Re: Can a dichotomous key reflect evolutionary history?

Dichotomous keys are not meant to exactly reflect phylogeny, but to allow
the user to identify an organism to a given level (say genus).  In "Spiders
of North America" we developed keys to families and then to genus within
family accounts.  While the spider keys do to some extent reflect
phylogenetic relationships (all jumping spiders in the family Salticidae
fall out together because of eye structure), some genera within a given
family occur in a key twice.  This may in part reflect our lack of
knowledge in that some genera may not be properly defined. This problem
occurs in some taxa even at the family level (for example some members of
the spider family Tengellidae have laterigrade legs, others do not, and so
the family appears twice in different sections of the key).

Thus the answer is that keys do not necessarily reflect evolution, but
many, if not most, keys obviously have some relationship to evolutionary
history. The extent of that relationship depends on the key characters used
and the extent of our phylogenetic knowledge.  However, it should be kept
in mind that as the main purpose of a key is identification it cannot serve
as a phylogenetic (or evolutionary) tree in substitute for a detailed
phylogenetic analysis.

Reference: Ubick, D, P. Paquin, P. E. Cushing, and V. Roth (eds) 2005.
Spiders of North America. American Arachnological Society. 377 p.