Shooting down a widely held scientific myth

Standard
Bullet ant image by Benoit Guenard

Bullet ant image by Benoit Guenard

Science is full of ideas that people somehow accept to be true, just because people say it’s true. We’ve all heard wonderful just-so stories that are waiting to be dispelled by data.

Let me tell you about three myths.

The first myth was that gastric ulcers are caused by stress. All kinds of medical treatments were predicated on this notion. When a researcher figured out that gastric ulcers were caused by bacterial infection, it was considered so outlandish that he had to infect himself to convince the medical research community. (In 2005, the Nobel Prize was awarded for this finding.)

For the second myth, consider the three-toed sloth. For about a century, it’s been said they specialize on Cecropia leaves. One twist on the story is that that the trees are tastier to sloths because they have weaker chemical defenses, because the plants are defended by ants. Then, in the 1970s, two biologists radio-tracked sloths for a couple years in Panama and found that yes, they eat Cecropia, along with many other plant species. If you track them with radio collars, then you get to see that they are not Cecropia specialists.

The people who radio-tracked the sloths did not receive a Nobel Prize. Continue reading

Ant science: Thieving ants know how to be sneaky

Standard
Ectatomma ruidum. Image by Alex Wild

Ectatomma ruidum. Image by Alex Wild

The most recent paper from my lab is a fun one. We show that thieving ants have a suite of sneaky behaviors, to help them avoid being caught in the possession of stolen goods. These differences are dramatic enough to classify thieves as a distinct and new caste of ant.

Continue reading

Ants With Superhero Powers and Real Ant-People

Standard

As an ant man, I’m psyched for the release of Ant-Man.

There are so many ants with real superpowers, that we know about because of amazing Real Ant People, genuine ant savants. Let me tell you about some ants with amazing superpowers.

Two classic superhero powers of ants are flight and invisibility. Continue reading

Can stealing from your neighbor be a mutualism?

Standard

Imagine that your neighbor sometimes goes into your house and takes some food out of your fridge. Sometimes you catch her, but you don’t get violent about it, you just push her out and tell her to not come back. But she keeps sneaking in.

Imagine that you’re also stealing food from your neighbors. Imagine that everybody in your neighborhood is stealing food from one another. Continue reading

Experiments can sell your science, even if they’re not going to work

Standard

We typically need manipulative experiments to truly know how a biological system works.

Nevertheless, on most days, I feel that the subculture of ecology suffers from a fetish for manipulative experiments. In some cases, people design experiments that don’t entirely make sense because they know that the reviewers and the community will value that experiment more than observational research. Even if the experiment isn’t really that informative. Continue reading

What happens in the canopy stays in the canopy.

Standard

For a few years, I’ve harbored a very cool (at least to me) natural history idea. But it’s a big technical challenge. The required fieldwork is never going to happen by me. So, I should write a blog post about it, right?

Bullet ants (Paraponera clavata) are one of the most charismatic creatures in Neotropical rainforests. My lab has done some work with them recently. These often-seen and well-known animals are still very mysterious. Continue reading

Ant foraging diversity: a simple and elegant explanation

Standard

Science can be creative and elegant.

To illustrate this fact, I want to bring to your attention a groundbreaking review paper that was recently published in Myrmecological News, written by Michele Lanan of the University of Arizona.

Usually the terms “groundbreaking” and “review paper” aren’t paired with one another. Review papers usually codify existing ideas, propose some new ones that may fall flat. And, if you chat with an editor, you’ll learn that good reviews really improve a journal’s impact factor.

Then there’s this amazing review I loved so much I had to write this post about it. Even if you don’t know a thing about ants, I’m betting you’ll love how the paper draws a clear and simple explanation from complex interacting phenomena.

Ant people are asked about foraging behavior quite often. How and why do ants make trails? Why do some species make trails and others don’t? Until now, our answers were vaguely correct but relied heavily on generalizations. Now, after Michele Lanan scoured pretty much every paper that’s ever collected data on foraging behavior and ecology, we have a quantitative and robust explanation that is powerfully simple and elegant.

We’ve known that foraging behaviors are structured by that ways in which food is available. Among all ants, there’s a huge variety of foraging patterns. Some are opportunistic hunter-gatherers, others are nomadic raiders, and some use trunk trails, as in the figure below. These patterns reflect differences in food availability.

Figure by M. Lanan

Figure from M. Lanan 2014, Myrm News 20:50-73.

How, exactly, is it that the properties of food availability can predict how ants forage? In an analytically robust and predictable manner, that works for all ants throughout the phylogeny? It doesn’t require an n-dimensional hyperspace to understand foraging patterns of ants. It only needs a 4-dimensional space.

figafromms

Figure from M. Lanan 2014, Myrm News 20:50-73.

Lanan took into account four properties of food items: size, spatial distribution, frequency of occurrence, and depletability. She arranged these variables along four axes (as on the right), and showed how this this 4-dimenstional space foraging patterns in the figure above.

How do these foraging patterns distribute across the major ant subfamilies? Are some lineages more variable than others, and what might account for these differences? What other beautiful figures and photographs are in the review that illustrate the relationship between spatiovariability of food and foraging biology? As they say on Reading Rainbow, you’ll have to read the review to find out!

Reference: Lanan, M. 2014. Spatiotemporal resource distribution and foraging strategies of ants (Hymenoptera: Formicidae). Myrmecological News 20: 50-73.

As a disclaimer, I should mention that the author of this paper is a collaborator and friend of mine. And she is leading The Ants of the Southwest short course this summer which I’m also teaching — and spaces are still available!

But that’s not why I’m featuring this paper. I am enthusiastic about this paper because it so obviously resulted from a labor of love for the ants, and is a culmination of years of reflection. This is just a downright gorgeous piece of science, and the more people that see it — and the more recognition that the author gets — the better.

The field ecology of a gut microbe inside bullet ants

Standard
The bullet ant Paraponera clavata. Image by Alex Wild.

The bullet ant Paraponera clavata. Image by Alex Wild.

This is the latest paper from my lab, which I’m really excited about. When we designed the project, several people told us that it would be useless. “It’s pointless to study the ecology of a symbiotic microbe in the wild when we have yet to specify its function inside the host.” It was only two days ago that Meg Duffy said that the microbiome is the most important recent conceptual advance in ecology, and I agree with her. That’s one of the reasons we did this project, to look at the ecology of gut microbe in the wild, which appears to be a true frontier.

There are plenty of advances that are yet to be made in the field biology of microbes, and these discoveries do not have an a priori requirement understanding of the comprehensive biology of an organism before understanding its ecology.

The microbial contents the guts of bullet ants are remarkably heterogeneous. In some colonies of bullet ants, we found oodles of a particular Bartonella microbe, closely related to those that facilitate N cycling in other animals. And most closely related (as far as we know) to other Bartonella inside ants on other distant continents. But, many bullet ant colonies lack this microbe. Perhaps not by accident, bullet ants have a remarkably varied diet, and some colonies eat more insects than anything else, and other colonies are functional herbivores. Perhaps the presence of this N-cycling microbe might be associated with – or even respond to – the trophic position of the ants?

Aren’t we getting ahead of ourselves by studying how diet affects microbes in the wild, when we don’t know what the microbes do? I say, phooey. Most of the ants that we study in tropical rainforest are just as mysterious as microbes. We don’t even know what most species of ants even eat! Nobody tells me I can’t study the ecology of ants without doing a comprehensive study of their diets and relationships to other organisms in the ecosystem. So, why do we need to know exactly what the role of microbe is in the gut of an animal before working to understand its distribution and ecology?

Working out the function of these microbes is mighty damn hard, if not impossible at the moment. But we can understand the distribution of these critters among colonies of ants an understand the environmental factors that shape its occurrence, as well as doing experiments to see how we can make incidence increase or decrease.

So, we ran an experiment that gave the ant colonies supplemental carbohydrates, or supplemental protein. (This was not easy at all, though you might think it would be. A post on this is forthcoming.) And we checked to see if how the microbes responded. It turns out that when you feed colonies sugar, this microbe becomes more prevalent. Moreover, the results from the manipulation recapitulate the ambient relationship between diet and microbial prevalence. Some colonies consistently collect more sugary nectar from the canopy than other colonies. (Learning this involved going out into the forest in the middle of the night, for an entire summer, to measure bullet ant colony diets.) The colonies that collect more nectar are more likely to have this microbe. So, we can clearly conclude that a sugary diet is predictive of the incidence of this particular Bartonella inside bullet ants.

And the stable isotopes tell an interesting story, too.

So what does this mean? While most ant species that forage in rainforest canopies are functionally herbivorous, bullet ants are true omnivores. They also don’t have the specialized obligate N-cycling microbes that the more herbivores canopy ants have. We found that the close bullet ant diets get to their competitors in the canopy, the more likely they have this facultative N-cycling microbe. If we’re trying to understand how the evolution of obligate sugar-feeding evolved among the dominant ants of rainforest canopies, then I suggest that understanding the ecology of the facultative bullet ant/Bartonella association is to get a window into the evolution this form of dietary specialization.

How this project happened inside a teaching institution

This was the Master’s thesis project of Hannah Larson. Hannah came to my lab with a specific interest in doing field ecology. Based on preliminary finds predating her arrival, Hannah and I developed this project in collaboration with Shana Goffredi, our microbial ecology collaborator. After taking courses for a semester, Hannah headed to the rainforest for eight months to conduct this project at La Selva Biological Station. Hannah found, marked and measured over a hundred bullet ant colonies (which became the start of a long-term monitoring project), and overcame a series of challenges in getting the molecular work done in a rainforest field station (with substantial help from our collaborating lab at the University of Costa Rica). Undergraduate Erica Parra is the one who (by her own choice I should point out) spent long nights in the pitch black of the rainforest at the base of actively foraging bullet ant colonies. The work was funded by an NSF-IRES grant OISE-1130156, though we scrambled for additional funds for reagents that were not in the project budget.

Reference:

Larson, H.K., S.K. Goffredi, E.L. Parra, O. Vargas, A. Pinto, T.P. McGlynn. 2014. Distribution and dietary regulation of an associated facultative Rhizobiales-related bacterium in the omnivorous Giant Tropical Ant, Paraponera clavata. Naturwissenschaften. DOI: 10.1007/s00114-014-1168-0

You can find a copy of this paper on my lab’s website.

Today is Taxonomist Appreciation Day!

Standard

Many fields of science are important, and many fields of science are appreciated.

The field with the greatest importance : appreciation ratio is taxonomy.

bhr_anders_pun2

BuzzHootRoar made this!

Taxonomy is critical for almost everything we do in biology, but few demonstrate appreciation for the hard work and expertise that is required for useful taxonomy to happen. Let’s change that!

We are deep in a taxonomic crisis. Our own species created the planet’s sixth major extinction event and we are lacking the expertise to understand what we are rapidly losing. Taxonomic work is the foundation for understanding how to save what we can and make plans for the future. Any fix to the taxonomic crisis requires a recognition of the essential nature of the work of taxonomists and systematists, and the value of museum collections and those who use them to explain our world. We must show taxonomists how much they’re worth to us. We need to back this up with the necessary resources, of course, but we all need to be showing them a lotta love too.

I’d like to write a bit about the taxonomist that’s made my work possible.

As an ecologist, most of what I do is only possible because because of the unfathomably detailed and dedicated work of one systematist and all-around-great guy, Jack Longino. I don’t even know where to begin with the awesomeness of Jack, and of what he’s done. En route to a bevy of discoveries in evolution and ecology, he’s provided a comprehensive picture of ant biology throughout Costa Rica, as well as Mesoamerica and beyond. Of course there’s always more work to do, and a lot of that is only possible because of the foundation of his natural history and systematic work.

Jack Longino worked on the ants of La Selva Biological Station under the umbrella of the ambitious Alas Project: The Arthropods of La SelvaWhile heading up (in part) this huge project funded by a series of four NSF grants, he focused on ants. In the process, he made the most comprehensive and easy-to-use guide to identifying ants to species for anywhere in the tropics, perhaps the world. In fact, it is easier for me to train a student to identify an ant in the rainforest of Costa Rica than in my home in California, because the tools that Jack created are just so perfect to get ants to species. And when you get to a species page, you get detailed natural history notes of the biology of the species, including the rare ones. (For great examples, check out his notes on Gnamptogenys banski and one of my favorite critters, the gypsy ant Aphaenogaster araneoides.) In recent years, he’s ported over to the globally comprehensive site Antweb, and expanded his range throughout Mesoamerica and northern South America. Which is much cause for rejoicing among myrmecologists in these areas. And NPR, too.

And, a spectacular part of all this is that he did this while serving on the faculty of The Evergreen State College. I’ve seen him in the field with students on several occasions, and he’s a thoughtful, attentive, realistic and enterprising mentor. (He’s recently moved to the University of Utah.) And whenever I have questions for him, he’s prompt, detailed and doesn’t even seem to mind. I don’t know how to make a taxonomy pun out of this, but he’s 100% class.

So when he went on an expedition sampling ants throughout remote areas of Mesoamerica, he took a bunch of undergraduates. Some of whom made this wonderful animation showing what an ant sampling field expedition looks like:

Acknowledgments: This year’s pun contest by BuzzHootRoar generated some great art and new attention to the importance of taxonomy for ALL of us scientists. I came up with the idea for Taxonomist Appreciation Day on a half-whim last year, but I’m serious about it. It’s an idea whose time has come. And I am so thankful for the people who’ve helped picked up the idea and shared it, including BuzzHootRoar, the NSF Division of Environmental Biology, and Alex Wild, and hopefully many more of you today. (If you’re a twitter person, #loveyourtaxonomist is the not-so-secret handshake.) The Smithsonian Department of Invert Zoology came up with an aptly timed post (beware: contains comic sans). Next year, let’s have a bigger and better Taxonomist Appreciation Day! I’m open to all kinds of ideas, in addition to the great ones of DEBrief.

Ant science: Ants try to eat protein beverages like solid food

Standard

Collectively, ants are efficient, and you might even call them smart. But individual ants are so dumb that they don’t even know how to feed themselves, as we show in the latest paper to come out of my lab. You could say that these ants have a drinking problem.

A bullet ant with a bubble of sugar solution in its mandibles. Image by Alex Wild

A bullet ant with a bubble of sugar solution in its mandibles. No scale bar is needed; this ant is about the size of your pinky finger, unless you have a small hand. Image by Alex Wild.

If you’re given a protein smoothie, you drink it. But if you give bullet ants a protein drink, they chomp and pull at it. If they knew how to use a fork, they’d probably try that, too.

The bullet ant Paraponera clavata has a boring diet: workers mostly collect sugar water from the rainforest canopy, supplemented with chunky prey items, like other ants and pieces of caterpillars. When they eat carbs, it’s in the form of a liquid which they gather in a droplet held by their mandibles. When they get protein, it’s in the form of a solid which they chomp and bite.

While attempting to do an experiment, we discovered that these ants are absolutely hopeless at drinking a liquid, if it’s a protein solution.

What does it look like when ants try to drink something and when they try to chomp at solid food? Here are two very short videos taken by Jenny Jandt:

We asked: what sensory cues do the ants use to decide whether to drink a fluid or to grasp at it as if it were a solid? We ran a field experiment with factorial combinations of various sugar (sucrose) concentrations and various protein (casein) concentrations, and used ethograms to measure behavioral responses. We replicated this across a bunch of colonies, randomized the order of presentation, and did other good stuff to make sure the experimental design wasn’t messed up. (We’re pros, you know.)

We mostly didn’t get stung while running the experiment. This matters because they are called “bullet ants” for good reason.

We found that the higher the concentration of sugar, the more likely the ants were to drink. If there was a little protein and no sugar at all, the ants would most likely grasp.  Once protein concentrations got near 1 micromolar concentration, however, the concentration of sugar did not affect the grasping response to protein.

So, if these ants are thinking, then this is what they’re thinking to themselves: “If I taste protein, it must be food. So I’ll chomp at it, even though it’s a liquid.” But, it doesn’t look like they’re thinking much at all.

We found that the ants demonstrate a fixed action pattern of feeding behavior in response to assessing the nutritional content of food. This operationally works for them in nature, because texture and nutritional content are coupled. When we experimentally decoupled texture and nutritional content, then we were able to identify the cues that the ants used to make their food handling decision. They decide to drink when they detect carbohydrates and they decide to chomp when they detect protein, and texture has little to do with the decision.

How this project happened in a teaching-centered institution

In the first half of 2011, Hannah Larson (a Master’s student in my lab) was spending several months at La Selva Biological Station in Costa Rica, working with a microbial symbiont of bullet ants. She discovered the phenomenon of bullet ants chomping at protein solutions when she tried to experimentally feed colonies a protein solution, and the colonies opted to dismember the plastic pipets instead of drinking from them. She worked out other ways of delivering protein for her experiments, but we wanted to document and further understand this discovery.

That summer, I paired up my colleague Dr. Jenny Jandt up to mentor a student from my university on a totally different project. We all found this protein-chomping behavior so cool, and Jenny made the time for a second trip to Costa Rica after I helped her flesh the project out. My undergrad Peter Tellez was her wingman, and they did the experiment using the template of the many colonies that Hannah established for her thesis work. In late 2011, I drove out to visit Jenny in Tucson for a couple days, to work on this and another manuscript, in which the bulk of the paper was put together. Jenny put the finishing touches on this paper with just a bit of help from myself, Hannah and Peter. As it was a side project for all of us, it lingered a bit but Jenny persisted and she’s pretty much everything I could ask for in a collaborator and mentor to our students.

Where are they now? Jenny took a postdoc in the rockin’ lab of Amy Toth at Iowa State. Hannah is now in her second year of the DPT program at the Univ. of Washington and Peter is now a PhD student in the lab of Sunshine Van Bael at Tulane.)

In short, this cool paper came together because I was able to talk my postdoc buddy Jenny into coming down to the rainforest to work with my students for about a month. She is otherwise a wasp and bee behavior person, and I was glad to give her an avenue to work with ants and tropical rainforests, and my students greatly benefited from her careful mentorship and expertise in individual and collective behaviors of social insect colonies.

Reference: Jandt, J., H.K. Larson, P. Tellez, and T.P. McGlynn 2013. To drink or grasp? How bullet ants (Paraponera clavata) differentiate between sugars and proteins in liquids. Naturwissenschaften. DOI: 10.1007/s00114-013-1109-3

A copy of this paper is available on my lab website here.

This work was conducted under support of the National Science Foundation (OISE-0854259 and OISE-1130156).

The conflict-cooperation model of faculty-admin relations, Part 3: How our universities run like social insect colonies

Standard

With the understanding that we are social animals and that principles of behavioral ecology for social groups can apply to us*, let’s look at six relevant concepts from ant societies.

1. Workers are in charge of ant colonies; faculty are in charge of universities. The stereotypical, and false, model of ant colonies is that they’re run by the queen. In fact, workers are the ones that are collectively running the show. The queen is the factory that produces eggs, but the workers actually benefit more from the reproduction of the queen than the queen herself (in terms of raw genetic relatedness). A queen is as much a slave of her own offspring than she is the leader of a band of her daughters. I’ll spare you the social insect lesson in detail, but the upshot is that most colony-level decisions are made collectively among the workers and the queen has little to no say in the matter. The queen is just along for the ride, and her life can be truly at risk if she doesn’t lay the right kind of eggs (by using the wrong sperm, or choosing to not use sperm at all). In universities, professors run the show, even when there is little true faculty governance. Even with a heavy-handed administration, we faculty control what happens. The best that admins can do is provide, or remove, incentives for particular activities. Regardless, faculty will do as they please. The good administrators recognize this fact and work within its bounds.

2. Limited resources affect how ant colonies compete with one another; limited resources predict how universities compete with one another. From the perspective of admins, universities are competing with one another for status and funding. Colonies under extreme resource limitation allocate their resources very differently than those that are not those limitations. Unpredictability of resources also affect allocation decisions. The way in which colonies compete with one another is structured by the ways in which resources are limiting.

3. Workers and queens have different interests in how the ant colony invests resources; admins and faculty have different interests in investing resources. It’s a longer story, but the upshot is that workers want different things than the queen. That’s a textbook conflict of interest, though slightly overgeneralized. (Find your local social insect biologist for a longer lesson.)

To make this messier, the workers themselves may not even be closely related to one another, because queens often mate with multiple males and colonies can have multiple queens. Many social insect colonies have behavioral bedlam at their core, with torn allegiances, nepotism, assassinations, and workers policing one another to make sure that they don’t cheat. The harmonious work-together-for-a-common-cause is a thin veneer that disappears once you start watching carefully.

In a university, faculty often have interest interests or agendas for resource allocation, so they can’t all agree. If the faculty can’t organize in a common agenda, then the administrative agenda is often the one that wins. When faculty with conflicting agendas can agree on shared priorities and can communicate these, they have a chance at winning in a conflict over resource allocation, if unified. When faculty are divided, then the ones who win are those whose priorities are consonant with the administration.

4. In ant colonies, the queen controls the productivity of the colony, but the workers have ability to shape that productivity; In universities, admins distribute funds but faculty members are the ones that make those funds go to work. Queens can control the ratio of male eggs and female eggs that she lays. The workers then can choose to help those eggs grow, or eat them. Likewise, administrators can spend all kinds of money on useless initiatives, but they will go to waste if they’re not useful to faculty.

5. While there is conflict in ant colonies and in universities, there is plenty of cooperation. By banding together in a colony, the fitness of any single individual is much greater than it would be if they were on their own. Colonies that don’t effectively work together have lower fitness, and then everybody would be worse off. Wise administrators will recognize that providing faculty with the resources that individuals need to be successful will contribute to higher levels of productivity at the level of the organization. Wise faculty members will recognize that flexibility in using the resources available from administrators, even if not efficiently allocated, is better than intransigence.

6. Developmental constraints have resulted in the exploitation of workers. Natural selection has favored the evolution of cooperation in ant colonies, however in “highly eusocial” groups that have worked cooperatively for a jazillion generations, there are likely to exist developmental canalizations and constraints that may result in workers that have no choice but to cooperate in a way that isn’t working in their best interests. If your mom creates you without ovaries, then well, you better help her reproduce, because otherwise you have no affect on your fitness whatsoever. (Note that this is not a fact that social insect researchers consider as often as they should.)

Likewise, universities have developed a system that exploits their workers that have little to no power to address inequitable distribution of resources. The conversion of teaching faculty into a caste of contingent employees without a voice in institutional governance has resulted in an excess of power in the administration that does not necessarily work in the best interest in the members of the community.

Next week: The consequences of our sociality.

*If you harbor some old-school critique of sociobiology, please take it elsewhere.

Ant science: how avoiding modeling led to a cool discovery

Standard

Here’s a specific example, from my own work, of how the avoidance of mathematical modeling led to a fundamental discovery that eluded modelers and experimentalist for decades.

At least, that’s how I see it when I’m not feeling humble. It’s about resource allocation in ants, not the grand unified theory, after all.

For context, for those newer to the site, consider this post as a coda to an ongoing series (and discussion of sorts with Dynamic Ecology) about approaches to designing a research program. I have advocated that exploration by tinkering with unexplained curiosities within natural systems often leads to the best discoveries as well as the most consequential research programs. This post from a few weeks ago provides a good summary of that series. Another precursor to this post is a discussion about the relationship between mathematical modeling, hypothesis development, and how much math you need to become a scientist.  That is also a precursor to this post, though it is a “long read,” for those averse to verbiage.

The subject of this post — the scientific discovery — came out in a paper last year (go read it if you wish), which I wrote with Sarah Diamond and Rob Dunn. In short, we discovered a fundamental pattern that could have been obvious to everyone, if anybody just looked in that direction. This pattern explains many unanswered ideas, going back to theories that E.O Wilson developed in the 1970s, along with George Oster.

A twig nest of Pheidole sensitiva. Photo: Benoit Guénard

A twig nest of Pheidole sensitiva.
Photo: Benoit Guénard

Oster & Wilson set out to understand what regulates the varying levels of investment into the different members of ant colonies. Most inhabitants of ant colonies are functionally sterile, and in some species, there are multiple physical castes of sterile ants.

The genus Pheidole is the most species rich ant genus, and they’re found pretty much everywhere. All Pheidole (aside from a few exceptions) do something that isn’t found in many other lineages: they have two discrete sterile worker casts. They make big-headed soldiers and tinier minor workers, both of which do a variety of work for the colony. Some think that this dimorphic worker caste, and potentially the flexibility tied to its production, has enabled these ants to not only become ecologically successful but also to diversify.

Anyhow, Oster & Wilson made a number of predictions about the adapability of the ratio of soldiers to minor workers in Phediole colonies. One of their big testable predictions, or perhaps it could be seen as model to be falsified, is that the colonies actively adjust the ratio of soldiers to workers in response to environmental challenges.

It entirely makes sense. If a Pheidole colony is in an environment that requires more soliders, they would make more soldiers. Right? The problem is, despite a lot of looking carefully at Pheidole colonies, this wasn’t found. Finally in the mid ’90s it was found in the lab of Luc Passera, that P. pallidula colonies made more soldiers when they were exposed, without contact, to neighboring colonies. When I say it was found in the lab of Passera, I mean it happened physically in his lab. These were captive colonies.

A similar thing was found in the field in 2002, when I and Jeb Owen published a paper showing adaptive soldier production in another Pheidole species. (Also, my labmate Samantha Messier did the same thing before the Passera group, in a field experiment involving Nasutitermes termites and a machete.) Our studies were done in the field. In my experiment, when I put clumps of supplemental food in the field for months on end, the food was defended by soldiers, and in a short time colonies made more soldiers.

One thing I didn’t mention at the time, though, was that I didn’t find adaptive soldier production in a whole bunch of other species. However, I had less statistical power, and it was the most common species that showed this pattern. Maybe the less common ones did, but it was harder to detect.

If you were to ask around and dig into the literature, you’d see that it’s pretty clear that most species of Pheidole actually do not overtly shift their caste ratios when you mess around with their environment. Not every colony produces the same ratio, but a systemic environmental manipulation doesn’t cause an increase. Other than the two papers I just mentioned, I don’t think anybody else has found adaptive caste ratios in Pheidole. Others have looked, but it hasn’t emerged very clearly.

So, if most species just don’t ramp up and ramp down soldier production in response to the environment, what controls soldier production? For decades, there has been a consistent amount of work asking this question from behavioral, physiological and developmental angles. In the course of all of this excellent work (a lot of it being done by Diana Wheeler, Fred Nijhout, and their associates), we’ve made a lot of progress in understanding how colonies regulate their activity and how development is regulated through genetic, biochemical and physiological mechanisms.

One thing that I’ve always wondered about is, why do some species produce more soldiers than others? I’ve cracked open lots of twigs, and the numbers of soldiers are highly variable. And my experiments have shown that most species don’t obviously change their soldier production in response to environmental changes. There has been lots of great work to understand variation within a single species, but interspecific comparisons have been scant.

I can understand why there hasn’t been much comparative work. Measuring caste ratios of entire colonies can be hard. Find a Pheidole colony in the back yard and compare the number of soldiers and workers. See, not easy, huh? You’ve got to dig them up. Unless, of course, your backyard is a rainforest. In that case, you just pick up twigs. Over the years, I estimate that I and my students have picked up over 106 twigs over the years. Thousands of these have had Pheidole colonies inside. The rainforest is diverse, so I have data on many species. How do they compare?

Well, I learned that the caste ratios were different among species. Some species produced way more soldiers than others. Considering that we know so little about the natural history of these species, there wasn’t a great basis for comparing many of these species to one another. But one thing we could examine, quite easily, was body size. And, as it turned out, that was super-duper predictive of solider investment. Smaller species produced more soldiers than larger ones. When this pattern emerged on my laptop, it was one of those moments of elation that are very cool, but then you don’t have anybody with whom to share.

Then, I dug through the literature so see if the information that we had about caste ratios and body size shows the same pattern that I found in my rainforest. It turns out that the relationship is as identical as you can get. Our local scale pattern recapitulated Pheidole from around the world, and across the phylogeny.

Now, if you ask someone, what controls soldier production in Pheidole? You can say the answer is quite clearly body size. How and why does body size control this? There is some cool work that’s been done on this intraspecifically, that presumably is a mechanism that works more broadly.

How did my discovery of this generalized relationship come about from avoiding models? If you look at the work on soldier production, ever since Oster & Wilson published their monograph in the 1970s, there’s been a strong emphasis on modeling the mechanisms that trigger and regulate soldier production. Meanwhile, nobody before me bothered to step back to look at the big picture and ask, “how are species different and what is predictive of that?” If they did, then they would have found the caste ratio data in the literature as I had, and looked at the most obvious predictor: body size. Others were modeling solider production. I was merely trying to find a pattern.

I’m not claiming that the discovery of this pattern is earthshaking or that it explains mechanistically how colonies make more or fewer soldiers at the proximate level. The main take-home message from this paper is that many of the differences we find are driven by constraints rather than by adaptation, or that selection on body size is coupled with selection on soldier production. This leads to a lot of exciting thoughts about community structure, which we’re now working on.

This work by no means diminishes all of the careful experiments that others have done over the years on Pheidole. Though I’m not a developmental biologist nor as much of a behaviorist, I was able to find something that will be (or at least, I think should be) at the basis of future conversations about the evolution of caste ants.

This is why my choice is to keep asking “What is the pattern?” rather than attempting to model patterns.

My all-time favorite scientific paper

Standard

Current events (E.O. Wilson saying that scientists don’t need to be good at math) give me a great reason to introduce what might be my favorite scientific paper.

I have three reasons for choosing this paper to share with you. One minor reason is that, from one ant man for another more illustrious ant man, I’d like to be one of the few scientists to publicly say something nice about E.O. Wilson this week without any kind of caveat.

Second, the content of this paper, and the fact of its existence, frames Wilson’s message about science and math that dovetails with my recent writing on how to design a research program.

Last, since this paper was published it has been a source of inspiration to me as a scientist.

Without further ado, here’s the paper:

Wilson, E.O. 2005. Oribatid mite predation by small ants of the genus Pheidole. Insectes Sociaux 52: 263-265. There is a paywall – email me if you’d like a copy.

Here is the abstract of this three-pager in its entirety:

Using “cafeteria experiments” with forest soil and litter, I obtained evidence that at least some small Neotropical species of Pheidole prey on a wide array of slow-moving invertebrates, favoring those of approximately their own size. The most frequent prey were oribatid mites, a disproportion evidently due in part to the abundance of these organisms. The ants have no difficulty breaking through the calcified exoskeleton of the mites.

What is the deal with this, and why is it inspirational? Please humor me by reading on if I haven’t lost you already.

This paper was published in the year 2005. In 2003, after several decades of effort, Wilson had published a monumental revision of the most species-rich genus of ant, Pheidole. Any taxonomist can appreciate the sheer enormity of this effort that had Wilson’s attention over the years. Clearly, it’s a work of love. Most Pheidole are tiny in size. They’re charming little ants, if nondescript, and not really different from one another in obvious ways that could account for their richness.

Like most years, 2005 was a good year for Wilson. He wrote three PNAS papers, two with his long-time friend and colleague Bert Hölldobler. He also wrote a controversial paper in Social Research arguing that altruism doesn’t principally arise from kin selection, a precursor to Wilson’s now full-fledged group selection posture. He had a book chapter come out, oh, and also he published a big book introducing the concept of gene-culture coevolution. And then there was this little paper, one of my favorite papers ever, in Insectes Sociaux.

If you want to understand and measure the diversity of ants, the first place to start is to sample the leaf litter. A whole book has been written about how to do this, actually. That’s where the action is, in terms of functional and taxonomic diversity. Pretty much wherever you go on the entire planet, the most common thing that you’ll find in the litter is Pheidole. They’re cosmopolitan, if not sophisticated. If the importance of a taxon is measured by its diversity, abundance and distribution, then Pheidole are the most important ants. (I guess you could argue for carpenter ants, too. But why? They’re so boring.)

Wilson has argued time and time again that ants are really important, they rule the world, they have the same biomass as people, and all that stuff. So, since Pheidole are the ants that rule among the ants, then we’ve got to really have figured out these ants, right? After all, they’re easy to find, they show up at baits, they’re easy to work with.

So what can we, as the community of ant biologists, tell you about the natural history, life history and habits of these Pheidole that live in leaf litter? Here’s a quick list of features:

  • _
  • _
  • _

That’s only a slight underexaggeration.  Okay, so, I can at least tell you what they eat.

No, I can’t.

Actually, I can.  Why? Because E.O. goddamn Wilson, at 79 years of age, after reaching the pinnacle of his career twenty different times and receiving every honor you could invent, decided to do the little experiment to figure this out. He wrote it up as a sole authored paper in a specialized journal.

It turns out they love oribatid mites. Now you know.

(This is not insignificant, actually, for the field of chemical ecology. Two years after the Wilson paper, Ralph Saporito sorted out that mite alkaloids end up in ants, which end up in poison frogs as their chemical defenses. The frogs also eat the mites directly, too.)

Wilson had spent decades slowly churning on the revision of Pheidole. After spending all that time at the scope and in the museum sorting out the genus, he can’t be blamed for thinking, “what do we know about these ladies after all?” Instead of just wondering, he did the experiment. You gotta love that spirit.

It’s rare for a midcareer PI of a typical lab to do a little experiment of one’s own like this and take the time to write it up. And then there’s EO Wilson doing his own experiments, among a string of high-profile papers, books, gala appearances and being a reliable stand-up mentor to junior colleagues. This communicates an unabashed love for these ants, for discovery, for natural history, and for answering unanswered questions wherever they lead you. Wilson is the consummate tinkerer.

This paper is by no means an outlier. Studies like these pepper his CV, sandwiched with his major theories and findings. To me, these are the actual meat of the sandwich. (Or tofu or something. I don’t eat meat.) To those of us who study ants, that’s what makes Wilson a rockstar. He’d be super-awesome without any of the books and big theories formulated by collaborations with mathematicians. His productivity, keen sense of natural history, an eye for observation and an interest in discovering questions as well as answers has been a trademark of his ant-centered work. The man loves ants, and it shows.

When this paper had come out, I had been working on the ecology of litter-nesting ants in tropical rainforests for about ten years. There were many ideas that I was pursuing, and I’m proud of what I’ve done and excited about what lies ahead. This has been rewarding because so little is known about the biology of these animals, despite their abundance and diversity.

After ten years, if you had asked me, so what do they eat? I wouldn’t have been able to tell you. How many zoologists do you know who can’t tell you the diet of their study organism?

Isn’t that odd that I didn’t know what these ants eat? That nobody knew, at all? Hell yes, it’s odd. Wilson saw it was odd. And he did something about it. The publication of this paper was but a speck, if a speck at all, on the face of his career. For those of us who study litter ants, this was very important. Any one of us could have done it. But you know what? We didn’t, while Wilson did.

That’s what badass science looks like, in my book. And it doesn’t require partial differential equations.

Footnote: You might be wondering, by the way, how can you not know what they eat if you work with them all the time? The answer is, essentially, that these are really small ants. A massive colony fits in a microcentrifuge tube, and a smallish one can fit in a 2 cm piece of straw. You won’t see what’s between their mandibles in the wild, and can’t make out the refuse in nests, either.

A field course about ants this summer (some self-promotion)

Standard

Last year, a new field course on ants launched at the Southwestern Research Station, in Portal, AZ, USA called Ants of the Southwest. It got rave reviews, and it’s happening again.  Are you interested in going?

Here’s how to sign up!

The course is designed to provide a generalized hands-on approach to the pragmatics about research with ants. How do you observe and manipulate behavior in the field and in the lab? What kinds of ecological experiments are possible, and how do you do them? How do you collect, identify and maintain a collection of ants? How do you keep colonies in the lab?antsofsw2

There is a diverse set of experienced and talented instructors (in addition, I’ll be there for much of the time).

antsofsw1Don’t mistake this course with the long-running and superb Ant Course run by Brian Fisher from the California Academy of Sciences, which focuses on identification, taxonomy, systematics and building a collection. The Ants of the SW course is a complement to the Ant Course as a different introduction to ant biology, emphasizing ecology and behavior. It’s targeted towards graduate students, but is accessible to folks with other levels of experience.

If you are thinking about using ants as a model system but don’t have years of experience with them, this course would be a great place to figure how to do things, what works and what doesn’t, and will give you the chance to spend time in a community of myrmecologists in a hotbed of ant diversity.

If you have any questions about the course, you can contact me or leave a comments, and of course you can follow the link to the course page and contact the station. I hope to see some of y’all in July!

How tinkering can work as a research program

Standard

This is the fourth and final post in a series, wherein I attempt to make the case that tinkering is a viable, and perhaps optimal, approach to conducting a research program, particularly for those at teaching-centered institutions. Here are the first, second, and third posts preceding the present post.

I’m a tinkerer. That means that I don’t typically design my research to fit the framework of a big theory, but instead I set out to answer a small little question that has occurred to me. I do experimental research, combined with observational research, to find the answers to open questions. I’m just not going after the big fish that other labs do. After all, I work in a small pond.

This is a personal narrative about how tinkering has worked for me. It’s hard to write about the concept in the abstract, so I’m going into the specifics about one line of tinkering I’ve done over the years. If I am going to make the case that tinkering works well for me, it’s easiest for me to to use specific projects to illustrate how tinkering has worked for me. So if you read on, you’ll be reading about ants. Consider yourself forewarned.

When I started as full-time faculty at a teaching institution, I found myself with the position of having a field season in front of me. What did I want to do?

I quickly decided that I wouldn’t continue along the lines of my dissertation, which was on the biology of invasive ants. There were so many questions about biological invasions that were interesting to me, but they all seemed too, well, big. For all of the specific big questions about invasiveness that I wanted to tackle, there were other labs that were going at it at the same time, full time with multiple collaborators, without teaching. (In the end, their work was — and still is — awesome in its creativity and quality, going well beyond my initial interests. In my position, I don’t think I ever could have run most of the experiments they have, at least not on the scale that they did. I admire their work a lot.)

My dissertation was one part of getting the invasive ant bandwagon rolling, but after taking a job at a teaching institution, I needed to find a better ride. I had a few papers that made a difference, by looking at the issue from a broader-than-usual perspective, and it was time to move on.

I knew that I wanted to get back to my field station in Costa Rica. It was a place that I knew well from my dissertation, and it had become kind of a second home to me, and I hadn’t been down there for 18 months. I had a few weeks on site, along with several undergraduate field assistants.

I wanted to pick a project that fit three criteria:

  • The project could be completed in a few weeks
  • The project lead to a modest publication, regardless of what the results were
  • It would be fun

Here was my thought process: This rainforest is chock-full of ants, everywhere. People study them all of the time. But they only study the cool and bizarre ones, like leafcutters, bullet ants, ant-plant mutualists, and army ants. There are hundreds of ants that make the forest run that are overlooked. I wanted to study one of those. So, I picked what I thought what was one of the most common, but unknown, species, and designed a cute little project around it. (By the way, free versions of all the papers in this post are found on my website.)

My main goal was to ask, “What is up with this extremely common species that we know nothing about?” I built it around a question about unpredictable resource heterogeneity, competition, and whatnot, but it was mostly a vehicle to play around, because I knew nothing about this species. And I wasn’t going to go down for a few weeks and not get a paper out of it.

Even though I designed that cute little project to be fail-proof (negative results would still be publishable), I barely eeked that paper out. That was because my sample size was dropping precipitously throughout the short experiment. We started out by marking a bunch of colonies in the field. As days progressed, the colonies flat out disappeared. Their nests were just empty holes. By the end of our experiment, we sorted out that they just moved nextdoor. Over the course of a few weeks, we’d lost well more than half of our colonies, but I didn’t have data on them after they moved.

The next field season — one year later, after my first year on the tenure track — I had a few more weeks with a team of undergrads. I wanted to understand the non-optimality of home range size. I was ready for nest movements, and built it into the experimental design. The answer was kind of interesting: foragers spent more time looking for food before giving up when the home range is of poor quality.

At this point, for two years on the tenure-track teaching a full courseload of new courses, I’ve gotten two okay papers out from two short field projects, while spending time on other projects as well. At the rate of a paper a year, I would’ve been well exceeding scholarly expectations at my university, as a decent first-authored paper per year is pretty good at a teaching institution with a heavy teaching load. I was okay with my publication rate, but I felt like I wasn’t taking this anywhere interesting.

I felt that I knew this critter pretty well. The most curious thing was nest movement behavior. Delving into the literature on nest movements in ants, I found that nest movements have been documented aplenty. But in each species, it was studied only once. It looked like everyone experienced what I did – they stumbled on the phenomenon which botched an experiment, and then they wrote up how the experiment was botched by nest movements. Then, they moved onto more tractable systems, using animals that don’t disappear when you’re not looking. Nobody had gotten far beyond the nest-movements-botched-my-study study.

I decided to directly tackle nest movements in my next field season, which was, again, with several undergrads for about a month. All I wanted to know was, “why do they move their nests all the time?” You can’t ask “why” questions with science, though, so I asked “how” and “with what consequences, correlates and a potential cause.” These results were really interesting to me. It turns out that they move, on average, about once per week, and it has nothing to do with food or competition.

After working on a variety of other things, I wanted to take some time to get back to these mysterious nest-moving ants. My earlier work suggested – only vaguely – that odors might play a role in how they move their nests. I wanted to see if this was the case. So, I ran an experiment by experimentally manipulating nest odors. It turns out that nest odors can keep them from occupying or staying in nests, but the manipulation had enough artifacts I can’t really trust that this experiment explained what was really happening.

While working on other stuff, this nest odor problem kept nagging at me. Eventually, while I had students doing a variety of other things, I cooked up a field manipulation for myself to run, by reducing odors within the nest. That made them like their nests more than they would otherwise. But then, again, what does this really show? If their endogenous odors make them dislike their nests, what’s the selective pressure behind nest movement? That’s a really hard question to address.

That was a few years ago. I’ve just returned to it last year. With one student student, I have (meaning, she has) rerun the earlier odor manipulation, but with narrow chemical fractions to identify which compounds are playing a role. We also have additional observational work happening to test some newer hypotheses. These projects are involving a chemical ecologist who I brought into this project, as I lack any of that mojo, as well as the equipment. (Sometimes not having the equipment is a good thing, I’ve already argued.)

All of these studies essentially have been a set of little side projects, that in all have amounted to a substantial line of investigation over the years. We know more about the ecology of nest relocation in this species, than any other. By the way, their name is Aphaenogaster araneoides. I eventually worked up a new official common name, “gypsy ant.” (That was Anna Himler’s idea.)

How were those experiments tinkering? Well, one thing you may or may not have noticed is that the only reason I did these experiments was to figure out what’s going on with these ants. I was curious about what they were doing, and so I tried to sort it out. I didn’t come in to working with this system with a big question about optimal foraging, neighborhood competition, or social organization in mind. I just wanted to know exactly what this one species was doing, because it was a mystery to me.

Because I was open to this species to telling me what it wanted to, I let it take me in the direction where I was led. You’re moving your nests all the time? Sure, I’ll try to figure that out. I wasn’t setting out to use nest relocation to evaluate any grand theory about social insect behavior or movement theory in ecology. I just wanted to know about what was causing them to move their nests.

In the process, I documented in some detail how they maintain multiple unoccupied nests, but only use one at a time. This was seen in a few other species, but it was a distinct and heretofore undescribed pattern of nesting. I thought to give it a new name — “serial monodomy” — which might stick. What else do you do when you find something that happens that doesn’t have a name?

This project has gotten me to think more about nest relocation in ants. It’s permeated a lot of my thinking about the biology of this community of ants, and has seeped over into my community-level work. I realized that nest relocation is biologically significant, and is not taken into account in so many studies. And we pick our study systems by focusing on the tractable species: those that don’t move. Looking at what is known, I found that most species are apparently mobile, and those are the ones that we don’t study for this reason. Our whole understanding about ants is very biased. I decided to write a review about that idea.

Ultimately, I think my work on nest movements on ants has had some influence on how our research community thinks about ant ecology. At least there’s been some movement (yes, that’s a pun) in that direction. Not too long ago, the prevailing notion was that typical ant colonies are like plants, that just don’t move. There are some oddballs, like invasive species and army ants, that move around, but everyone else is anchored down.

I’m pointing out to others that this notion is false. I’ve only done work addressing nest relocation with this one species, but in the process I’ve called attention to all of those other species that have been found to do similar things but are overlooked.

Of course, anybody who really knows ants easily realizes that nest relocation happens in a bunch of species. But this fact hasn’t been broadly appreciated, nor had it been documented. By working on this phenomenon, in detail, within one species, I was given the perspective that allowed me to make this concept more tangible across the phylogeny.

If you asked me after I finished my dissertation, what are you going to work on? I never would have said, “nest relocation.” I wouldn’t have identified any major concept or theory. I mostly was focused on teaching, after all. I wanted to do some cool projects when I had the chance. This brought me to working with a very common ant, which compelled me to figure out its nest movements because that’s a basic part of its biology. I was just tinkering around with it to figure it out, that’s all. But following that direction, once in a while over the years, I’ve built together a set of substantial ideas, that I imagine will continue to matter for some time to come.

This work on nest relocation on ants isn’t earth-shattering. But it is changing, just a little bit, how we think about ants, including changing some long-held and mistaken assumptions. This is just the result of five trips to the rainforest for 2.5-5 weeks each, over the last 13 years. That’s not too bad.

I think if I went down to the rainforest trying to test a big theory, I would have come back empty handed, or with a few papers that mostly would be collecting dust by now. But simply by wandering off without a specific vision of big theories, I think I’ve done something that results in tangible, if not big, progress.

So, that’s my case for why tinkering is a good way to do science. You might stumble on something amazing, or you might come upon something just mildly curious, but no matter what happens, you’ll learn something genuinely new.

Just imagine what else we’d be learning if other scientists doing basic research, in all kinds of disciplines, started doing research in obscure directions on things that were mysterious to them but didn’t seem of much obvious consequence. I think we’d be learning a lot more about the world and probably develop many new ideas more quickly than we are now.

Ant science: Thievery persists in a world of plenty

Standard

I can forgive people for overlooking the fascinating behaviors of the thieving ant Ectatomma ruidum. There are so many ants with peculiar and amazing features (like agricultural ants, and those with rampaging armies). Some just fly under the radar.

Here’s the latest from my lab.

A few decades ago, Mike Breed and his students were studying behavior, and one part of the work involved using baits to feed ants. He noticed that sometimes, when a colony brought a good piece of bait underground, a different ant took it out of the colony, and carried it in a straight line to a neighboring colony. With a set of careful observations, excavations, labeling workers and some nestmate recognition chemistry, he described a unique phenomenon.

The sneaky thief

The sneaky thief

Colonies of E. ruidum steal from one another, all the time. They have a caste of specialized thieves that spend their time hiding out in a particular neighboring colony. When some good food comes along, they bring it back to their own colony. The best food items move around from one colony to another like uneaten Christmas fruitcake, only everybody wants it instead of passing it off.  The behavior of the thieving has been worked out well by the Breed lab, in a great set of papers. (And, I’m biased, because Mike Breed was my own PhD advisor, the best one I could have had.)

I wanted to understand how this thieving can persist, with everybody stealing from everyone else. This phenomenon makes a jumble of most game theoretical models, because everyone seems to be cheating, all of the time. What makes thieving happen? If they have plenty of food, do they stop thieving?

We ran an experiment in which we gave the colonies as much food as they ever could have wanted. It turns out that the rate of thieving did slow down.

The surprising result was that they kept continuing to steal from their neighbors, even when they had everything they could ever want.

This raises many more questions about the function, evolution and maintenance of thievery. We’re actively working on that, with some work finished and more in the works, and I’ll share more as it comes out.

How this project happened in my teaching institution

I’ve long wanted to work on the ecology of thieving, ever since I helped out on a project with these ants. However, I never had the time to set aside.

In 2008, a friend of mine had a PhD student who was working on poneromorph ants, who was interested in getting some time in the tropics. I was down in Costa Rica with a group of undergrads at the field station, and Benoit Guénard joined us a few weeks. He was a tremendous influence on my students with his enthusiasm, natural history talent, and the most robust work ethic I’ve ever seen. Seriously. We knocked out this project together, with Benoit taking the lead.

So, it took 4 years to get this paper out. In that time, Benoit completed his dissertation on the invasion of the Giant Needle Ant and also has done some top notch work on the macroecology of ant diversity patterns. Once his dissertation was out of the way, he focused on writing up this thieving experiment that we started early on in his dissertation. (I also have a few other collaborations with grad students, and former grad students, that are also awaiting a writeup. We’ll get to them, eventually. There are worse things than a backlog of papers that need to be written.)

Ant Science: litter ants follow sunflecks

Standard

When something fresh does come out of my lab, I’ll share it. I also will share the process by which the paper got published, in the context of working in a teaching institution.

Here’s the latest.

Plants living on the forest floor are starving for light.

I was wondering if the same is true for ants, as light brings heat, which regulates ant activity.

In the 1970s, ecologists sorted out some big ideas about how communities assemble (even if they didn’t use the word “assembly” often). It turns out that access to light is a key variable, for plants. This is especially true for plants that live at the bottom of the forest, chained to the ground and not yet reaching the sky. They live and die by the tiny little flecks of sunlight that poke through the forest canopy to provide energy.

Myrmecologists were late to this story, because they were sidetracked by an obsession with interference competition. When you drop some tuna or a cookie on the ground, it turns out that ants go nuts. Now that many of us have accepted the fact, in real life, they don’t get regular tuna and pecan sandies from the sky, we are focusing on what really makes ant communities tick on a day to day basis. Particle physicists might have to smash their subjects in order to understand them, but as ecologists we can be more subtle.

One fundamental way that ant colonies are different from the plants is that they move around on the forest floor. The ants in rainforest litter move their colonies every few weeks from twig to twig. Maybe their nest movements reflect changes in the light coming through the canopy. Some ants might want to avoid the bits of sunlight and stay in shaded areas.

So, I ran an experiment by giving ants free nests, and putting them in a variety of light environments, including experimental shade treatments.

There were some taxonomic differences in who arrived at the supplemental nests, regardless of light environment. That’s not much of a surprise. What was more interesting was that the shade treatment radically affected the size of the colonies that occupied the nests. Generalist foragers like Pheidole and Solenopsis had much smaller colonies in the shade. In fact, the shade treatments had multiple Solenopsis foundress queens, who apparently prefer a shade microhabitat to start out their nests. On the other hand, the slow-moving specialized predators of litter microfauna, the dacetines (mostly Pyramica and Strumigenys) had larger nests in the total shade and much smaller ones in when there was some canopy light. Across the board, among all ants, colonies were smaller as the canopy became more closed. Just a few percentage points of change in the canopy radically affected the ants on the forest floor.

So, light – and its consequent effects on the temperature microclimate – affects how these ants move around their nests in the litter.

In short, sunflecks matter for ants as much as they do for plants, it seems. There is still a lot to learn about this, and we’re working more on it this upcoming field season. With fancier equipment than photosensitive paper to measure light, like we did in this one.

How this paper happened, from start to finish, in my teaching institution:

I went down to my field station in Costa Rica in January 2009, for two and a half weeks, with a group of five students. Travel was mostly funded by our campus AMP program (and some from an NSF grant to bring students to Costa Rica). I left for Costa Rica as soon as my son in first grade went back to school, and stayed down as long as I could before I had to return for classes in late January. My spouse was helpful in parenting 100% while I was gone, counting on ‘the village‘ once in a while.

All but one of us worked together on this single project, which is the foundation for this paper. (One student was prepping part time for the next field season for her MS thesis). The undergraduate in charge of data management was Melinda Weaver (third author). We found that the time span wasn’t enough to get enough of a sample size – it was very cold at the start of that dry season so the ants were not moving their nests much. So, we set up the experiment to cook over the whole season. In the summer of 2009, I took on an REU student from the field station’s REU program, Aura Alonso-Rodríguez (second author), from the University of Puerto Rico. At the end of the summer, a few people pitched in with Aura to finish data sampling (especially those who Aura had already helped out earlier in the summer). That summer, I was on station for a few weeks at the start of the summer, and then returned for a week and a half as the field season was winding down. That was a lot of time to be away from home, but I also had to return to handle a personnel issue, to prevent a different experiment from exploding or melting. This is a rarity.

We worked on the draft of the manuscript, on and off, for a year, and first submitted it in August 2010. (On my website, along with reprints, I provide the reviews of my papers throughout the review sequence). It got rejected after review, and then in the summer of 2011 I got around to submitting it out again, with some big changes to the analyses but mostly ignoring the biggest criticisms in the first rejection. This came back as a reject/resubmit, and I got it back just a couple days before my three month window for revisions expired. The reviews were far more useful than normal, as they caught a couple egregious errors in the analysis. It came back for minor revisions which I knocked out within a month.

Aura is now in grad school at the University of Puerto Rico, with her fieldwork based in Costa Rica. Melinda is now in a PhD program studying animal behavior at Arizona State.

I’m now developing a grant to examine the thermal biology of the community in more detail, in the context of community assembly and biodiversity, as the lowland rainforests get hotter than they already are. Even if the grant doesn’t come in, we’ll still find a way to work on this project for the next couple years.