If those phylogenetic studies advance all becomes related and, in the end, all has the same genus-name…

    And in 2014 they did forget to give Teleutomyrmex kutteri an other specific name when it was moved to Tetramorium… Yes, there is a valid subspecific name kutteri in Tetramorium already long before 2014…

    And even, Strongylognathus has priority over Tetramorium and is a name so much used! Why trying to take away it’s priority because you don’t like the name???

    Like you see, I’m in favor of keeping Teleutomyrmex, Anergates, Chalepoxenus, Myrmoxenus (= Epimyrma),… They are all clear morphological recognizable groups8

  2. ‘the sunk genera look different, and we feel it more useful that the difference is reflected in a unique name.’

    That’s the same argument Ward used to justify renaming Camponotus gigas to Dinomymrex gigas.

    ‘Dinomyrmex is a distinctive camponotine, confined to southeast Asia, and recognized by the combination of very large size (HW 3.25–5.35), elongate antennae and legs, and the presence of a metapleural gland. The species also has characteristic mandibular dentition, with teeth occurring on both the masticatory and basal margins of the mandible (Emery 1925).’

    1. I don’t think these two scenarios are equivalent. Not only is Dinomyrmex phenotypically distinct, it’s also phylogenetically distinct; while the social parasites are also phenotypically distinct, the current evidence finds they arose directly from Tetramorium and Temnothroax ancestors. Dinomyrmex gigas is what it is now because Camponotus, as a polyphyletic taxon, was split into three names to maintain monophyly without sinking all the Camponotini into Camponotus.

      I think better parallel to the argument in this editorial would be keeping the genus names Forelophilus, Phasmomymrex, Echinopla, Calomyrmex, Opisthopsis, and Polyrhachis because they are phenotypically distinct groups, while also retaining a Camponotus that is paraphyletic to all of these.

  3. Buckle up, looooong rant below:

    I am not an expert, but my two main takeaways from this are 1) this is all hella confusing and I’m going to have to reread this later, and 2) I basically agree with you that the information content argument is moot. The number of names affected will be relatively small (though I do agree that including all Tetramorium names in Strongylognathus is ridiculous and impractical), and the sinking of the parasites within their host genera is more ecologically and evolutionarily informative than retaining their old names, which merely reflects phenotypic distinctiveness. My question is, if we want to reconcile keeping these names with maintaining monophyly of Temnothorax and Tetramorium, why don’t we just split Temnothorax and Tetramorium? Autapomorphies are autapomorphies, big or small, morphological or molecular, right?

    Re: the original intent of Linnaean taxonomy, I don’t really care, even if it is foundational to modern systematics. Maybe I’m being glib, but imo we should care more about classifying species based on shared ancestry and reconstructing the evolutionary history of taxa, as we already do. I don’t think it’s controversial to say that taxonomy should be dictated by and uphold these principles, and that binomial names should, if possible, reflect monophyly of these groups based on best available evidence of shared ancestry, rather than undefineable “distinctiveness”. I’m mystified by the assertion that “if we are classifying all the products of evolution, every taxon we recognize (apart from the original one) must make another taxon paraphyletic” but either way I don’t see why the inherent paraphyly of evolutionary trees makes an argument for retaining these names as opposed to others.

    And finally, I’m skeeved out by the assertion that “external morphology, presenting the most obvious expression product of nuclear genes, should remain the backbone of binominal nomenclature.” What about cryptic, non-interbreeding species distinguishable only be genetics, ecology, and behavior? What about extremely similar morphological traits, like floral chambers in Rafflesiaceae, that evolved independently and emerge by unrelated developmental processes? And in the case of highly modified parasites, or even difficult-to-place free-living taxa like hoatzins and turtles, how else do we determine their classification but with the support of good molecular data? I agree that morphology is important and acknowledge that the weighting of different types of data is unclear, but if we have the tools and understanding now to re-evaluate morphogically based hypotheses, we can’t just cry foul when they don’t agree. And while I understand the practicality of phenotypic investigation, practicality in itself is irrelevant the theoretical question of why coding sequences and their products should have more weight than noncoding sequences.

    1. Marc "Teleutotje" Van der Stappen

      Just two small remarks.
      One. Strongylognathus is a valid, much used name that nobody complained about untill Ward et al 2014, arounď 150 years later… It has priority over Tetramorium and should be the normal name in their phylogeny. They want to replace it because they don’t like it as a name for a big genus. So, all names can, from that moment on, be used at will… No. The name should stay according to normal rules.
      Two. If you take on the argument of phylogenetic relatedness, all living things shoulď be classified under one genus name… No, divide Tetramorium and Temnothorax up in more genera and resurrect the old parasitic genera!!!

      1. Thanks for your reply Marc!
        My response to your first point: It’s true that Strongylognathus has priority over Tetramorium, and technically under the rules of the ICZN all Tetramorium should be synonymized under Strongylognathus. However, if it comes to that point, isn’t it possible to resolve this by simply petitioning the ICZN to keep the name Tetramorium, synonymize Strongylognathus under that name, and revise the type species?
        Second point: I agree that we can divide Tetramorium and Temnothorax and retain the parasitic genera, which is why I’m confused as to why I haven’t seen this option addressed as a possible solution. As for the phylogenetic relatedness issue… well I suppose that since all life shares the same set of LUCAs all life is technically monophyletic, but that’s extreme. For the most part we can easily subdivide life (or metazoa, at least) into monophyletic groups based on when lineages diverge from each other, so what’s wrong with insisting on the strict monophyly of taxonomic groups? It’s not a perfect solution given what we know about gene introgression between ‘species’, as the editorial says, but it’s the best system we have.

        1. Why not keep the name Strongylognathus? It’s older, it’s valid, it’s not forgotten, it’s also good for the species it was made for,…. and yes, following the rules it is the name to be used. We made the rules for something, not to let everybody who wants to do different do different. And the argument the name doesn’t match the “Tetramorium”-species, here’s news for you: The name Tetramorium also doesn’t match the “Teleutomyrmex”-species (and “Anergates” and maybe still others!)!!!
          I don’t want to put all living things under one genus name but I think Ward et al go to far. Yes I want to keep the social parasitic genera under their own name. Why? Because they are very easily recognizeble. So Teleutomyrmex, Strongylognathus, Harpagoxenus,…., all with their own morphological and behavioral characters. And Tetramorium? Since the Sanetra and Buschinger article from 2000, yes 2000, I’m a big supporter of dividing Tetramorium in at least 8 smaller genera. And I think Temnothorax should be looked at to see if it must be divided in smaller genera too. I think with the Myrmicinae the same is happening as with the Ponerinae, first start lumping and later do like the older systematicists and divide the genera again in smaller groups, and for Myrmicinae this should be done NOW! For the Ponerinae this works very good, why shouldn’t it for the Myrmicinae?

  4. Linnean taxonomy (and later phylogenetic methods) was used because it grouped organisms into usable chunks, instead of older ways of looking at nature which grouped snakes and worms, bats and birds, whales and fish together simply because they “seemed to be similar” while in fact they are not closely related. We still use this system because its scientifically sound and provides the best “model” to view the world. I dont think anyone questions the validity of this, then why argue against it at genus level? The obvious thing would be to extend this concept all the way down to genus and species level.

    This conflict is basically an argument to go back to the “fish and whales” view, although at a much lower taxonomic level, something I dont really see a good reason for. If its such a good idea to keep snakes and lizards together instead of snakes and worms, why should we group parasitic ants apart from their closest of kin?


    1. Marc "Teleutotje" Van der Stappen

      Because: Their morphology is distinct, their behavior is very different and they even produce different chemicals (or different combinations of them). It would be logical to keep them separate. And that is possible… Keep the parasitic genera and break up Teramorium and Temnothorax. And for those that say that biodiversity- and phylogenetic information gets lost by dividing those genera, I wonder why? The relations are still clear to see and even more noticible.

      With the synonymy there disappears some obvious easy to see information. Find to ex-Teleutomyrmex species with a changed name between 4 to 500 Tetramorium species… Very clear!!!!

      1. I can kinda understand your way of seeing this. But I would argue that your points are supporting the inclusion of the parasitic genera into Themnothorax, at least in my view:
        1) By having radically “different” (morphology, CHC, behaviour, lifehistory and so forth) species in the same (monophyletic) genus instantly tells you a lot of things about them. Firstly that despite their differences they are closely related, to the degree that some of the “normal” Themnothorax are closer to the parasitic Themnothorax than to other “normal looking” Themnothorax sp.!
        2)That the radiation of the parasitic “groups” are rather recent (at least compared to the radiation of Themnothorax as a whole) and importantly seems to be evolutionary preadapted to occur, since it has happened several times. Which in it self is astounding and a great opportunity to study all manner of things, as you have independent groups evolving the same traits from a somewhat “common stock” of social species. How are these parasitic groups similar and different to each other, is there some things that appear to be obligate traits for a social parasite? Genetic changes, co-occurances, competition, global patterns of distribution and much more. [[continued below…]]

      2. 3) Keys or identification guides will not be affected at all, just key out different parts of the genus at different places and create subgenera/species groups/etc and split up the species keys accordingly. If we instead split the genera into small monophyletic genera of their own as you suggest,keying out the different social genera from each other will be almost impossible, such that keys would not be able to tell you which genus you arrive into. And then to find out what genus a specimen belongs to you would have to identify it to a particular species in some sort of common key to the species of a whole tribe or subtribe. This essentially renders the concept of “genera” completely useless. Say you find a social ant that used to belong to the large “Themnothorax”, then you would have no idea which small social, monophyletic genus it is actually part of. If you determine specimens at a collection and you cant reliably identify specimens (undescibed species, uncertainty, etc) you would basically have to write on the det. label “Social genus1, Social genus2, Social genus 3, etc” since you only know its a member of the old social part of “Themnothorax” but you cant find which of the many social genera it actually is. My assumption here is that many of these proposed monophyletic parts of the old “Themnothorax” are morphologically hard to distinguish from each other. I mean if they arent they would probably have been assigned into monophyletic groups already, no?

      3. 4) Its quite easy to group the different monophyletic subgroups which shares the same biology in subgenera or species groups to keep track of them. Sure, if the names are long it takes some space, but really is the character count of scientific articles more important than their actual content to the degree it should influence taxonomy? I’d argue absolutely not.

        That’s at least how I reason. I’m not an ant person, I’m into Chrysididae, so my views might be wrong/absurd/unfounded. But I can comment on the effect of large, inclusive genera. Even if the genus in question is currently paraphyletic/polyphyletic, since some odd looking groups are probably split of as their own genera “incorrectly”, but no sequence analysis has been published yet, but I think some are in the works. The genus “Chrysis” is massive, contains around 1000 described species (1/3 of the family), morphologically heterogeneous, and full of tricky species pairs. But it works, its often easy to directly tell what informal “species group” (eg ignita-group, inaequalis-group) a specimen belongs to, and as these species groups are not bound by monophyletic requirements they simply include all species with the same habitus which essentially makes it as easy as possible to narrow down the number of possible species to a few tens or so. Sorry for a overly long post/rant!

    1. Marc "Teleutotje" Van der Stappen

      Very negative blogpost and only saying not good, not good, not good, … Let him say what it should have been…. and let us see what the arguments from the other side are. And the paraphyly can be resolved… Divide Tetramorium and Temnothorax in smaller genera…

      1. I am happy to take advice on how to write better, but I am a bit confused about how to write a positive commentary when I disagree with all of a paper’s arguments.

        What should have been? Easy: IMO this paper should not have been written. But if you mean whether paraphyly should be resolved by splitting or lumping, that is for myrmecologists to decide, not for botanists. My interest is in examining the logic of pro-paraphyly arguments in general.

        Also taking this opportunity to say: Great blog! I had fun showing my daughter the video of the millipede hunters.

    2. Marc "Teleutotje" Van der Stappen

      Can’t post a comment on his blog….
      Wanted to say a few things mentioned here already.. tried it two times but it won’t accept my post (logged in like I should be).

  5. There is something about a load of ants all jostling over their food that just makes my skin crawl. I’m sure they are friendly enough 🙂

  6. This post reminds me of my childhood days and how I enjoyed watching those ants carrying tiny pieces of spilled foods.

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  8. It’s interesting to see how some people are passionate about ants (and I’m not saying it in a condescending way). Personally, I can’t stand the little buggers, especially when they start crawling around my room. However, I am fascinated by their level of communication and cooperation. You can’t disagree with the fact that ants are extremely efficient.

    Thank you for the great post.

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    1. Van der Stappen Marc

      Prof. Those people never found out that I am a biologist and made my thesis on honeybees. Why not on ants? Because I wanted to do that… but one of the universities (not the one I followed) didn’t allow me to do that. A few years later my university also started research on ants… but too late for me. Should have come to your university…

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