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Hi. My name is Dr.
Alexandra "Sasha" Wright.
I'm an associate professor at
the University of Minnesota
Twin Cities Campus in
the Department of
Ecology, Evolution,
and Behavioral Biology.
My research is studying
the positive
cooperative types of
interactions between plants
and plant communities.
I'm a community ecologist.
Today, I'm going to be
talking about cooperation and
competition species interactions
across environmental gradients.
0:33
What are we going to cover
today in this lecture?
We're going to talk
about competition and
the conditions for
competition to operate.
We're going to talk about
competitive exclusion,
coexistence, and a topic
called the maintenance
of biodiversity.
We're going to talk about
theory so the mathematics
is just a little bit of the
mathematics of competition.
Then, we're going to
flip to the other side
of cooperation and the form of
cooperation that I focus on in
plant communities, which
we call facilitation.
We're going to use examples
from plant community ecology.
We're going to talk about
different mechanisms
for facilitation of
nutrient enrichment,
herbivory avoidance,
plant soil feedback, and
then what we study in my lab,
which is microclimate
amelioration.
We're going to talk about
microclimate effects of vegetation,
and then trade-offs
in competition and
microclimate facilitation
across environmental gradients.
1:31
Competition: what is it?
The theory of competition and
the study of competition is that
two species meet either they
grow next to each other or
they're mobile species.
They meet in some physical space
and they're negatively
affected by the encounter.
In order for this to happen,
both species must use or
depend on a common resource.
Again, this can be in any type
of ecological community
plants or otherwise.
What's the common resource?
For plants, the common
resource can be water.
It can be nutrients.
It can be light.
But for other organisms,
it might be more
obvious food sources.
Two birds might compete
over a particular seed.
Two competitor
cats might compete
over a smaller mammal
as a food resource.
The resource that they're
competing over must be
in limited supply, or else
competition won't happen.
As a result of the encounter,
individuals of one species
will suffer reduced fitness.
