El Nino and Butteflies

[Daniel Glaeske]

Kondla, Norbert FOR:EX wrote:
> 
> interesting topic. persons looking for research projects may wish to
> consider exploring this on the prairies and foothills of southwestern
> Alberta where it is not unusual to have dry winters or long dry periods
> within winters where the parched soil and lack of snow cover conditions
> occur due to strong winds known as 'chinooks'. these cause dramatic
> fluctuations in temperature and soil moisture.  from a purely anecdotal
> perspective i can observe that butterfly populations in that area seem
> to have survived these conditions for thousands of years-altho one can
> reasonably speculate that particularly severe oscillations may result in
> equally significant oscillations in the populations of particular
> species. in a natural, pre-settlement situation this would not be a
> problem due to habitat connectivity allowing recolonization for those
> populations that would be extinguished by combinations of natural events
> suchas dry winter/grass fire. in modern times it is an issue for persons
> managing protected areas due to habitat destruction by agriculture and
> the resultant fragmentation which impairs recolonization of residual
> habitat
> 

I suspect that the butterflies of southwestern Alberta may be
particularly adapted to this sort of climate.  In fact, J.Nordin
observed that Yvretta rhesus was more common in areas without snow cover
in South Dakota.  However, there is a dramatic difference in
temperature  at ground level with and without snow cover.  I'm thinking
that many species at the northwestern edge of their range (e.g.,
Ancyloxipha numitor, some hairstreaks, Erynnis, etc.) may be affected if
the pupa are not as cold hardy and rely on the fairly mild temperatures
(-10 C to 0 C) at ground level with snow cover.  On the other hand, more
westerly species of Hesperia, Yvretta, or Amblyscirtes may emerge
earlier due to the rapid warm-up in spring of the bare soil.

Any comments, observations, speculations?