As Cladistics and "Eclecticism", Aves, paraphyly flow on

John Grehan jrg13 at PSU.EDU
Sun Feb 3 23:20:17 CST 2002

>The rocks are pretty obvious, although no one seems to want to look at
>them.  For example, we all know (although some insist the contrary) that
>evolutionary events are not exclusively dichotomous.  This is a simplifying
>assumption that is necessary for the technique to work well, but our
>favoured model of speciation (allopatry) could easily generate multiple
>simultaneous branching events.  Sympatric speciation may be locally
>dichotomous, but is also open to the generation of multiple species from a
>single ancestral species (as recent work on frogs demonstrates

If one read the panbiogeographic literature it would be apparent that in this
field at least the question of multiple 'simultaneous' branching events is
not only addressed, but accepted as a common normal event with the result
that there can be some interesting geographically incongruous biological
relationships (i.e. the nearest geographic neighbor in a vicarious non-disjunct
series is not necessarily most closely related in biological characters).
The most
extreme form is even given its own name - wing dispersal (i.e. the 'wings'
of a
distribution range are more closely related than either wing is to the 'center'

>importantly, it is becoming increasingly obvious that reticulate evolution
>is important in many, if not most, sexual groups.

Actually I would suggest that it has been as 'obvious' all along - just not
popular with
traditional evolutionary models (I would call them 'Darwinian' models -
pejorative or
not). Croizat referred to reticulate evolution as character recombination.

John Grehan

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