Perispore Morphology of Bolbitidoid Ferns (Dryopteridaceae) in Relation to Phylogeny

Abstract

The perispores of 48 species of bolbitidoid ferns (Mickelia, Arthrobotrya, Bolbitis, Elaphoglossum, Lomagramma, and Teratophyllum) were studied with an SEM. The species studied were those used in a published phylogenetic analysis. For each species, five perispore characters were scored and optimized onto a published molecular tree. A loose, nonappressed perispore with broad folds optimizes as ancestral for the bolbitidoids. The only exception is Lomagramma, for which the perispore adheres tightly to the exospore—a character state that optimizes as a synapomorphy for that genus. In the bolbitidoids, thin crests evolved from broad folds seven times. The presence of thin crests in Mickelia optimizes as a synapomorphy for that genus. The presence of fine surface detail, here termed “microstructure,” was present in nearly all bolbitidoids and optimized as ancestral. Microstructure consisted of spicules, minute crests, and verrucae. The presence of verrucae optimizes as a synapomorphy for Lomagramma. The perispore of Bolbitis appendiculata is visually striking because it is highly reticulate throughout, a character that is autapomorphic in this analysis. No correspondence was observed between perispore characters and the transition series going from terrestrial (Bolbitis) to hemiepiphytic (Mickelia, Arthrobotrya, Lomagramma, and Teratophyllum) to epiphytic (Elaphoglossum) genera. The spore images of all species studied are publicly available at http://www.plantsystematics.org.