Scaling-up effects of intra-specific phenotypic polymorphism on lake ecosystems : experimental approaches

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We tested how phenotypic plasticity or polymorphism of algae and fish, which are regarded as primary producers and top-predators in lake ecosystems, respectively, can affect food web and ecosystem properties, using microcosm and mesocosm experimental systems. Taking the advantage of molecular technique, such as transcriptome and QTL analyses, we elucidated that fish trophic polymorphism(planktivory-benthivory species pair) is under the control of polygenic variation in a large number of loci with small additive effects and found that the expression pattern of swimming performance-related genes is shared among different phylogenies with species pair, suggesting the possibility of convergent evolution of adaptation to pelagic environments. We also experimentally demonstrated that fish trophic polymorphism altered not only food web properties, such as food chain length, prey-predator mass ratio and community-average trophic level, but also community respiration as ecosystem functioning through trophic cascading effects. Using theoretical models, we finally corroborated that the evolution of phenotypically plastic or polymorphic traits have ecosystem consequences in terms of food web configuration and stability.