1995/07/01 by Larry Hufford
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Flowering Plant Growth and Cultivation #Plant Diversity and Evolution #Plant and Fungal Species Descriptions
paper · doi:10.1086/297279
openalex publication_date 1995/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
Seed morphology of Hydrangeaceae was explored to describe the parameters of diversity, define characters and character states, and hypothesize monophyletic groups in the family on the basis of derived features. Eleven seed characters were defined that delimit four basic aspects of morphology, including (1) shape, (2) primary sculpture, (3) secondary sculpture, and (4) appendages. Character states could not be delimited readily in some aspects of diversity, including transectional shape and length of seeds. Despite continuous variation in seed length, when mapped on previous cladograms these data supported the hypothesis that seeds less than 1.0 mm long were plesiomorphic and that seed size had increased separately in different subclades. Seed size increased in association with wing loss in Fendlera, Fendlerella, and Whipplea. A shift from apical, interstylar dehiscence of fruits that produce a very limited gap for seed emergence in most members of the hydrangea clade to fruit wall fragmentation may have permitted an increase of seed size in Decumaria, Pileostegia, and Schizophragma. The data help to support hypotheses of monophyly for Deutzia and Philadelphus, although relevant character states appear to display parallelisms. The data also help to demonstrate the paraphyly of Hydrangea as traditionally circumscribed. A derived urceolate seed form allies Broussaisia and Dichroa with Hydrangea hirta and Hydrangea luteovenosa. These data indicate that fossil seeds recognized as Dichroa from the Middle Oligocene of Europe may be indistinguishable from those of certain Hydrangea species. Hydrangea heteromalla and Hydrangea paniculata share derived long, spindle-form seeds with a flange at the micropylar pole with Decumaria and Schizophragma, and these taxa may form a monophyletic group that includes Pileostegia. The tropical species of Hydrangea section Cornidia share a derived rarity of anticlinal crosswalls in the seed body. Current phylogenetic hypotheses indicate that the micropylar cowls that Cardiandra and Deinanthe share with Deutzia are evolutionary parallelisms. A derived funicular appendage supports prior hypotheses of monophyly for Fendlerella and Whipplea. These two genera may be most closely related to Fendlera, with which they share seed coat cells with convex long axes.