homology in biogeography and biology

[John Grehan]

Tom DiBenedetto wrote

>Yeah,  homology means "the same feature found in different organisms,
>as a result of descent from a common ancestor".
>
>>The concept
>>of homology is a major issue in biogeography since it refers to the criteria
>>by which any one distribution may or may not be said to be homologous
>>to another.
>
>Could you please explain what you really mean by this, and how I could
>fit that into the concept which I defined above?

If the concept of homology is restricted to similarity of features (or same
feature)
found in different organisms, then by definition there is no such thing as
homology in biogeographic distributions.

If one takes a broader concept of homology to refer to the same or similar
feature
found in any two or more units of comparison, then homology is a concept that
could apply to biogeography. In panbiogeography any two distributions sharing
the same geological/geomorphic feature (i.e. their tracks both cross this
feature)
may be said to be homologous with respect to that feature. The feature
constitutes
a biogeographic character present in those distributions.

So for those who restrict homology to biological features, there is no such
thing
as homology in biogeography and I have no problem with that (i.e. I have a
different perspective and recognize the right of others to view the situation
differently). For those who do accept homology as a concept applicable to
biogeography (and without homology there is no possiblity of constructing
biogeographic classifications), the issue becomes one of what homology
criteria are deemed appropriate, and how different research programs
generate new
discoveries etc. through the application of the classification of homolous and
non-homologous distributions.

John Grehan