Phylogenetic analyses show Hydrangeaceae to be a monophyletic group in
the Cornales, and this article uses parsimony analysis of morphologic
al data to identify evolutionary relationships in the family. All of t
he most parsimonious cladograms show that (1) Jamesia, Fendlera, Fendl
erella, and Whipplea a form a monophyletic group that is the sister gr
oup of the rest of the family; (2) Philadelphus is monophyletic and is
the sister group of Carpenteria; (3) Deutzia is monophyletic; (4) Can
diandra and Deinanthe form a monophyletic group; (5) all species of Hy
drangea, 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. T
he results indicate that Hutchinson's tribe Carpenterieae is paraphyle
tic and includes some of the most basal clades in the family. Earlier
hypotheses that Deutzia was derived from Philadelphus are not consiste
nt 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 Di
chroa, two tropical genera with fleshy fruits, are sister Laxa in a cl
ade that includes Hydrangea hirta, H. scandens, and H, macrophylla. Hy
drangea heteromalla and H. paniculata are most closely related to;he c
limbing ''genera'' Schizophragma, Pileostregia, and Decumaria. Most sp
ecies of Hydrangea form part of the ''anomala'' clade, which includes
species circumscribed as section Cornidia as well as H, involicrata, H
. aspera, N. quercifolia, H, sikokiana, H. arborescens, and H. anomala
. These results, together with those from a phylogenetic analysis of t
ile family based on rbcL gene sequences, indicate that classifications
of Hydrangeaceae require extensive revision to provide greater utilit
y and reasonable insights on evolutionary relationships.