David Wright wrote,

>Consider the case of Baltimore and
>Bullock's orioles. Originally these populations were recognized as
>distinct species. Later, the AOU decided they were really subspecies of
>a single species, so they lumped two "species" into a single one,
>Northern Oriole (also Abeille's oriole was lumped in here, too, I
>think). But the *taxa* involved -- the populations in question and the
>more-inclusive taxon that embraces them -- remain unchanged; all that
>has changed is which one(s) we call species. Now the AOU is reversing
>its early conclusion and splitting/unlumping Northern Oriole. Now the
>AOU is reversing its earlier conclusion and splitting/unlumping Northern
>Oriole.

The Northern Oriole is not simply a change in man's interpretation, the
populations involved did NOT "remain unchanged." The split is on the basis
of a change in the nature of the hybrid zone on the Great Plains. In
locations where previously hybrids only existed, both Bullock's and
Baltimore now co-exist. This is a highly dynamic situation and illustrates
exactly the point you are trying to make.

Jerry_Tangren at tfrec.wsu.edu