On the spore ornamentation of the microsoroid ferns (microsoroideae, polypodiaceae)

Abstract

Microsoroideae is the third largest of the six subfamilies of Polypodiaceae, containing over 180 species. These ferns are widely distributed in the tropical and subtropical regions of the Old World and Oceania. We documented the spore ornamentation and integrated these data into the latest phylogenetic hypotheses, including a sampling of 100 taxa representing each of 17 major lineages of microsoroid ferns. This enabled us to reconstruct the ancestral states of the spore morphology. The results show verrucate ornamentation as an ancestral state for Goniophlebieae and Lecanoptereae, globular for Microsoreae, and rugulate surface for Lepisoreae. In addition, spore ornamentation can be used to distinguish certain clades of the microsoroid ferns. Among all five tribes, Lecanoptereae show most diversity in spore surface ornamentation.

A revised subfamilial classification of Polypodiaceae based on plastome, nuclear ribosomal, and morphological evidence

“…Thus, the phylogenetic framework could be used to assess the infrafamilial ranks within Polypodiaceae, and we are now in a position to re‐evaluate the delimitation of subfamilies and synapomorphies that may serve as important characters uniting them. Although frequent parallel evolution and homoplasy in morphology have been reported in Polypodiaceae (e.g., Hovenkamp, 1996; Schneider & al., 2009; He & al., 2018), one solution for a stable infrafamilial classification might be identifying diagnostic combinations of characters (Table 3) that are predicted to be of systematic value including stele arrangement in rhizomes and petioles, venation pattern, and spore ornamentation (De la Sota, 1973; Van Uffelen & Hennipman, 1985; Van Uffelen, 1992, 1993, 1997; Tejero‐Díez & al., 2010; Chen & al., 2021), instead of using a single synapomorphy. For instance, the combination of rhizome scales, leaf shapes, venation patterns and features of paraphyses is effective for distinguishing clades/subclades within Lepisorus , Pleopeltis , and grammitid ferns (Ranker & al., 2004; Otto & al., 2009; Wang & al., 2010a,b; Zhao & al., 2020a), and such an approach is also applicable at higher levels of classification.…”

“…The generic circumscription of Leptochilus , Microsorum , and Phymatosorus needs further investigation, though recent phylogenetic study has indicated the need for further subdivision of Microsorum and Phymatosorus (Chen & al., 2020, 2021). The recognition of Ellipinema from Lepisorus (Zhang & al., 2020a) is problematic and should be rejected because evidence from plastid and nuclear data indicates that the type of this genus, Lepisorus jakonensis , and its allied lineages (e.g., Lemmaphyllum , Lepidomicrosorium , Neocheiropteris , Neolepisorus , Tricholepidium ) may have experienced ancient hybridization events within Lepisorus (Wei & al., 2021b).…”

De Novo Transcriptome Assembly of Two Microsorum Fern Species Identifies Enzymes Required for Two Upstream Pathways of Phytoecdysteroids

“…Currently, the genus Microsorum can be divided into at least 98 species [37]. At present, a limited number of studies associated with the members in the genus Microsorum has been reported.…”

Thylacopteris minuta (Polypodiaceae), a new fern species from Myanmar

“…To estimate the phylogenetic position of the accession of interest, plastid rbcL sequences of Polypodiaceae were obtained from Genbank ( https://www.ncbi.nlm.nih.gov/genbank/ ), covering all genera accepted in PPG I (2016) as far as data availability enabled. To reflect recent progress in our understanding of the natural classification of Polypodiaceae , the treatment of some taxa deviated from PPGI by adapting new concepts ( Testo et al 2019 ; Zhao et al 2020 ; Chen et al 2021 ). In the Genbank database, some accessions contained indels, which should not be present in rbcL since it is a protein-coding gene; we removed such low-quality accessions.…”

“…Considering the reported results of phylogenetic studies focusing on Polypodiacae, Thylacotperis was included in a broadly defined Microsoroideae in PPG I (2016) . Reflecting its isolated phylogenetic position, Chen et al (2019 , 2021 ) introduced a tribe Thylacoptereae only including Thylacopteris .…”