FIGURE 4.1 The tree of eukaryotes showing the relative positions of Alveolata and Euglenozoa. This tree is a reflection of many kinds of evidence that are summarized in Keeling et al. (2005), Hampl et al. (2009), and Keeling (2009). The Alveolata consists of 3 main groups, dinoflagellates, apicomplexans, and ciliates (illustrated in Upper Left; scanning electron micrographs of Protoperidinium, Selenidium, and an unidentified ciliate), whereas the Euglenozoa consists of euglenids, kinetoplastids, and diplonemids (illustrated in Upper Right; scanning electron micrographs of Lepocinclis, Leptomonas, and Diplonema). Alveolates are members of the supergroup Chromalveolata, whereas eugenozoans are members of a different supergroup, the Excavata. Neither supergroup is without controversy (e.g., the rhizarian supergroup is shown within chromalveolates to reflect recent phylogenetic analyses), but the relationships of alveolates and euglenozoans to some other eukaryotic groups to the exclusion of one another, and the relationships within alveolates and euglenozoans, are both consistently well supported by molecular analyses.
to contain fully integrated and photosynthetic plastids (Oborník et al., 2009). Photosynthetic dinoflagellates play important roles as planktonic primary producers in oceanic ecosystems, and some of the lineages form symbiotic relationships with corals (e.g., Symbiodinium) and are critical for maintaining the health of reef systems around the world. Nonphotosynthetic plastids have independently evolved in some dinoflagellates and in apicomplexans, which are all obligate parasites of animals and a few are exceedingly important disease organisms of vertebrates (e.g., Cryptosporidium, Toxoplasma, and Plasmodium). Although plastids have not been definitively demonstrated in ciliates, several independent lineages