Which is not a reason of maximum diversity in tropics?

Options

A. Higher pest pressure
B. Evolutionary older zone
C. High rate of out-crossing
D. Greater environmental variations

Answer

To determine which option is not a reason for maximum diversity in the tropics, let's analyze each option step-by-step:

1. **Higher Pest Pressure**:
- In tropical regions, higher pest pressure can actually lead to greater biodiversity. This is because the presence of more pests can result in more natural enemies (predators) and a variety of plant species that have adapted to cope with these pests. Therefore, higher pest pressure can contribute to biodiversity rather than detract from it.

2. **Evolutionary Older Zone**:
- The tropics are considered to be evolutionary older zones. This means that they have had a longer period of stability and development, allowing for more species to evolve and coexist. This factor supports the idea that the tropics have high biodiversity.

3. **High Rate of Outcrossing**:
- Outcrossing refers to the mating between different individuals of the same species, which increases genetic diversity. In tropical regions, the high rate of outcrossing can lead to the production of more resilient offspring that can adapt to various environmental conditions, thus promoting biodiversity.

4. **Greater Environmental Variations**:
- This option suggests that increased environmental variations would lead to higher biodiversity. However, in the tropics, there are generally less seasonal variations, which means the environment is more stable. A stable environment can support a greater number of species, while greater environmental variations can lead to stress and reduced biodiversity.

Based on this analysis, the correct answer to the question "Which is not a reason of maximum diversity in tropics?" is **Greater Environmental Variations**.

### Summary of Steps:
1. Analyze the impact of higher pest pressure on biodiversity.
2. Evaluate the significance of the tropics being an evolutionary older zone.
3. Consider the role of high rates of outcrossing in promoting genetic diversity.
4. Assess the effect of greater environmental variations on biodiversity in the tropics.