Lecture 18 (higher level)

What does an LV isocline represent?

The set of population combinations where one species’ growth rate = 0. [Slide 3]

What key observation did Gause’s Paramecium experiments support?

The competitive exclusion principle. [Slides 4–7]

When does species 1 exclude species 2 in LV models?

When species 1’s isocline lies farther from the origin on both axes. [Slides 10–11]

What assumption of LV does predation violate?

hat no third species influences competition. [Slide 17]

What leads to unstable coexistence?

When each species limits the other more than itself (α > 1). [Slide 12]

Why does coexistence require α < 1 for both species?

Because intraspecific limitation must exceed interspecific limitation. [Slide 14]

What was Tilman’s central finding in the diatom experiments?

Different species win under different limiting resource ratios. [Slides 23–24]

How do multiple resources promote coexistence?

By providing different axes for species to partition niches. [Slide 20]

What did Tansley’s bedstraw experiment illustrate?

Environmental gradients can mediate coexistence. [Slide 27]

How did Paine show predation supports coexistence?

Predators remove strong competitors, preventing exclusion. [Slide 28]

Why is intermediate disturbance beneficial for coexistence?

It balances exclusion and extirpation to maintain diversity. [Slide 29]

What is the significance of warbler niche partitioning?

It demonstrates evolutionary divergence in resource use. [Slides 30–32]

What is character displacement?

Competition-driven trait divergence to reduce niche overlap. [Slides 36–38]

What alternative explanation must be considered in MacArthur’s warbler data?

Behavioral plasticity rather than evolved partitioning. [Slide 34]

How can global change affect coexistence mechanisms?

By altering resource distributions and shifting selective pressures. [Slide 39]