Species Richness Vs Diversity

Species Richness Vs Diversity, Abundance, Evenness and Composition

Species richness vs diversity indicates that species richness only evaluates the number of species in an area, while species diversity evaluates both the number of species and the relative abundance of organisms in each specie.

This article discusses species richness vs diversity, abundance, evenness and composition, as outlined below;

 

 

-Species Richness Vs Diversity

-Species Richness Vs Abundance

-Comparison of Species Richness and Species Evenness

-Species Composition Vs Species Richness

-Conclusion

 

 

 

 

 

 

Species Richness Vs Diversity

Two differences between genetic diversity and species richness are; species richness is more specific and less complex; and genetic diversity controls adaptation and inter-species interaction while species richness controls basic ecologic resilience and functioning.

Species richness is a numerical estimate of the species present in a defined ecological area; while diversity (also called species diversity, biodiversity or genetic diversity) is more complex and covers both species richness and relative abundance, or evenness [3].

The example of species diversity and species richness is; a grassland ecosystem with 500 different species of grass has a high species richness with respect to its plant community; but if the population size of each specie is not significant and balanced relative to other species, then the species diversity of the ecosystem is low.

Species Richness Vs Diversity: Multiple Species as an Indication of High Species Richness (Credit: Mathisen, Jim 2006)
Species Richness Vs Diversity: Multiple Species as an Indication of High Species Richness (Credit: Mathisen, Jim 2006)

 

 

This further emphasizes the link between species richness and diversity, as well as the high complexity of diversity relative to richness.

Higher species richness means higher diversity, provided species evenness is high as well. While there is a directly-proportional relationship between the two parameters, species diversity depends on both richness and evenness of species distribution. This means that a high species richness alone does not always imply high diversity.

 

The table below summarizes the species richness vs diversity (or biodiversity vs species richness) comparison;

 

Comparison Criteria

Species Richness

Species Diversity

Component(s)

Species number

Species number and relative abundance (evenness)

Relative Complexity

Low

High

Ecologic Relevance

Controls ecologic functioning

Controls adaptation and inter-species interaction

Determinant Factors

Ecosystem age, productivity

Age, available bioenergy, productivity

 

 

 

 

 

 

Species Richness Vs Abundance

The meaning of species abundance is; the number of individual organisms of a given specie in an ecosystem, and it differs from species evenness which is a measure of relative abundance between two or more species [4].

The difference between species richness and species abundance is that species abundance is a more narrowed, specific parameter that gives information on a singular specie, while species richness is a broader parameter that gives information about an entire eco-region.

To calculate species richness and abundance respectively, different methods are used; so that species richness is calculated as the ratio of number of species to size of area; while species abundance is calculated as the number of organisms in a given species, in an ecosystem.

Species richness does not account for abundance of organisms in a given area, because it considers only the species as individual units of the ecosystem, without necessarily including the number of organisms per specie, in its assessment.

 

Below is a table that summarizes the species richness vs abundance comparison;

 

Comparison Criteria

Species Richness

Species Abundance

Component(s)

Species number

Number of organisms per specie

Relative Complexity

High

Low

Ecologic Relevance

Controls ecologic functioning

Controls rate of organic activity

Determinant Factors

Ecosystem age, productivity

Age, adaptability, productivity

 

 

 

 

 

 

Comparison of Species Richness and Species Evenness

Species evenness is a comparative measure of the abundance of organisms across various species that are present in a given ecosystem.

In any given ecosystem, species evenness is high when the different species in the ecosystem have similar and significant population size.

It is important to note that species evenness is a variant form of species abundance that takes into account the numerical similarity or dissimilarity between various species. This implies that species evenness is a more complex parameter than both species richness and abundance.

The main difference between species richness and species evenness is that species richness assesses an ecosystem at the species level only, while species evenness assesses the ecosystem at both species and individual organic levels.

Species richness must be accounted for alongside species evenness, in order to determine species diversity of any ecosystem. These two parameters are therefore arguably the most important with regards to understanding the biological make-up of ecosystems.

 

 

 

 

 

Species Composition Vs Species Richness

Species composition means the identity of species that are present in an ecologic system or community [2].

It is a very important metric because it reveals the biological make-up of the ecosystem in detail, more than that which is made available by other metrics like species richness and diversity.

The difference between species composition and species diversity is that species diversity focuses on numerical estimates of species number and relative abundance, while species composition focuses more on taxonomic details.

Species composition can be expressed as percentage that indicate the relative contribution (numerical or biological) of the different identified species, to the overall population and productivity of the ecosystem..

An example of species composition is a distribution of 40% Cottongrass (Eriophorum callitrix), 35% Polar Grass (Arctagrostis latifolia), and 25% Vahl's Alkali Grass (Puccinellia vahliana) as the grass species in a tundra biome. This instance is a basic species composition report that includes the identities of species present, as well as their relative proportions in the ecosystem.

Species composition can be measured and reported alongside species richness, to gain a more comprehensive insight into ecological processes in a given biome [1].

 

 

 

 

 

Conclusion

Species richness vs diversity can be assessed at various ecologic levels and in various contexts, and shows that diversity is broader and more complex, being a combination of species richness and species evenness.

 

The comparison of species richness vs abundance shows that species richness does not account for the size of species populations, while species abundance is only concerned with how many individuals occur in a given specie.

 

Species richness and species evenness are two essential metrics of the ecologic makeup of any biome. The difference between them is that species richness deals only with the number of species, while species evenness is more complex and also accounts for the number of individuals in each specie, relative to other species populations.

 

Species composition differs from species richness by including details about the identity of species in an ecosystem. This is because species composition gives us details about who inhabits an ecosystem. It is an important metric because it gives information on both the number and characteristics of species. For example, an ecosystem consisting of a thousand ants and one elephant has the same species richness as an ecosystem with a thousand ants and a frog. However, their species compositions differ due to the presence of an elephant in one and a frog in the other.

 

 

 

 

 

References

1). Aggemyr, E.; Auffret; A. G.; Jädergård, L.; Cousins, S. (2018). "Species richness and composition differ in response to landscape and biogeography." Landscape Ecology 33(12). Available at: https://doi.org/10.1007/s10980-018-0742-9. (Accessed 6 March 2023).

2). Cleland, E. E. (2011)."Biodiversity and Ecosystem Stability." Nature Education Knowledge 3(10):14. Available at: https://www.nature.com/scitable/knowledge/library/biodiversity-and-ecosystem-stability-17059965/. (Accessed 6 March 2023)..

3). Pyron, M. (2010). "Characterizing Communities." Nature Education Knowledge 3(10):39. Available at: https://www.nature.com/scitable/knowledge/library/characterizing-communities-13241173/. (Accessed 6 March 2023).

4). Travlos, I. S.; Cheimona, N.; Roussis, I.; Bilalis, D. (2018). "Weed-Species Abundance and Diversity Indices in Relation to Tillage Systems and Fertilization." Frontiers in Environmental Science 6. Available at: https://doi.org/10.3389/fenvs.2018.00011. (Accessed 6 March 2023).

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