[Taxacom] FW: The 'reality' of species boundaries -- Once Again (UGHHH!)

[Stephen Thorpe]

[Richard Z. said] Your example of two populations, in my opinion merely beginning to differentiate into two different species, assumes that continued gradual dissruptive selection or drift or whatever will eventually give us expressed traits that will distinguish them, so why not name them as species now on a statistical basis? This is rushing things

[reply] If you are talking about the Blanus example from today's Zootaxa, this is not how I interpret it! The authors are, I suggest, saying that the (non-obvious) morphological differences, taken together with the molecular differences, are sufficient evidence that the two populations have already crossed the biological species boundary, and are therefore already distinct. Whether or not any external diagnostic characters evolve in future is irrelevant. If the two populations may soon overlap and hybridize and return ... , then the author's hypothesis would turn out to be incorrect. Too bad for them, but no prob to BSC ...


________________________________
From: Richard Zander [Richard.Zander at mobot.org]
Sent: Thursday, 17 September 2009 12:34 p.m.
To: Stephen Thorpe
Cc: taxacom at mailman.nhm.ku.edu
Subject: RE: [Taxacom] FW: The 'reality' of species boundaries -- Once Again (UGHHH!)

Stephen:
Stop agreeing with me! My observation that many taxonomists may be unthinkingly using indirect biological species concepts criteria was an observation of human whimsy. What they are actually doing is using much the same criteria to support differentiation of species supported by disruptive selection or budding, then stabilizing selection. This is not whimsy but inadvertent correct method.

Your example of two populations, in my opinion merely beginning to differentiate into two different species, assumes that continued gradual dissruptive selection or drift or whatever will eventually give us expressed traits that will distinguish them, so why not name them as species now on a statistical basis? This is rushing things. The two populations may soon overlap and hybridize and return to non-statistical differentiation. I would hazard, on general principles, that you can take ANY two slices from an accepted species and find statisical differences between the slices (a"multiple comparisons" problem in statistics). I doubt this is a good example of BSC reasoning, but instead an extreme.



_______________________
Richard H. Zander
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166 U.S.A.
richard.zander at mobot.org<mailto:richard.zander at mobot.org>


________________________________
From: Stephen Thorpe [mailto:s.thorpe at auckland.ac.nz]
Sent: Wed 9/16/2009 4:44 PM
To: Richard Zander
Cc: taxacom at mailman.nhm.ku.edu
Subject: RE: [Taxacom] FW: The 'reality' of species boundaries -- Once Again (UGHHH!)

Hi Richard:

Thanks for being perhaps the only one to still think this thread discusses anything important. Others seem to think "who cares what 'species' means? Let's just aggregate info on each of them!"
Anyway, a paper published just minutes ago in Zootaxa has some relevance:
http://species.wikimedia.org/wiki/Blanus_mariae
I quote the abstract:


A recent phylogeographic study using mitochondrial and nuclear DNA revealed the presence of two well defined

allopatric clades of Blanus cinereus in the Iberian Peninsula. Using both univariate and multivariate statistical analyses,

we show evidence of morphological differentiation between the two clades. Despite the lack of visually diagnosable

morphological characters, the morphological and molecular data suggest that differentiation between the two clades was

significantly enough to prevent in the past gene flow and therefore to warrant a specific status for each of the two clades


This is another good example of BSC reasoning. Note "significantly enough to prevent in the past gene flow" (=reproductive incompatibility) "and therefore to warrant a specific status" ...

You say: An interesting point here is that many taxonomists who might not salute the biological species concept when asked about it actually "act as if . . . " in that they look for evidence of no or little gene flow

I agree. I think that is exactly what is happening! It has become "trendy" to slag-off the BSC, but you can't actually do much without it, so "call it something else, and keep your head down"! Like Jim Edwards' comment that looking at genitalia is really MSC because it is morphological differences in genitalia that you are looking for!

Stephen