[Taxacom] Examples for Eurasian-Australian distribution

Kenneth Kinman kennethkinman at webtv.net
Wed Jul 21 20:03:31 CDT 2010

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.  
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. 
Oliver Hawlitschek 

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