Agreement yet?

Robert Mesibov mesibov at SOUTHCOM.COM.AU
Thu Jul 11 18:05:30 CDT 2002

Tom DiBenedetto's most recent posts are admirably clear statements of his
intellectual position.

He argues that 'discovering relationships is a coherent discipline unto
itself.' Results from studies in this discipline can then be synthesized
with those from other evolutionary studies to give us a hypothetical
evolutionary narrative. However, information from other studies may be
seriously misleading, because it is not derived from heritable characters,
which constitute the only directly relevant evidence for relationship
through descent. (My paraphrase)

Looking through earlier posts, I see that I inadvertently introduced some
confusion into what was being debated. (My fault, comes from doing email
once a busy day) There were differing interpretations of the term
'phylogenetic hypothesis' (following Haeckel, I understand 'phylogeny' to
be the history of evolutionary events within a group, not just a barebones
schema of relationships), and while Tom was asking 'How can I possibly use
biogeography in my evolutionary sub-discipline?', I was asking 'How can you
possibly ignore biogeography in developing a hypothetical evolutionary

So the question remains: how do you integrate relationship information from
Tom's sub-discipline with relationship information from other evolutionary
sub-disciplines? Tom seems particularly concerned with conflict, and says
that if it comes to a crunch, he'll back character-based evidence over
biogeographical evidence, because character-states are inherited and
locations aren't.

I doubt that conflict of this kind will arise very often, especially at
lower taxonomic levels. Picture 3 newly discovered species of orchid on a
single mountain in the Peruvian Andes. The flowers of all 3 are frequently
visited by wasp species in the same small, regional genus. I will bet
dollars to donuts that a character-based analysis will support the idea
that the 3 orchids are a clade. My hunch is based on two kinds of
non-character relationship evidence: spatial data and the fastidious tastes
of insects. I would accept all 3 kinds of evidence (character-states,
biogeography & host/insect ecology) when synthesising an evolutionary
hypothesis for the clade, an hypothesis which includes the 'where' and
'how' of this clade's history.

If Tom is at all uncomfortable with the last paragraphs, it's because I
used 'relationship' as an adjective in the sentences beginning 'So the
question..' and 'My hunch...' Sorry, Tom, but I do see history in data
items other than characters. But please notice that I only used those
non-character historical signals in my synthesis, so the integrity of your
sub-discipline is untouched.

Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 64371195; 61 3 64371195

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