Links I like

Stephen Pratt (ASU)

S.I.R.G. (ASU)

Eldridge Adams (UCONN)

Walter Tschinkel (FSU)

Larry Gilbert (UT)

Alex Wild (U Illinois)


The Ant Course








Research Interests

Self-organization is a process in which patterns emerge at a global level as a result of the interactions of local-level components lacking global knowledge. Self-organization is found in a wide variety of circumstances, and is particularly important for social insect decision-making. When two self-organized groups engage in aggressive behavior toward one another, emergent patterns can be referred to as self-organized conflicts. The emergence and resolution of conflicts between colonies of social insects is not clearly understood, especially from the level of the individual.

The goal of my research is to understand the central components of territoriality as a self-organizing conflict between neighboring colonies. In addition to understanding the behavioral mechanisms behind territorial battles and how these mechanisms relate to colony level responses, this research will also provide the basis for models of the dynamics of two self-organizing groups of individuals in conflict. This generalized model of self-organizing conflict will be of interest to a broad range of disciplines, from neurology to military operations research.

1) Foraging ecology of Messor pergandei.

M. pergandei is a beautiful black harvester ant found in the Sonoran desert. Central place foragers, these ants send all their foragers out into a single foraging column each day. Over the course of days and weeks, the foraging column slowly moves, rotating like the hand of a clock. I am interested in the ecology of this behavior- from the individual behaviors that generate the group behavior to the selective factors which have shaped this complex behavior.

Right: Thousands of individual foragers create a foraging column which leaves the nest in a different direction each day. Over a period of time, the foraging column sweeps around full circle (stylized representation, after Rissing 1976).

2) Territorial behavior in Tetramorium caespitum.

T. caespitum is a small brown ant with Palearctic distribution. Neighboring colonies engage in spontaneous battles involving thousands of fighting ants. These battles occur at boundaries between territories which are defended throughout the active season during the warmer months of the year.

Interest in the dynamics of group behavior has brought much attention to social insects as model organisms for the study of self-organization (Bonabeau et al. 1997, Camazine et al. 2003, Seeley 2002). Although many studies have examined how the properties of group behavior arise from distributed decision-making among individuals, much less is known about the dynamics of encounters between two or more self-organizing groups. Territorial battles among social insect colonies exemplify this kind of interaction. Understanding battle dynamics requires knowing how each colony organizes its defensive behavior, but also how interactions between the two groups drive changes in the distribution and intensity of fighting.

3) Models of aggressive group interactions.

Modeling inter-group processes is useful for testing hypotheses about mechanisms of complex group behaviors in social insects.  Similar to models made of army ant raiding processes, which can describe their foraging patterns in terms of distribution of food resources (Solé et al. 2000), the goal of models of aggression is to be able to incorporate different behavioral mechanisms such as assessment and recruitment processes, and to be able to generate realistic inter-group behavioral patterns.  Models of self-organized conflicts can additionally aid in generating hypotheses about which behaviors are likely to be the most important contributors to group level dynamics.

4) Territorial behavior in the invasive fire ant Solenopsis invicta.

Territory defense can affect the spatial distribution of ant colonies (e.g., Wiernasz & Cole 1995), and can exert a strong regulatory force on ant populations (Adams & Tschinkel 2001). The control of territory size in ants is best understood in the fire ants, S. invicta (Adams 1998, Adams 2003, Adams & Tschinkel 2001, Tschinkel et al. 1995). Field experiments showed that changes in food supply have little effect on territory area, but that changes in worker population cause large and rapid shifts in boundary positions (Adams 2003).

As Dr. E. Adam's graduate assistant, I studied the behavior of individuals and groups at territory boundaries. In addition, I used S. invicta as an experimental system to test the predictions of Lanchester's laws (Plowes & Adams 2005). There is a considerable amount of theoretical research on determinants of mortality, much of it originating in studies of human warfare (selected references: Lanchester 1916, Hartley 1995).  Franks and Partridge (1993) proposed that Lanchester’s (1916) models of mortality should serve as the basis of a theory of ant combat. By analyzing mortality rates of fire ants fighting in different numerical ratios, we provided the first quantitative test of Lanchester's model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.

5) Invasive biology of the invasive fire ant Solenopsis invicta.

Solenopsis invicta is in an invasive species from South America . In South America there are at least 18 species of Phorid flies in the genus Pseudacteon that are known to parasitize fire ants. Research in Dr. L. Gilbert's lab concentrated primarily on one species P. tricuspis, which is species-specific for S. invicta. Field work and lab experiments investigated the life histories and complex interactions of Phorids, S. invicta and the native ant community. The first experimentally released Phorids have now successfully established in Florida and Central Texas.

  In 1999 I performed a survey of the ant fauna in 13 Texas counties in collaboration with the Texas Department of Agriculture. Specimens collected from surveys and fieldwork were identified. I made field guide to the common ants of Texas. In collaboration with Dr. U. Mueller at UT Austin, a web version of the key was constructed for public use. (Texas Ant Key)