Spores of Plagiochila (Dumort.) Dumort.: the taxonomic relevance of morphology and ultrastructure

Abstract

Plagiochilaceae is a family of leafy liverworts that are distributed worldwide. It is of great importance due to its taxonomic and ecological implications among bryophytes. Most species of the family belong to the genus Plagiochila, but there is no consensus regarding its infrageneric circumscription. There have been few palynological studies involving Plagiochilaceae and Plagiochila. Here, we describe the spore morphology of seventeen species of Plagiochila and discuss the taxonomic value of palynological characters for these taxa. The spores were processed by standard palynological techniques and analyzed using light and electron microscopy. The spores were found to be apolar, spheroidal, released monads that vary in size from 13µm to 58µm (small to large size). The sporoderm comprises an intine (stratified), a nexine, and a sexine. The spore surface is ornamented with granules that vary in shape and morphology, thus allowing the studied species to be grouped into four spore types: regular and delicate granulate, irregular and coarse granulate, long granules with flattened apices, and long and straight granules. Hierarchical cluster analysis revealed five different groups of species, evidencing the importance of spore information for taxonomic and phylogenetic studies.