MOLECULAR PHYLOGENY OF PHYCOCYANIN-CONTAINING CRYPTOPHYTES: EVOLUTION OF BILIPROTEINS AND GEOGRAPHICAL DISTRIBUTION(1).

Abstract

Of 34 strains assigned to the cryptophyte genera Chroomonas Hansg., Hemiselmis Parke, and Komma D. R. A. Hill, distribution patterns of biliproteins, habitats, and sampling sites across a phylogenetic tree have been examined. The combined data set assembled from nuclear SSU rDNA, partial nuclear LSU rDNA, and nucleomorph SSU rDNA sequences comprised 4,083 positions and yielded an almost completely resolved tree. Spectrophotometry of the biliproteins and mapping of the different types of biliproteins onto the phylogenetic tree unveiled a complex evolutionary history. Different from other cryptophyte clades, the types of biliproteins were not generally congruent with clades or subclades of the genera Chroomonas (paraphyletic, phycocyanins [PCs] 645 or 630), Hemiselmis (PCs 612, 630 or phycoerythrin [PE] 555), and Komma (PC 645). At least one putative character reversal took place in the genus Chroomonas. Several changes in biliproteins have been found in the genus Hemiselmis, including two new biliprotein variants that probably originated by slight modifications from PC 612 and PE 555, respectively (PC 577 and PE 545/555). Freshwater and marine/brackish taxa were intermingled across the tree without displaying a specific pattern. In four terminal clades, genetically identical strains have been found to occur both in Europe and in the USA. The Chroomonas/Hemiselmis/Komma clade proved to be the most diverse of all cryptophyte clades concerning types of biliproteins and distribution of clades across marine or freshwater habitats.