Answer: Species-specific seed predators and pathogens causing high mortality near parent trees, preventing any one species from dominating.
- A Exclusion of weaker competitor tree species through sustained direct resource competition, a resource-competition explanation rather than one involving natural enemies
- B Species-specific seed predators and pathogens causing high mortality near parent trees, preventing any one species from dominating
- C Differences in the amount of sunlight reaching the forest understorey alone, excluding any role for host-specific seed predators or pathogens
- D Gradual gradients in soil nutrient availability across the forest floor, excluding any role for natural enemies near the parent tree
Correct answer: B. Species-specific seed predators and pathogens causing high mortality near parent trees, preventing any one species from dominating
Explanation: Janzen-Connell hypothesis: host-specific herbivores and pathogens accumulate near parent trees, causing density-dependent seedling mortality. This prevents any single tree species from dominating local patches.
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.