A Phylogenetic Analysis of Hydrangeaceae Based on Morphological Data

Phylogenetic analyses show Hydrangeaceae to be a monophyletic group in the Cornales, and this article uses parsimony analysis of morphological data to identify evolutionary relationships in the family. All of the most parsimonious cladograms show that (1) Jamesia, Fendlera, Fendlerella, and Whipplea form a monophyletic group that is the sister group of the rest of the family; (2) Philadelphus is monophyletic and is the sister group of Carpenteria; (3) Deutzia is monophyletic; (4) Cardiandra and Deinanthe form a monophyletic group; (5) all species of Hydrangea, as well as Broussaisia, Dichroa, Decumaria, Pileostegia, and Schizophragma, form a monophyletic group (the "hydrangea" clade); (6) three monophyletic groups-the "anomala" clade, the "heteromalla" clade, and the "macrophylla" clade-make up the "hydrangea" clade; and (7) Platycrater is the sister group of the "hydrangea" clade. The results indicate that Hutchinson's tribe Carpenterieae is paraphyletic and includes some of the most basal clades in the family. Earlier hypotheses that Deutzia was derived from Philadelphus are not consistent with the results. The paraphyly of Hydrangea is consistent with the results of an earlier phylogenetic analysis based on sequences of the chloroplast gene rbcL. In the "hydrangea" clade, Broussaisia and Dichroa, two tropical genera with fleshy fruits, are sister taxa in a clade that includes Hydrangea hirta, H. scandens, and H. macrophylla. Hydrangea heteromalla and H. paniculata are most closely related to the climbing "genera" Schizophragma, Pileostegia, and Decumaria. Most species of Hydrangea form part of the "anomala" clade, which includes species circumscribed as section Cornidia as well as H. involucrata, H. aspera, H. quercifolia, H. sikokiana, H. arborescens, and H. anomala. These results, together with those from a phylogenetic analysis of the family based on rbcL gene sequences, indicate that classifications of Hydrangeaceae require extensive revision to provide greater utility and reasonable insights on evolutionary relationships.