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Message: <blockquote data-quote="l_raty" data-source="post: 1360065" data-attributes="member: 24811">There is hybridization and hybridization...When two taxa coexist broadly in sympatry, hybridize from time to time but nevertheless remain clearly distinct (vast majority of the birds looking 'pure') and do not at all seem to be in the process of merging into a single taxon, you can't treat them as a single species. (Whatever species model you choose to work with.)When two taxa are mainly allopatric (the teals live on different continents), are in contact in an area that is very small in comparison to their entire range, and hybridize in this area, the interpretation is much more difficult. And indeed the decision to split or lump may be rather arbitrary.Pochard and Tufted Duck are in no way comparable to the teal case. If you want something a bit more comparable, I'd suggest Baltimore/Bullock's Oriole. In the case of the Aleutian teal populations, I do not know what 'freely hybridize' means exactly in quantitative terms, and I even think the relevance of this observation could possibly be questioned, even under the BSC. The Aleutians are remote islands. If what happens there is that the local population is only supplied from time to time with birds coming from one or the other direction, these newly arriving birds could simply have no other choice than 'do as the others do' to find a local mate. If so, what is going on there could have very little predictive value for what could happen, should the ranges of the two taxa suddenly come in much broader contact. But on the other hand, it remains true that, if this is the only existing contact zone, this is the only evidence we have at hand to try predicting the outcome of such an event.</blockquote>

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