In some butterfly and grasshopper species in Europe the wings are lengthening because of
moving north. Their reproductive output is decreasing so it is a trade-off. It varies by species.
(Refer to overhead) This is Neotoma cinerea which is a wood rat. It is our native rat. The other
name is ‘pack rat’ which means you hate to throw things away. Here you see the range of the
wood rat. What you find on the chart is the average body size and the temperature on the graph.
This is part of the thermal window of this particular native rat species. We have native rats here
and they are highly selected to live beside us. This one is a nice native rate in this overhead. I
worked in Jasper and we stayed in a warden station. We prevented people from coming in and
poaching. On the ceiling it looked like someone had urinated and they had. They live in the
attic. So with the wood rat as the temperature increases they get smaller (July & January) so this
tells you something fundamental. There is selection about large body size here and where it is
colder. There are biological reasons for this. As global change occurs you will see a change in
body size in this particular species. They could actually pinpoint a 2 -> 3 degrees rise in
temperature was the driver of body size and it wasn’t correlated to changes in precipitation.
Figure #3: you see two different scenario’s here. You can see fitness (# of babies that you have)
and at the top you have a stable or changing climate. The phenology during the stable period is
stable and the change is change. This is the optimistic scenario where fitness doesn’t change.
The full line is temperature and the dotted line is phenology i.e. wing length, body size, # of
babies, etc. So it is constant and it declines and the phenology of this optimistic species the
animal/plant compensates. As it does fitness remains constant. Just as good under change as
under stable. The alternative is that you see fitness trying to hold its own then you get outside
the thermal tolerances and things change. So temperature goes down and the phenology remains
constant. There may be no more genetic variation to allow them to compensate for the change
S:Is one theoretical and the other actual?
P:No. I will give an example though. What drives an animal or plant to extinction? This is
what you have. In all likelihood we don’t know. We have this accordion going on with regards
to glaciation so we don’t know the answer to that. It isn’t like animals/plants are adapted to
constancy either over the short term or long term. There are many genes that make a particular
trait i.e. body size.
Figure #4: this is a red squirrel and they are about 200 or 250 grams. Why do they have those
eye colours? This guy lives in the southern Yukon. If you take yourself back with respect to
temperature change, where will we feel it most dramatically in Canada? We will notice it in the
north. If I look at Whitehorse temperatures in January it is the same as Toronto quite often. If
you look at the average spring temperature over a period of about 31 years you see the
BGYC58H3F.November,20,, 2007 LECTURE 10 2