[Taxacom] Hygrobia distribution

Jason Mate jfmate at hotmail.com
Thu Jul 22 13:17:47 CDT 2010


The distribution is not suggestive of a relictual pattern (i.e. the Hungarian Diopsid). Even if Hygrobidae was a Gondwanan element that only survived in Australia, why is it that it successfully invaded the Palearctic, became practically ubiquitous in "Europe" (the geopolitical unit) and became extinct in between except for a western Chinese species?
As for water/weather requirements, they are remarkably flexible. The beastie occurs in pools of utterly stagnant, pratically putrid water in fairly acidic waters in Morocco; and in pretty clean ponds on chalkland in the UK. They fly and very effectively disperse to other ponds as these are often ephemeral, so it can obviously move about. As an adult and larvae it is a bottom predator on tubifex and the like. As for predation, you would still need to figure why predation is not an issue in Europe, Western China and Australia.

Jason
> From: cavexplorer at gmail.com
> To: jfmate at hotmail.com; Taxacom at mailman.nhm.ku.edu
> Subject: Hygrobia distribution
> Date: Thu, 22 Jul 2010 18:36:34 +0200
> 
> The species habitat might be more complex than suspected (chemical), besides 
> there might be (or have been) concurrence or predation in other locations 
> that look superficially suitable now. This (ancient) species group might 
> also have lost the ability to disperse.
> There are plenty of other examples, the relict populations of Diopsidae, 
> some striking relict pseudoscorpion genera, ..
> 
> Hans Henderickx
> 
> 
> ----- Original Message ----- 
> From: "Jason Mate" <jfmate at hotmail.com>
> To: "Taxacom" <taxacom at mailman.nhm.ku.edu>
> Sent: Thursday, July 22, 2010 6:04 PM
> Subject: Re: [Taxacom] Examples for Eurasian-Australian distribution
> 
> 
> >
> > Because it is a fairly old taxon; widely dispersed but species-poor (only 
> > 5 species); and with a very common habitat (stagnant water). So, if it 
> > spread so widely why is it absent from so much potentially optimum 
> > habitat? It is curious.
> > Jason
> >
> >
> >> Date: Thu, 22 Jul 2010 08:38:15 -0400
> >> From: jgrehan at sciencebuff.org
> >> To: taxacom at mailman.nhm.ku.edu
> >> Subject: Re: [Taxacom] Examples for Eurasian-Australian distribution
> >>
> >> Why should the absence of Hygrobia from all the rest of the world be a
> >> problem since all taxa are absent from somewhere eles.
> >>
> >> John Grehan
> >>
> >> -----Original Message-----
> >> From: taxacom-bounces at mailman.nhm.ku.edu
> >> [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Oliver
> >> Hawlitschek
> >> Sent: Thursday, July 22, 2010 4:12 AM
> >> To: taxacom at mailman.nhm.ku.edu
> >> Subject: Re: [Taxacom] Examples for Eurasian-Australian distribution
> >>
> >> As stated by Ken, our problem is in fact the current absence of Hygrobia
> >> from all the rest of the world, which probably means that today's
> >> Hygrobia species show a relic distribution. Of course there may be other
> >> species yet to be found. I should note that the Chinese Hygrobia davidi
> >> Bedel, 1883 is known from the type specimen only and has never been
> >> found afterwards.
> >>
> >> In: Benton, M.J. (1993) The fossil record 2, a Miocene fossil of
> >> Hygrobia is mentioned, but with no further information. Does anybody
> >> know more about this?
> >>
> >> Best regards
> >>
> >>
> >> Oliver
> >>
> >>
> >>
> >>
> >> -------- Original-Nachricht --------
> >> > Datum: Wed, 21 Jul 2010 20:03:31 -0500
> >> > Von: kennethkinman at webtv.net
> >> > An: taxacom at mailman.nhm.ku.edu
> >> > Betreff: [Taxacom] Examples for Eurasian-Australian distribution
> >>
> >> > Hi Oliver,
> >> >       I don't really understand John's response that there are
> >> > "innumerable" such cases.  My understanding of your question would be
> >> > cases where a taxon has a disjunct distribution in Europe, China, and
> >> > Australia, but NOT elsewhere.  If so, such cases would probably be
> >> > relatively small in number.  The European species of Hygrobia is
> >> > apparently also found in North Africa, which might tend to restrict
> >> such
> >> > cases even further.   Off hand, I don't know of any other such cases,
> >> > but I will give it more thought.
> >> >       Anyway, I would agree with you that this distribution is not the
> >> > result of recent dispersal.  Since Hygrobia is a relatively primitive
> >> > taxon, it most likely had a wider distribution in the past and many
> >> > intermediate populations of Hygrobia (species or subspecies) simply
> >> went
> >> > extinct due to (1) competition with certain (presumably more derived)
> >> > taxa, and/or (2) loss of habitat which offered their particular
> >> > requirements.  I would also add that it is perhaps possible that some
> >> > intermediate species still exist, especially in southeastern Asia,
> >> which
> >> > have simply not yet been discovered.
> >> >           ---------Cheers,
> >> >                            Ken
> >> > ------------------------------------------------------------
> >> > Oliver Hawlitschek wrote:
> >> > Dear all,
> >> > I have a biogeographical question: the aquatic beetle genus Hygrobia
> >> > (Dytiscoidea) is present with one species in Europe, one in China and
> >> > four in Australia.
> >> > Does anybody know any other group of organisms showing a similar
> >> > distribution? Probably, it is not the result of recent dispersal.
> >> > Thanks
> >> > Oliver Hawlitschek
> >> >
> >> >
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