34. β-diversity is defined as diversity
(1) Between two different ecosystems
(2) Overall large area
(3) Within a sampling area
(4) within a community

What Is Beta Diversity?

Beta diversity (β-diversity) measures the variation in species composition between two or more ecosystems, habitats, or communities. It quantifies how different or similar the species assemblages are as you move from one ecosystem to another. In other words, beta diversity captures the “species turnover” between areas, helping ecologists understand how biodiversity changes across landscapes and environmental gradients.

Why Is Beta Diversity Important?

• Comparing Ecosystems: Beta diversity allows scientists to compare the diversity between different ecosystems, such as forests, grasslands, wetlands, or agricultural fields23468.

• Assessing Environmental Change: It helps in assessing the impact of habitat fragmentation, land-use change, or climate change on biodiversity by revealing how species composition shifts across different areas36.

• Conservation Planning: High beta diversity indicates that different ecosystems have unique species, highlighting the need to protect multiple habitats to conserve overall biodiversity36.

How Is Beta Diversity Measured?

Ecologists use various indices to quantify beta diversity, such as:

• Jaccard Index

• Sørensen Index

• Bray-Curtis Dissimilarity

These indices calculate the degree of similarity or dissimilarity in species composition between two or more areas34.

Beta Diversity vs. Alpha and Gamma Diversity

The Correct Definition

Given the options:

1. Between two different ecosystems

2. Overall large area

3. Within a sampling area

4. Within a community

The correct answer is:

(1) Between two different ecosystems

Beta diversity specifically refers to the diversity or difference in species composition between ecosystems, not within a single area or community23468.

Conclusion

Beta diversity is a vital ecological metric that helps us understand how species composition varies across different habitats or ecosystems. By measuring the diversity between ecosystems, beta diversity provides insights into landscape-level biodiversity patterns and informs effective conservation strategies.

Correct answer:
(1) Between two different ecosystems