SYSTEMATICS OF ULVA AND ENTEROMORPHA (ULVALES), WITH EMPHASIS ON SPECIES FROM THE NORTHEAST PACIFIC

Abstract

Hayden, H. S. & Waaland, J. R.Department of Botany, University of Washington, Seattle, WA 98195Ulva L. and Enteromorpha Link are two of the most common macroalgal genera world wide and are well known for their role in “green tides” and marine biofouling. Traditionally, these genera have been distinguished from one another by their different morphologies: Ulva species have distromatic blades, and Enteromorpha species form monostromatic tubes. Despite the distinct morphological difference between these two genera, morphological simplicity and plasticity of algae within each of them have confounded systematic and taxonomic efforts. Recent molecular studies of primarily European taxa indicate that Ulva and Enteromorpha are not reciprocally monophyletic yet within the Ulva/Enteromorpha assemblage several species can be identified. A study of Pacific Ulva and Enteromorpha was undertaken to reconstruct phylogeny and test species hypotheses based on morphology, development and hybridization experiments. Multiple samples of the eleven currently recognized Ulva and Enteromorpha species along the Pacific coast of North America were collected from Alaska to southern California. Collections were identified using existing morphological descriptions, and when possible, growth in culture. Sequences for the internal transcribed spacers of nuclear ribosomal DNA and the chloroplast‐encoded gene for the large subunit of RUBISCO were determined for these samples and additional ones from Australia, Chile, Hawaii and Japan. Sequences for Pacific collections were combined with those for European taxa in phylogenetic analyses using the maximum parsimony criterion. The results provide improved understanding of species diversity and biogeography in Ulva and Enteromorpha and additional evidence for the polyphyly of these genera.