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Hi-
We have a huge colony that has seems quite mature. Has been there for a long time. They are small black and red ants and they have a nasty little bite. Unfortunately we need to place a structure right over the ants colony. We do not want to harm the ants and would prefer to somehow move the colony.

It may a good time of year to do something with a deterrent, as they are very active. I thought we might be able to lift the whole colony, using some sort of bucket, during the night, so they are not away from the nest. I imagine this would cause havoc and might not succeed.

We live in Victoria, on Vancouver Island.
Any suggestions? Any input would be appreciated.

Thanks!

Joan

Good afternoon, Joan!

Interesting question! It sounds like you have a colony of the quite charsimatic Western thatch ant, Formica obscuripes, in your yard. Fortunately I have experience with this species, given that there is considerable variation in the construction of thatch nests among the species in North America. Unfortunately, it may not be possible to relocate the colony without destroying it. The above-ground thatch---while impressive in stature, especially in the Pacific Northwest---is not the primary housing-unit of the colony. The thatch is like a compost pile which is warmed internally by the decomposition of the organic material used to construct it. In this way the above-ground component of the nest functions like an incubator, where the ants will place their developing young during the late winter and early spring months, allowing the young ants to grow even when there is snow on the ground. Now, the problem is that the most important members of the colony---the queens---don't like to stay in the thatch part of the nest. The queens are usually encountered in underground chambers which may extend several feet beneath the thatch. Thus, in order to relocate the colony you would need exquisite timing so that way you may move the thatch with the queens in it. Perhaps the best time of day for this would be in the morning or late afternoon when it is cooler out as the queens may migrate up into the thatch (although this idea has not been tested).

If you were to attempt to move the thatch there would be no way to do it without upsetting the workers as they are very territorial and aggressive about their mounds, and there is no guarantee that even if a queen were in the nest that she would be able to successfully excavate a new nest once moved. However, if you wanted to go through with the move I would recommend bringing a few 5-gallon buckets, a shovel, gloves, and duct-tape. What you could do is tape the gloves over long sleeves and your socks over your pants (trust me on this one!), then take the shovel and transfer as much thatch and soil from beneath the mound as fast as possible into the buckets (which hopefully you have lids for). You could take these and dump them together in an area very similar to where the colony is now, presumably near some Douglas firs. You might not have to dig too far down into the ground, as I have found queens at the soil surface and just below---less than a foot. I'm pleased with how considerate you are about these colonies! They may live for over a decade and house several thousand busily working individuals, let alone the fact that this species is ecologically important in your region.

Good luck with the ants, and I hope I helped answer your question!
Best,
Brendon Boudinot & the Ant Ask Team



Hello,
When comparing human infrastructure and ants what would you say is their most common behaviors? Do you think there is anything humans could learn from ant behavior?

Dear Jacqueline,

When human designers, architects, engineers, and computer scientists turn to other organisms for inspiration, it is often referred to as "biomimicry." In recent years, more and more people have turned to the other species on Earth for inspiration. Recent and ongoing work in Biomimicry is highlighted in this TED talk (by the main popularizer of the term "Biomimicry").

However, the speaker doesn't mention much about ants (and neither have I, so far...). One of the reasons ants are so interesting is that they display a wide variety of life-styles, from farming fungi, to raiding termite nests, to foraging in the shifting sands of the desert. And they're able to do all this with very little of what I would call "individual-level intelligence." Ants, like other social insects, function without central control, using what has been referred to as "swarm intelligence." (for more of my ramblings on swarm intelligence, see a previous post here, and also this more coherent article from National Geographic).

So, by studying ants and other social insects (like bees, termites, and certain wasps), we can learn more about true, blind democracies, and how to get things done without central control. For example, by studying processes different kinds of ants (and other social insects) use to find food and tell each other about it, computer scientists and engineers have been inspired to think of new ways to route traffic, solve resource distribution problems, and perhaps even program robots. The tricky thing about biomimicry right now is that many of these are still just potential lessons we could learn from ants - they haven't yet changed the way we get things done in our own lives.

The other tricky thing about biomimicry is that, like things you read in a blog post, sometimes what seem to be cogent lessons need to be evaluated and taken with a grain of salt. For example, in this article, the author uses the example of fungus-growing ants as a system of agriculture that we should learn from (perhaps just because of that charismatic image), but in the same paragraph alludes to the dangers of monoculture, which is exactly what fungus-growing ants (and termites) do: they cultivate a single species of fungus. They can get away with it, because they've evolved the ability to secrete antibiotics and fungicides from glands in their bodies, and they have the labor power to strip acres of vegetation around their nest and bring it back to fertilize their gardens (the most charismatic ants that farm fungi are the leaf cutter ants; other types of fungus-farming ants and termites use some combination of things like soil, partially decayed vegetable matter, the exoskeletons of dead insects, and caterpillar frass to fertilize their fungal gardens). Worse, there are different kinds of ants that make slaves of other ants, ants that are very lazy (surprise!), and ants that just hang from the ceiling all day collecting sugar water in their abdomens (which I would probably try for a while, but might lead to diabetes after a few weeks). So just like the Japanese scholars studying at the "Institute for the Study of Barbarian Books" in the 1800s did with knowledge from "The West," we should study nature (ants included), but pick and choose which lessons to incorporate into the society we wish to build for ourselves.

Hope this helps!
best,
Jesse Czekanski-Moir & the AntAsk Team

Can I train ants? (Ryan)




Hello Antblog,

I am interested in conducting some experiments with ants and I had a few questions I'd like to ask before I get started and I thought your site would be a good place to start.


1) Can queens of different varieties be trained(forced) to co-exist in one colony if an abundance source of food is present?

2) What is the smartest breed of ants?

3) Could ants in an ant farm learn to farm aphids? How might I go about doing this?

4) Could ants survive on honey alone?

5) Could ants be trained to use little man made tools for things such as cutting or digging through rock?

6) Can ants smell and identify different metals such as iron, nickel, gold, etc.?

I understand these questions are very vague and I do not expect a direct answer for all of them, but any information is appreciated. I'd even like additional links I could go explore myself.
I am only a grade 12 student but I am very interested in ants. My ultimate goal is to create a super ant farm to test the capabilities of ants as well as teach them to advance as a species.

Hi Ryan,

I apologize in advance: this post is probably too long and too speculative. The answers to a few of your questions are simple: (6) I don't think so; (4) some ants can; (3) it's thought that this is not a learned behavior, but some ants do facultatively tend aphids; (1) no, unless they are social parasites (for more stuff on social parasites, click here, here, and here).

Questions #2 and #5 are pretty complicated, philosophically and biologically, so I'm going to spend most of the rest of this post talking about them.

But real quick, before I dive into a heady diatribe about the philosophy of psychometry: ants and honey:

Could ants survive on honey alone? Adult ants don't need very many nutrients, and can survive for at least a week or two (often more) on just sugar water or diluted honey. It is the egg-laying ability of the queen, and the growth of the larva that depends on more protein-rich food sources, like (depending on the ants) seeds or insects. Several groups of ants seem to have bacteria living in their guts that can help them make nitrogen (one of the important building blocks of life that we need to synthesize proteins), but I'm not sure if anyone has quantified how only raising these ants on carbohydrates influences how many eggs the queen can lay, and how fast the larvae can grow. For many ants, we don't know their exact dietary requirements, but by and large, the ants that are most likely to be able to get by on a sugar-water or honey-only diet are arboreal (spend most of their time in trees). Carpenter ants (genus Camponotus) and Acrobat ants (genus Crematogaster) are among the most likely candidates that you'd run into outside of the tropics. Similarly, with respect to your question (3), many of the same ants that are largely herbivorous will occasionally tend aphids or other related phloem-sucking insects. But I'm not aware of a learning component to this behavior: I think it's hard-wired.

Okay. Onwards and upwards.
You know, when I tell people that I study ants, I am often asked (by males especially) if I am working on weaponizing them or figuring out how to harness them for industry. Ants are, after all, famously industrious. There is even an ancient Greek/Indian/Russian legend about ants that mine gold (sort of). I read about it in the book "Shalimar the Clown" by Salman Rushdie (which is a great novel if you're interested in 20th century geopolitics, but doesn't have much useful information about ants).

In general, the major hurdle to training ants for any specific anthropocentric end is the way in which they actually get things done. Deborah Gordon has a really nice book about ant behavior called "Ant Encounters" that I highly recommend. One of the key aspects of ant behavior she does a really good job explaining (not least because she pioneered this research) is "emergence." Her research, and the research of other people who study social insects, is much of the inspiration towards work in "Swarm intelligence" in robotics and computer science. Basically, the problem-solving ability of the colony, or "intelligence" does not arise from the leadership or intelligence of a few ants, but emerges from the trial and error of many non-intelligent individuals. Thus, to train a swarm, you'd really need to understand how voting works in these true, blind democracies. Here are a few links you can check out if you want to learn more. Deb Gordon and Tom Seeley are some of the most eloquent speakers and important researchers on the biological side of swarm intelligence (read/listen/watch more here, here, and here).

The most compelling examples of humans modifying ant behavior are not the results of training, but of trickery. It's easy to get ants to walk where you want them to walk, think a given nestmate is dead, and become alarmed by isolating one of the pheromones they use to communicate, and applying it in the right way. However, I can't think of a way in which you could use pheromones to trick ants into picking up tools, or finding gold, unless you could splice the gene for pheromone production into a bacteria that preferentially grew and expressed that gene in the presence of that metal. This is not completely implausible, and as we learn more about the genomic architecture of ants, and the metabolic pathways involved in pheromone production, using a genetically-modified bacteria-ant system could potentially become economically viable (and probably less ecologically destructive than most current mining techniques). One could aerially spray genetically-modified bacteria over an area that already has high ant densities, using the bacteria to trick the ants into collecting soil particles with high concentrations of metal oxides. Then, a few months later, when the ants have collected the clumps of soil with the most metal oxides, one could find large ant colonies and spray another strain of genetically-modified bacteria directly into the nests, that would make the "dead ant" pheromone in the presence of high concentrations of the metal oxide. After a few days, one could go around collecting the midden piles at the surface of the nest, which would be enriched in the target metal oxide. This sort of strategy would probably work best in desert or grassland environments, where a few species of ants build conspicuous nest mounds, like Pogonomyrmex in the American Southwest. It's possible one might be able to do this chemically, without genetically modified organisms of some sort, but if there was a much simpler way of using ants to work for us, someone (especially in Greece, Russia, or India) probably would have figured it out.

Beyond pheromonal trickery, it is possible that we'll be able to eventually trick ants electrochemically, as you can "currently" (get it? like, electrical current?) do with cockroaches: https://backyardbrains.com/products/roboroach
It's possible that, by controlling one ant with electrical impulses, you could convince the rest of the colony to do your bidding. However, as Tom Seeley found with bees, nestmates might need to be convinces themselves of the validity of the scouts choice, in which case you'd need to coordinate quite a few ants to agree that, for example, a vein of gold is a food source. The trickery arguments above apply primarily to ants that often recruit to a food source; however, there are ants that primarily hunt alone.

As you may have figured out by now, your question "which ant is most intelligent?" depends on what kind of intelligence you're talking about. The types of ants most likely to exhibit high degrees of swarm intelligence are the ants that form the biggest colonies, and need to forage collectively. Leaf cutter ants (especially Atta and Acromyrmex) and army ants (especially Eciton and Dorylus) form colonies of hundreds of thousands of individuals in the wild, and many types of invasive ants (such as the Red Imported Fire Ant, Solenopsis invicta) form sprawling super-colonies that can cover acres in their introduced ranges. I'm not aware of a "swarm intelligence" test (but see Seeley's work on, for example, nest-finding abilities of honey bees in Maine), but the number of worker ants involved, the foraging range of the colony, and the complexity of the environment would all likely factor in. It would be interesting to compare how quickly swarms of different sizes and species could solve a maze, for example. I'm not aware of a study like this: perhaps you could set something up!

Observations of ants in the wild can allow one to make at least cursory qualitative statements about swarm intelligence in ants. The complexity and scale of leaf cutter ant nest architecture, the many tasks involved in maintaining a fungal monoculture, and the hazards of foraging in tropical savannas and forests leads me to suggest that the attines may exhibit the highest degrees of emergent, swarm intelligence, perhaps surpassed only by the fungus-growing termites of the African and Australian tropics. A foraging swath of army or driver ants (Eciton or Dorylus) may be collectively be processing millions of environmental signals per second: scent and vibrational cues about proximity of prey and colony members, light ant dark cues, etc., which is similarly impressive.

Basically everything listed in the paragraph about ants here (and the suspiciously similar list here) is a result of "swarm intelligence," and not at all related to the individual intelligence of any of the colony members. Personally, I don't think there is a clear winner between ants and termites in terms of the complexity that emerges from the swarm intelligence of their respective superorganisms. And I'm somewhat tempted to write a whole 'nuthur blog post on what is wrong with these two articles... perhaps some other time.

So far as individual, organism-level intelligence goes: again, I can only speculate. I am tempted to guess that the ants that have small colonies and have large workers that forage by themselves are most likely be more individually intelligent, because colony fitness will depend to a greater extent on the problem-solving ability of ants acting individually, rather than the emergence of intelligence from trial-and-error and blind democracy. Conversely, I would expect very small ants that live in very large colonies to be the least intelligent, individually, because, as a colony, they can rely on swarm intelligence to effect reproduction. In primates, the "social brain hypothesis" (also, see here) suggests that group size should be positively correlated with brain (neocortex) size. An assumption this hypothesis makes is that intelligence is necessary to maintain group cohesion through diplomacy, strategy, and individual recognition. In most social insects, group cohesion is pheromonally-mediated, so intelligence need not scale with group size. However, in some groups of ants and wasps, there is a shifting dominance hierarchy, which might mean individuals have to remember each other and behave according to past experiences. Elizabeth Tibbetts, to the astonishment of the behavioral and entomological communities, demonstrated face recognition in certain wasps with changing social hierarchies that are reinforced by in-fighting, rather than solitary wasps or eusocial wasps with hormonally-mediated social hierarchies. Thus, the ants that are most individually intelligent (e.g., the most train-able) may be ants that have shifting social hierarchies, and/or spend much of their time hunting by themselves. We're still learning more about the social lives of different species of ants: if you include species that haven't been described or discovered, there are probably more than 20,000 ant species in the world, and many of them have remarkably divergent ways of life. Several species I can think of which have to contend with a reality of changing dominance hierarchies (often due to unconventional reproductive strategies) throughout the lifetimes of individual workers, include ants in the genera Pristomyrmex, Platythyrea, Myrmecia, and Cerapachys. Myrmecia include some of the largest and most visually-oriented ants (two factors often correlated with increased brain size). They are also among the largest of ants, and very effective solitary hunters. So I would guess that some member of the genus Myrmecia might be the smartest ant, on an individual basis. Other strong contenders include ants that forage alone and use visual cues to navigate back to their nests, such as Gigantiops destructor, Cataglyphis, and Melophorus.

"Tandem running," a behavior in which one ant basically takes another ant by the hand and leads them to a food source (actually, they just tap each other's antennae pretty much the whole time) has been proposed as the first example of "teaching" in insects (by their definition, the "waggle dance" of bees is simply "broadcasting").
However, a critique of this article by some of the leading non-human intelligence researchers takes issue with this definition of learning, with implications for how intelligence might be defined (not to mention an implicit critique of the education system). Definitely check out the Lars Chittka's publications page for a veritable treasure trove of readings on insect intelligence.

Not to end on too preachy a note, but your statement "help them advance as a species" is problematic on two counts: (1) ants are a family, the Formicidae, which is comprised of more than 14,000 described species, and (2) "advance" has very strong teleological overtones. Teleology is an understandable (Nietzche was all about it, and would have been really happy with you for using that sort of reasoning). But it's not the way I think biology works. Saying you would like to domesticate ants, or modify them behaviorally or biologically so that they are more useful to humans is one thing, but the advancement of a species is an empty concept. Evolution is change, not change towards a goal.

To wrap it all up: swarm intelligence has many advantages at the colony level, but should not be confused with the individual intelligence of organisms. Without broad, cross-species comparisons of either kinds of intelligence, I can only speculate (perhaps beyond the limits of my own intelligence) about which ant is the smartest. Both types of intelligence would require different approaches to training or other types of behavioral manipulation. If there were an easy way to train ants for industry, someone would have probably figured it out by now. Emerging biotechnologies may make the use of ants (and/or ant cyborgs... cy-ants?) possible, but assembling little robots (equipped with both swarm and individual intelligence) from scratch might be prove to be easier, at least in the short run.

Whew! Was that enough to get you started? :)
Best,
Jesse Czekanski-Moir & the AntAsk Team


Hi!

I came across your interesting website and I wanted to find out if there are any images available for what ant dung looks like.

Many thanks,

Cristina

Hi Cristina,

Thanks for your question! I have to admit, although I've spent a fair amount of time looking at ants, they're usually either dead or foraging: I've never caught one in the act, so this was a fun question for me to try to answer. Luckily, I have access to some other people with lots of ant experience, so I'm able to share their insights.

First, though, let's start with some terminology. When insects eliminate undigested waste, it's called "frass." This is a general term, that also (depending on who you ask) encompases other little particles and exudates that result from insect activities. For example, wood dust that results from carpenter ants gnawing through wood is sometimes considered "frass," even though the carpenter ants don't actually eat the wood - they just cut through it. Since your question is obviously directed towards elimination, we'll focus there.

Something about ants that many people don't realize is that as adults, they are unable to consume big chunks of food. Their jaws are often good at holding and/or cutting through objects, but not well-adapted for chewing food into pieces small enough to swallow. Some ants can eat pollen grains, but solids much bigger than that will not pass through the narrow constrictions at an ant's neck and waist. In a peculiar reversal of the "mamma bird" situation we've all seen on nature shows (and in real life, if you're lucky), adult ants must bring solid foods back to the nest, where the ant babies (larvae) eat it, and then vomit some of the chewed and partially digested food back into the mouths of the adults.

Because adult ants never eat solid foods, their frass tends to be a dark-colored liquid--at least as far as the ants that AntAsk Team members Corrie, James, and Steffi are familiar with are concerned. They (the ants, not the people) also excrete metabolic waste, analogous to urine, in the form of white urate crystals, which James describes as mixing together with the feces in various proportions: "sort of like coffee creamer."

The ant larvae, however, are a different story. They only eliminate waste once during their development, in the form of a dark, compacted mass (can I say "turd" on this blog?) shortly before pupation. This cuts down on diaper changes considerably. Interestingly, albeit disgustingly, sometimes adult ants eat this meconium (reported in Cerapachys biroi by Ravary and Jaisson 2002, and Cephalotes rohweri by Creighton and Nutting 1965). I apologize if you're reading this right before a meal.

As I wrap up this post, I realize I haven't actually pointed you in the direction of any real pictures. There are some pictures of meconia among Alex Wild's excellently curated collection of ant pictures, but I'm not aware of any pictures of an adult ant in the act of defecating. Refuse piles in subterranean ant nests, and below arboreal ant nests are more commonly photographed, but they often contain the bodies of dead workers and discarded prey parts, in addition to frass in the strict sense. So the best I can do is leave you with James' vivid image of a fine white powder mixing into a dark drop of liquid, like creamer into coffee. If I find a good picture of an ant in the act of "frass-ing", I'll let you know!

Hope this helps!
Best,
Jesse Czekanski-Moir & the AntAsk Team

ps. if you're interested in other things that come out of ants, please see this previous post about ant pee:
http://www.antweb.org/antblog/2010/08/why-do-i-get-itchy-when-an-ant-crawls-on-my-skin-carrie-austria.html



I have another question involving ants.

About three years ago, I put a hummingbird feeder outside my office in the home. I fill it with a mixture that is four parts water and one party plain old white sugar.
A few female and male hummingbirds visit every day.

However, black ants would also walk down the pole that the feeder hangs from and actually enter through the holes designed to admit hummingbird beaks and wind up dead in the so-called nectar inside the feeder. I looked for an online solution and found what is called an "ant moat." It's the red cylinder that the feeder is suspended from. It holds water and this prevents ants from crawling down to the feeder.

It works great and I haven't had a single drowned ant in the nectar since I installed the ant moat.

Amazingly, though, over the last two years I've only seen one ant actually walk down the pole, discover the moat, and retreat. *Just one*. Granted I'm not watching every minute, but I'm looking out there enough to be surprised that I've only seen one ant and that was last year when I first installed the moat.

It strikes me that perhaps that original ant left a chemical message for others that communicates that the nectar is inaccessible so don't even try.

What do you think?

Many thanks,

Ted

AntMoatHB-Feeder.jpg
* * *

Dear Ted,

Thanks for all of the details on your ant deterrent, it seems to be quite effective! In fact, there are many potential ways that the colony of ants learned to avoid your trap, likely involving some of the avenues of ant communication discussed in this post. One thing to keep in mind is that collective foraging often works on signals of reinforcement by multiple foragers. Thus, if none of the ants were able to return back to the nest with the nectar, then they would have a hard time "convincing" any other ants to forage in that direction, and there would be little reason to walk towards the moat other than random chance.

Hope this helps!

Max Winston & the AntAsk Team



Dear Ant Blog,

All the photographs I see show ants using their mandibles like tongs. Can they rotate them like we can rotate our arms?

Katrina

------------

Dear Katrina,

Despite the fact that ants use their mandibles for a multitude of different functions including prey capture, manipulation, and escape, there are no ants that have been proven to have fully rotational mandibles. Humans have a ball-and-socket joint that allows great range of motion, and although ants have a ball-and-socket joint for their antennae, their mandibles usually have a single plane of motion. Although this limits range of motion, it allows for much greater strength.

In case you are interested in reading more about mandibles, Chris Schmidt wrote a basic introduction to mandibular function as a part of the Tree of Life project. There are also several academic papers that detail the movements of mandibles (see Jurgen Paul), as well as some of the most extreme mechanical "trap-jaws" that have been convergently evolved by several ant species.

Hope this answers your question!

Best,

Max Winston & the AntAsk Team



Hello!

Thanks for taking the time to answer my question. I was recently traveling in Costa Rica and happened to take a camera shot of some interesting ant behavior. I have no idea what is going on here, but would sure like to find out. Have you ever seen this kind of behavior before? (see attached image)

Please let me know.

Mike

IMG_0056.JPG

---

Mike,

Great image! What you have documented here, quite beautifully, is a number of Azteca workers "spread-eagling" a Pachycondyla gyne (future queen). This is an interesting and well-known behavior of the genus Azteca (Dejean et al., 2009), which is well known for its mutualistic associations with plant species (Cordia, Cecropia). The mutualism between the plants and the ants relies on the plants providing food and shelter to the ants, and the ants fervently defending the plants from herbivores and other competitive plants. This behavior, known as "spread-eagling", is usually employed by the workers to protect the plants from insect herbivores or intruders, and is not restricted to the plant alone.

Because the Pachycondyla gyne has not started her colony yet and become a queen (you can tell because she has not dropped her wings yet), it is likely that the Azteca ants are showing this aggression to defend their territory before she can start a colony and get a foothold in their area. Although the pictures don't show it, I'm guessing the gyne did not escape alive.

Hope this answers your question, I've included the reference below.

Thanks,

Max Winston & the AskAntTeam

Dejean, A., Grangier, J., Leroy, C., & Orivel, J. (2009) Predation and aggressiveness in host plant protection: a generalization using ants from the genus Azteca. Naturwissenschaften. 96:57-63.



Hi guys,

First of all: this blog is really helpful, great work!

So now, while trying to write a report on ants --focusing on aspects of evolution-- I stumble upon many many questions. I'm hoping you can help me out!

1a. Micro-evolution
I was thinking about invasive species that are nowadays found in several continents, like for instance the Argentine fire ant.. Do all of their populations still belong to the same species? (no subspecies)
If so, how come? And would a male and female both from a different continent still recognize each other as potential mating partners or not. (If not, what's the term for that?)

What are specific factors that trigger origination of (sub)species of ants, or what causes the absence of it.

1b. Macro-evolution.. Can we speak of macro-evolution within the ant family, since there are so many different varieties. If not, could the relation between wasps and ants be an example of macro-evolution or is macro-evolution really about even bigger events?

2. Sexual selection
In the mating of ants, is there any 'conscious' selection going on from either gender. Are there species where an individual for mating is picked over another, based on qualities perceived?

Thank you!

Greetings :)
Zoe

Dear Zoe,

Thanks for your questions! You've gotten to some really awesome, fundamental evolutionary biology questions here, and you're asking me to make generalizations across a family of insects with more than 100 million years of evolution and more than 10,000 species, so I'm not sure I can do them justice in a blog post, but I'll try!

Your sub-question under heading 1a: "what are the factors that trigger origination of (sub)species of ants, or what causes the absence of it," is a question that can only be answered in a very generalizable way: speciation occurs when some factor causes populations of organisms to begin separate evolutionary trajectories. Often, as you suggest with respect to invasive species, this happens because of geographic isolation (allopatric speciation), but there are many theoretical and empirical studies that allude to the possibility of sympatric speciation, which is when speciation happens while populations of organisms are still within "cruising range" of each other. A previous blog post elaborates on speciation in the context of nest parasites.

Your first question about invasive species is great and very timely! There have been at least two studies in the past few years which demonstrated that Argentine ants (Linepithema humile) from different continents actually recognize each other as nestmates! So I can't imagine there would be any trouble with mating there.

The authors of both papers suggest that nestmate recognition is maintained across different continents because there is a steady stream of new arrivals, which prevents the populations from drifting apart. However, the question of when exactly a speciation event happens is very difficult to pin down. In a classic paper on the "Evolutionary species concept," the icthyologist EO Wiley states that "A species is a single lineage of ancestral descendant populations of organisms which maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate."

By this definition, you would really have to be able to predict the future: how can you know whether a newly isolated population will come into contact with propagules from its ancestral range? The idea that newly isolated populations are incipient species is tempting, but in practice, species can only be delimited if there are morphological and/or molecular differences in them, or, if you subscribe to the biological species concept, things could be argued to be different species if they generally choose not to mate with each other (for more information, you might want to look up pre-zygotic isolation and assortative mating...). In the case of the Argentine ant, I would expect a sudden drop in propagule pressure would result in the actual isolation of the disparate populations, but I would only expect this to happen if humanity drastically changed or ceased its practice of global trade and travel.


Sexual Selection
Speaking of pre-zygotic isolation and assortive mating, I think it makes sense to talk about sexual selection in the context of micro-evolution, because that's potentially a pretty important driver of speciation and trait evolution in sexually-reproducing organisms. Stearns and Hoekstra, an often-recommended text in evolutionary biology, defines sexual selection as: "The component of natural selection that is associated with success in mating." While at first somewhat disappointing, I think this definition is useful because it underscores the fact that sexual selection is a component of natural selection. Many ants form mating swarms, or leks, especially in desert and temperate zones. In these cases, there is a certain amount of "scramble competition," and differential levels of mating success have been demonstrated to correlate with individual traits. However, I am not aware of anything approaching the level of mate choice and the resultant secondary sexual ornamentations that has been demonstrated in some butterflies, odonates (dragonflies and damselflies), or other animals.

For a variety of reasons, the exaggerated secondary sexual traits that seem to emerge in classical examples of sexual selection (i.e., the tail of male peacocks) seem to be less likely to develop in eusocial insects (for a more in-depth perspective on this, check here, here, and here). In lekking species, there is likely to be a very important trade-off between the relative sizes of the flight muscles and the testis and ovaries. Some species of ants do not lek, and either engage in within-nest mating (intranidal mating: for example, some Cardiocondyla exhibit this incestuous behavior), and others engage in "mate-calling," like some moths. For these species, ability to give off (for the females) and recognize mating cues (for the males) is likely to be selected upon, but, to the best of my knowledge, selection on particular traits in these species has not been selected upon. By Stearns and Hoekstra's definition, sexual selection is likely to occur in any sexually-reproducing species, regardless of escalating selection for mate-choice.

Macro-evolution
I'll defer to Stearns and Hoekstra again for their definition of macro-evolution: "The pattern of evolution at and above the species level, including most of fossil history and much of systematics." By this definition, macro-evolutionary patterns are evident in any taxon above the species level, for example, the fact that genera such as Pheidole, Strumigenys, and Camponotus have many species, while Paraponera, Tatuidris, and Rostromyrmex have very few species is a macro-evolutionary pattern. More ant genera than usual seem to have arisen when the earths terrestrial vegetation came to be dominated by flowering plants, which is another macro-evolutionary pattern.

Traits can also exhibit macro-evolutionary patterns: ants are all eusocial - we don't know of any solitary ants. Asexual reproduction has cropped up several times in a variety of ant lineages, but does not seem to have persisted beyond a speciation event. The ability to cultivate fungus has only occurred once in the ants. The processes that gave rise to these patterns are somewhat outside of the realm of macro-evolution, but the justification for using the term "macro-", instead of referring to these patterns as just plain old "evolution," is that they cannot be predicted by an understanding of intra-specific evolution alone. This is analogous to the anti-reductionist argument that cell biology cannot be usefully predicted by chemistry alone--simply understanding osmosis and organic chemistry would not allow us to predict the utility of sexual reproduction, which in some situations can give rise to heterogamy, which in turn drives the emergence of a fertilization envelope, uniparental organelle inheritance, and, in one case, the tail of the peacock. In another case, irreducible patterns and processes random-walked their way to the population of weird little wasps that would become the ancestors of all ants.

As I said at the outset, one would need quite a bit more time and space to fully answer your questions, but I hope I've at least given you some food for thought.

best,
Jesse Czekanski-Moir & the AntAsk Team

Hello,

How come when it gets really hot ants are still able to run around on bitumen and pavers without burning their feet?

Regards
Anna W
-------

Dear Anna,

Although the thermotolerance of ant tarsi (feet) on hot bitumen or pavement has not been directly studied, there are a few biomechanic studies out there that can help us make some educated guesses.

Part of the reason ants may be able to run quickly over hot pavement is that their tarsi are composed of sclerotized chitin, which is a really tough polymer of many connected glucose molecules. The toughness of this biomaterial is often compared to the keratinized tissue seen in vertebrate hooves--such as horse hooves--many of which are also able to walk on hot bitumen and pavement. This is very different than human feet, which have many nerves and soft, burnable tissue on the bottom of our feet. Yet, even humans can walk on hot pavement if repeated friction and pressure forces the formation of calluses that insulate the sensitive tissue in your foot from the pavement.

While this explanation helps us understand how ants don't burn their tarsi (feet), it does not get around the larger of issue of how the ants on hot pavement deal with the increased body temperature (ants are small!). Well, as it turns out, there are some extremely interesting studies on ants that have adapted to hot, dry environments. One ant in particular--the Sahara Desert ant (Cataglyphis bicolor)--has adapted such a high thermotolerance that its proteins can operate at higher temperatures (4-5 degrees Celsius) and it can forage normally at body temperatures above 50C or 122F. Considering this ant makes a living by running on the hot sand to find and consume insects that have died of heat exhaustion, it makes sense that it can withstand this heat. While you wouldn't commonly find Cataglyphis running on pavement, there has been recent research showing that ants found in urban and suburban areas are more likely to come from hotter, drier habitats because of the prevalence of open areas in the urban and suburban landscape. Thus, it is logical that the ants you see running around on pavement might have also have some thermotolerance themselves!

Thanks for your question,

Max Winston & the AskAnt Team

Acacia-ant mutualism?


Hi there.

I am a science teacher who traveled to Northern Kenya in July. While in Ndonyo Wasin (near Archer's Post), I observed many ant mounds under acacia trees. I was wondering if you could identify the type of ant that built this mound. I am also interested in learning more about their mutualism. I am writing a science curriculum about the environment that surrounds our sister school there, and would really love to learn more about the ants that inhabit the region. Any help would be greatly appreciated.

Thanks,
Maria
**********

IMG_0381.JPG


Dear Maria,

The mounds in your pictures were made by termites, not ants. They are potentially interesting for their complicated caste system and symbiosis with certain fungi, similar to Attine leaf-cutting ants in the Americas.

However, I am guessing that the mutualism you are referring to is that between acacia trees and ants, not between termites and fungi. Such relationships do occur in Kenya between Acacia drepanolobium and three species of ant in the genus Crematogaster and one species in the genus Tetraponera. Unfortunately, the plant pictured here is not an Acacia drepanolobium, but that does not mean they are not present in the area. These plants typically grow on "black cotton" soils and are often the only overstory plant in the area.

Acacia drepanolobium trees are very easy to identify because they are full of hollow swollen thorns and are typically rife with ants, as in the picture below.

IMG_5797.jpg
Photo by Eric Denemark

The basic idea behind the mutualism is that the plants grow the hollow thorns pictured as well as extra-floral nectaries and protein-rich food bodies. Ants nest in the thorns and feed on the nectar and food bodies and in exchange, they aggressively protect their host plants against herbivores. The ants are so effective that they can even protect their plants against elephants (Goheen and Palmer 2010)! The ants will not nest anywhere else and without ant residents, the acacias are quickly destroyed, making the mutualism obligate. Both organisms involved are completely dependent on each other. However, when researchers (Palmer et al. 2008) used fences to exclude large herbivores from a plot of acacias for a period of ten years, the plants actually stopped producing resources for the ants, because they no longer needed their protection. Without their host plants, these ants have nowhere to nest. This is yet more evidence that the extinction of single species can have wide-ranging and unexpected results.

In reality, the acacia-ant mutualism is much more complex than what I have outlined. For example, there is a high level of competition between ants of both the same and different species for nesting space because nearly every tree is occupied and founding new colonies or expanding current colonies necessarily means that confrontation must occur. The dominance hierarchy between species is closely related to average colony size (Palmer et al. 2000). No single ant of a species involved here is much better at fighting than any other ant so the largest colony usually wins. Ants also provide differing levels of protection to their hosts so plants experience different benefits depending on who is nesting in their thorns.

If you do find these plants and ants in the area, I would strongly encourage you to incorporate them into your curriculum. The four species of ant are easy to tell apart by the shape of their body and coloration of segments. See how the first two segments are red and the last segment is black in the ants in the picture? That means they are C. mimosae. C. nigriceps is black, black, red and C. sjostedti is all black. The single Tetraponera species, T. penzigi is also all black but has a long and thin body unlike the stocky Crematogaster species.

As you may have guessed, a lot of research has been done on the Kenyan acacia-ant relationship, predominantly by Todd Palmer's research group at the University of Florida and Maureen Stanton's group at the University of California Davis. I have listed a number of their publications below but you should definitely check out their websites as well. They have been featured in quite a few popular science articles that may be useful.

Thanks for your question and good luck,
Ben Rubin, James Trager & the AntAsk Team

Goheen JR, Palmer TM. 2010. Defensive plant-ants stabilize megaherbivore-driven landscape change in an African savanna. Current Biology 20, 1768-1772.
Palmer T. 1994. Wars of attrition: colony size determines competitive outcomes in a guild of African acacia ants. Animal Behaviour, 68, 995-1004.
Palmer TM, Brody AK. 2007. Mutualism as reciprocal exploitation: African plant-ants defend foliar but not reproductive structures. Ecology 88, 3004-3011
Palmer TM, Stanton ML, Young TP, Goheen JR, Pringle RM, Karban R. 2008. Breakdown of an ant-plant mutualism follows the loss of large herbivores from an African savanna. Science. 319, 192-195.
Palmer TM, Young TP, Stanton ML, Wenk E. 2000. Short-term dynamics of an acacia ant community in Laikipia, Kenya. Oecologia, 123, 425-435.
Stanton ML, Palmer TM. 2010. The high cost of mutualism: effects of four species of East African ant symbionts on their myrmecophyte host tree. Ecology 92, 1073-1082
Stanton ML, Palmer TM, Young TP. 2002. Competition-colonization trade-offs in a guild of African acacia-ants. Ecological Monographs, 72, 347-363.

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