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Research

(above: a view inside Kaspari's mind)

In the essay "Systematics Ascending", E. O. Wilson contrasted two ways of doing science based on Krogh's rule, and its inverse. In the former camp lies the notion that "For every biological problem, there exists an organism ideal for its solution". We in the AntLab maintain that Brown Food Webs are a pert' near perfect system to do comparative community ecology. The major players are small enough to be counted with quadrats, and to be grown in the lab and studied in the field. They also regulate the carbon cycle. Not too shabby.

At the same time, after a brief fling with ornithology, I threw my lot in with ants in 1988 and never looked back. For me, and other fellow myrmecologists, there are so many fascinating questions one can address with ants, from life history evolution to foraging ecology, from thermal adaptation to ecosystem impacts. Ants are also a good example of Krogh's inverse, as viewed by Wilson: that for every taxon, there are a great, but limited, set of questions for which they are model organisms. Actually, I may be biased, but there are relatively few questions for which inserting "ants" in the "taxon studied" box doesn't at least suggest some interesting directions. OK, you can't do primatology with ants. Nor will they tell you much about the regulation of polar krill populations. But that, I maintain, is a quibble.

Folks in the AntLab thus spend most of their time studying ants, brown food webs, or some combination thereof, although there are moves afoot to include herbivorous insects. I can be fairly confident, however, that we will never work on lemurs. Not directly, in any case. So...you lemur aficianados, just move on. Nothing for you here.

To get a more complete picture of our work check out our reprints.

Ants as Model Organisms

Alates--an important but poorly understood sliver of time in the life of a colony

It is commonly speculated that 99% of colony mortality occurs in the time when the proto-colony (i.e., queen) leaves her nest, mates, establishes a nest, lays eggs, and waits for her first brood. Yet we know very little about this time in an ant colony's life cycle. In the 1990s, I took it upon myself to quantify the flight times of Barro Colorado's common ants and discovered, to our (then) surprise, that they were flying most of the time, countering the (then) common wisdom that every species has a narrow flight window. Since then, my students (Jon Shik, and, more recently, Jackson Helms) have addressed a variety of questions re alate biology, from the scaling of lifespan, to the rules by which these ungainly fliers make it through the air.

Macroecology of New World Ant Communities

The ants are common and dominant parts of most terrestrial ecosystems. We travelled across the New World, from tundra to tropical rainforest, sampling soil ant communities along the way to answer the question, how and why do these communities vary in size, abundance, and diversity? We found that two key ecosystem variables, temperature and productivity repeatedly helped us understand why some habitats had a 100 times more ants, more species, as well as some suprising variability in the average size of an ant colony as you move from place to place across the planet. MORE

The stoichiometry of ant communities

Ants, given their ubiquity and ecology diversity, are a model system in ecology. The goal of this grant is to build a functional understanding of ant communities using energetic and stoichiometric theory. We are exploring how traits of ant colonies (e.g., colony size, body size, metabolic rate/velocity, colony growth rate, and aggressiveness) are themselves built from molecules with differing quantities of C, N, P, and other elements. Toward this end we are quantifying the biochemistry and natural history of ca. 70 of the 400 species of ants on Barro Colorado Panama, measuring the abundance of ants across natural gradients in CNP availability, and experimentally manipulating the availability of carbohydrates, proteins, and micronutrients at the landscape scale.

Towards a Biogeography of Brown Food Webs

Our lab explores the biogeography of brown food webs—the microbes and invertebrates that use detritus as both home and food, and, in the process, shape the earth’s nutrient cycles. A shared theme through most of our work is a focus on natural history and the principles of organismal biology toward predicting the behavior of communities and ecosystems (Figure 1).

Figure 1. An illustration of how our lab approaches ecology. Differences in the natural history of individuals--how body size, biochemistry, and plasticity affect performance—determine how they respond to abiotic gradients. We use a mix of energetics and ecological stoichiometry--Metabolic Theory—to predict performance. When this information is plugged into Trophic and Diversity Theory it yields predictions regarding how abundance and biodiversity map onto abiotic gradients. Finally, the summed abundance and biodiversity in a given ecosystem feeds back on ecosystem processes like rates of decomposition and nutrient storage. Our model systems are ants and brown food webs—the microbes and invertebrates that break down Earth’s detritus. Their small size and tractable nature allows us to achieve basic ecological insights at scales from m2 plots to the biosphere.

 

Towards understanding patchiness in brown food webs

Forty meters below the lush green of tropical canopy is the brown world where bacteria and fungi rot the dead. In doing so these microbes feed a diversity of organisms and recycle the forest's nutrients. The brown world is intriguingly patchy--the abundance of BFW critters in adjacent bits of litter can vary 100-fold, some litter patches buzzing with life while others are strangely sterile. We propose that this patchiness arises from the interaction of predators, defenses, and the chemistry with which they build new hyphae, exoskeletons, and toxins. MORE

The biogeography of sodium limitation

Life is built from ca. 25 chemical elements. Yet ecologists, in their first forays into biogeochemistry have largely focused on C, N, and P. We have been exploring how gradients of numerous other elements can leave their mark on the performance of individuals, community abundance, and ecosystem function. Of particular interest is sodium, Na, one of the few elements of little use to plants but vital to the decomposers and herbivores that feed on plants. The need for these two trophic groups to find and concentrate environmental sodium has important consequences for the physiological adaptations to find and use Na, the lower population densities and poor consumer performance in Na-poor ecosystems, and the subsequent low rates of decomposition in Na-poor ecosystems. Na also has a geography: it is deposited in oceanic aerosols. Using a one-year experiment, we are testing the prediction that inland forests are unexpected carbon sinks, since photosynthesis proceeds unabated but decomposition rates decline as Na inputs diminish. If true, this premise will transform our understanding of how biogeochemistry feeds back on the geography of abundance and nutrient cycling.

Experimental MacroEcology: the effects of temperature on biodiversity

One of the strongest statistical patterns in biodiversity is the correlation between temperature and species richness, yet the mechanisms underlying this pattern remain elusive. This unique collaboration will develop and test theory in an iterative fashion over four years toward shedding light on the origin and maintenance of biodiversity. We do so by combining studies of the diversity and dynamics of the woody plants, soil invertebrates and soil microbes across six sites in North and Central America. The grant’s primary focus is the development of a first-principles model of decomposition succession in the brown food web—plant detritus, microbes and invertebrates—which will be tested in the field and in growth chambers. A deep understanding of the temperature dependence of this fundamental earth system has clear implications for the cycling of carbon and the maintenance of biodiversity in a warming world.

Thought for the day

"I predict there will be erected a two- or three-way classification of organisms and their geometrical and temporal environments, this classification consuming most of the creative energy of ecologists. The future principles of the ecology of coexistence will then be of the form “for organisms of type A, in environments of structure B, such and such relationships will hold”. 
Robert MacArthur 1972

art by Debby Kaspari  Author: Mike Kaspari Last Updated: 19Dec2012
 



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