Key Difference – Species Richness vs Species Diversity
 

The term biodiversity originates from words ‘biological’ and ‘diversity’. It refers to the variety of life and includes all living organisms such as plants, animals and microorganisms and their unique characteristics. An ecosystem with a high level of biodiversity is more resistant to the environmental change and such ecosystems are rich in a variety of living organisms. Biodiversity is measured using biodiversity indexes. Species richness and species diversity are two different biodiversity indices, which influence and support the stability of an ecosystem. Species richness is defined as the number of different species present in a given area, region or in a particular ecosystem. Species diversity is defined as the variety of species in a given area, region or a particular ecosystem. The key difference between species richness and species diversity is that species diversity has two components namely species richness and species evenness whereas species richness is a part of species diversity. Species evenness measures how evenly the species are represented in the area.

CONTENTS
1. Overview and Key Difference
2. What is Species Richness
3. What is Species Diversity
4. Understanding the Difference Between Species Richness and Species Diversity
5. Side by Side Comparison – Species Richness vs Species Diversity
6. Summary

What is Species Richness?

Species richness is the number of different species found in a given ecosystem, region or a particular area. Species richness is the most common type of biodiversity index. It simply counts the number of different kinds of species present in a particular area or the sampling area. The size of the sample should be decided correctly according to the sampling guidelines and should represent a big area or a large population. When the number of species in a particular location is high, this means the sample has higher species richness. When the number of species counted is low, it indicates the low species richness. The number of individuals of each species is not included into species richness. It does not also account for the abundances of the species or their relative abundance distributions

Species richness is an important index when thinking about conservation of a given habitat to decide what level of conservation measures need to be taken.

Figure 01: Different species in a particular location

What is Species Diversity?

Earth has a tremendous diversity of species. It is the home of all living species. Evolution is the main mechanism which creates biodiversity in which each species plays a key role in the ecosystem.  A large variety of species is present in an ecosystem. Species diversity is defined as the number of species and the abundance of each species that live in a particular area. Species richness and species evenness are the components of species diversity. The number of species living in a particular area is known as species richness. Species evenness refers to the relative abundance of each species in a particular area and it is a measure of whether a particular ecosystem is numerically dominated by one species or is represented by a similar number of species. Species evenness compares the number of individuals between species to produce a relative abundance of each species.

In other words, species diversity can be defined as the variety of species in a given ecosystem. Species diversity indicates whether most of the individuals of the community belong to one species or not, and how the species are distributed. Species diversity is an essential part of an ecosystem since each species fulfills a role of the ecosystem.

A community dominated by one or two species is considered to be less diverse than another community in which several different species have a similar abundance. When species richness and evenness increase, species diversity is also increased in that region.

Understanding the Difference Between Species Richness and Species Diversity

Consider the following data obtained from two different biological communities A and B.

By looking at the data of two communities, the species richness and the diversity can be explained as follows. Species richness of the two communities is equal and the value is 6. Species A numerically dominates community A. In community B, all the species are evenly represented. Hence, it can be concluded that though the species richness and the total number of individuals in both community are the same, community B is more diverse than community A. Therefore, it is necessary to account the relative abundance of each species when considering the species diversity.

Figure 02: A rainforest – Most diverse ecosystem

What is the difference between Species Richness and Species Diversity?

Summary – Species Richness vs Species Diversity

Species richness and species diversity are two important measures in a particular region which produce clear inference about the biodiversity of that region. The number of different species in a particular region is known as species richness. It does not look into the number of individuals in each species. Species diversity is a measure of the number of different species present in a particular region and their abundance. Species diversity counts the number of species, number of individuals in each species and compares them to measure relative abundance of each species. This is the difference between species richness and species diversity.

Reference:
1. Bock, C. E., Z. F. Jones, and J. H. Bock. “Relationships between species richness, evenness, and abundance in a southwestern savanna.” Ecology. U.S. National Library of Medicine, May 2007. Web. 25 May 2017
2. “Species richness.” Wikipedia. Wikimedia Foundation, 11 May 2017. Web. 25 May 2017. <https://en.wikipedia.org/wiki/Species_richness>

Image Courtesy:
1. “Rain Forest Daintree Australia” By Thomas Schoch – Thomas Schoch at  (CC BY-SA 2.5) via Commons Wikimedia
2. “View from Bukit Terisek” By Sze Ning from Malaysia – Flickr.com –  (CC BY 2.0) via Commons Wikimedia

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