The development of plastids among the alveolates is uncertain. Cavalier-Smith proposed the alveolates developed from a chloroplast-containing ancestor, which also gave rise to the [[Chromista]] (the [[chromalveolate]] hypothesis). However, as plastids only appear in relatively derived (as opposed to ancestral) groups, others argue the alveolates originally lacked them and possibly the dinoflagellates and Apicomplexa acquired them separately.
It appears that the alveolates, the dinoflagellates and the [[ Heterokont|heterokont algae]] acquired their plastids from a red algae suggesting a common origin of this organelle in all these clades.<ref name=Janouskovec2010>Janouskovec J, Horák A, Oborník M, Lukes J, Keeling PJ (2010) A common red algal origin of the apicomplexan, dinoflagellate, and heterokont plastids. Proc Natl Acad Sci USA 107(24):10949-10954</ref>