Jonathan Badger wrote:
> So you are saying that protists with a non-mitochondrial plastid, had
> mitochondria, lost them, did perfectly fine without any plastids for
> a while, and *then* picked up non-mitochondrial plastids at a later
Nothing so elaborate. Simply, some protists such as Trichomonas
vaginalis do not have mitochondria at the moment. Their ancestors
clearly HAD mitochondria (Horner et al., Proc. Roy. Soc. Lond. B series.
1996) but the extant species does not have one. This is not the only
example, but to split protists up on the basis of
mitochondrion-containing and mitochondrion-lacking is not a proper
phylogenetic division either.
I'm sure there was a single mitochondrion-forming endosymbiont, but its
descendents are not present in all the hosts descendents today.
Don't think that I disagree with you on the question of the monophyly of
protists. I don't think that anyone will argue that all non-plant,
non-fungi, non-animal eukaryotes are a monophyletic group called
protists (or even protoctista). Its just that their primary split is
not on the basis of possesion of a mitochondrion.
Dr. James O. McInerney Ph.D. Phone/Voicemail: +44 171 938 9247
Senior Scientific Officer, email:j.mcinerney at nhm.ac.uk
The Natural History Museum,
London SW7 5BD
Whenever I think of the past, it brings back so many memories...