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KINGDOM ALVEOLATAE

Taylor (1999) described the "Alveolata" as a member of the crown eukaryotes and a sister to the Heterokontae.  More recently, Baldauf (2003) summarized molecular and ultrastructural information to condense the eukaryotes into eight supergroups, one of which was the alveolates.  Her summary both confirmed the natural status of the alveolates and dismissed the concept of the crown eukaryotes as an artifact of single gene comparisons.   Harper et al. (2005) used a 6-protein phylogeny of eukaryote taxa and provided strong evidence that they are part of a larger clade (alveolates+heterokonts) and have a weak association with the cryptomonad+haptomonad clade.  Keeling (2004) also suggested the same relationship in a supergroup called the chromalveolates [formalized to Chromalveolata].

The alveolates are now seen as an organization of three well-defined and seemingly disparate phyla: Dinoflagellata, Ciliata, and Apicomplexata.  The connection between the dinoflagellates and the ciliates was first proposed by Taylor (1976).  The association of the apicomplexan sporozoans with the others and the coherence of the group were confirmed by Gajadhar et al. (1991).  Patterson (1999) said that the main synapomorphy (and the one that Cavalier-Smith (1993) used to name the group) for the group is the occurrence of alveoli or membranous sacs that lie beneath the plasmalemma.  The alveoli form a layer beneath the cell membrane that is broken only by extrusosomes (e.g. trichocysts).  Their flagella (or cilia), when present,  usually come in pairs, one of which has a cross-striated root. 

Notable differences between the phyla of this system and Margulis and Schwartz (1998) include the union of their phyla Dinomastigota (Pr-7), Ciliata (Pr-8), and Apicomplexa (Pr-9) into a separate kingdom.  Margulis and Schwartz (1998) also show the derivation of the Plants and the Chlorophyta (Pr-28) from the alveolate line, a view that I cannot support. (The Domain Eukarya Page)

A more complete taxonomy (to Order) of the Alveolatae.

Concepts and Terms.

REFERENCES.

This page maintained by Jack R. Holt.  Last revised: 10/01/08.