The question describes a 'checkerboard' pattern observed in the distribution of sister bird species across islands in an archipelago. This pattern means closely related species are found on different islands, even when the islands are geographically close.
Explaining the Checkerboard Pattern
The most fitting ecological process to explain this specific distribution pattern is Competition. Here's why:
- Interspecific Competition: Sister species are likely to have similar resource needs (food, nesting sites, etc.). When competing for limited resources on an island, one species might be a superior competitor and exclude the other.
- Competitive Exclusion: To avoid intense competition or potential local extinction, one species might colonize one island, while the sister species colonizes another. This leads to their distributions being segregated across the islands, creating the observed 'checkerboard' effect.
- Island Colonization: Over time, successful colonization events might lead to this pattern, where initial colonists establish themselves, and their close relatives avoid settling on already occupied islands due to the implicit threat of competition.
Why Other Options Are Less Likely
- Mutualism: This involves beneficial interactions between species. It wouldn't cause species to actively avoid each other.
- Predation: While predation impacts species presence, it doesn't specifically explain why *sister* species, with potentially similar resource needs, would be mutually exclusive on islands. Predation might affect population sizes but not necessarily lead to complete avoidance between closely related competitors.
- Commensalism: This is a one-sided interaction where one species benefits, and the other is unaffected. It does not explain the avoidance behavior between sister species.
Therefore, the intense negative interaction characteristic of competition best explains the checkerboard pattern where sister species are absent from the same island.
Important Questions from Competition
Fly larvae of a species feed simultaneously on a shared rotting fruit. If the density of fly larvae is high, then all the larvae grow up to be smaller sized adults than if the larval density were low. Which one of the following processes best describes this observation?
- Two bird species, A and B, are found on a single mountainside. A is a low-elevation species, found between 500 m and 1500 m Above Sea Level (ASL), while B is a high-elevation species, found between 1000 m and 2000 m ASL. At 1250 m ASL, species A and B have very different bill morphologies, but the bill morphology of species A at 500 m is very similar to the bill morphology of species B at 2000 m ASL. Which one or more of the following explain(s) the difference in bill morphology at 1250 m ASL?
- In an assemblage of coexisting wild cat species, the size of canine teeth was found to be strikingly different between these species. Which one or more of the following statements explain(s) this observation?
The barnacle species, Chthamalus stellatus (CS), is found only in the high intertidal zone whereas Balanus glandula (BG) is found only in the low intertidal zone. A researcher transplanted CS from the high to low (T-CS), and BG from the low to high (T-BG) intertidal zones. Additionally, they allowed the species to grow alone or in competition with each other, and quantified survival.
Which one or more of the following inferences is/are consistent with the experimental results shown below?- Which one of the following processes is not likely to lead to the stable coexistence of two species at the same trophic level within an ecological community?
