Flexible defense strategies in a self-organized system

Turtle ants

Some species of ants have a caste of workers that are particularly big and strong. In the genus Cephalotes, commonly known as turtle ants, this "soldier" caste stands out because of their heavily armored, disc-shaped heads. Colonies live in trees, in multiple cavities hollowed out by beetle larvae. The soldiers act like armored doors, physically blocking cavity entrances with their heads. Each colony has a limited number of soldiers that can be deployed among their different nests, so how do they choose who goes where? Essentially, they're playing the game of Risk: the best deployment strategy depends on how valuable each nest is, how hard each one is to defend, and how likely it is that they will be attacked. But there's a complication: the ant colony doesn't have a central decision-maker that can assess the situation and dispatch soldiers where they're most needed. Instead, each soldier moves among cavities and makes her own decision about which one to defend. Is it possible for the soldiers to deploy themselves in a way that's optimal for the colony as a whole, even without a general to direct them? (With Scott Powell.)

The value of communication in collective foraging

Honey bees

In some group-living animals, each individual seems to act fairly independently—exploring the environment on her own, and using the information she has gathered herself. In others, individuals share information with each other about what they find, sometimes in pretty spectacular ways. Think of the massive trunk trails of leaf-cutter ants, or the waggle-dance recruitment of the honey bee. Usually it is the biggest groups that seem to rely most on communication to organize their collective behavior. Why? Is it because big groups need communication more—without it they would be hopelessly disorganized? Or is it because big groups somehow have more to gain from communication—only they can really take advantage of its full power? How does the environment affect which strategy makes more sense: the honey bee strategy of huge groups of cooperative foragers, or the bumblebee strategy of small groups of independent foragers?

The value of information in an uncertain environment

Desert annual plants live in a highly unpredictable environment; in some years there simply isn't enough rain to successfully germinate and reproduce. One strategy they use is called seed banking, in which only a fraction of viable seeds germinates in any given year. The remainder wait for another year, so a lineage can persist even in case of drought. This kind of random-choice strategy, known as bet-hedging, works well when it's impossible to predict drought years. Sometimes, however, environmental cues can help determine how likely a drought is. How could the seed best use the information those cues provide, and what's the adaptive value of doing so?

The evolution of meaning in animal communication

Animals communicate with each other in an enormous variety of ways, but do the signals they use have any meaning, in the sense that nouns in human language do? The famous predator-specific alarm calls of vervet monkeys are a particularly nice example: the way that individuals produce and respond to particular calls suggests that one call means leopard, one call means snake, and a third means eagle. In an evolutionary setting where one individual produces a signal and a second individual can react to that signal, how might the appearance of meaning emerge?

Matina Donaldson-Matasci

Postdoctoral Researcher
Dornhaus Lab
Ecology & Evolutionary Biology
University of Arizona
Tucson, Arizona, USA

Ph.D., Bergstrom Lab
Department of Biology
University of Washington
Seattle, Washington, USA

Contact:
matina@email.arizona.edu