PARENT SESSION
Contributed Oral Session 104: Predator - Prey Ecology: Communities; Defenses
Wednesday, August 10, 1:30 PM - 5:00 PM, Meeting Room 521 A, Level 5, Palais des congrès de Montréal

Coupling between predator phenotype and prey community structure for alewife populations and their zooplankton prey.

Palkovacs, Eric^*,1, Post, David¹, ¹ Yale University, New Haven, Connecticut, USA

ABSTRACT- Population-level divergence in morphological and life history traits may commonly occur as adaptive responses to ecological conditions. Less well studied, however, is the feedback whereby trait differences, in populations of a dominant predator for example, shape their prey communities. We investigated the relationship between predator phenotype and prey size and community composition for populations of landlocked and anadromous alewives (Alosa pseudoharengus) and their zooplankton prey in four southern New England lakes. Landlocking in fish occurs when normally anadromous or migratory species develop wholly freshwater populations. Here we show that landlocked and anadromous alewife populations differ in important ecological traits related to feeding efficiency, including gape size and gill raker spacing. Diet data indicates that these morphological differences underlie differences in prey selection. Differences in zooplankton communities in lakes with landlocked versus anadromous alewife populations suggest that size-selective alewife predation exerts strong pressure on the size and species composition of the prey community. This leads to the hypothesis that alewife morphology and zooplankton community structure have diverged in concert. We conclude that a closer examination of the coupling between predator phenotypes and prey communities in a variety of systems may help explain patterns of morphological and community divergence.

Key words: Alosa pseudoharengus, local adaptation, size-selective predation