Question

An ornamental shrub species was brought from Japan in the early 1800s to India, where it was planted frequently in gardens and parks. The species persisted for many decades without spreading, and then began to spread invasively fifty years ago. Which one or more of the following processes could have led to it becoming invasive?

• A. Evolutionary adaptation to the environment
• B. Open niches due to recent habitat degradation
• C. Climate change
• D. Recent introduction of a specialized herbivore of this shrub species

Hint:

In invasion ecology, always consider {lag effects}. Introduced species may become invasive long after introduction due to {adaptation, disturbance, or environmental change}.

Answer 1

The Correct Option is A

Step 1: Recognize the invasion lag phase.
Many invasive species show a long lag phase, during which they persist at low abundance before rapidly expanding.
Such delayed invasions are common and can be triggered by ecological or evolutionary changes.
Step 2: Analyze option (A).
Over time, introduced species may undergo evolutionary adaptation to local conditions, improving growth, reproduction, or dispersal.
This can convert a benign introduced species into an invasive one.
Hence, (A) is correct.
Step 3: Analyze option (B).
Habitat degradation can reduce native competitors and create open ecological niches.
Such disturbances often facilitate biological invasions.
Hence, (B) is correct.
Step 4: Analyze option (C).
Climate change can alter temperature and precipitation regimes, making environments more suitable for previously constrained species.
This can trigger rapid population expansion of introduced species.
Hence, (C) is correct.
Step 5: Analyze option (D).
The introduction of a specialized herbivore would increase biotic resistance and suppress shrub populations.
This would reduce, not promote, invasiveness.
Hence, (D) is incorrect.
Step 6: Conclusion.
Delayed invasions can be driven by evolutionary change, habitat disturbance, and climate change.
Therefore, the processes that could have led to invasiveness are: \[ \boxed{(A),\ (B)\ \text{and}\ (C)} \]