16S-like rDNA sequences from Developayella elegans, Labyrinthuloides haliotidis, and Proteromonas lacertae confirm that the stramenopiles are a primarily heterotrophic group

Summary A phylogenetic analysis of the 16S-like ribosomal RNA coding regions from Labyrinthuloides haliotidis, Developayella elegans, Proteromonas lacertae and other organisms corroborates morphological evidence that proteromonads and other eukaryotes with tripartite tubular hairs form a monophyletic group of organisms, the stramenopiles. Within the stramenopiles, the heterotrophic groups (proteromonads, Labyrinthulida, bicosoecids, Developayella and oomycetes) diverge before the radiation of the “heterokont algae”, the autotrophic stramenopiles. The stramenopiles were initially “protozoan” but their ecological success is largely attributable to the late symbiotic acquisition of chloroplasts. The stramenopiles and other taxa with chlorophyll a+c containing chloroplasts (cryptomonads, dinoflagellates, and haptophytes) do not share a common autotrophic ancestor. These photosynthetic assemblages acquired their plastids independently.