PARENT SESSION
Oral Session #4: Animal Population Ecology.
Presiding: L. Mitchell
Monday, August 5. 8:00 AM to 11:30 AM. Gila Meeting Room, TCC.
Individual specialization and population dynamics: implications for trophic polymorphisms.
Svanback, Richard*,1, Persson, Lennart2, Wahlstrom, Eva2, Westman, Erika2, Bystom, Par3, 1 Uppsala University, Uppsala, Sweden2 Umea University, Umea, Sweden3 Swedish Agricultural University, Umea, Sweden
ABSTRACT- Resource polymorphism is common among animal populations although many animals have a generalized diet. Studies have shown that at high competition diet choice of individuals depends on that individuals specialize on resources they consume at high efficiency. We have in earlier studies on perch, Perca fluviatilis, shown correlations between morphology and diet. We analyzed individual specialization of perch as a function of the population dynamics of perch over a nine-year period. During this time period, perch experienced a more than tenfold change in density suggesting different levels of intraspecific resource competition. During high population densities of perch, the condition factor was lower than at low densities, indicating high intraspecific competition. Individual niche breadth remained constant, whereas the population niche breadth expanded at high population densities and consequently individual specialization was highest at high perch densities. At low perch densities the benthic invertebrate abundance was high, and due to low cannibalism among perch, the zooplankton level was low and the diet of the population consisted mainly of benthic invertebrates. At high perch densities on the other hand, the benthic invertebrate abundance was low, and due to high cannibalism among perch, the zooplankton level was high and zooplankton were included in the diet of perch. Our results show that individual specialization might fluctuate with population density through feedback mechanisms on resource levels. Such fluctuations may have profound implications on the evolution of resource polymorphisms.
KEY WORDS: individual specialization, density dependence, niche breadth, population dynamics