Molecular phylogeny of the arthrostylidioid bamboos (Poaceae: Bambusoideae: Bambuseae: Arthrostylidiinae) and new genus Didymogonyx

Abstract

We present the first multi-locus chloroplast phylogeny of Arthrostylidiinae, a subtribe of neotropical woody bamboos. The morphological diversity of Arthrostylidiinae makes its taxonomy difficult and prior molecular analyses of bamboos have lacked breadth of sampling within the subtribe, leaving internal relationships uncertain. We sampled 51 taxa, chosen to span the range of taxonomic diversity and morphology, and analyzed a combined chloroplast DNA dataset with six chloroplast regions: ndhF, trnD-trnT, trnC-rpoB, rps16-trnQ, trnT-trnL, and rpl16. A consensus of maximum parsimony and Bayesian inference analyses reveals monophyly of the Arthrostylidiinae and four moderately supported lineages within it. Six previously recognized genera were monophyletic, three polyphyletic, and two monotypic; Rhipidocladum sect. Didymogonyx is here raised to generic status. When mapped onto our topology, many of the morphological characters show homoplasy.

Flora of Guaramacal (Venezuela): Monocotyledons

“…This genus has been a catchall among arthrostylidioid bamboos, and as a consequence, the current concept is polyphyletic (Judziewicz and Clark, 1993;Tyrrell et al, 2012 [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] or more secondary branches; branches subequal or with 1 more robust than the others. Culm leaves: 20-47 cm long, scabrous, deciduous; sheaths 8-17 cm long; blades narrowly triangular, 11-36 cm long, erect, persistent, apices acuminate, bases with tiny fimbriate auricles on 1 side only.…”

“…Culms unarmed, erect or scandent, hollow; midculm nodes usually bearing a single, dominant branch; internodes subequal; secondary branches solitary or numerous, the same thickness as the main culm or slightly thinner. Tyrrell et al (2012).…”

“…The two species of Didymogonyx were included most recently in Rhipidocladum s.l., albeit in a section readily distinguished from Rhipidocladum s. str. by having alternating long and short internodes along the culm, culm leaf fimbriae, spikelets in pairs and triads, and several other distinctive morphological and foliar anatomical characters Tyrrell et al, 2012 fig. 108.…”

Three new species of <i>Rhipidocladum</i> (Poaceae: Bambusoideae: Arthrostylidiinae) from South America

“…Rhipidocladum appears to be more restricted, known only from montane forests in South America, mainly along the Andes, from northern Colombia to Bolivia at elevations of 1200-2800 m (Fig 1). Morphological investigation of Rhipidocladum as a part of recent phylogenetic work (Tyrrell et al 2012) uncovered several distinctive specimens that we were able to separate into three new species. Here we describe and illustrate two new species of Rhipidocladum sect.…”

“…The genus has a distinctive fan-like branching architecture that is mirrored in allied genera Actinocladum (McClure in Soderstrom 1981: 1201, Didymogonyx (L. G. Clark & Londoño 1991: 1271 C. D. Tyrrell, L. G. Clark & Londoño (2012: 146) and Merostachys Sprengel (1825: 132). Rhipidocladum species are differentiated from these by having a basic caryopsis (Actinocladum and Merostachys possess a nucoid caryopsis) and uniform culm internode lengths (Didymogonyx is characterized by alternating short and long internodes along the culm; Tyrrell et al 2012). The genus is divided into two sections: the monotypic Rhipidocladum sect.…”