BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="Tannin" data-source="post: 1468989" data-attributes="member: 2018">Rasmus, I'd make three points here. First, I was not writing for clarity, not detail. So yes, the minutiae does become a bit more complex!Secondly, I don't see how you can write that "numerous subspecies come into contact, and if there was little or no intergradation, they would be species rather than subspecies". Ultimately, of course that is the case, but are we not talking about the now, not the remote future here?  Finally, variations in the actual practical application of a set of rules do not make those rules invalid. As you say, once you go beyond the species level, it all becomes rather arbitrary. (And I for one don't see how this could not be so.) Also, as you say, to assign subspecies (or species) rank to a population there must be an observable difference - but difference alone does not define a species! And whatever the practice commonly is, the theory which (mostly) guides that practice is quite clear. (I'm assuming that we are talking BSC here - once we start veering off into alternative species concepts the water becomes so muddy that you could drink it with a fork.) The general practice in my part of the world (and I believe in yours as well) over the last 20 or so years has been to gradually whittle away the inconsistencies in the way we have assigned species and subspecies rank to populations between which substantial gene flow exists. The sitellas are a case in point: they used to be regarded as individual species but are no longer. The present classification of them as subspecies endures for the time being because we simply don't know enough about them to discard our current (clearly unsatisfactory) classifications and replace them with new ones. It appears clear that the Varied Sittella (current sense) is paraphyletic, but it isn't clear whether the best response is to re-split, or to lump them with the related New Guinea taxa. So the current unsatisfactory classification remains. (We may well discover that the sitellas are yet another of those troubling examples where the observed facts of nature refuse to fit in neatly with our (inevitably simplified) artifical classification schemes.)Nevertheless, many former bird and mammal subspecies have been merged into a single taxon in recent years on the basis of evidence of substantial interbreeding. Little by little, our "map" of the biological world starts to better resemble the territory.</blockquote>

Verification