Whooper; Canadian geese split; paraphyly.

Peter Stevens peter.stevens at MOBOT.ORG
Wed Nov 17 10:38:11 CST 2004


>We go on maundering about monophyly and paraphyly, but if you read
>the papers, we have an absolutely facscinating evolutionary story to
>talk about to introductory biology students - which I do.


Peter S.




>Thomas,
>      I am a non-strict cladist, and I am concerned with clades too
>(very much so).  But our insight into the branching patterns for
>some groups (reptiles) will always be severely impaired (lack of
>fossils, and piecemeal even when we do have them).  Those are the
>places in the tree of life where a bit of formal paraphyly can be
>our friend (and complete cladification our worst enemy).  We can
>slowly improve the internal cladification of groups like Class
>Reptilia, but the complete cladification of the Tree of Life is
>wrong-headed---as is its resulting radical attacks on every
>perceived paraphyletic group and the total abandonment of taxonomic
>ranks (ranks are human constructs, but very useful ones).
>
>       As for the barnacle goose, we have to be careful to root the
>cladistic analyses properly.  It seems to me just as likely that
>populations of barnacle geese gave rise to cackling geese,
>populations of the latter gave rise to large-bodied Canada geese
>(and they gave rise to the nene goose)-----a series of single
>paraphylies, with barnacle geese as more primitive (not derived).
>Relying too heavily on mitochondrial genes can be cladistically
>risky.  And trying to raise a generation of strict cladists that are
>taught that paraphyly is bad or unnatural, well, that's just plain
>horrifying (even without a phylocode to institutionalize it even
>further).  I am pro-cladist, just anti-strict-cladist.   I am for as
>much holophyly as we can discover, but definitions and codes cannot
>make paraphyly go away (and strict cladists are ignoring and/or
>attacking a very useful concept and classificatory tool).
>               ------ Ken Kinman
>
>*****************************************************
>Thomas Pape wrote:
>Ken: Strict cladists are concerned with clades, and rank is a human construct.
>Paraphyly is comparable to insufficient knowledge and it is
>challenging mainly for this reason. As we just heard from Laurent
>Raty, the Barnacle Goose appears to make the unsplit Canada Goose
>twice paraphyletic. Again, our growing insight into the process of
>evolution stems from the definition of clades and the branching
>pattern they form.




More information about the Taxacom mailing list