Lectures on species interactions and competition

Summary
• Major types of competition: (1) interference competition (species directly interfere
with each other, e.g. allelopathy), (2) exploitation competition (mediated by
exploitation for a shared resource, most plant competition is of this type), (3)
apparent competition (mediated through a third species such as an herbivore).
• Regular or clumped distribution patterns can be used to infer competition in some
cases.
• Gause s competitive exclusion principle for animals and the Verhulst-Pearl equations
can be applied to plants in modeling situations, but in the real world, plants often
coexist because natural populations may not come into equilibrium very often, or
other interactions may limit the full competitive interaction between species.
• Spatial and temporal variation in resource availability allows for the coexistence of
several species. This can be inferred using differences in dispersal abilities, or
differences in above- and below-ground allocation.
• Tilman focused on resource competition as the basis for most competitive
interactions. His resource-ratio models are based on species relative abilities to
compete for resources.
• Grime s models predict the strongest competition in high resource environments.
Plants able to convert resources to high growth rates are the best competitors in
these situations.
• Allelopathy is an example of an amensal (0,-) interaction (or interference competition).
Many plants release allelochemicals that are inhibitory to the growth of other species.