Interesting Facts
Variation between Individuals:
Due to the great variation of ecosystems that the Western Fence
Lizard occupies, different populations with unique physiological
characteristics have sprung up to best suit the
environment
(McMillan et al., 2011). With this in mind, an experiment has
been conducted chronicling how sprinting speed and expression of
certain proteins change amongst groups of Western Fence Lizards in
differing environments. The study measured this idea by taking
four different samples of lizards; two different geographic
locations (north and south) and splitting those locations into high
and low elevation in order to provide four unique sampling
locations. Before conducting experimentation, the researchers
found that temperature was significantly warmer in the low elevation
sample sites as opposed to the high elevation sites (Mcmilan et al., 2011).
At this point the lizards were put onto makeshift racetracks and all
of the lizards from each of the locations had their
sprinting speed
recorded by the use of photo gates at 22 degrees Celsius (Mcmilan et
al., 2011). It was found that in this control trial,
lizards from low elevation areas had a mean sprinting speed that was
considerably faster than their high elevation counterparts. The
collective pool of lizards were then broken down into control and
experimental groups, with the control group having their sprinting
speeds measured at 22 degrees Celsius once again, and the
experimental group had their speeds measured at 40 degrees Celsius.
It was found during these trials that the sprinting speeds of all
groups were negatively affected when exposed to high heat. In the
experimental trials, the lizards taken from higher elevation
locations were shown to have a dramatic drop off in sprint speed,
with them moving at roughly half the speed as they did during
control conditions.
In addition to sprinting speed, hsp70 (which is a protein designed
to combat excessive heat and shield cells from excess stress) levels
were measured in the Western Fence Lizards’ as well. It was found
that under control conditions, the levels of hsp70 proteins were
relatively consistent in all groups except the southern high
elevation group, which displayed high levels of the protein even at
a normal temperature. In addition, the lizards taken from higher
elevations displayed higher levels of hsp70 proteins, which
demonstrates a negative correlation between sprinting speed and
hsp70 concentration. The high levels of heat denatured the proteins
involved in muscle contraction in all lizards, but those lizards
from elevated locations suffered the most as they weren’t accustomed
to the high level of heat (Mcmilan et al., 2011). There
is a great deal of variability amongst individuals of the same
species of Western Fence Lizard.
Relationship with Malaria:
A common source of mortality in all animals is through
pathogens. One of the most deadly human pathogens in the world,
malaria, has also been said to be a major problem in the Western
Fence Lizard population as well (Eisen, 2001). Due to this fact, a
great deal of experimentation has been done attempting to discover
the true connection between
malaria and mortality rates in the
Western Fence Lizard. A malaria causing organism Plasmodium
mexicanum, has been known to parasitize the Western Fence Lizard,
causing such harmful changes as; damage to host
reproduction,
decreased ability to store fat (which was previously thought to
dramatically increase mortality rates during winter months), as well
has having negative repercussions on social behaviors and oxygen
carried in red blood cells. All previous scientific experiments
involving the Western Fence Lizard and the malaria causing agent
were all done in the lab, with the researchers concluding that
malaria is very much positively correlated with mortality rates
(Eisen, 2001).
Due to the fact that all previous experiments had been conducted in
the lab, there was a desire to measure the connection between the
two organisms in nature. With this in mind scientist captured
individual lizards’, determining if they have been infected with
malaria, marking them accordingly and sending them back out into the
wild (Eisen, 2001). For four years, the lizards’ were collected
after every summer and winter with any missing lizards’ being
considered dead. At the end of the four years, it was deduced that
there was no statistical significance between the rates of mortality
and malaria infection in Western Fence Lizards. However, while the
Western Fence Lizard was able to survive the infection, sexual
reproduction as a whole suffered as a result of infection. In the
lizards that were collected, males had smaller testes and showed a
lower ability to acquire a mate; and in general reproduction rates
for females were down nearly twenty percent (Eisen, 2001).
It could be reasoned that the environment played a huge role in this
finding; predators or natural events could have caused mortality in
individuals that would have died as a result of malaria in the lab
(Eisen, 2001). Also, it’s possible that being in the lab, a foreign
environment may have triggered the pathogen to cause more damage.
This reduction of reproductive success means that populations of
Western Fence Lizards will become less abundant and diverse. It
looks as if the Western Fence Lizard is able to survive malaria
infection at a very high rate; however the reproductive damage
caused by the pathogen may be felt in future generations (Eisen,
2001).