THE PHYLOGENETIC Neil Snow2 UTILITY OF LEMMATAL MICROMORPHOLOGY IN LEPTOCHLOA S.L. AND RELATED GENERA IN SUBTRIBE ELEUSININAE (POACEAE, CHLORIDOIDEAE, ERAGROSTIDEAE)' ABSTRACT Micromorphological features of the lemma were investigated in the subtribe Eleusininae (Poaceae) using scanning electron microscopy. Ninety-two taxa were studied, which included 48 genera and ail currently recognized species of Leptochloa s.l. Ail species of Leptochloa and a majority of genera in Eleusininae have cork cells, but silica cells are mostly absent in Leptochloa and most related genera in Eleusininae. Enneapogonoid-type microhairs are reported for Cladoraphis cyperoides and Psammagrostis wiseana, representing only the second report in Eleusininae. Although bicellular microhairs occur in most taxa, variations in microhair type, coupled with the occurrence of partitioning membranes, give them supra-specific phylogenetic utility. The occurrence of papillae on short and long cells varies within Leptochloa and between genera. Prickles are ubiquitous in Leptochloa and most related genera. Macrohairs are present in ail species of Leptochloa but absent in some related genera. Clavicorniculate macrohairs are reported for one species each of Leptochloa and Coelachyrum, and a corniculate macrohair was observed in Cynodon. A crispate macrohair occurring in three species of Coelachyrum is described for the first lime and probably represents a syn-apomorphy in that genus. The analysis of Leptochloa suggests that micromorphological characters vary little within a genus, and thus have the potential to serve as phylogenetic markers at the generic level. Uncertainty concerning the homologous relationships of papillae, hooks, prickles, and macrohairs is discussed in light of this study and previous literature. RESUMEN Las caracterfsticas micromorfol6gicas de la lema en la subtribu Eleusininae (Poaceae) se examinaron utilizando microscopfa electr6nica de barrido. Se estudiaron 92 taxa, 48 g�neros, y todas las especies de Leptochloa hasta ahora reconocidas. Todas las especies de Leptochloa y la mayorfa de los g�neros de Eleusininae tienen c�lulas suberificadas, pero las c�lulas silicfferas est�n ausentes en Leptochloa y en la mayorfa de los taxa de Eleusininae. Se reporta porsegunda vez en Eleusininae la presencia de micropelos bicelulares de tipo enneapogonoid para Cladoraphis cyperoidesy Psammagrostis wiseana. Aunque los micropelos bicelulares se presentan en casi todos los taxa, variaciones en eltipo de micropelo, junto con la presencia de membranas divisorias les dan valor diagn6stico para estudios filogen�ticossupraespecfficos. La presencia de papilas de c�lulas cortas y estrechas es variable en Leptochloa y entre los otrosg�neros. Los aguijones se encuentran en todas las especies de Leptochloa y la mayorfa de los g�neros relacionados.Los macropelos est�n generalmente presentes en todas las especies de Leptochloa pero est�n ausentes en algunos taxarelacionados. Se reportan macropelos clavicorniculados para un especie de ambos g�neros Leptochloa y Coelachyrum,y un macropelo corniculado se reporta para Cynodon. Un macropelo crispado en tres especies de Coelachyrum esdescrito por primera vez, y quiz� represente una sinapomorffa de cierto nivel en ese g�nero. El an�lisis de Leptochloaindica que las caracterfsticas micromorfol6gicas varfan poco, y por tanto tienen valor para estudios filogen�ticos su-praespecfficos. La dificultad sobre las relaciones hom�logas de papilas, ganchos, aguijones, y macrotricomas se discutecon base a 1o hallado en este estudio y con datos anteriores de la literatura. Cladistic estimations of phylogenetic history with easily defined character states. This tendency maymorphological characters tend to favor the use of reflect the potential pitfalls discussed by Chappilldistinct qualitative characters, or those possessing (1989) and Stevens (1991) in the uncritical use of ' Mike Veith facilitated the work with assistance at the Electron Microscopy Laboratory at Washington University. 1thank the curators of B, BM, BRI, CANB, MO, PRE, and US for sending loans and for granting permission to sampledirectly from herbarium specimens. S. Hatch sent an original version of Morden's dissertation, and helpful discussionsANN. MISSOURI BOT. GARD. 83: 504-529. 1996.
The Phylogenetic Utility of Lemmatal Micromorphology in Leptochloa S. L. an Related Genera in Subtribe Eleusininae (Poaceae, Chloridoideae, Eragrostideae)
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