The biodiversity of a locality can be measured by knowing the taxonomic diversity and the levels of biodiversity -alpha, beta and gamma-, although there is no single measure that manages to capture the concept of biodiversity in a value.
However, there are a number of empirical measurements that have allowed biologists to characterize and compare sites of interest. The best known indices are the species richness, the Simpson index and the Shannon index..
Biodiversity is a term used to refer to the biological diversity of an ecosystem or locality. It can be defined as the sum total of all biotic variation, from the level of genes to that of the ecosystem..
Note that this concept is extremely broad and quantifying diversity has posed a series of challenges for biologists interested in measuring it..
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Biodiversity is the variety of life forms that exist within a limited area, call it a study site, ecosystem, landscape, among others. Biodiversity is defined, and quantified, in terms of an attribute that has two components: richness and uniformity..
The first of these, wealth, refers to the number of groups that are genetically or functionally related. In other words, richness is measured based on the number of species and the parameter is called species richness..
In contrast, uniformity is the proportion of species - or other functional groupings - at the site in question. Uniformity increases as the proportion of species found in similar.
Similarly, a locality with a few very dominant species and a significant number of rare species is a region with low uniformity..
Biological diversity can be approached at different levels. At the genetic level, diversity can be understood as the number of species or varieties that inhabit the ecosystem.
Leveling up, we can focus it based on the forms of life present. If we are interested in studying biodiversity in a forest ecosystem, and we focus on plant life forms, we will be able to distinguish grasses, mosses, ferns, among others..
In a similar way, we can point out different functional groups in the study area. For example, we will group all organisms capable of fixing nitrogen into a single category.
Generally, biodiversity is a measure that combines the two parameters mentioned above: richness and uniformity..
There are different indices and parameters used by biologists to quantify biodiversity. Below we will describe the most used and the most popular.
If you want to assess community biodiversity in terms of taxonomic diversity, there are several measures to do so:
It is one of the easiest and most intuitive ways to measure diversity. It is understood as the number of species that inhabit the community of interest.
To measure it, you simply count the species. It is a parameter that does not take into account the abundance or distribution of each of the species.
This index measures the probability that two individuals chosen randomly from a sample are of the same species. It is quantified by taking the table of the proportional abundance of each species, and adding these values.
This index measures the uniformity of the importance values across all the species that exist in the sample. When there is only one species, the index value is zero.
Thus, when all species are represented by the same number of individuals, the value is the logarithm of the total number of species.
Biological diversity can be measured or monitored across different spatial scales. In this way, we can distinguish between alpha, beta and gamma diversity..
It is also called species richness (parameter discussed in the previous section). It is the number of species in a particular community and can be used to make comparisons between the number of species in different biological communities or in different geographic areas..
Refers to the degree of change that exists in terms of species composition along a gradient, whether environmental or geographic
For example, beta diversity would measure the degree of change in bat species composition on an altitudinal gradient. If a single bat species inhabits the entire gradient, the beta diversity would be low, while if the species composition changes substantially, the diversity will be high..
It applies to regions or geographic areas on a larger scale. For example, it seeks to quantify the number of species in a wide region, such as a continent.
To exemplify the previous measures, let's imagine a region where we have three sub-regions. Species A, B, C, D, E and F inhabit the first; in the second B, C, D, E and F; and in the third A, B, C, D, E, F, G.
In the previous zone, the alpha diversity will be the species per mountain, that is, 6. The gamma diversity will be the species per region, 7. And finally, the beta diversity, which is a relationship between the gamma and the alpha, which in this hypothetical case yields a value of 1.2.
When we say that an area has a “high diversity”, we instantly associate it with positive aspects.
A diverse ecosystem is, generally, a healthy ecosystem, with high values of stability, productivity and resistance to invasions or other potential disturbances..
However, although it is rarely considered, there are negative aspects linked to high diversity. On some occasions, fragmented sites exhibit high values of diversity. In these regions, much of the richness is due to the presence of disturbed species.
In plant communities, high diversity translates into an ecosystem that is difficult to manage. If you want to implement grazing, it will be a difficult task, since each plant has its specific tolerance to grazing..
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