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

[Stephen Thorpe]

By FREELY INTERBREED, I mean more than just a bit of hybridisation around the edges! If the Centropyge FREELY INTERBRED, then hybrids would take over the whole range and the whole darn lot would become one. If you think that is (slowly) happening (and you are correct), then they are the same species. If you think the bulk of them are retaining integrity, with just a bit of mixing at the border (and you are correct), then they are distinct species.

Many parasitic Hymenoptera are so sexually dimorphic that there are no morphological features to match up males with females. Why are they still males and females of the same species? Because they FREELY INTERBREED!

________________________________________
From: taxacom-bounces at mailman.nhm.ku.edu [taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard Pyle [deepreef at bishopmuseum.org]
Sent: Saturday, 12 September 2009 11:59 a.m.
To: 'TAXACOM'
Subject: [Taxacom] The 'reality' of species boundaries -- Once Again (UGHHH!)

With sincere apologies to Robin Leech (and others who share his
sentiments)....

> IF QUITE DIFFERENT MORPHOTYPES FREELY INTERBREED,
> THEN THEY ARE THE SAME SPECIES, PERIOD!

So, given that this morphotype (widespread western Pacific):
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=388967542

And this morphotype (widespread south-central Pacific):
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=1774961360

Freely interbreed wherever they co-occur (a few island groups along the
border between their respective ranges), without any apparent disadvantage
to the hybrid offspring:
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=1922645980
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=1690520359
http://www2.bishopmuseum.org/PBS/images/JER/detail.asp?ID=1773380990

...then you would say, "THEY ARE THE SAME SPECIES, PERIOD!"

Is that correct?  But when I gave you this example previously, and noted
that nobody had ever treated these two morphotypes as the same species, you
wrote back to me:

"Centropyge: you said it yourself, "nobody has ever suggested they should be
regarded as synonyms"! Why! Because of the (objective) facts! The biological
species concept isn't quite as simple as I was indicating for the sake of
simplicity, but still applies to this case..."

If I read your quote correctly, you are saying that the objective facts in
the context of a not-so-simple biological species concept lead to the
conclusion that these two morphotypes "are" different species.  This seems
to contradict your statement that, "IF QUITE DIFFERENT MORPHOTYPES FREELY
INTERBREED, THEN THEY ARE THE SAME SPECIES, PERIOD!"

So which is it?  Are these the same species (because they freely interbreed
when given the opportunity in nature)?  Or are they different species
(because the objective facts have led all previous and current workers to
treat them as separate species)?

And no, this is *not* an exceptional example!  There are many more examples
like this in reef fishes, and I suspect many, many, many more examples in
other groups.

Aloha,
Rich



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