Comparative Floral Structure and Systematics of Fouquieriaceae and Polemoniaceae (Ericales)

Abstract

Floral morphology, anatomy, and histology are comparatively studied in Fouquieriaceae and Polemoniaceae, and previous studies are reviewed. In recent molecular phylogenetic analyses, the two families form a strongly supported clade within the asterid order Ericales, while they were generally placed far from each other in premolecular classifications. This study documents unexpectedly diverse floral features for Polemoniaceae, including various corolla aestivation patterns, different types of anther attachment and anther morphology, as well as two types of nectary structure. Prominent features shared by the two families include determinate‐terminal inflorescences, hyaline sepal margins, similar patterns of floral vasculature, late sympetalous corolla development, similar degrees of sympetaly, sterile connective protrusions, short thecal septa, endothecium‐like cells in the connective, trimery in the gynoecium, a stylar canal, parietal, and axile and placentation in the same ovary, similar patterns of ovule arrangement and ovule orientation, distally curved micropylar canals, mesophyll‐type nectaries with stomata, winged seeds, and seed coat epidermal cells with helical or annular wall thickenings. Several of these features represent potential synapomorphies for the clade with Fouquieriaceae and Polemoniaceae. In addition, potential synapomorphies are also identified for the individual families. While the results of this investigation further support the close relationship of Polemoniaceae and Fouquieriaceae, they also emphasize that it is necessary to abandon preconceptions about the “systematic importance” of certain characters that turn out to be more homoplasious than previously thought.