Palynology of Selected Species of Blechnaceae (Polypodiopsida: Polypodiales)

• Published in: Palynology 2021-07, Vol.45 (3), p.507-520
• Main Authors: da Silva, Dilma Melo, da Silva Sylvestre, Lana, Ferreira Mendonça, Cláudia Barbieri, Gonçalves-Esteves, Vania
• Format: Article
• Language: English
• Subjects: Aquatic plants; Austroblechnum; Blechnaceae; Blechnoideae; Blechnum; Classification; Doodia; Electron microscopy; electron microscopy data; Ferns; Filaments; Genera; Geographical distribution; Identification; leptosporangiate ferns; living taxa; Morphology; Morphometry; ornamentation; Paleobotany; Palynology; palynomorphs; palynotaxonomy; Parablechnum; Perforation; Phylogeny; Plantae; Polyploidy; Polypodiales; Polypodiopsida; Pteridophyta; Scanning electron microscopy; SEM data; Species; Species classification; Spores; Stenochlaenoideae; Taxonomy; Woodwardioideae
• ISSN: 0191-6122; 1558-9188
• DOI: 10.1080/01916122.2021.1872728

The Blechnaceae is a family of leptosporangiate ferns with a wide geographical distribution. Recent phylogenies revealed several lineages within the family, culminating in a classification system comprising 25 recognized genera grouped into three subfamilies. Spore surface morphology has major importance in the taxonomy of the group, but there is limited information on the relevance of other palynological characters. This study aimed to examine whether spore morphology aids in distinguishing genera of Blechnaceae according to the current phylogenetic classification. Spores from 28 species distributed in 12 genera of the subfamilies Blechnoideae, Stenochlaenoideae, and Woodwardioideae were examined. Specimens were acetolyzed, measured, described, and illustrated using light and scanning electron microscopy. The analyzed spores were medium to large in size, with a monolete scar of varied size, straight, and without margo. The perine was three-layered, except in the subfamily Stenochlaenoideae, which showed a single-layered perine. Blechnoideae was the most palynologically diverse subfamily. Woodwardioideae and Stenochlaenoideae spore characters had high diagnostic value for identification at the genus level. Austroblechnum and Blechnum showed high similarity; no single spore character could be used to discriminate between species of these genera. Blechnum anthracinum was the only species within its genus to exhibit cristate spores, with filaments and perforations. Morphometric analysis did not prove to be a useful tool for differentiating subfamilies or genera, possibly because of the influence of polyploid individuals. This investigation revealed unique spore characters for some genera and provided morphological descriptions that allow identification at the species level, contributing to the taxonomic study of Blechnaceae.