Phylogenetic relationships among 13 strains of three forms of <i>Volvox carteri</i>.

<p>The tree was inferred using the maximum-likelihood (ML) method based on alignment of 471 nucleotide sites in the internal transcribed spacer 2 sequences of 10 operational taxonomic units of <i>V</i>. <i>carteri</i> strains and <i>V</i>. <i>obversus</i> strain UTEX 1865 (the outgroup). Bootstrap values (50% or more) for the ML and maximum parsimony analyses are indicated at the respective nodes. The scale bar shows 0.05 nucleotide substitutions per position. The presence (+) or absence (-) of rickettsial endosymbionts based on the data of Kawafune et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.ref012" target="_blank">12</a>], and those of the present study (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.s001" target="_blank">S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.s002" target="_blank">S2</a> Figs.), are shown in the central column. Possible nuclear-encoded, rickettsial gene homologs detected in the present study (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.g002" target="_blank">Fig. 2E</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.s003" target="_blank">S3 Fig.</a>) are shown in the column on the right. The gene names shown in bold were used in phylogenetic analyses (Figs. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.g003" target="_blank">3</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.g004" target="_blank">4</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.s004" target="_blank">S4</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.s005" target="_blank">S5</a> Figs.). The letters A-D following gene names correspond to the forms of genetic composition shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116192#pone.0116192.g002" target="_blank">Fig. 2</a>. No rickettsial gene-like sequences were detected (in the present study) in strains UTEX 2903, UTEX 1874 or UTEX 2904.