Forest in a tropical region of Equator has ten times more vascular plants than a forest in temperature region of Midwest of the USA, although both are equal in terms of area . This is an example of

Options

A. Latitudinal gradient
B. Longitudinal gradient
C. Temperature gradient
D. Altitudinal gradient

Answer

To solve the question, we need to analyze the information provided about the forests in tropical and temperate regions and understand the concept of species richness in relation to latitude.

### Step-by-Step Solution:

1. **Understanding the Context**: The question compares the vascular plant species richness between a tropical forest at the equator and a temperate forest in the Midwest USA. Both forests are of equal area, but the tropical forest has ten times more vascular plants.

2. **Identifying the Key Factors**: The primary factor influencing the difference in species richness is the climate, particularly temperature and sunlight availability. The equator receives direct sunlight, leading to a warmer climate, which supports a greater diversity of plant life.

3. **Recognizing the Gradient**: The concept being illustrated here is known as the "latitudinal gradient." This ecological principle states that species richness tends to be higher in tropical regions (near the equator) and decreases as one moves towards the poles (temperate and arctic regions).

4. **Conclusion**: Since the question specifically asks about the example of the difference in vascular plant richness due to the geographical location (latitude), the correct answer is that this is an example of the **latitudinal gradient**.

### Final Answer:
This is an example of the **latitudinal gradient**.

---