Print PageNumerous studies document herbivore adaptations to plant defenses. However, the consequences of these adaptations for communities and ecosystems are rarely studied. We used laboratory feeding assays to identify Daphnia pulicaria genotypes tolerant of a diet containing toxic cyanobacteria (Microcystis). We then conducted a limnocorral experiment in a hypereutrophic reservoir, focusing on two broad questions: (1) Can cyanobacteria-tolerant Daphnia suppress blooms of cyanobacteria in the field? and (2) Are cyanobacteria-tolerant Daphnia genotypes functionally redundant? Our four treatments included a no Daphnia control and one of three genetically distinct, cyanobacteria-tolerant Daphnia clones.
Results/Conclusions
Initial phytoplankton biomass was high across all treatments (chlorophyll a = 75 µg L-1), and phytoplankton communities were dominated by the filamentous cyanobacterium Anabaena circinalis. We found no differences among the three Daphnia genotypes in their population growth rates and carrying capacities, and all three Daphnia genotypes reduced phytoplankton biomass similarly relative to the control treatment. By the conclusion of the experiment (day 45), Daphnia had completely eliminated cyanobacteria from all enclosures, regardless of their genotype. Therefore, Daphnia adaptations to toxic cyanobacteria (as measured in the lab) translate into large effects on cyanobacterial abundance in the field.
