The key difference between alpha beta and gamma diversity is that alpha diversity measures the diversity of a particular area or an ecosystem, usually by expressing the species richness or the number of species, while beta diversity measures the diversity between ecosystems by measuring the species change between ecosystems and gamma diversity measures the overall diversity across a large geographic region.
Biodiversity is the variability among living organisms on Earth. In other words, it refers to the variety of life on Earth. It measures the variation at genetic, species and ecosystem levels. Alpha, beta and gamma diversity are three types of biodiversity measures described over a special scale. In 1972, R. H. Whittaker explained all these three terms. Alpha diversity describes species diversity in an ecosystem. Beta diversity describes species diversity between communities or ecosystems. Gamma diversity measures biodiversity in a large region.
CONTENTS
1. Overview and Key Difference
2. What is Alpha Diversity
3. What is Beta Diversity
4. What is Gamma Diversity
5. Similarities – Alpha Beta and Gamma Diversity
6. Alpha vs Beta vs Gamma Diversity in Tabular Form
7. Summary – Alpha vs Beta vs Gamma Diversity
What is Alpha Diversity?
Alpha diversity is a measure of species diversity in a particular area or an ecosystem. Alpha diversity is expressed as the number of species present in the area of concern. Therefore, alpha diversity gives us species richness in that particular ecosystem. It is a small scale measure compared to beta and gamma diversity. Species richness is a valuable measure when compared to species diversity within different ecosystems. Species richness can be measured through a transect drawn within the ecosystem. The species we see along the transect is counted, and the number of species is taken.
What is Beta Diversity?
Beta diversity is the term that refers to the change in species diversity between communities or ecosystems. Hence, beta diversity allows the comparison of biodiversity between ecosystems. In beta diversity, the number of species that are unique to each system is counted. For example, if the beta diversity between ecosystem A and ecosystem B is 10, it tells us that there are a total of 10 species that are unique between two ecosystems. Ecosystem A may have 8 unique species which are not seen in ecosystem B, while ecosystem B has 2 unique species that are not seen in ecosystem A. Therefore, the beta diversity between the two ecosystems is 10.
Figure 01: Beta Diversity
Beta diversity increases when the interaction between adjacent communities is low. Human land use is one of the main reasons that prevent the movement of species between two ecosystems. Beta diversity can be controlled by allowing the free movement of species among communities.
What is Gamma Diversity?
Gamma diversity is the measure of overall biodiversity in a large geographic region. Therefore, it measures the total diversity of every ecosystem in that region. Total diversity depends on two things: mean species diversity in an ecosystem and differentiation of species diversity among those habitats. Gamma diversity is a type of geographic-scale species diversity.
Figure 02: Alpha, Beta, and Gamma Biodiversity
Compared to alpha and beta diversity, gamma diversity is a very large scale measure. Today, we can observe a decline in gamma diversity all over the world. Mass extinction in places around the world is one of the main reasons for decreased gamma diversity.
What are the Similarities Between Alpha Beta and Gamma Diversity?
- Alpha, beta, and gamma diversity are three terms that measure biodiversity based on the special scale.
- All three types are very important in the context of monitoring and preserving biodiversity.
- Habitat fragmentation is one of the reasons for the loss of biodiversity.
What is the Difference Between Alpha Beta and Gamma Diversity?
Alpha diversity measures the species diversity in an ecosystem while beta diversity measures the change in species diversity mainly between two communities or two ecosystems. Whereas, gamma diversity measures the overall biodiversity of a large geographic region. So, this is the key difference between alpha beta and gamma diversity.
The below infographic summarizes the difference between alpha beta and gamma diversity in tabular form.
Summary – Alpha vs Beta vs Gamma Diversity
Alpha, beta, and gamma diversity are three types of biodiversity measures. Alpha diversity describes the species diversity or species richness in an ecosystem. It is a small scale measure. Beta diversity describes the species diversity between two ecosystems or communities. It is a large scale measure. Gamma diversity describes the species biodiversity in a large geographic region. It is a very large scale measure. All these measures are important in protecting the biodiversity of the world. Thus, this is the summary of the difference between alpha beta and gamma diversity.