PHYLOGENETIC ANALYSES OF TRIBE NITELLEAE (CHARACEAE) USING RBCL SEQUENCE DATA.

Karol, K. G. 1 , McCourt, R. M. 2 , Casanova, M. 3 , Proctor, V. 4 & Delwiche, C. F. 11 Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD, 20742, USA; 2 Department of Botany, Academy of Natural Sciences, Philadelphia, PA, 19103, USA; 3 'Langmorn', RMB L620, Westmere, Victoria 3351, Australia; 4 Department of Biology, Texas Tech University, Lubbock, TX, USA The tribe Nitelleae (Characeae) currently includes two genera, Tolypella and Nitella. Wood and Imahori's monograph of the Characeae divides Tolypella into two sections and Nitella into three subgenera with seventeen sections. We determined sequence data for the gene rbcL from representatives of both sections of Tolypella and the three subgenera of Nitella to test the monophyly of these groups. Phylogenetic analyses support the monophyly of the Nitelleae as well as Tolypella and Nitella. Both sections of Tolypella were also found to be monophyletic. Within Nitella, subgenera Hyella and Tieffallenia formed monophyletic groups sister to each other. Subgenus Nitella, however, formed two paraphyletic lineages, one including Nitella acuminata, N. bastinii, N. clavata and N. praelonga and the other including N. opaca and N. stuartii. Subgenus Nitella is defined by one‐celled dactyls terminating the branchlet rays, while subgenera Hyella and Tieffallenia exhibit more complex dactyl morphology. The molecular data appear to resolve certain inconsistencies in Wood's classification. For example, in the rbcL analysis, N. hookeri, a multiple‐dactyl species that has nevertheless been placed in subgenus Nitella, falls in a clade characterized by multiple‐dactyl species. Thus, although the traditional sectional classification of Wood does not divide the genus into monophyletic groups, a combined morphological and molecular approach holds promise for erecting a natural classification of Nitella.