Quantifying Niche Partitioning along an Acquired Phototrophy Gradient

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Phycological Society of America
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Area/s of Research
Ecology and Evolution

Kleptoplastidic microeukaryotes transiently obtain photosynthetic abilities by retaining stolen chloroplasts from their algal prey. These organisms therefore provide insight into the endosymbiosis pathway that led to the permanent incorporation of plastids into diverse extant eukaryotic phytoplankton lineages. However, while much attention has been paid to the cell and molecular biology of these organisms (e.g., quantifying photophysiology, carbon budgets, and gene expression, and identifying horizontal gene transfer events), comparatively little is known about the ecology of these organisms, particularly how they partition their niche space and achieve ecological success in the context of a diverse planktonic community. This proposed research uses the Mesodinium genus, which contains sister species of ciliates ranging from entirely heterotrophic grazers to entirely phototrophic acquired phototrophs, as a model system to study niche partitioning as acquired phototrophs emerge from a heterotrophic background. Specifically, this work will use a combination of laboratory co-culture experiments and mathematical models to test for niche partitioning along axes of prey specialization and light availability, and then use these data to predict the evolutionary trajectories that led to the emergence of the modern eukaryotic phytoplankton. This work is synergistic with existing studies of Mesodinium physiology and ongoing efforts to sequence the genomes of several Mesodinium species, and also lays the foundation for future research testing other axes of niche partitioning.