Fig. 3.

Evolutionary tree of volvocine algae based on the nucleotide sequences of five chloroplast genes. This phylogenetic analysis indicates that multicellularity evolved only once in this group. In contrast, a partial germ–soma division of labor evolved independently in three different lineages and was lost twice (Nozaki et al. 1997; Herron and Michod 2008; Herron et al. 2009). A full germ–soma division also evolved three times. The meanings of symbols and letters are given in the figure. Names of strains are given in gray behind the species names. The species shown on the photomicrographs in Fig. 1 are indicated with filled black circles. This tree was adapted from Herron and Michod (2008) and others (Sachs 2008; Herron et al. 2010); some additional information was added (Lerche and Hallmann 2009; Ueki et al. 2010)