Carotenoid compositions of Cladophora balls (Aegagropila linnaei) and some members of the Cladophorales (Ulvophyceae, Chlorophyta):: Their taxonomic and evolutionary implication

Photosynthetic pigments were analyzed by HPLC for 27 samples of the Cladophorales (Ulvophyceae, Chlorophyta). The carotenoid compositions of the examined algae were classified into three types based on the final compound of biosynthesis of the alpha-carotene branch: lutein type, characterized by containing lutein as a major carotenoid and lacking loroxanthin and siphonaxanthin; loroxanthin type, characterized by containing loroxanthin and lacking siphonaxanthin; and siphonaxanthin type, characterized by containing siphonaxanthin. We constructed molecular phylogenetic tree of the species examined in the present study using 18S rRNA gene sequences and mapped the carotenoid types of the species onto the tree. The molecular phylogenetic analysis divided the Cladophorales into two major clades, clade 1 and Aegagropila-clade (clade 2), and divided clade 1 into subclade 1-1 and subclade 1-2. All the examined species positioned in the Aegagropila-clade and those of the subclade 1-1 belonged to the loroxanthin type, whereas both lutein type and siphonaxanthin type appeared only in the subclade 1-2. The clades delineated by molecular phylogenetic analysis were congruent with distribution of the carotenoid types, indicating that the carotenoid types are of taxonomic significance in the Cladophorales. Considering the distribution pattern of these carotenoid types and minimum state changes in the Cladophorales, we concluded that the loroxanthin type was the primitive (plesiomorphic) state and the siphonaxanthin type and lutein type appeared in the subclade 1-2 as advanced (apomorphic) state within this order and suggested that the cladophoralean siphonaxanthin type would have been secondarily acquired.