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

Answer 1

The Correct Option is A, B, C

The question pertains to the ecological and evolutionary dynamics of a shrub species brought to India in the early 1800s. Initially, the species did not spread invasively, but it began spreading significantly approximately fifty years ago. To understand this phenomenon, let's evaluate the possible processes:

1. Evolutionary adaptation to the environment:

   Over time, the shrub might have undergone evolutionary changes that made it more suited to the local environment. Such adaptations could include alterations in reproductive strategy, resistance to native pests, or changes in growth patterns that allowed it to compete better with native species. These adaptations would make it more capable of spreading and becoming invasive.

2. Open niches due to recent habitat degradation:

   Human activities such as deforestation, urbanization, or agriculture often lead to habitat degradation. This process creates open ecological niches, reducing competition from native species that might have been dependent on the original habitat conditions. The shrub could exploit these new opportunities, thereby increasing its chances of becoming invasive.

3. Climate change:

   Climate change can alter the environmental conditions such as temperature, rainfall patterns, and seasonal cycles. These changes might favor certain species over others. If the environmental changes have now become more favorable to the shrub's growth requirements, this could contribute to its invasive spread.

4. Recent introduction of a specialized herbivore of this shrub species:

   The introduction of a specialized herbivore is unlikely to make a plant species invasive. Typically, herbivores reduce plant populations rather than increase them. Hence, this option does not contribute towards the shrub becoming invasive.

Based on the explanations above, the processes that could have contributed to the shrub's invasive spread include: Evolutionary adaptation to the environment, Open niches due to recent habitat degradation, and Climate change. The introduction of a specialized herbivore is eliminated as it is unlikely to facilitate invasiveness.

Answer 2

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: \[ \boxed{(A),\ (B)\ \text{and}\ (C)} \]