Molecular phylogeny suggests transfer of Hemidiscus into Actinocyclus (Coscinodiscales, Coscinodiscophyceae)

Abstract

Hemidiscus cuneiformis, type of the family Hemidiscaceae, is a diatom with a distinctive semi-circular shape in valve view. A strain of H. cuneiformis was established from the coastal region of the tropical southwestern Atlantic Ocean off Brazil. Cells of this strain showed semi-circular to asymmetrically elliptical valves, indicating morphological plasticity. In the small subunit (SSU) rDNA phylogeny, the type species of Hemidiscus branched between two clades of Actinocyclus, one of which was a sister group, the other in a basal position. Beyond cell shape, there are no significant morphological differences between Hemidiscus and Actinocyclus. We propose the transfer of H. cuneiformis and H. kanayanus into Actinocyclus. The family Hemidiscaceae remains for the genus Actinocyclus.

Keywords:

• Bacillariophyta
• DNA barcoding
• molecular phylogenetics
• new combination
• pseudonodule
• pseudonodolus

ORCID

Fernando Gómez http://orcid.org/0000-0002-5886-3488

Additional information

Funding

This work was supported by the Brazilian Conselho Nacional de Desenvolvimento Científico e Tecnológico [grant numbers BJT 370646/2013–14 to F.G., and 402759/2012–5 and 311936/2013–0 to R.M.L.]; United States National Science Foundation [grant number EF-0629624 to S.L.]; Chinese Visiting Scholarship Council and the National Natural Science Foundation of China [grant number #41330959 to L.W. and S.L.]. This is contribution of MEL, Xiamen University.