Species from the same genus tend to need very similar things, so when they share a site, the question is really about which strategies let them avoid fighting over the exact same niche.
- Species 1 has high frequency calls, Species 2 has low frequency calls: separating their calls in frequency stops the two species from jamming each other's signals during mating calls. This divides up the acoustic niche and supports coexistence.
- Species 1 and 2 specialise on the same limited resource: this is the opposite of partitioning. Both species pulling on one scarce resource in the same way sets up direct competition, and the competitive exclusion principle says this cannot be stable forever. This works against coexistence.
- Species 1 nests near the ground, Species 2 nests in the canopy: using different physical layers of the habitat for nesting keeps the two species out of each other's way. This is spatial niche partitioning and supports coexistence.
- Species 1 and 2 breed at different times of the year: breeding at different times keeps peak demand for mates and nesting resources from overlapping. This is temporal niche partitioning and supports coexistence.
So three of the four strategies split the niche along a different axis, sound, space, or time, and only the resource-sharing option pushes the species toward competitive exclusion instead of coexistence.
Let's summarize:
- Niche partitioning by sound, space, or time reduces direct competition between closely related species.
- Sharing the identical limited resource in the identical way does the opposite and threatens coexistence.
The correct options are (A), (C), and (D).