Lecture 17 (higher level)

What determines whether intraspecific or interspecific competition dominates in LV models?

The magnitude of α relative to 1; α < 1 means intraspecific limits growth more strongly, promoting coexistence. [Slide 6]

Why are competition coefficients interpreted as “per-capita effects”?

They quantify how much one individual of one species affects another species’ growth relative to its own individuals. [Slide 6]

Why does interference competition often reduce coexistence more than exploitation?

Because physical exclusion removes access independent of efficiency, giving disproportionate advantage to the defender. [Slide 3]

What is the main assumption behind LV competition models?

That species compete for the same limiting resource in a linear, density-dependent manner. [Slide 5]

When does species 1 “win” in the phase-plane analysis?

When its isocline lies farther from the origin, meaning it can tolerate more competitive pressure. [Slide 12]

What causes unstable coexistence in LV systems?

When each species limits the other more than it limits itself (α > 1 for both). [Slide 13]

Why is symmetry in α values considered unrealistic?

Real species differ in behavior, resource use, and competitive strategies, making effects asymmetric. [Slide 9]

How do surrogate resources alter apparent competition?

They shift competition onto a non-limiting resource, making niche overlap appear misleadingly high or low. [Slide 1]

Why does α = 0 imply no competitive interaction?

Because the species’ presence has no measurable effect on the other’s growth. [Slide 6]

What ecological insight is gained by comparing α to 1?

It reveals whether self-limitation or heterospecific limitation is stronger. [Slide 6]

How do density effects influence the strength of competition?

Higher conspecific densities intensify intraspecific pressure, shifting α’s effective impact. [Slide 7]

Why can mixed-species herbivore groups consume more total resource than single species?

Behavioral shifts or complementary feeding patterns produce emergent effects. [Slide 6]

Why doesn’t LV handle multi-species interactions well?

Because competition is not strictly additive; species interactions modify one another. [Slide 9]

What makes coexistence most likely under LV?

When each species self-limits more strongly (α < 1 for both). [Slide 12]

Why is early mastery of competition models emphasized?

Because competition underlies many ecological interactions and α values determine system outcomes. [Slide 10]