A Myrmicine Phylogeny Shakes Things Up

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Monomorium kiliani

Monomorium kiliani, an Australian myrmicine. The narrow, two-segmented waist is characteristic of this subfamily.

We’re only halfway through the year, but already 2014 will be remembered as pivotal for studies of ant evolution and classification. Following right on the heels of Schmidt & Shattuck’s massive ponerine revision comes an important new study from the Ant Tree of Life group. Ward, Brady, Fisher, and Schultz (2014) have reconstructed the first thorough genus-level phylogeny of the great ant subfamily Myrmicinae.

How important is this study?

Roughly half of all ants are myrmicines, both in abundance and in species diversity. Their numbers include fire ants, harvester ants, leafcutter ants, big-headed ants, acrobat ants, and so on, to the tune of some 6,000+ species.

So… Boom! Suddenly, we’ve been given a detailed picture of the evolution of half the ants. This is big. It is so big I cannot cover the paper in detail. Instead, I’ll just give a few preliminary thoughts, as follows:

1. This is a well executed study, as we’ve come to expect from the Ant Tree of Life team, applying a thorough analysis to over 250 carefully selected taxa and 11 genes. It’s also a shining example of an older generation of genetic techniques, alas, and while I am confident the stronger results will mostly endure, be aware that an incoming next-gen tide of full genomes, and the 6,000 yet-unsampled myrmicine species, may yet overturn some of the findings.

2. The deep history of Myrmicinae, starting 100 million or so years ago, mostly occurred on those continents that drifted to become the Americas. Echos of these earliest divisions are heard in six clear, genetically distinct groups that Ward et al have formally set the up as a new system of tribes, replacing an earlier, messier scheme. The six groups are listed here in their order of divergence: Myrmicini (MyrmicaManica), Pogonomyrmecini (Hylomyrma & Pogonomyrmex), Stenammini (AphaenogasterMessorStenamma, and relatives), and three sprawling groups with thousands of species: Solenopsidini, Attini, and Crematogastrini. 

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The myrmicine big picture. (Sharpie on office paper, 2014, limited edition print available, unless I recycle it).

3. The news is not all good. The clarity deep in Ward et al‘s tree fades for slightly younger events. Early relationships within some of the the six tribes are discouragingly ambiguous. This study has resolved some problems, myrmicine taxonomists face a difficult road ahead. Many of the world’s greatest genera do not form natural groups and will have to be redone. These include Aphaenogaster, Pheidole, Tetramorium, and especially Monomorium, which splatters almost comically across the Solenopsidines.

What, really, is Monomorium? Modified from Figure 1 of Ward et al (2014).

Distressingly, fuzzy resolution in a data set with this many markers and taxa means achieving proper resolution, if at all, will likely be expensive. Myrmicines may have speciated so explosively that we may never be able to reconstruct what happened with confidence.

4. The authors correct a few of the more obvious instances of paraphyly. Notably, the New World “Messor“, being unrelated to their old world doppelgangers, were moved to a revived Veromessor, and several social parasites like Protomognathus and Anergates have been sunk into the host genera from whence they evolved: Temnothorax and Tetramorium, respectively. There are other changes, too; they are listed in the abstract

Most of the identified problems- such as what to do with Monomorium and Aphaenogaster- were left for targeted future research.

5. Remember the dispute over Pyramica vs. Strumigenys? The argument was fundamentally over how ant mandibles evolve. Apparently, high energy trap-jaws arise easier than anyone imagined. According to Ward  et al, not only is the assemblage of trap-jaw ants formerly included in dacetini a polyphyletic splatter, even within the genus Strumigenys the trap jaw has arisen at least twice.

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A phylogram of Strumigenys, modified from Figure 1 in Ward et al 2014, showing strong support for the parallel evolution of trap-jaws in the genus.

6. The rare and bizarre African myrmicine genus Ankylomyrma is not a myrmicine at all! Rather, Ward et al‘s results unambiguously tie it to the equally bizarre Tatuidris of the Neotropics, sitting on a distant branch of the ant tree. Peas in a poneromorph pod…

Ultimately, Ward et al have crafted a sobering view of how little we still know about ant evolution, and how much remains to be done.

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Aphaenogaster fulva, photographed in Illinois.


source: Ward PS, Brady SG, Fisher BL, Schultz TR (2014) The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae). Systematic Entomology, online early. DOI: 10.1111/syen.12090

disclosure: I received my Ph.D. from Phil Ward’s lab where much of this study was completed, and I contributed a few of the samples, but I was long gone by the time the study was initiated and have had no other involvement with the research.

A Texan Future For Myrmecos

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texana20ut

Atta texana - photographed at Brackenridge Field Laboratory at the University of Texas in Austin.

 

Big news!

On January 1st I will be starting as Curator of Entomology at the University of Texas in Austin.* I can’t even begin to convey how excited I am about this unexpected progression of my career. I will be managing a working research collection of over 1 million invertebrates, teaching entomology, and returning in full to ant evolution research. Mrs. Myrmecos (who has concurrently landed a postdoctoral spot in Nancy Moran’s microbiome evolution lab) and I are looking forward to this move for hundreds- perhaps even thousands!- of reasons. Among them: the caliber of our colleagues at UT, the fantastic research environment, the vibrant Austin culture, our many friends in town, a rich subtropical insect fauna. Plus, there are nests of Atta texana leafcutter ants right outside my new office. I mean, really. It’s like the search committee planted them there on purpose.

I mentioned this move was unexpected, and it really was. I began the year with no intention of anything other than moving forward with the insect photography business. My toes had been out the academic job pool since I went indie in 2011, and I’ve been happy running my own show. But a recent visit to the Austin revealed that the particulars of this curator position could be an unusually close fit for both me and for the University of Texas. So, I jumped. We’ll be pulling up our prairie stakes and moving in late fall.

See you in Texas!
 


*Since nearly everyone who heard the news asked about it, the photo business will continue as a sideline, as it was for many years before I went full-time. The insect photography galleries will remain in place, accumulating new content as time allows. I will no longer have time for private lessons and commissions, alas. The BugShot series of workshops is awesome, of course, and will live on.

Everything Old Is New Again – Ponerine Taxonomy Returns To Its Roots

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striata1m

Pachycondyla striata, from Brazil, is one of the few names to remain stable after Schmidt & Shattuck fragmented Pachycondyla.

A monumental day for ant taxonomy! The mythical Schmidt & Shattuck ponerine revision, long rumored to be in the works, has emerged from the mists of legend and lore. It’s real! All 242 pages are in Zootaxa:

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I don’t wish to speak for the entire myrmecological community, but I think it is safe to say that Chris Schmidt and Steve Shattuck’s ponerine revision has been the most awaited taxonomic paper of the past decade. Ponerine ants comprise one of the greatest subfamilies in terms of abundance and species diversity, particularly in the tropics. Ant people know ponerines. The group is the most purely predatory of the large subfamilies and contains some spectacular insects: trap-jaw ants, matabele ants, various and sundry predators and huntress ants.

Schmidt & Shattuck’s paper is significant for two reasons. First, nearly all ant researchers will be affected by the taxonomic changes. And second, the changes themselves are large, especially for the hundreds of species that used to belong to the sprawling polyphyletic genus Pachycondyla. Under the Schmidt & Shattuck hammer, Pachycondyla in the strict sense remains just a shadow. All but a handful of Neotropical species move to 19 different genera, some new, most revived from older literature. There are about a third more ponerine genera to learn than there were yesterday. That’s a lot to digest.

You might think such large changes would invite controversy, but I anticipate that the new scheme will be widely accepted and largely stable.

1. The work itself is thorough, involving morphology and several different genetic markers. There is good reason this paper was years in the making.
2. Many of the newly valid names are resurrected from the older literature, and as such they already reflect gross morphological groupings as seen by earlier generations of myrmecologists.
3. Ant taxonomists are more uniformly phylogenetic in their outlook than the preceding cohort. The polyphyly of Pachycondyla was not an accident born of ineptitude; rather, it was designed that way by Bill Brown, who was operating under a different philosophy of systematics more popular in the middle of the last century. Since Brown’s school has faded from prominence, most biologists are uncomfortable with polyphyly. As Schmidt & Shattuck are dragging ponerine taxonomy back into the comfort zone of most evolutionary biologists, I expect the new scheme will be popular.

In the big picture, Schmidt & Shattuck have put this important group of ants on a stronger taxonomic foundation. In the small picture, we are faced with the mundane realities of re-memorization.

Pachyondyla apicalis? No longer. Get used to Neoponera apicalisPachycondyla stigma? Nope. It’s Pseudoponera stigma. Plus, there’s Brachyponera, PseudoneoponeraMesoponera…


source: Schmidt, CA, Shattuck, SO (2014) The Higher Classification of the Ant Subfamily Ponerinae (Hymenoptera: Formicidae), with a Review of Ponerine Ecology and Behavior. Zootaxa 3817 (1): 001–242.

 

Guest Post: Crowdfunded study of maternal care in leaf beetles

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The following is a guest post by entomologist Guillaume Dury.

In the tropical forests of South America, survival can be tough for a small larva. Ravenous predators are on the prowl and deadly parasites soar nearby. Even faced with these threats, most species simply abandon their offspring, usually eggs. My favourite solution to survival of offspring is maternal care, but this raises the question: “Why do some insects care for their young while most do not?”

Comparatively few people study maternal care in insects and I’d like your help to be one of them. Insects are my passion, below is a photo of me at 4 years old, in the Swiss Alps with my insect net. Since then, I’ve obtained a B.Sc. in biology and ecology and I’ve finished my M.Sc. working on leaf beetles. I’m a BugShot 2012 alumnus and love insect photography, you can find my portfolio and my complete research C.V. on my website: http://www.gjdury.com/

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Guillaume, 4 years old, with his insect gear in the Swiss Alps.

My project is partially funded by a National Geographic Young Explorer’s grant. I’m collaborating with Dr. Windsor of the Smithsonian Tropical Research Institute and Dr. Bede of McGill University, we propose a series of observations and experiments to determine how Proseicela vittata Fabricius (Chrysomelidae: Chrysomelinae) mothers defend their offspring, and from what threats, and how it differs from a closely related species without maternal care.

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Proseicela vittata guarding a brood of larvae. Photo by Dr. Donald Windsor.

Leaf beetles feed on leaves exposed to predators and parasites, parents of some species guard their progeny. The picture above is a mother Proseicela vittata with her larvae. In P. vittata, the mother beetle protects her eggs by gestating them, then, after giving birth to small larvae, she remains with them for all of their development.

The mother beetle doesn’t feed her larvae, but prepares their first meal. She will cut the veins of the first leaf the larvae eat. The leaves are those of the toxic Solanum morii (Solanaceae), and no one is certain about why the mothers cut the veins, we think it makes the leaves less toxic for the newborn larvae.

If you can share my project and spare a few dollars, it will make a big difference for me and I’ll do my very best to give back the best science I can! I am collecting funds through an Indiegogo campaign:

https://www.indiegogo.com/projects/study-of-maternal-care-in-leaf-beetles

The Many Talents of Trap-Jaw Ants…

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…include swimming gracefully across water. Astounding:

This, from a new study by Steve Yanoviak in the Journal of Experimental Biology:

Abstract: Upon falling onto the water surface, most terrestrial arthropods helplessly struggle and are quickly eaten by aquatic predators. Exceptions to this outcome mostly occur among riparian taxa that escape by walking or swimming at the water surface. Here we document sustained, directional, neustonic locomotion (i.e. surface swimming) in tropical arboreal ants. We dropped 35 species of ants into natural and artificial aquatic settings in Peru and Panama to assess their swimming ability. Ten species showed directed surface swimming at speeds >3 body lengths s−1, with some swimming at absolute speeds >10 cm s−1. Ten other species exhibited partial swimming ability characterized by relatively slow but directed movement. The remaining species showed no locomotory control at the surface. The phylogenetic distribution of swimming among ant genera indicates parallel evolution and a trend toward negative association with directed aerial descent behavior. Experiments with workers of Odontomachus bauri showed that they escape from the water by directing their swimming toward dark emergent objects (i.e. skototaxis). Analyses of high-speed video images indicate that Pachycondylaspp. and O. bauri use a modified alternating tripod gait when swimming; they generate thrust at the water surface via synchronized treading and rowing motions of the contralateral fore and mid legs, respectively, while the hind legs provide roll stability. These results expand the list of facultatively neustonic terrestrial taxa to include various species of tropical arboreal ants.

source: Yanoviak, SP, Frederick, DN. 2014. Water surface locomotion in tropical canopy ants. J Exp Biol 217, 2163-2170. doi: 10.1242/​jeb.101600

BugShot 2014: The Aftermathening

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Sapelo_group

The group in front of Reynold’s Mansion, antennae extended. (photo by Ian Wright)


 
I have returned from coastal Georgia and from another spectacular BugShot workshop! Once again, the annual event surpassed my expectations. It wasn’t just the gorgeous natural environment, either, or the discovery of the extremely enigmatic Zoraptera. It was an extraordinary group of enthusiastic participants who made this workshop worth doing.

Rather than recap the festivities myself I will leave you in the capable hands of participants. I’ll update the list as more material works its way to the internet.

Blogs:

 
Others:

 
If you feel you missed out by not attending, don’t worry! We have our next event coming up in September in Belize.

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