is temp the limiting factor on range

[Michael Gochfeld]

I think that the phenomenohn Ron describes for Phoebis sennae is an example of
my question.  Range limited by some other ecologic factor than cold temperature
(i.e. the die off of the hosts). But why should Cassia disappear in South
Carolina or is it a problem of leaves dying in some years but not others. The
plants themselves should be cold tolerant.

P. sennae comes to NJ in most years (rare as early as June, more often not
until mid-summer). Some years they're abundant, other years unrecorded in NJ
(and Long Island). I don't think anyone has identified a pattern of abundance
related to cold winters in the Carolinas.  However, on the 64 Fourth of July
Counts, held through 1996, the only records for Cloudless Sulfurs occurred in
1992 after an unusually mild winter in the southern states.  Art Shapiro wrote
in 1966 that it occurred in NJ Sept-Oct, so perhaps it actually is occurring
earlier now than 30 years ago (so phenology, i.e. arrival time, if not
abundance) seems to be related to mild winters elsewhere).
.
MIKE GOCHFELD
===================================================
Ron Gatrelle wrote:

> (I am passing this along to carolina leps group as the subject matter will
> be of interest to many of them.)
>
> Charleston SC is the type locality of Phoebus sennae eubule (Cloudless
> Sulphur). Is this based on a resident or dispersed population?  I have gone
> back and forth for this for a long time. Having done no structured study on
> this I have come to an opinion. All stages of eubule survive the mild
> winter here just fine - it rarely snows here and seldom gets below freezing
> (or far below) in the dead of winter. (Charleston is a great place.)
>
> The problem is host plants. If we have a few days of really cold for us -
> below 32 for a couple of nights and into mid 40's in the days - followed by
> 70s for two or three days one is apt to see eubule out on those warm days
> all winter. In spring there are often many freshly emerged eubule that
> obviously came from "overwintering" pupae. Then as early summer comes
> around there is a big drop off. The weedy hosts are not up and subspecies
> eubule "dies out" - except in warmer winters where more southern specimens
> are now coming back into the area - so adults are seen but oviposition is
> not occurring. There is quite possibly some secondary plant(s) that may be
> used as host in early summer - not known to me though.
>
> This is related to the temp factor on range as eubule is certainly able in
> all stages (which the most?) to cope with cold. A good college research
> project here. How far north are eubule found in winter? Which stage is the
> most cold resistant? How many other southern leps may fit the same
> scenario. We think they are limited by cold but actually "die out" due to
> lack of host plant rather than "retreat south" due to drop in temps. ????
> Ron
>
> ----- Original Message -----
> From: "Michael Gochfeld" <gochfeld at EOHSI.RUTGERS.EDU>
> To: "lepslist" <leps-l at lists.yale.edu>
> Sent: Monday, September 03, 2001 7:20 AM
> Subject: is temp the limiting factor on range
>
> > With regard to the Queen of the Carolinas thread, Ron wrote about the
> > "possibillity of overwintering in sheltered situations on the Carolina
> > coast itself in the mildest years."
> >
> > I have made what I assume is the same assumption that winter temperature
> > (or perhaps snow cover) limits the overwintering of southern species in
> > the northern part of their range (or north of their normal range).
> >
> > The assumption follows that this accounts for the die off of species in
> > the fall, and the re-invasion the following year (or at longer
> > intervals) of southern species into (for example, NJ or New England).
> >
> > If this were the case, the overwintering stage of a species should be
> > temperature sensitive with cold temp either killing outright or delaying
> > development.
> >
> > But I wonder for how many of these northward invading species there is
> > actual experimental evidence that cold in winter IS the proximate
> > limiting factor.  We do see adult survival limited by the early or
> > delayed arrival of winter (but that seems to be a different question).
> >
> > For example, My wife, Joanna Burger, showed experimentally that summer
> > temperature influencing incubation and development (rather than winter
> > temperature influencing adult survival) might impose the northern range
> > limit on a snake species.
> >
> > Or, how often do we see survival in the north  (and early spring
> > emergence) of such species after truly warm (snowless) winters (i.e.
> > after 1999-2000 or 1998-1999).
> >
> > Mike Gochfeld
> >
> >
> >
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