Taxonomic reappraisal of Monostromataceae (Ulvophyceae: Chlorophyta) based on multi-locus phylogeny

Abstract

Monostromataceae have been considered a morphologically discrete group of green algae having thalli made up of a single layer of cells; the family is ubiquitous in intertidal zones of marine and estuarine habitats across the world., However, this view blocks the real complexity of these algae. Using phylogeny reconstruction methods based on five independent molecular data sets (namely, ITS1, ITS2, 5.8S, nrDNA 18S, and rbcL), evolutionary history of this family was inferred for the first time. Results show that monostromatacean algae that have the typical Codiolum-stage sporophyte in the life cycle belong to three clades within Ulotrichales. The present study also suggests that both Ulotrichales and Ulvales are polyphyletic. This report demonstrates for the first time that the 5.8S gene, an often overlooked nucleoribosomal cistron, is a powerful locus for algal phylogeny reconstruction at higher taxonomic levels.

Keywords:

• 5.8S
• 18S
• algae
• Bayesian inference
• internal transcribed spacer
• maximum likelihood
• molecular systematics
• phylogenetics
• rbcL
• Ulotrichales
• Ulvales
• Ulvophyceae

Acknowledgements

This work was supported in part by a PhD fellowship from MEXT, Japanese Government awarded to FB and an INSPIRE Faculty Award from the Department of Science and Technology, Government of India. Profound thanks to Satoshi Kubota and Kazuo Okuda who supported this study. Christine A Maggs and Frédéric Mineur helped us in the sample acquisition from Northern Ireland, UK Frédéric Mineur also contributed by translating a key French reference to English and by suggesting some methodological modifications that greatly helped. Maria Kahlert helped us with translation from Swedish. Ian Jenkinson kindly provided an important offprint reference.