9306842 Peckarsky The objectives of the proposed research are to (1) determine how much of the death rate of the stream-dwelling larval mayfly, Baetis bicaudatus, is due to stonefly and trout predation, and to parasitism by nematode worms, (2) measure the consequences of reduced feeding by mayflies while avoiding competitors, predatory stoneflies and trout in terms of female egg production and size-related male mating success, and (3) using methods to estimate mayfly population growth, determine the relative impacts of predators, parasites and competitors on the mayflys' ability to sustain populations over the long term. Meathods proposed to meet those objectives include: (a) experiments conducted in small (25cm) and large (1.5m) enclosures to measure the effects of stonefly and trout predation on mayfly death rate, (b) behavioral experiments to determine the risk of trout predation to mayflies that have entered the water column to escape stonefly predation, (c) dissections of mayfly larvae and adults to estimate stages and sexes of infection, sterilization and death cause by nematode worms, and (d) experiments conducted in small and large enclosures to measure the effects of predator on mayfly growth rates, sizes of adults and egg production, (e) field experiments will determine whether larger male mayflies have greater mating success, and (f) sizes and egg production and mayflies that completed their larval stage in sites or streams with different densities of predators competitors. These data will illustrate whether any effects of predator avoidance observed at a smaller scale (in enclosures) can be detected a t larger scales in natural streams. Data from these experiments will be used to compare mayfly population growth in the face of stonefly and trout predators, parasites and competitors. Filed estimates of mayfly population growth will be obtained as a "reality check" on experimentally derived population growth rates. The key contribution of this research is a unique investigation of connections between factors affecting larval morality and behavior and adult reproductive success. No previous studies have compared the consequences of a suite of selection pressures such as predation, parasitism and competition on one stage of a natural population, and interpreted these impacts on population growth in context of the complete life cycle. $ ! ! !8 ! F ( Times New Roman Symbol & Arial * " h k k 7 Crystal Blackshear Crystal Blackshear
