PROBLEMS AND PROMISE IN CODING MORPHO‐LOGICAL CHARACTERS FOR PHYLOGENETIC ANALYSIS: AN EXAMPLE FROM AULACOSEIRA (BACILLARIOPHYCEAE)

Edgar, S. M. & Theriot, E. C. Section of Integrative Biology, University of Texas at Austin, Austin TX 78713 USA Understanding the phylogenetic relationships among species of Aulacoseira Thwaites (formerly Melosira, in part) and their relationships to other genera is important for several reasons. Aulacoseira is globally distributed and is often a large component of planktonic communities in lakes, ponds and large rivers. Consequently, it plays a significant ecological role as a primary producer in grazer‐based aquatic food webs. Although species of Aulacoseira (along with other diatom species) are used profitably as tools for reconstruction of paleo‐environments, ecological monitoring, and other ecological studies which have generated a large amount of data, much of this data is not really informative for a systematic understanding of the group. There are currently around 60 extant and 20 extinct described species of Aulacoseira. However, there is no estimate of phylogeny within this genus that includes more than five species. Here we present the first comprehensive estimate of phylogeny for 30 species of Aulacoseira based on a cladistic analysis of morphological features gathered from the literature. Complications of gathering morphological data from the literature that was largely focused on refining species identifications for practical purposes of ecological identification will be addressed. Morphological characters chosen for the analysis and challenges associated with coding of characters will be discussed along with the resulting Aulacoseira phylogeny and our methods of its estimation.