Proposal for an Expanded Distichlis (Poaceae, Chloridoideae): Support from Molecular, Morphological, and Anatomical Characters

Abstract

The Distichlis clade comprises Distichlis (7 species), Monanthochloë (2), and Reederochloa (1). All species except D. distichophylla (endemic to Australia) and D. spicata (widespread in the New World) are restricted either to North or South America. We investigated phylogenetic relationships within the clade using chloroplast (trnL–F and ndhF) and nuclear ribosomal (internal transcribed spacers and 5.8S) DNA sequences. We also studied lemma micromorphology, leaf blade anatomy, macromorphology, and biogeography in a phylogenetic context. The Distichlis clade is strongly supported in the molecular analyses. A morphological synapomorphy for the clade is the presence of a single papilla on the center of each subsidiary cell of lemma stomata. Other diagnostic features include dioecy, rhizomes or stolons, conspicuously distichous leaves, 5–13 lemma nerves, dumbbell- or flask-shaped bicellular microhairs with sunken basal cells, and growth in alkaline or saline soils. The nuclear and chloroplast phylogenies indicate that Monanthochloë and Reederochloa are nested within a paraphyletic Distichlis, and a number of structural characters, including leaf blade length, number of spikelets per inflorescence, and number of florets per spikelet, also fall within the range of variation in Distichlis. Therefore, we propose expanding the circumscription of Distichlis to include Monanthochloë and Reederochloa, and make the following new combinations: Distichlis acerosa, D. eludens, and D. littoralis. Biogeographical analysis revealed that the group likely originated in North America followed by a number of long-distance dispersal events, including back dispersals.

A classification of the Chloridoideae (Poaceae) based on multi-gene phylogenetic trees

“…Villamil, both members of a clade with M. littoralis (=Distichlis littoralis (Engelm.) H. L. Bell & Columbus) and Reederochloa that was sister to all other species of Distichlis (Bell and Columbus, 2008b).…”

“…We also support this view since at least three (Buchloe, Cathestecum, and Opizia) were included in our analysis and all our trees depict a strongly supported Boutelouinae (excluding Neobouteloua). In a three gene study (ITS, ndhF, and trnL-F) of the Monanthochloinae, Bell and Columbus, 2008b proposed expanding Distichlis to include two species of Monanthochloe and Reederochloa eludens (=Distichlis eludens (Soderstr. & H. F. Decker) H. L. Bell & Columbus).…”

X. Subfamily Chloridoideae Kunth ex Beilschm. (1833)

“…Clayton and Renvoize (1986) suggest that the presence of microhairs with the basal cell sunken in the epidermis may be synapomorphic for this genus. Bell and Columbus (2008) show clearly that this sort of microhair also occurs in Eragrostis obtusiflora, and hint that the latter species may be sister to Distichlis rather than part of Eragrostis. Distichlis could be placed in its own subtribe, Monanthochloinae Pilg.…”

“…The inclusion of Reederochloa and Monanthochloë in Distichlis is supported by multiple characteristics of morphology and anatomy, as well as molecular data (Bell and Columbus 2008). Clayton and Renvoize (1986) suggest that the presence of microhairs with the basal cell sunken in the epidermis may be synapomorphic for this genus.…”

Adiciones y nombres actualizados de las gramíneas de Durango, México

“…Dávila et al (2006) compiled and edited the corresponding data of the accepted names and synonymy for the Mexican taxa in the "Catálogo de las Gramíneas de México". The present article is based on these two last catalogues, and has been further enriched by recently published treatments (e.g., Finot et al 2004, Bess et al 2006, Zuloaga et al 2007, Bell and Columbus 2008, Valdés-Reyna et al 2009, Columbus and Smith 2010, Peterson et al 2010, Chemisquy et al 2010, Peterson et al 2012) and/or additions of new described species (Finot et al 2004, Peterson and Columbus 2009). In addition, I have included new reports based on review of recently collected grass specimens in the state of Durango (Herrera Arrieta et al 2004, Herrera Arrieta and Cortés Ortíz 2009, Herrera Arrieta et al 2012.…”