Comments to Cladistics/Eclecticism

[Thomas Pape]

Dave Walter wrote: 
> Here's a question I'm dreading some student asking me one day:
> "If the symbiotic theory of evolution is correct, are the prokaryotic 
> domains paraphyletic and is Eukaryota polyphyletic?"

The 'symbiotic theory of evolution' certainly does not make Eukaryota polyphyletic if we have evidence that the ancestral eukaryote symbiont and all her descendants are covered by that taxon name. Phenomena like symbiosis and hybridization will give reticulate patterns in taxon evolution simply because we DEFINE and NAME species the way we do. Eukaryotic cells, lichens, figs and fig-wasps are all examples of more or less intimate symbiotic relationships evolving 'together'. Figs and fig wasps have names of their own as there is as yet no need to name the combined 'lineage'. We use scientific names for lichens, e.g.,  http://linnaeus.nrm.se/botany/kbo/ach/ao/l1437.html.en when communicating about certain fungus-algal associations, yet we can still produce cladograms for the component lineages (e.g., http://www.bot.ku.dk/staff/gargas/science.htm). Ultimately, the replicating DNA travelling through time still presents a dichotomous branching pattern.

Thomas Pape - Naturhistoriska riksmuseet