In a coastal mangrove ecosystem, which organism is most likely to be considered a keystone species because its removal would cause a dramatic shift in community structure?
Answer
(a) Mangrove crab
The correct answer is (a) Mangrove crab — Conclude that the mangrove crab’s ecological engineering role makes it the keystone species, so the correct choice is (a).
Step-by-step solution
- Recall that a keystone species has a disproportionate effect on its environment relative to its abundance.
- Evaluate each option: (a) Mangrove crab burrows and aerates sediment, facilitating plant growth and providing habitat for many organisms.
- (b) Fiddler crab also burrows but usually has a smaller effect on sediment chemistry compared to mangrove crabs.
- (c) Mangrove tree is a primary producer but its removal would affect the ecosystem; however, it is not classified as a keystone because many other tree species could fill similar roles.
- (d) Mudskipper fish occupies a niche but does not control community dynamics as strongly as the crab.
- Conclude that the mangrove crab’s ecological engineering role makes it the keystone species, so the correct choice is (a).
Common mistake: Choosing the mangrove tree instead of the crab
Concept tested: keystone species identification
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