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Phylogenetic Relationships and Generic Boundaries in the Episcieae (Gesneriaceae) Inferred from Nuclear, Chloroplast, and Morphological Data

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Episcieae is the most diverse tribe of Gesneriaceae, with 22 genera and over 700 species, or roughly 21% of all Gesneriaceae. The tribe is restricted to the Neotropics and is characterized by axillary flowers derived from a pair-flowered cyme inflorescence by reduction, a three-trace trilacunar node with split lateral bundles, superior ovaries, and with most members having a haploid chromosome number of n = 9 [n = 8 in Codonanthe and Nematanthus]. Most traditionally recognized genera in Episcieae are either known to be non-monophyletic or have not been represented adequately in phylogenetic analyses to test their monophyly. This paper presents phylogenetic analyses utilizing two molecular [the internal transcribed spacer region of 18S-26S nuclear ribosomal DNA (ITS) and the trnH-psbA intergenic spacer for 155 species] and one morphological (99 characters for 120 species) datasets, combined in a total evidence analysis. All traditionally recognized genera of Episcieae except for the monotypic genus Lampadaria are represented. Of the 21 sampled genera in Episcieae, 16 are represented by the generic type species. The genera Glossoloma and Crantzia are segregated from the genus Alloplectus as traditionally recognized. Other genera that are strongly supported as monophyletic include Alsobia, Columnea (with the inclusion of C. dielsii), Corytoplectus, and Episcia. Drymonia is weakly supported and is shown here to be morphologically diverse and in need of further evaluation. Evolution of fruit structure is examined in the context of the phylogenetic results presented here with two previously unreported features that are here referred to as capsules with tardily dehiscent and non-dehiscent endocarps. Three independent origins of resupinate flowers are inferred for Glossoloma, Nematanthus, and Crantzia. Strongly supported clades have centers of diversity in southeastern Brazil (Nematanthus, Codonanthe, Codonanthopsis, and Paradrymonia anisophylla), northern South America (Alloplectus, Drymonia, Columnea, Neomortonia), Central America (Alsobia, Oerstedina, Rufodorsia, Cobananthus), and two clades with diversity in the Guiana Shield [(Paradrymonia, Nautilocalyx, Chrysothemis) and (Lembocarpus, Cremersia, Rhoogeton)]. Neomortonia, a genus of three species, is poorly supported due to conflict among datasets.
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... The separation by pollen types adopted in this study con rms the morphological data already reported for the subtribe; that is, Columneinae is made up of morphologically diverse species (Wiehler 1983;Weber 2004a;2004b;Clark et al. 2006;Clark 2009). It was possible to verify that even species with similar external morphology (positioned in the same genus) differ in pollen grain morphology. ...
... The analyses by Clark et al. (2006), Clark et al. (2012), and Mora and Clark (2016) pointed out the need for taxonomic reorganization for the clade composed of Paradrymonia, Nautilocalyx, and Chrysothemis since these are probably non-monophyletic genera, and the morphology of the pollen grains of their species can be used, together with other data, to assist the taxonomy of the group. Thus, other studies involving the palynology of Columneinae may clarify the taxonomic relationships of the subtribe. ...
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Columneinae, a morphologically diverse Neotropical group of Gesneriaceae, is strongly supported as a monophyletic, but many of the genera are weekly supported and lack diagnostic characters at the generic level. Predominantly distributed in the Andes and Amazon biomes, this group has not been evaluated from a palynological context. To address this gap and initiate comprehensive pollen studies within Columneinae, we conducted analyses on 28 species belonging to the genera Centrosolenia Benth., Chrysothemis Decne., Columnea L., Drymonia Mart., Glossoloma Hanst., Lesia J.L.Clark & J.F.Sm., Nautilocalyx Linden., and Trichodrymonia Oerst. Pollen grains were subjected to acetolysis, measurement, and light microscopy, with select species also examined under scanning electron microscopy. Quantitative data underwent statistical analysis tailored to the sample size and multivariate analysis. Variability was observed in size, shape, aperture type, aperture number, ectoaperture length, endoaperture shape, and exine ornamentation. The diverse morphological features led to the identification of distinct pollen types within Columneinae clades. Our findings suggest that eurypalynous pollen grains define most Columneinae and that stenopalynous pollen grains define Chrysothemis ; however, comprehensive palynological studies involving a broader array of species within the subtribe are imperative to enhance our understanding of its palynology.
... Hanstein (1854) initially recognized Glossoloma as a genus but later (Hanstein 1865) lumped it with four other genera into Alloplectus Mart. The non-monophyly of Alloplectus was recognized through phylogenetic studies (Clark and Zimmer 2003;Clark et al. 2006) and resulted in a reclassification of several genera, including most of the currently recognized species in Glossoloma (Clark 2005). Glossoloma is differentiated from other genera in the Gesneriaceae by the presence of resupinate flowers, a character not mentioned by Hanstein (1854Hanstein ( , 1865, but more recently defined as a morphological synapomorphy for the genus (Clark and Zimmer 2003;Clark 2005;Clark et al. 2006). ...
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... The genus Glossoloma is defined by resupinate (upside down) flowers, a feature that was recently documented and discovered as a morphological synapomorphy (Clark and Zimmer 2003;Clark et al. 2006;Clark 2009;Clark et al. 2012). Glossoloma corollas are usually tubular, apically pouched and appear laterally compressed. ...
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