monarchs and swan plants

[Nigel Venters]

Worth reiterating that at this time (1800's) nobody could conceive that
long distance migration could take place. Writing at this time would always
conclude that new species would arrive on ships, I wouldn't mind betting
that the foodplants arrived on ships, but the Monarchs had been arriving in
these areas (And many other unsuitable areas like UK)  for hundreds of
thousands of years. Only when acceptable foodplant was available did they
colonise the new areas. If you are concerned about the distances involved,
be aware that US Monarchs make it across the Atlantic most years.
Nigel

Paul Cherubini <paul at CONCENTRIC.NET> wrote in article
<83F2A61F.21D0 at concentric.net>...
> John Grehan wrote:
> 
> > It was my understanding that the monarch was already in NZ and
Australia
> > before human introduction of the host-plant, but that they were not
able
> > to permanently establish in the absence of the hostplant. I also
understand
> > that there is no migration phenomenon like that in America - is that
correct?
> 
> A monarch biogeographer, Richard Vane-Wright has studied the situation in
detail and 
> found the monarch became established in Hawaii and many other central and
south 
> Pacific islands is the mid-late 1800's. This timing coincides with the
advent of fast 
> moving steam powered trading ships. It is interesting to note that the
areas in Australia 
> where the weedy swan plant became established are the same areas where
the native 
> eucalyptus forests were clear cut to accomodate agricultural interests.
> 
> The seasonal migration/overwintering phenomenon in Australia is just like
that in America 
> except the numbers of butterflies involved and the distances they travel
are smaller. Right 
> now is late autumn in the Sydney area and hundreds of monarchs can be
found clustering 
> in at least a dozen eucalyptus groves slightly west (inland) of the city.
Clustering also 
> occurs in New Zealand at this time of the year, but the migration there
has no been 
> studied in detail.
> 
> Paul Cherubini, Placerville, California
> 
>