Real species and ideology

SKÁLA Zdeněk skala at INCOMA.CZ
Tue Apr 20 09:50:48 CDT 2004

Barry Roth:
"...a species comprises all the individual organisms predicted on the basis of available evidence to prove to compose a least inclusive monophyletic unit recognized in a formal phylogenetic analysis.[snip] The relevant evidence of monophyly is apomorphic character states."

1. Polarization of character states (apo/plesio) is the *output* of the analysis / outgroup comparison. Hence, you can hardly define the species (input to the analysis) by polarized character states - you need to have species first, analyze character matrix and then ask about the polarity of their character states. The same is (obviously) true for the "monophyly" of species.
Phylogenetic species concept can be discussed but not in terms of apomorphy/monophyly; such a concept is something what contradicts the very nature of cladistic analysis.

2. As was correctly pointed by Curtis Clark: after analysing the character matrix you can find that there are some "species" existing without any autapomorphy. You can indeed lump them with their sister taxa on the base of the next synapomorphy - but:
(a) you will often lump units quite distinct in terms of interbreeding, morphology, genetics, history etc. 
(b) even more importantly: such "plesiomorphic" lineages can be rooted rather basally in the cladogram, so you will have to decide: either lump together many taxa differing by a set of (syn)apomorphies or leave the plesiomorphic lineage as a species - here you will fall into a logical inconsistency of your approach.
(Example: imagine e.g. a cladogram (A(BC)) with a synapomorphies defining ABC, BC and autapomorphies for B and C - hence A lacks any (aut)apomorphy and you need to either leave it as a species or lump (ABC) together as one species).

Zdenek Skala

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