Fig. 1.

Cladogram and photographs of volvocine genera. Depicted evolutionary relationships derived from Lindsey et al. [11] with Goniaceae modified to be monophyletic based upon more recent evidence from Ma et al. [12]. The three multicellular volvocine families (Tetrabaenaceae, Goniaceae, and Volvocaceae) are represented by orange, purple, and green font and borders. Unicellularity is denoted by black font and borders. Blue lines correspond to anisogamous lineages, and blue to pink gradient lines represent lineages in which oogamy has evolved. A single asterisk (*) denotes somatic cell differentiation, and double asterisks (**) denote complete germ-soma differentiation. Superscript letters correspond to their respective photographs. Photographs are arranged in the following order: (A) Tetrabaena socialis, (B) Chlamydomonas reinhardtii, (C) Gonium pectorale, (D) Astrephomene gubernaculifera, (E) Platydorina caudata, (F) Colemanosphaera charkowiensis, (G) Pandorina morum, (H) Volvulina compacta, (I) Yamagishiella unicocca, (J) Eudorina elegans, (K) Pleodorina starrii, (L) Volvox carteri. Photos are not to scale. Figure Credit for (B) and (C): Deborah Shelton