Fig. 1.

Genetic diversity of Phaeocystis found worldwide in symbiosis with Acantharia. The figure shows a RAxML phylogenetic reconstruction of the genus Phaeocystis based on concatenation of the ribosomal 18S and 28S rDNA genes and the plastidial psbA and rbcL genes (131 taxa and 3.1 kb aligned positions). Sequences of Phaeocystis in symbiosis are colored according to their geographic origin, and the number of host specimens examined (representing different species) is indicated. Cultures of free-living Phaeocystis and their corresponding geographic origin are in black. All sequences were produced in this study except for those indicated in boldface type (from GenBank). Bootstrap values ≥60% and Bayesian posterior probability ≥0.7 are given above and beneath the node, respectively. The outgroup contains five sequences from other members of the Haptophyta. See SI Materials and Methods for one-gene phylogenies (Figs. S1–S4).