Fig. 1.

Maximum likelihood (ML) phylogenetic tree of the opisthokonts constructed with 227 complete 18S rDNA sequences (1,436 informative positions). Exclusively environmental clades are indicated with *. The last bar on the right indicates the main environmental origin of the different clades: blue (marine), green (freshwater), and yellow (symbiont). Clades indicated as symbiont are those in which the species are known to be symbiont and that had almost no environmental sequences (maximum one sequence). Environmental clades consisting of a single sequence have not been named. Because of the increasing number of new clades described and for the sake of clarity, the names have been changed from del Campo and Massana (2011) (supplementary information S1, Supplementary Material online). 1,000 pseudoreplicate ML bootstrap values over 50% are indicated with a black dot for the defined clades. The scale bar indicates 0.09 substitutions per position. The complete tree is shown in the supplementary information S2, Supplementary Material online. The order and class names given are based on Cavalier-Smith and Chao (2003), Shalchian-Tabrizi et al. (2008), and Cavalier-Smith (2009). MACHO, marine choanoflagellates; FRESCHO, freshwater choanoflagellates; MAOP, marine opisthokonts; FRESHIP, freshwater ichthyosporeans; MAIP, marine ichthyosporeans; FRESHOP, freshwater opisthokonts.