A biosystematic study of the genus Erioneuron Nash (Poaceae, eragrostideae)

Abstract

A biosystematic treatment was made of the New World genus Erioneuron. Materials for morphological, electrophoretic, anatomical, and cytological studies were collected from naturally occurring populations, and from herbarium specimens throughout the range of the species in this genus. The scanning electron microscope was used to examine the lemma micromophology of Erioneuron and 30 other genera of the Eragrostideae. The lemma surface of the genera of the tribe exhibited typical chloridoid characteristics. However, an unique and previously unreported silica deposition, called a silica pore, was observed. Four distinctive patterns of silica deposition were noted: 1) silica pore with silica cell, 2) silica pore without either the silica cell or prickle hair; 3) silica pore with siliceous papillae; and 4) silica pore not observed. These results show that the silica body distribution has taxonomic significance within the Eragrostideae tribe. A morphological analysis was made on 59 population samples of Erioneuron (sen. lat.). Phenetic and basic biostatistical techniques were used to delineate and define taxa. Based on these results, four distinct species were defined. An electrophoretic study was conducted on seedlings representing 33 natural populations. Individuals were assayed for five enzyme systems: PGI, GOT, IDH, PGM, and MDH. The results show that variation at the molecular is concordant with the morphological characters for the separation of taxa. Anatomical characters of both leaf epidermis and leaf cross-section were studied, and descriptions were made of the taxa. Differences between Erioneuron pulchellum and the other species of Erioneuron were evident on leaves studied in cross-section. Leaf anatomy was typical of the C4 photosynthetic pathway, specifically the NAD-me subtype. Based on these studies three species and seven varieties are recognized. Evidence gathered supports the recognition of Dasyochloa (D. pulchella) as a monotypic North American genus. The descriptions given for each of the recognized taxa are a summary of the population sample data analyses.