Question

Fungus S infects elm trees and fungus T infects chestnut trees, and both kill their hosts within a year of infection. A forest with equal density of elm and chestnut trees is colonized by both pathogenic fungi. A 100 years later, the elm tree population has declined and the chestnut trees have become extinct. Which one of the following mechanisms would NOT contribute to this outcome?

• A. Fungus S is dispersed by flightless beetles and fungus T disperses by wind
• B. Elm trees reproduce much more quickly than chestnut trees
• C. Elm seeds disperse far away from the parent, while chestnut seeds fall near the parent
• D. Fungus S reproduces much more quickly than fungus T

Hint:

In ecological studies, when considering the spread of diseases or pathogens, focus on factors such as dispersal mechanisms, reproductive rates, and the speed of pathogen reproduction, which have more direct impacts on species survival.

Answer 1

The Correct Option is D

Step 1: Understand the ecological dynamics between the species and the fungi.
Elm trees and chestnut trees are equally colonized by their respective pathogens, fungus S and fungus T.
For the pathogens to have more effect on one tree species than the other, mechanisms like reproductive rates, dispersal, and fungal reproduction speed need to be considered.

Step 2: Examine each option.
Option (A): Is plausible because different dispersal mechanisms for the fungi would allow them to spread at different rates.
Option (B): Is plausible because faster reproduction of elm trees would contribute to their higher resistance or recovery from fungal infection.
Option (C): Is less likely to contribute to the outcome because the distance of seed dispersal is not directly related to fungal spread. Both trees can still be colonized by their respective fungi regardless of seed dispersal distance.
Option (D): Is less relevant because although fungus S might reproduce quickly, this fact alone does not explain why chestnut trees declined—it doesn't establish a direct causal link for chestnut tree extinction.

Final Answer: (D)