Intraspecific Competition.

4. Four characteristics of intraspecific
competition:
• (1) Decrease in fitness:
• The ultimate effect of competition is a decrease in the fitness of all
interactants (thus it is a “-,-” interaction):
• Often via decreased survivorship or fecundity.
• Fitness reduction must be measurable to conclude that competition occurred.
• (2) Limited supply of resources:
• The resource for which individuals compete must be in limited supply.
• (3) Reciprocity:
• Even if the detectable competition is either mostly one-sided, or
balanced, it must be reciprocal and have a negative impact on both
interactants (symmetrical and asymmetrical).
• (4) Density dependence:
• The probability of an individual being adversely affected increases with
increasing competitor density (in contrast to density independent effects).
BIOS 6150: Ecology - Dr. S. Malcolm. Week 3: Intraspecific Competition Slide - 4