EVOLUTIONARY MORPHOLOGY OF THE EUGLENID CHLOROPLAST: TAXONOMIC IMPLICATIONS

Abstract

Brown, P. J. P. B1, Farmer, M. A.1 & Zakrys, B.2 1Department of Cellular Biology, The University of Georgia, Athens, Georgia 30602 USA; 2Department of Plant Systematics and Geography, Warsaw University, PolandThe euglenophytes are a monophyletic assemblage within the Euglenida. The use of chloroplast morphology as a tool for taxonomy is nearly as old as euglenid systematics. Different taxa have been united based on the morphology of the chloroplast margin, the structure of the pyrenoid (if present), and the relative size and number of plastids. The previous taxonomies based on chloroplast morphology have not, however, had the benefit of modern ultrastructural and molecular biological techniques to aid in their evaluation. The current study uses morphological characters as discerned from confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM) to discern monophyletic sub‐groups within the Euglenophyta (sensu‐stricto). These hypotheses are being independently tested with molecular characters in the form of intron content in the plastid encoded gene rbcL. The current project is a pilot study using chloroplast ultrastructure in six species of euglenophytes from four genera to assess the validity of a heretofore unidentified group. Initial observations suggest that a monophyletic group with an inward projecting pyrenoid, capped by a cupped shape paramylon grain exists within the euglenophytes. We propose to name this group the Mucoglena based on an apomorphic secretion of mucilage unlike that seen in other euglenophytes.