Phylogenetic relationships of choanoflagellate strains isolated within this study to environmental sequences from hypoxic habitats based on partial 18S rRNA sequences using MrBayes. New species are presented in white bold characters; environmental clonal sequences of hypoxic habitats are shown in bold face letters. Posterior probability and bootstrap values above 0.5 and 50 are indicated. Values above 0.99 and 99 are presented as bold face branches. Scale bar represents 0.1 mutations per position. Amoebidium parasiticum (Ichthyosporea) was used as outgroup representative.