PARENT SESSION
Contributed Oral Session 67: Modeling: Nutrient Cycling; Food Webs
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Modeling plant-herbivore evolutionary rates using a graph theoretical approach.

Kyu, Shuya^*,1, Leary, Chris¹, Hartvigsen, Gregg¹, ¹ SUNY College at Geneseo, Geneseo, NY, USA

ABSTRACT- An individual-based, evolutionary model of plant-herbivore dynamics was used to determine how network structural relationships among individuals within species, between species, and across trophic levels change over evolutionary time. Each individual carries a pseudo-genetic sequence (interaction code) whose hamming distance (the number of changes required in a conversion from one bit string to another) determines the ability to mate and feed. Mutations and recombination occur during mating. Each individual is treated as a vertex in a network graph and individuals that can mate are connected by edges. Assuming that a connected component is a species within the trophic level, we analyzed the rate of evolution and characteristic path length of the major component (dominant species) for plants and herbivores. The rate of evolution is obtained by measuring the movement of the center of mass of the dominant species in sequence space. Increased feeding pressure increases the rate of evolution through sequence space. In addition, the characteristic path length for the dominant species of plants decreased as the feeding pressure increased. We found a negative relationship between the sequence distances between plants and herbivores and the size of the herbivore population (when herbivores are relatively maladapted to plants their populations are low). The characteristic path length of the plants is negatively related to the intensity of herbivory and results in the more rapid evolution of plants away from herbivores.

Key words: Rate of evolution, Plant-herbivore coevolution, Genetic algorithms, Graph theory