Vegetative morphology and rbcL phylogeny of some members of the genera Botryocladia and Irvinea (Rhodymeniaceae, Rhodophyta)

Abstract

R.J. Wilkes, L. McIvor and M.D. Guiry. 2006. Vegetative morphology and rbcL phylogeny of some members of the genera Botryocladia and Irvinea (Rhodymeniaceae, Rhodophyta). Phycologia 45: 481–494. DOI: 10.2216/05-11.1

Botryocladia is a genus of marine red algae (Rhodophyta) generally found in tropical, subtropical and warm temperate seas. There are currently 35 described species, but the taxonomic status of many of these remains confused. Recently, the genus was split into two genera, with the new genus, Irvinea, described based on morphological and molecular evidence. Only one species, I. ardreana, is currently assigned to the newer genus. For this study, a number of cultured Botryocladia and Irvinea strains from the Mediterranean and Caribbean were examined. Each was examined microscopically and the key features currently used for identification were evaluated. Up to 1277 bp of the rbcL gene was PCR amplified for each isolate and directly sequenced. The molecular data confirm that the species currently considered as Botryocladia do not form a monophyletic group. Botryocladia boergesenii grouped in a clade with I. ardreana with the remaining Botryocladia species in a separate grouping. We propose the transfer of B. boergesenii to the genus Irvinea on the basis of the molecular and morphological data. Morphological and molecular data for the other species examined were also evaluated although little correlation between the morphological features and the rbcL data was observed. The taxonomic utility of some of the morphological features is called into doubt, although clear differences between the genera Botryocladia and Irvinea can be seen. In addition to the morphological features currently regarded as important intergeneric characters, the presence of branched vesicles as an indicator for species of Irvinea should be added.

Key Words::

• Botryocladia
• Irvinea
• Molecular taxonomy
• rbcL
• Rhodymeniaceae
• Rhodophyta
• Systematics

ACKNOWLEDGMENTS

We thank J.A. West, C. Battelli, A.J.K. Millar, J. Huisman, H. Pakker and W.C.H.F. Kooistra for collecting and isolating the cultures used in this investigation. We also thank Wendy Guiry for maintaining the cultures over the last 26 years. Funding was provided by the Irish Higher Education Authority's Programme for Research in Third Level Institutions Cycle 2 to the Environmental Change Institute, NUI, Galway.