Morphological phylogenetic analysis of living and fossil Chloranthaceae

To investigate relationships and character evolution in the angiosperm family Chloranthaceae, and to integrate fossil specimens into the phylogeny of extant taxa, a parsimony analysis was carried out using morphological data from 38 extant and six fossil species. Ten taxa - Amborella, two Nymphaeales, and other members of the basal "ANITA'' grade and Winteraceae, Saururaceae, and Asaroideae, representing woody and herbaceous eumagnoliids - were used as outgroups. Morphological- and molecular-based outgroup arrangements gave essentially identical ingroup relationships and support values. The resulting cladograms support the monophyly of the Chloranthaceae as well as the four extant genera Chloranthus, Sarcandra, Ascarina, and Hedyosmum. Hedyosmum is sister to the remaining Chloranthaceae and Ascarina is sister to Sarcandra and Chloranthus, as indicated by molecular analyses. The results indicate that the common ancestors of the family were trees or shrubs with either bisexual or unisexual flowers, a simple perianth, and monosulcate pollen. Derived features that mark important clades within genera include fleshy floral bracts in Hedyosmum, female cymules and single stamens in Ascarina, and elongate stamen lobes in Chloranthus. Early Cretaceous fruits with three tepals and Asteropollis pollen belong near the base of Hedyosmum, but Couperites fruits with "Clavatipollenites'' pollen, compared with Ascarina, may be either nested within the family or sister to it. Late Cretaceous tripartite androecia appear to be stem relatives of extant Chloranthus, but an Albian tripartite androecium is not confidently related to the family.