Cladists on reciprocal illumination

[Ken Kinman]

      I think the appropriate amounts and types of reciprocal illumination
varies a great deal, depending on the context.  Robert Mesibov has already
argued (and I agree) that "place" is most important at lower taxonomic
levels (populations and species) and gradually loses its relative importance
as you go to higher taxonomic levels.
      The importance of paleontology and stratigraphic data also varies
greatly.  Very important for vertebrates and some invertebrates, but
negligible for fossil worms or bacteria.  And more important for
pteridophytes and pinophytes, than for magnoliophytes.  One of the few
arthropod groups in which paleontology plays a fairly minor role is spiders,
so perhaps that partly explains Platnick's stronger leanings toward
character analysis (and the dispersal ability of ballooning spiders must
also reduce the value of biogeography for them).  I have studied spiders for
decades, but I would hate to be a spider biogeographer or fossil hunter.
     So it depends on what kinds of organisms one is interested in (and also
at what taxonomic level) that would determine how much and what kinds of
reciprocal illumination might be helpful.  I certainly think it is an
overstatement to say that reciprocal illumination is another name for
circular reasoning.  Circularity could be a risk if you use it too much or
inappropriately, but that is no reason to condemn reciprocal illumination
across the board (which would leave a lot of bad cladograms unchallenged for
long periods of time, which would have terrible ramifications).
     Then there's the debate over whether molecular and morphological data
sets should be separate or combined, but that is another "can of worms"
(which again probably depends on the context of what organisms you are
studying).
           ----- Ken Kinman
P.S.  And now that I have run out of speculative possibilities on Oreobolus,
I will start looking for some of that "empirical evidence" of a southern
origin and trans-Antarctic dispersal.  Will begin with Seberg's analysis and
go from there.   By the way, anybody know what genus might be sister group
to Oreobolus?


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