Required Readings Summary
Human Activity Mediates Trophic Cascade Caused By Wolves
Banff national park.
Wolves recolonized in 1986.
Human activity divided the community into high wolf areas and low wolf
Elk population density diverged over time in the two treatments.
Female elk survived more often in low elk areas.
Higher recruitment without wolves.
Wolf exclusion decreased aspen recruitment.
Where there is more elk, there are fewer beavers.
Support the wolf-caused trophic cascade hypothesis.
Recolonization of wolves had a substantial direct effect on elk
Predictions made by the trophic cascade hypothesis are supported.
Believed that top down trophic impacts were more significant.
Elk compete with beaver for willow.
Management based on trophic impact of large carnivores has support.
On Classifying Interactions Between Populations
Critical of current way of classifying interactions.
Thinks a simple (+,-) style excludes many interactions and shapes
ecologists world views.
Believes we need to define indirect and direct effects.
Ambiguity problem – changing population density, growth rate, etc. can
all change the interaction between species.
The effects on individual fitness do not necessarily have the same effect on
population growth or size.
Signs do not provide adequate information about the range of interactions
that may occur.
Inadequate classification may have also played a role in biasing what
World’s diversity makes it impossible to create a perfect classification.
Prevent current scheme from distorting perception of the natural world. Lecture Three
Conceptual Synthesis in Community Ecology
Patterns in community ecology are influenced by only selection, drift,
speciation, and dispersal.
Organizing the material of community ecology according to this