Meeting Abstract

P2.29  Friday, Jan. 4  Individual diet specialization in wild three-spine stickleback populations SNOWBERG, L. K.*; BOLNICK, D. I.; University of Texas, Austin; University of Texas, Austin snowberg@mail.utexas.edu

Ecological theory often treats all individuals within a species as ecologically equivalent. On the other hand, evolutionary theory assumes that individuals may differ in their resource use and individuals compete more strongly if they are more morphologically similar, leading to evolutionary diversification under high competition. In recent years there has been an increased recognition that a population�s niche width may be composed of individuals with narrow niches with heterogeneity between individual�s diets (individual specialists) or individuals with wide, highly overlapping niches (individual generalists.) Here we study individual variation in diet of populations of wild three-spine sticklebacks (Gasterosteus aculeatus). We use gut content analysis and stable isotope analysis to assess the level of individual specialization and the consistency of specialization through time. Levels of among-individual variation in resource use were high in all populations, but fish within populations did not form discrete clusters specializing on different food types, contrary to prior work on stickleback populations. Nonetheless, morphology was related to both gut contents and isotope signature. Studies of among-individual variation in diet are important for our understanding of evolutionary forces, such as frequency-dependent competition. In addition, this study reinforces that individual-level variation is widespread and there is therefore a need for models that explore the role of among-individual diet variation in ecological models that have traditionally treated all individuals as ecologically equivalent, such as food webs.