Pigment signatures and phylogenetic relationships of the Pavlovophyceae (Haptophyta)

Variations in the HPLC-derived pigment composition of cultured Pavlovophyceae (Cavalier-Smith) Green et Medlin were compared with phylogenetic relationships inferred from 18S rDNA sequencing, morphological characteristics, and current taxonomy. The four genera described for this haptophyte class (Diacronema Prauser emend. Green et Hibberd, Exanthemachrysis Lepailleur, Pavlova Butcher, and Rebecca Green) were represented by nine different species (one of which with data from GeneBank only). Chlorophylls a, c1, c2 and MgDVP (Mg-[3,8-divinyl]-phytoporphyrin-132-methylcarboxylate) and the carotenoids fucoxanthin, diadinoxanthin, diatoxanthin, and β,β-carotene were detected in all cultures. Species only differed in the content of an unknown (diadinoxanthin-like) xanthophyll and two polar ch1 c forms, identified as a monovinyl (chl c1-like) and a divinyl (chl c2-like) compound. This is the first observation of the monovinyl form in haptophytes. Based on distribution of these two chl c forms, species were separated into Pavlovophyceae pigment types A, B, and C. These pigment types crossed taxonomic boundaries at the generic level but were in complete accordance with species groupings based on molecular phylogenetic relationships and certain ultrastructural characteristics (position and nature of pyrenoid, stigma, and flagella). These results suggest that characterization of the pigment signature of unidentified culture strains of Pavlovophyceae can be used to predict their phylogenetic affinities and vice versa. Additional studies have been initiated to evaluate this possibility for the haptophyte class Prymnesiophyceae