FIGURE 3. A in A synthesis of hornwort diversity: Patterns, causes and future work

FIGURE 3. A. Majority rule consensus tree of phylogenetic relationship of hornwort genera with their respective localities inferred from rbcL and nad5 genes (redrawn from Villarreal et al. 2010). The three integers above branches represent MP, ML bootstrap support and posterior probabilities (as a percentage), except when all values are the same. The subfamily Dendrocerotoideae is highlighted (grey box). B. Schematic representation of Burr's hypothesis (1970) of chloroplast evolution in Nothoceros (formerly Megaceros). Color coded boxes: Green for taxa with no pyrenoid and multiple plastids (e.g. N. fuegiensis); Blue for taxa with no pyrenoid and one (rarely two) plastid (N. aenigmaticus) and Red for monoplastidic taxa with a pyrenoid (N. vincentianus s. str.). A plesiomorphic condition of a pyrenoid present in N. vincentianus, an intermediate step of monoplastidic cells without pyrenoid up to more specialized cells with multiple plastids without a pyrenoid in N. fuegiensis. C. A diagram of a subtree with species of the genera Nothoceros, Megaceros, Dendroceros and Dendroceros (subfamily Dendrocerotoideae, gray box). Using Megaceros as an outgroup, the trend of plastid evolution in Nothoceros is more complex than previously hypothesized (Burr 1970). The multiple plastids without pyrenoid seem to be the plesiomorphic condition in Nothoceros (Austral Nothoceros) with most nested taxa (Neotropical and Eastern US taxa) having a single plastid with or without pyrenoid (see text for more explanation). Scale bars: 10 µm in Figure 3B.