[Taxacom] Why Australians are more real than Americans: implications for taxonomy!

[Stephen Thorpe]

Richard,

I think the list can benefit from new angles on old and tired debates, so I am replying to the list, despite your advice that this will just bore people to death! :)

> There are gaps at all scales.  To say that species boundaries are "real" is to say that the gaps that cluster around at the species level are somehow special -- more real than the gaps at higher or lower levels

I agree! I wasn't trying to imply that species level boundaries are any more or less "real" than any other level can be, except that lumping/splitting of genera, say, is more subjective than lumping/splitting of species, at least if you follow a biological species concept. The whole Hominidae could just as correctly be a single genus, for example. Lumping/splitting species is a bigger can of worms.

I think I see where you are coming from: consider allopatric populations which differ only slightly (=very small gaps). Are they the same species? Well, there is a determinate answer (independent of us)  if you follow a biological species concept, it is just that the answer can perhaps only be guessed at, and never known for sure. The nitty gritty now becomes clear: if you follow a morphological species concept, then ought ANY consistent gaps be species distinctions, or is there room for subjective choice regarding how much of a gap is required?

Thought experiment: imagine that all the species out there look the same as they actually do, but they don't breed, they just exist! So, no chance of a biological species concept. Could we still do meaningful (descriptive) taxonomy? The same patterns of morphology and "gaps" would still be there to describe...

I'm now less certain of my views, but one thing strikes me: if we follow a morphological species concept, for it to make any coherent sense, we might have to consider ANY consistent morphological gap to be a species boundary! The only reason why we often do ignore such small differences between allopatric populations is that we consider the gaps to be insufficient to produce reproductive isolation...

The reason why all this is relevant at present, has to do with the correct understanding of "identification" (at least at the species level):
if you are right, then two identifiers can disagree PURELY subjectively about the identity of a specimen - one of them can be correct relative to his concept, and the other can also be correct relative to the other's own concept. There would be no "fact of the matter". In that case, an identification without specification of the relevant taxon concept would be fairly meaningless.

But, on my Australia analogy, to identify a specimen is to say that a given land coordinate is part of Australia (forgetting all the little inshore islands and Tasmania), and there is a fact of the matter about this.

So, it all seems to come down to which species concept is used/best/true. The subjective view on species identification presupposes a morphological species concept with subjective choice on how wide the gaps need to be. On either a biological species concept, or a "gap or no gap" morphological species concept, there is only a single true species identity for any given specimen...

Stephen