text: Nearly all research in algal biofuels has focused on culturing single species, or monocultures, of microalgae. However, ecological theory and empirical studies have demonstrated that plant and algae polycultures, i.e. groups of multiple species, tend to produce larger yields than monocultures. Experiments have also shown that more diverse aquatic microbial communities tend to be more stable through time than less diverse communities. Recent studies found that polycultures of microalgae produced significantly higher lipid yields than monocultures. Polycultures also tend to be more resistant to pest and disease outbreaks, as well as invasion by other plants or algae. Thus culturing microalgae in polyculture may not only increase yields and stability of yields of biofuel, but also reduce the environmental impact of an algal biofuel industry.