Fig. 2.

Mixoplankton span an evolutionary and physiological spectrum. Top: Phago-mixotrophy is found across numerous lineages of the eukaryotic tree of life (some examples shown). Middle: These mixoplankton span a gradient of reliance on photosynthesis, from almost completely phagotrophic to almost completely photoautotrophic. Bottom: As such, mixoplankton also present an opportunity to study the evolutionary transition from phagotrophy to phototrophy, particularly by examining two key evolutionary transitions: (i) the evolutionary gain of phototrophy (here, exemplified by kleptoplasty in the Mesodinium genus, in which lineages become increasingly photosynthetic as they become more evolutionarily derived; Johnson et al., 2016) and (ii) the evolutionary loss of phagotrophy (here, exemplified by the diatoms, which lost phagotrophy prior to undergoing an extensive radiation). Illustration by Catherine S. Raphael (NOAA/GFDL) and Holly Moeller.