[Taxacom] disjunct distributions (was Hygrobia)

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Sun Jul 25 21:12:57 CDT 2010


Hi Ken,
This particular N.Z./Chile example (Rhopalomerus tenuirostris) is surely a bit 
more curious than you seem to think? I cannot think of another case where a 
single species is native to both countries (with little variation) while at the 
same time the genus has radiated in N.Z. to become quite speciose here, while 
the shared species is the only congener in Chile.
Stephen




________________________________
From: Kenneth Kinman <kennethkinman at webtv.net>
To: taxacom at mailman.nhm.ku.edu
Sent: Mon, 26 July, 2010 1:45:35 PM
Subject: [Taxacom] disjunct distributions (was Hygrobia)

Hi Stephen,
      Disjunct distributions in Chile and New Zealand don't surprise me
in the least.  Populations simply went extinct in between when
Antarctica totally froze over and some islands south of New Zealand
became submerged.  I don't find such distributions very curious at all.
Some island hopping was probably involved (especially getting from New
Zealand to Antarctica, or vice versa), but nothing that is particularly
mysterious.              
      As for Gymnusini, it is a questionable taxon that may actually be
polyphyletic.  Ashe apparently suggested that their shared characters
could have evolved somewhat independently (or in parallel) from a
related Tribe.        
      The true distribution of the fungal taxon is obviously
questionable for the reason you suggested.  Sampling in understudied
taxa is always a problem.
      So the only example which you gave that I might find
biogeographically interesting (enough to pursue at all) is Agyrtidae.
Got to pick your biogeographic battles carefully or you end up painting
too many biogeographic puzzles with too broad a brush as mere
speculation.  Some of them are actually not that hard to explain and
thus not really all that curious.              
      -------Cheers,
                          Ken
-----------------------------------------------------------

Stephen wrote: 
    how about this little known example: the weevil genus Rhopalomerus
occurs in N.Z. and Chile (and maybe Australia and New Caledonia). Most
species are from N.Z., including R. tenuirostris - the only Chilean
species, which occurs in native forests from sea level to the high
mountains throughout Chile and New Zealand, and appears to be native to
both countries! then there are gymnusine staphylinids, restricted to the
Holarctic, except for one species from the subantarctic Auckland
Islands! similarly agyrtids, Holarctic except for a New Zealand genus
... apparently there is a fungal taxon known only from N.Z. and Cuba,
but in this case that is also the distribution of experts on the taxon.


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