PHYLOGENETIC RELATIONSHIPS AMONG THE CHROMISTA: A REVIEW AND PRELIMINARY ANALYSIS

Abstract- It is now well established that the algae do not constitute a monophyletic group. A number of brown and golden algae are related to various heterotrophic protists, which have recently been characterized and described as a kingdom, the Chromista. The kingdom was defined primarily by two ultrastructural features: the presence of tubular, tripartite hairs (mastigonemes) on the surface of at least one flagellum, and the presence of a chloroplast endoplasmic reticulum. This included the watermoulds which, although they lack chloroplasts, do have mastigonemes. In addition, a number of heterotrophic flagellates also possess mastigonemes and should therefore be considered in the determination of interrelationships. This paper presents a cladistic analysis that focuses on 79 ultrastructural, cytological and biochemical characters. The unpigmented taxa appear at the base of the cladogram, suggesting a single origin for the chromophytic chloroplast. The crytomonads and Eustigmatophyta, usually considered primitive taxa, are sister to all the chrysophycean taxa which, with the exception of two monotypic genera and the Sarcinochrysidales, are monophyletic. The Prymnesiophyta, Bacillariophyta and Phaeophyta form a monophylectic group.