Ants

Fossils and DNA tell different stories about ant evolution. Or do they?

Did modern ants evolve up from subterranean ancestors? Or did they diversify from above-ground species?

This straightforward question about ant history does not have a straightforward answer. If we look at early ant fossils, most sport the long limbs and large eyes typical of surface-dwelling species. Consider the Cretaceous ant Haidomyrmex:

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Haidomyrmex scimitarus (via antweb.org)

If the fossils tell a tale of large-eyed, surface-dwelling ancestors spawning the modern ant fauna, genetic data from modern species give an apparently conflicting story. A recent paper by Andrea Lucky and others in PLOS ONE took the known habits of modern ants and triangulated back over an evolutionary tree to infer the ancestral state. The odds of a subterranean ancestor were more than 90%:

Modified from Figure 1 of Lucky et al 2014.

 

Which story do we believe?

Possibly, both. The existence of a conflict depends on how the extinct, large-eyed species are related to modern ants. Many of them are in the subfamily Sphecomyrminae, and their phylogenetic position is not known with certainty. If sphecomyrmines are merely another ant lineage contained within the other known ants, as beautifully illustrated in the below diagram that took  at least 2 minutes to sketch, then we indeed have a conflict.

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If, instead, sphecomyrmines are a separate lineage that diverged earlier in ant evolution, then there isn’t  a conflict at all. tree

In this latter scenario, one particular lineage went underground (where they were less likely to be preserved as amber fossils) and from there radiated into the ants we know and love today. Meanwhile, their sphecomyrmine sisters persisted, large-eyed and above ground, until extinction. It is entirely possible that the diversity and success of modern ants traces to modifications forced by this subterranean existence.

Finally, the underground result of Lucky et al depends on particular assumptions of how traits evolve. Specifically, that above- and below-ground species go extinct at similar rates. If subterranean ants tend, on average, to go extinct less often than their above-ground relatives, then many of the surviving members of older lineages will be subterranean and we might infer a subterranean ancestor as an artifact.

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Leptanilla is an ancient lineage of blind subterranean ants.

source: Lucky A, Trautwein MD, Guénard BS, Weiser MD, Dunn RR (2013) Tracing the Rise of Ants – Out of the Ground. PLoS ONE 8(12): e84012. doi:10.1371/journal.pone.0084012

Ants are wild animals

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Confession: I am not much of an ant-keeper. In spite of my myrmecophilic appearance, I prefer to watch ants in their natural habitat.

Still, I pay attention to online fora where ant-keepers hang out to exchange the latest husbandry tips. I like people’s enthusiasm for the little animals. The best materials for artificial nests. Nutrition. Hibernation protocols. And many, many questions about why the insects are or are not behaving in particular ways.

It’s easy to get frustrated when a queen ant doesn’t lay eggs for months, or when a supposedly granivorous species doesn’t take the seeds offered, or when a colony sets up shop in the wrong part of the ant farm. Ants don’t always do what ant-keepers want or expect of them. Yet the failure of ants to thrive in ant farms shouldn’t make an aspiring ant keeper feel bad, because of this:

Ants are wild animals.

This observation is worth remembering. Livestock, dogs, cats, hamsters, even many pet store lizards are human inventions, molded by artificial selection for success in captivity. Ants aren’t at all like these familiar domesticated creations. While some species survive in artificial nests by way of latent ecological flexibility, others are as ill-adapted to a test tube life as a wolf is to a New York apartment. Without just the right food sources, or temperature regimens, or humidity, colonies of many species wilt. Ants weren’t designed to live in ant farms, that some can is a sort of lucky coincidence. So remember the wildness of ants, and marvel when they succeed indoors.

Ant Hunting in a Rare Illinois Sand Prairie

Sand Ridge State Forest, Illinois

It’s been too long since I’ve done a good old-fashioned anting expedition. So I took a break on Wednesday to see a part of Illinois rumored to be profoundly different from the rest of the state: Sand Ridge State Forest, a quiet patch of public land southwest of Peoria.

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The unique character of Sand Ridge stems from its geologic history. The glaciers ended here, dumping a pile of sand atop the resident clay. The soils here are dry and well drained, a stark contrast to the surrounding tallgrass prairie. As Sand Ridge is too nutrient poor to farm, the land was preserved as a blend of shortgrass sand prairie and woodland. (more…)

Be cautious when using Alexanderwild.com for identifications

And now, a public service announcement.

While I am flattered that many of you use my photo galleries to identify mystery ants, please be aware my site has limitations as a diagnostic tool. In particular, I am missing a lot of species, even some common ones, and even in North America.

Of the 33 North American species of the common genus Lasius, I have only 11:

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That’s typical. Here, as an additional example, is how I am faring with Pogonomyrmex harvester ants:

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Thus, when browsing my galleries looking for a match, bear in mind there’s more diversity than what I’ve posted. Often, much more. I’m just a guy with a camera, and progress happens only as time and budget permit.

If you’ve got ants needing reliable ID, you’ll do better consulting a site designed for species diagnosis like Antweb.org. Or better yet, use the primary literature.

Thief ant mating flights…

…happening this evening in Urbana. Photographic evidence:

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Solenopsis molesta, thief ant winged queen

Thief ants are among the most abundant insects in the midwest, but most people will never see them. They are small- only about 2mm long- and spend most of their time underground. The large relatively large size of the queens indicates a species capable of raising new colonies from workers fed entirely on the body reserves of young queens like this one. She will fly off, mate, and tunnel underground when she finds a suitable nesting site.

Incidentally, this whole drama played out on our front walkway. Urban lots can host plenty of nature for those willing to look.

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Solenopsis molesta, thief ant queen
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Solenopsis molesta, thief ant queen

photo details:
Canon MP-E 65mm 1-5x macro lens on a Canon EOS 7D
ISO 250, f/13, 1/250 second
Diffused macro twin lite

How Many Ants Are There?

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Over at Your Wildlife, Rob Dunn speculates:

How many ants are there in New York? The math is simple enough. We know from work that Britne Hackett and Benoit Guenard began (and Amy Savage is following up upon) that in a sample of one square meter of leaf litter there are about fifty ants, a village. Slightly more in the parks, slightly fewer in more stressed environments such as medians. But fifty is a good round starting place.

Now, how much green space is there in the city? We found one set of land use tables in which “open space” is a measure of part of the green space in the city; it does not include small patches of green such as medians or privately owned abandoned lots, but it is a starting point. If we multiply the number of ants in a square meter by the number of square meters in each borough and then double our estimate (to very conservatively account for the ants under ground at any moment) we get the following…

Lots_o_Ants

At a glance, those numbers don’t look great for people. But do they mean anything?

Functionally, would biomass be a more relevant comparison than body count? And, in light of the many simplifying assumptions underlying Rob’s calculation, might other methods be more accurate?

Young ants only poop once

If you’ve ever looked at ant cocoons, you may have noticed they always have a dark spot at one end:

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Lasius alienus – brood nest showing stained cocoons (Illinois).

What’s up with the spot?

There is no way to put it delicately: it’s poop. The dark spot is at the butt end of the developing ant. But this spot is not just any old poop. It’s a rather special one called a meconium.

Although young ants have been alive and eating for many weeks by the time they spin a coccoon, they never once passed their food all the way through. Ant larvae are massively constipated. Their waste builds up in the digestive tract as a strong, concentrated mass clearly visible through their translucent bodies:

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Ochetellus sp. (Victoria, Australia)

Larvae hold the pellet in as it gets larger through several molts, and don’t expel it as a meconium until they transition to the pupal stage. So, young ants only poop once.

Of course, there is good reason for the extended constipation. Living in large groups in fixed nests, ants have a public health interest in not continuously soiling their nurseries.

Speaking as an expectant father myself, I admit to a little bit of jealousy of a species that manages but a single diaper change per offspring.

Florida, already the capital of non-native species, has received a new carpenter ant

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Camponotus novogranadensis, as drawn by Mark Deyrup. (Adapted from Deyrup & Belmont, Figure 1).

Want to see the world’s species, but lack the wherewithal to travel to the earth’s farthest corners? You could do pretty well just visiting Florida. The state’s warm climate and constant human commerce make for an easy home-away-from-home for a staggering number of introduced species. Pythons from Asia, trees from Australia, birds from Europe, frogs from Cuba, bees from Africa, retired hominids from Wisconsin, these are just a few of the many species that have turned Florida into into a sampler of trampy biota.

Now they’ve got another arrival, a carpenter ant from the Neotropics:

An established population of a Neotropical carpenter ant, Camponotus novogranadensis Mayr, is reported from Estero, Lee County, Florida.  This species is similar in general appearance to C. planatus Roger, differing in color, pilosity, and clypeal shape. Camponotus novogranadensis is known from disturbed sites in Mexico, Central and South America; it has not previously been reported established outside its presumed native range. It is not known to cause economic or ecological problems.

Having seen this ant in South America, it’s not my impression that C. novogranadensis will become much of a pest. Still, in a novel environment, all bets are off.

As an etymological aside, this ant was described from northern South America by the pioneering Austrian myrmecologist Gustav Mayr, and at the time the territory went by New Granada. Hence, novogranadensis. Or is this an entomological aside? Hmmm…


source: Deyrup, M., Belmont, R. A. 2013. First Record of a Florida Population of the Neotropical Carpenter Ant Camponotus novogranadensis (Hymenoptera: Formicidae). Florida Entomologist 96(1):283-285. 2013 doi: http://dx.doi.org/10.1653/024.096.0148

The Ant Parasites of Konza Prairie

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A redbud blooms along the eastern border of Konza Prairie, April 2013.

The prairies of central North America are especially harsh environments. Half a continent removed from the buffering effect of oceans, temperatures in the plains soar in summer and crash in winter. Winds, and often fires, surge across the landscape. The prairie is not an easy place.

Prairie is also an environment I don’t spend much time exploring, in spite of my current situation living as I do at their eastern edge in Illinois. So I was pleased when the entomology students at Kansas State University invited me out for a seminar last month. I spent a morning at Konza Prairie on the advice of James Trager, who had an unorthodox way of persuading me:

I hope you’ll get a chance to spend some quality time at Konza Prairie, especially in any recently burned areas, and have some good anting weather. On the several occasions I’ve been there, I’ve gotten the impression that ant abundance and diversity are both oddly low there, and you will be there at a really good time of year to check on this. I have visited there only in the heat of (a very hot) summer and early fall, less propitious times for anting.

An oddly low ant diversity?  (more…)

An Acrobat Ant’s Acrobatics

If you’ve ever wondered why Crematogaster acrobat ants have such an odd shape, take a look at this:

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Crematogaster & Pheidole, Kibale Forest, Uganda

In Uganda’s Kibale Forest last summer, I smeared a bit of cookie cream along a rock as ant bait. A pleasingly yellow Crematogaster soon arrived to feed. All was well until a second species, in the big-headed ant genus Pheidole, attempted to sneak a taste.

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Crematogaster & Pheidole, Kibale Forest, Uganda

Instantly, the acrobat ant swung her agile abdomen forward – while still feeding (!) – and warded off her competition with a dab of venom. Like many myrmicines, Crematogaster has a stinger, but the structure has evolved from a piercing weapon to a soft, flexible, brush. The unique shape of the acrobat ant abdomen allows these ants to deploy their chemical weaponry in nearly any direction.