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The taxonomic subdivision of Cyatheaceae, a family containing over 600 species of scaly tree ferns, has troubled pteridologists for more than one century. Recent molecular analyses have revealed four monophyletic groups (Alsophila R. Br., Cyathea Sm., Gymnosphaera Blume, and Sphaeropteris Bernh.) within this family. However, one of the four groups, Gymnosphaera, was still submerged in Alsophila in a modern classification proposed by the Pteridophyte Phylogeny Group due to Gymnosphaera being phylogenetically underrepresented in previous studies. In this study, we add the sampling of Gymnosphaera from its main distribution area (southeastern Asia) and conduct phylogenetic analyses of datasets containing individual and combined five chloroplast DNA regions (rbcL, rbcL-accD, rbcL-atpB, trnG-trnR, and trnL-trnF) of 120 scaly tree ferns using three methods (maximum parsimony, maximum likelihood, and Bayesian inference). The result is congruent with previous studies, consistently resolving scaly tree ferns as four well-supported clades with Sphaeropteris sister to the other three, and shows a probability for the first time on the relationships between Alsophila, Cyathea, and Gymnosphaera, i.e., Alsophila is sister to Gymnosphaera and then together as sister to Cyathea. As supported to be distinct from Alsophila in molecular phylogeny, in morphology, and in sporogenetic mechanism, Gymnosphaera is reinstated here, with a minor emendation in circumscription, as a separate genus. To facilitate the application of species' names and future revision, we provide a checklist of 43 taxa now known in Gymnosphaera with information of nomenclatural types and general distributions; among them 25 are new combinations.
A taxonomic revision of the species belonging to the Didymopanax group of Neotropical Schefflera J. R. Forst. & G. Forst. (Araliaceae) is here presented. This monophyletic group is currently recognized only informally, and comprises 37 species mostly restricted to small areas of lowland to mid-elevation tropical regions across Brazil and adjacent southern Venezuela. Five names are newly placed in synonymy: Didymopanax gardneri Seem. var. ellipticus Marchal [= Schefflera glaziovii (Taub.) Frodin & Fiaschi], D. morototoni var. sessiliflorus Marchal [= Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin], Schefflera megacarpa A. H. Gentry [= Schefflera confusa (Marchal) Harms], Schefflera morototoni var. angustipetala (Marchal) Frodin [= Schefflera tamatamaensis Maguire, Steyerm. & Frodin], and Schefflera yutajensis Steyerm. & B. Holst [= Schefflera quinquecarinata Steyerm.]. Thirty-two names are lectotypified: D. angustissimus var. conspicuus Marchal [= Schefflera angustissima (Marchal) Frodin], D. anomalus Taub. [= Schefflera angustissima], D. claussenianus Decne. & Planch. ex Marchal [= Schefflera calva (Cham.) Frodin & Fiaschi], D. falcatus Marchal [= Scheffleraangustissima], D. gardneri var. ellipticus Marchal, D. morototoni var. poeppigii (Decne. & Planch.) Marchal [= Schefflera morototoni], D. morototoni var. sessiliflorus Marchal, D. venulosus Taub. [= Schefflera vinosa (Cham. & Schltdl.) Frodin & Fiaschi], Panax sericeus Pohl ex DC. [= Schefflera vinosa], P. speciosus Willd. [= Schefflera morototoni], P. splendens Kunth [= Schefflera morototoni], Scheffleraangustissima, Schefflera burchellii (Seem.) Frodin & Fiaschi, Schefflera calva, Schefflera cephalantha (Harms) Frodin, Schefflera confusa,Schefflera cordata (Taub.) Frodin & Fiaschi, Schefflera decaphylla (Seem.) Harms, Schefflera distractiflora (Harms) Frodin, Scheffleragardneri (Seem.) Frodin & Fiaschi, Schefflera glaziovii, Schefflera longipetiolata (Pohl ex DC.) Frodin & Fiaschi, S.lucumoides (Decne. & Planch. ex Marchal) Frodin & Fiaschi, Schefflera macrocarpa (Cham. & Schltdl.) Frodin, Schefflera malmei (Harms) Frodin, Scheffleramorototoni, Schefflera morototoni var. angustipetala, Schefflera paraensis Huber ex Ducke [= Schefflera decaphylla], Schefflera selloi (Marchal) Frodin & Fiaschi, Schefflera succinea Frodin & Fiaschi, Schefflera vinosa, and Sciodaphyllum paniculatum Britton [= Scheffleramorototoni]. Additionally, D. pachycarpus Marchal [= Schefflera calva] is neotypified. We also provide information on the taxonomic history of Didymopanax Decne. & Planch., general morphological comments on the Didymopanax group, an identification key to species, and for each of the accepted species, the geographic distribution, preferred habitats, diagnostic features, illustrations, maps, a list of examined material, and nomenclatural comments. A list of exsiccatae with all examined specimens is also provided.
This study, the fifth in a series investigating palynological characters in angiosperms, aims to explore the distribution of states for 19 pollen characters on five early diverging orders of Superasteridae (Berberidopsidales, Caryophyllales, Cornales, Ericales, and Santalales) plus Dilleniales. To illustrate the character states found in the pollen of this group, we examined pollen grains of 15 species exemplifying 15 families across all studied orders using light, scanning, and transmission electron microscopy. We reconstructed the phylogeny of the early diverging Superasteridae and related taxa with eight genetic markers for 172 genera, using maximum likelihood (ML) analysis. Nineteen pollen characters were coded for the genera used in this phylogeny and compiled into two morphological matrices using two coding strategies. The characters were then optimized on the newly generated ML tree plus two constrained trees differing in the position of Dilleniales, using three methods of inference. Taxa in this grade show a striking diversity of pollen morphologies, particularly in certain characters such as size, tectum sculpture, and aperture number. The plesiomorphic condition for the early diverging Superasteridae is unambiguously and consistently inferred to comprise monad-dispersed, isopolar, spheroidal, circular in outline, equatorially arranged, tricolpate pollen grains with granular aperture membranes, a smooth tectum, and endexine present. We identify diagnostic character states and synapomorphies for several monophyletic groups, and explore the palynological evidence that may shed light on some unresolved relationships. For example, the hypothesis that Dilleniales is sister to Superrosidae is better supported than alternative hypotheses, being consistent with a number of shared palynological state changes including transitions to presence of costae, reticulate tectum, and columellar infratectum structure. Across this part of the angiosperm phylogeny, most state transitions occur repeatedly, and their frequency varies among both clades and characters. We discuss the impact of optimization method, tree topology, and coding strategy upon ancestral state reconstruction.