ZOOL 452 – March 18, 2014
Model Systems in Parasite Ecology
• Ecology = used to figure out things that explain the kinds of organisms that are
seen and the numbers that we find.
o Behaviour evolution and systematics are also taken into account
• Historical perspective on parasite ecology
o First studies that were done just documented the parasite lifecycle. People
used to find different stages of the same organism and recognized them as
different ones. Took a long time to find out that the same organism can
transform into other forms
o 1930s▯Birth of modern parasite ecology. Dogiel proposed considering
parasitic fauna as an entire group. He looked at the different patterns of
organisms and still took a descriptive approach
o 1950s ▯quantitative study of ecological processes began.
Chandler and Reid described the crowding effect that occurs in
animals. This really altered the way that people thought about
parasites. Parasites that are overcrowded tend to be stunted in their
growth. Suggests that there is a resource limitation. Changed the
way that people thought.
• “Crowding effect” facts
o When you look at the growth of parasites compared
to the total per host, the graph is sort of logarithmic
with a point at which the graph tapers off.
o When you look at a graph of the number of
parasites compared with the size, there is a negative
sigmoidal sort of relationship. Less parasites grow
to be larger. When you have higher numbers of
parasites, the size of the parasite decreases.
o When people realized that there are actually
constraints on parasite growth, there was a
realization that parasites do not just grow in a way
that is not limited.
o 1960s S ▯ tudents of Chandler and Reid did research on ecological
processes that govern the growth of the parasites. This sort of stuff was
published on for a very long time.
Species of parasites that are in the same host compete for resources
between species (competition with the other species) and within
species (competition between members of the same species).
Doing experiments on multiple parasites in the same host was very
different. There is a massive number of potential combinations that
are involved and a lot of variable to consider.