Phylogeny of the genus Mallomonas (Synurophyceae) and descriptions of five new species on the basis of morphological evidence

Abstract

Jo B.Y., Shin W., Kim H.S., Siver P.A. and Andersen R.A. 2013. Phylogeny of the genus Mallomonas (Synurophyceae) and descriptions five new species on the basis of morphological evidence. Phycologia 52:266–278. DOI: 10.2216/12-107.1

We used a molecular analysis based upon three genes, coupled with the ultrastructure of scales and bristles, to investigate phylogenetic relationships within Mallomonas, with a focus on the section Planae. Fossil taxa discovered in Middle Eocene lacustrine deposits from northwestern Canada were used to calibrate a relaxed molecular clock analysis and investigate temporal aspects of species diversification. Four new extant species, Mallomonas lacuna, M. hexareticulata, M. pseudomatvienkoae, M. sorohexareticulata, and one new fossil species, M. pleuriforamen, were described on the basis of morphological differences, including the number, distribution, and size of base plate pores, the secondary structures on scale surfaces, and characteristics of the bristles. Four of the new species align with M. matvienkoae and the fifth with M. caudata. Molecular phylogenetic analyses inferred using nuclear-encoded small-subunit ribosomal (r)DNA and large-subunit rDNA and plastid-encoded rbcL sequences placed four of the new species with M. matvienkoae, the fifth with M. caudata, all in a strongly supported clade within the section Planae. A Bayesian relaxed clock analysis showed that the genus Mallomonas diverged into two major clades about 133 Ma (Early Cretaceous), one of which represents the section Planae. The earliest diverging lineage within the section Planae was M. bangladeshica, followed by M. heterospina and M. oviformis, and most recently by M. sorohexareticulata and M. hexareticulata.

Key Words::

• Cretaceous
• Mallomonas
• Molecular phylogeny
• Morphology
• Scale
• Ultrastructure

ACKNOWLEDGEMENTS

This study was supported by the survey of Indigenous Biological Resources of Korea and Korean Tree of Life research program from National Institute of Biological Resources to WS; grants DEB-0716606, DEB-1049583 and DEB-1144098 to PAS from the US National Science Foundation; grant DEB 0949211 to RAA from the US National Science Foundation.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/12-107.1.s1.