Thought y'all might be interested in some recent outcomes on genetic stuff
done on Hypseleotris in the Murray-Darling Basin by some folks at the South
Australian Museum.
There was a recent article in Marine and Freshwater Research by Bertozzi,
Adams and Walker (2000) titled species boundaries in carp gudgeons from the
River Murray, South Australia: evidence of multiple species and extensive
hybridization. 51: 805-815 (I have it in pdf if anyone wants it)
Anyway, this article provides a somewhat different story to my own recent
article on this group in Fishes of Sahul. I made the statement that hybrids
appeared to be very rare. Well, this turns out to be very incorrect.
Here is the abstract from the article:
Allozyme analyses of carp gudgeons (Hypseleotris) from five sites in the lower
River Murray revealed three distinctive taxa designated HA, HB and HC,
diagnosable from one another by fixed differences at 3-5 loci, and three
apparent F1 hybrid forms, HAxHB, HAxHX and HBxHX, where HX denotes a taxon not
sampled in its 'pure' form. Of all fish sampled, 25% were hybrids, although
only one hybrid form was found at any one site, and never in company with both
parental taxa. No hybrids involving HC were found, although this was the most
common taxon, and no HAxHB hybrids were present at the one site of
demonstrated sympatry between the parental taxa. Morphological analysis and
the lack of introgression confirm that HA, HB, and HC are distinct biological
species. Partial meristic data suggest that HC corresponds to H. klunzingeri
s.l., 'Midgley's carp gudgeon' is a composite of HA, HB and HAxHB hybrids, and
'Lake's carp gudgeon' may be a composite of HX and one of its hybrids (HBxHX).
We speculate that one or more of the hybrid classes may be 'unisexual
lineages' (clonally reproducing, usually all-female forms derived from
hybridization between congeners).
For clarification,
HA=Murray-Darling carp gudgeon
HB=Midgley's carp gudgeon
HC=H. klunzingeri
HAxHX (and probably other hybrids)=Lake's carp gudgeon (to some extent, but
there are probably several hybrid taxa present, but we have little idea of
what they are like morphologically)
HX=a presently unfound, probably extinct taxon.
All the hybrids are F1, which wouldn't be a big deal except that HX has only
been found in hybrid combination which says that the hybrids are perpetuating
themselves without one of the parental species being present. These can be
thought of as unisexual lineages which usually only consists of females, or
more rarely only males. However, both sexes are present which is pretty
unusual (although males dominate in the HAxHB hybrids from the lower Murray
River).
More work has been conducted beyond this initial study involving aquarium bred
specimens where the parentals and offspring have been genetically identified.
This confirmed that they are indeed either gynogenetic or hybridogenetic (in
the former they are totally clonal, in the second some transfer of genetic
material occurs). There may in fact be as many as 5 F1 hybrid types including
hypseleotrids from the Lake Eyre, Murray-Darling and East Coast drainages.
Hypseleotris galii also appears involved.
In retrospect some of this makes good sense as "Lake's carp gudgeon" is always
the rarest species, and it never occurs alone, whereas each of the other three
species can be found on their own. Additionally, I have spawned Lake's carp
gudgeon twice, but they never hatched whereas all the other species have.
Anyway, thought that might be of interest to some of you. This entire story
isn't likely to be unravelled from some time, but more work is continuing on
fish from throughout their entire range, and so far the same pattern appears
to be holding up. There is also some broader phylogenetic stuff being done by
Christine Thacker at LA County Museum and myself which might shed some light
on who HX is most closely related to if their mtDNA still exists.
This whole thing threw me for a bit of a loop as I thought I had a really good
handle on how to tell all these little buggers apart, but it is clear that I
was potentially somewhat full of shit (what's new!). But it does make for
some extremely exciting stuff to explore and think about. I know it's got me
almost orgasmic!
Cheers
Peter J Unmack peter.unmack at asu.edu
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DESERT FISHES RULE: To boldly thrive where no other fish can make it!
Desert Springs Action Committee at http://www.tkphotos.com/dsac/
Desert Fishes Council http://www.utexas.edu/depts/tnhc/.www/fish/dfc
Australian Desert Fishes as above just add australi or click on Australia
Australian Freshwater Fish Biogeography at http://www.peter.unmack.net/biogeog
North American Native Fishes Association at http://www.nanfa.org
Native Fish Australia at http://www.nativefish.asn.au
Aquatic Conservation Network at http://www.acn.ca
"The biggest cause of trouble in the world today is that the stupid
people are so sure about things and the intelligent folks are so full
of doubts." -Bertrand Russell