Multigene Phylogeny, Morphological Observation and Re-examination of the Literature Lead to the Description of the Phaeosacciophyceae Classis Nova and Four New Species of the Heterokontophyta SI Clade.

Abstract

The relationships among the Aurearenophyceae, Phaeothamniophyceae, Phaeophyceae and Xanthophyceae lineages of the Heterokontophyta SI clade are not well known. By adding previously unexamined taxa related to these classes in a five gene phylogeny (SSU rRNA, atpB, psaA, psaB, rbcL), we recovered an assemblage of taxa previously unrecognized. We propose the class Phaeosacciophyceae class. nov., that includes Phaeosaccion collinsii, Phaeosaccion multiseriatum sp. nov., Phaeosaccion okellyi sp. nov., Antarctosaccion applanatum, Tetrasporopsis fuscescens, Tetrasporop- sis moei sp. nov., and Psammochrysis cassiotisii gen. & sp. nov. We re-examine the literature for Chrysomeris, Nematochrysis, Chrysowaernella and the invalid name “Giraudyopsis” and conclude some taxa in previous studies are misidentified or misnamed, i.e. Chrysomeris and Chrysowaernella,respectively. We also show that Nematochrysis sessilis var. vectensis and Nematochrysis hieroglyphicamay belong in the recently described class Chrysoparadoxophyceae. The phylogenetic relationships ofPhaeobotrys solitaria and Pleurochloridella botrydiopsis are not clearly resolved, but they branch nearthe Xanthophyceae. Here we describe a new class Phaeosacciophyceae, a new order Phaeosacciales,a new family Tetrasporopsidaceae, a new genus Psammochrysis and four new species.