An updated phylogeny and infrageneric classification of the genus Sisyrinchium (Iridaceae): Challenges of molecular and morphological evidence

Abstract

Taxon delimitation and classification remains one of the fundamental bases of evolutionary studies and is especially challenging because processes by which new biological entities arise are complex and non‐linear over time, although continuous. Sisyrinchium (ca. 140 to 216 taxa) is one of the most species‐rich genera of Iridaceae, largely widespread in the Americas. Recent molecular phylogenetic studies have shown that the systematics of the genus is in need of substantial revision. Different data sources were investigated to establish an updated infrageneric classification based on phylogenetic principles. Monophyletic sections of Sisyrinchium were circumscribed using a new phylogenetic framework established from an increased sampling of taxa (107 species), and complementary approaches were combined to provide the most comprehensive infrageneric treatment of the genus proposed so far. Additionally, numerous molecular synapomorphies were identified to reinforce previous taxonomic treatments of tribe Sisyrinchieae (six genera) at the generic level. Major lineages of Sisyrinchium were concordantly resolved with mostly strong to full support by the DNA regions used in the study and ten sections characterized by unique combinations of molecular, morphological and geographical diagnostic characters were recognized. The phylogenetic trees respectively based on plastid + mitochondrial and nuclear ITS DNA regions were generally congruent except for two unplaced species (S. chilense, S. elegantulum) for which ancestral reticulation events were detected. New circumscriptions were provided for seven sections (sect. Cephalanthum, sect. Echthronema, sect. Hydastylus, sect. Segetia, sect. Sisyrinchium, sect. Spathirhachis, sect. Viperella) while three sections (sect. Morphanthus, sect. Rhizilineum, sect. Trichoparcus) were newly described. This work constitutes a robust contribution to elucidate the systematics of Sisyrinchium and emphasizes the need of integrative taxonomic approaches using multiple data sources, not only to improve the delimitation of taxa but also to investigate their evolutionary history.

A comprehensive species sampling sheds light on the molecular phylogenetics of Calothecinae (Poaceae, Pooideae, Poeae): Evidence for a new subtribe and multiple genera within the Chascolytrum clade

“…Incongruences between the nuclear and plastid DNA datasets were explored through visual comparison of topologies and support values between conflicting branches. Incongruent topologies were considered strongly supported with a minimum of 85% bootstrap support (Baker et al, 2011; Tkach et al, 2015) or 0.99 posterior probability (Inácio et al, 2017). After assessing incongruence, we performed analyses of the combined nuclear and plastid DNA datasets.…”

Molecular phylogeny and species delimitation of Stachyuraceae: Advocating a herbarium specimen‐based phylogenomic approach in resolving species boundaries

“…Before combining the ITS and cpDNA datasets, we undertook rapid bootstrap (BS) analysis for each dataset with 1000 replicates. Tree congruence was assessed by visually comparing topologies and support values between conflicting branches, and no remarkable conflicts were observed between the two datasets (i.e., maximum likelihood (ML) BS > 70%, Hillis & Bull, 1993; posterior probability (PP) > 0.99, Inácio et al, 2017). Unambiguous aligned insertions/deletions (indels) were manually coded and appended to the sequence matrix (Table S4).…”

A taxonomic synopsis of Cypella (Iridaceae) in Brazil

“…The list of Iridaceae reported in this project encompasses 160 species distributed among 18 genera . Subsequently, knowledge on systematics and taxonomy of Iridaceae was expanded through increasing collections, phylogenetic approaches (Chauveau et al 2011;Lovo et al 2012;Alves et al 2014;Inácio et al 2017;Stiehl-Alves et al 2017); multivariate statistical treatments (Pastori et al 2018); and various new species publications (Lovo & Mello-Silva 2011;Deble et al 2012c;2015a;b;Aita et al 2013;Chauveau et al 2014;Gil et al 2014;Oliveira et al 2016;Inácio et al 2018). Despite considerable advances, various genera still need to be broadly and thoroughly explored to assess their taxonomic delimitation and infrageneric classification (Chauveau et al 2012;Pastori et al 2018).…”