Competition between mixo- and heterotrophic ciliates under dynamic resource supply

The outcome of species competition strongly depends on the traits of the competitors and associated trade-offs, as well as on environmental variability. Here we investigate the relevance of consumer trait variation for species coexistence in a ciliate consumer – microalgal prey system under fluctuating regimes of resource supply. We focus on consumer competition and feeding traits, and specifically on the consumer’s ability to overcome periods of resource limitation by mixotrophy, i. e. the ability of photosynthetic carbon fixation via algal symbionts in addition to phagotrophy. In a 48-day chemostat experiment, we investigated competitive interactions of different heterotrophic and mixotrophic ciliates of the genera Euplotes and Coleps under different resource regimes, providing prey either continuously or in pulses under constant or fluctuating light, entailing periods of resource depletion in fluctuating environments, but overall providing the same amount of prey and light. Although ..., Organisms used and culture conditions
We used four freshwater ciliates belonging to the genera Coleps and Euplotes that differed in trophic mode, feeding preference and average cell size (see Table 1 for characteristics and origin of the organisms used). Coleps hirtus and Euplotes octocarinatus are heterotrophic, whereas Coleps viridis and Euplotes daidaleos are mixotrophic. Both ciliates carry phototrophic symbionts. We did not perform sequence analysis on the symbionts of our E. daidaleos and Coleps viridis strains. However, Chlorella vulgaris has been identified for other E. daidaleos strains, whereas Micractinium conductrix is the endosymbiont of several Coleps viridis strains (Pröschold et al. 2011, Pröschold et al. 2021). None of the cultures used are axenic and are accompanied by a microbial community consisting of bacteria and heterotrophic flagellates. All ciliates were fed with a non-axenic culture of the microalga Cryptomonas sp. (referred from hereon as Cry), a flagellate wh..., , # Competition between mixo- and heterotrophic ciliates under dynamic resource supply

[https://doi.org/10.5061/dryad.wh70rxwww](https://doi.org/10.5061/dryad.wh70rxwww)

Data were collected during a 48-day chemostat experiment investigating competitive interactions of different heterotrophic and mixotrophic ciliates of the genera *Euplotes* and *Coleps* under different resource regimes. Prey was provided either continuously or in pulses, and light was either constant or fluctuating, overall providing the same amount of prey and light. Although ultimate competition results remained unaffected, population dynamics of mixotrophic and heterotrophic ciliates were significantly altered by resource supply mode. However, the effects differed among species combinations and changed over time. Whether mixotrophs or heterotrophs dominated in competition strongly depended on the genera of the competing species.

## Description of the data and file structure

The set contains biovolume data (total, m...