PARENT SESSION
Oral Session #58: Theoretical Ecology.
Presiding: M. Neubert
Wednesday, August 7. 8:00 AM to 11:30 AM. Grand Ballroom East, Radisson.

Size, complexity and function of theoretical and real food webs.

Morris, James^*,1, Christian, Robert², Ulanowicz, Robert³, ¹ University of South Carolina, Columbia, SC² East Carolina University, Greenville, NC³ University of Maryland, Solomons, MD

ABSTRACT- Random food webs of varying complexity, ranging up to 446 nodes and 68000 connections were generated using ecologically realistic constraints. Trends in biomass, net productivity, production efficiency, flow diversity and throughput (TST) were analyzed as functions of network size, connectivity, and gross primary production (GPP). Production efficiency (net consumer production/net primary production) of the random webs increased asymptotically to about 2 with increases in the number of nodes (biodiversity) and with the number of network connections, and appears to be insensitive to GPP. Flow diversity (a measure of complexity) and average mutual information (AMI, a measure of order) increased asymptotically to 7 and 3 bits, respectively, with an increase in the number of nodes and connections. Total system biomass and primary producer biomass declined, while TST increased, with increases in the number of nodes and network connections. Thus, biomass turnover rate increased with increasing network size. The flow diversity and AMI of 32 real food webs having at most 125 nodes increased with the number of nodes to about 5.5 and 2 bits, respectively. Although the empirical food webs tend to cluster at the very low end of the size spectrum of the theoretical food webs, the trends are similar and indicate that the structure of a food web and its function are closely related.

KEY WORDS: network analysis, food web, theoretical ecology