The Hill numbers [10] combine species richness and evenness. Hill defined a set of diversity numbers of different order.
If two data-sets have identical numbers of species and equivalent patterns of species abundance, but differ in the diversity of taxa to which the species belong, it seems intuitively appropriate that the most taxonomically varied data-set is the more diverse.
As long as the phylogeny of the data-set of interest is reasonably well resolved, measures of taxonomic diversity are possible. The index has different forms: taxonomic diversity and taxonomic distinctness.
The distance can be seen as the length of the path connecting these two organisms through a phylogenetic tree also called dendrogram or a Linnean classification [11].
This index includes aspects of taxonomic relatedness and evenness,. This index is measure of pure taxonomic relatedness,. The positive relationship between ecosystem functioning and species richness is often attributed to the greater number of functional groups found in richer assemblages see also Resilience and resistance.
Petchey and Gaston [13] proposed a method for quantifying functional diversity. It is based on total branch length of a dendrogram , which is constructed from species trait values. One important consideration is that only those traits linked to the ecosystem process of interest are used. Thus a study focusing on bird-mediated seed dispersal would exclude traits such as plumage color that are not related to this function, but traits such as beak size and shape should be included. With standard clustering algorithms a dendrogram is then constructed.
For example, a community with five species with different traits will have a higher functional diversity than a community of equal richness but where the species are functionally similar.
When recording the abundance of different species in a sample, it is invariably found that some species are rare, whereas others are more abundant. This feature of ecological communities is found independently of the taxonomic group or the area investigated. An important goal of ecology is to describe these consistent patterns in different communities, and explain them in terms of interactions with the biotic and abiotic environment.
Several models have been developed to describe species abundance data Fig. These models are based on species abundance observed in particular ecosystems. It describes the way in which the individuals are divided among the species, which is a measure of diversity.
The log series takes the form:. The distribution over species thus changes with sample size. Preston [16] first suggested to use a log-normal distribution for the description of species-abundances distributions.
Samples are considered with a large number of species and a large number of individuals. Contrary to the log-series distribution Eq. The more equal species are in proportion to each other the greater the evenness of the site. A site with low evenness indicates that a few species dominate the site. Diversity can be use to describe variation in several forms:. Biodiversity is a measure that combines richness and evenness across species.
It is often measured because high biodiversity is perceived a synonymous with ecosystem health. In general diverse communities are believed to have increased stability, increased productivity, and resistance to invasion and other disturbances.
Though seldom acknowledged, there are also disadvantages to high biodiversity:. Notify me of new comments via email. Notify me of new posts via email.
Search for: Search. Why Biodiversity Matters Biodiversity is important for many reasons. Measuring Biodiversity As an approximation of ecosystem functioning, ecologists are increasingly measuring the biodiversity of a given community, assemblage or ecosystem by looking at the range of functions performed by species in an ecosystem.
Selectively-logged forest, Sabah, Malaysian Borneo. Note the open canopy level, dense understorey vegetation, and the clearance for a road. View of the selectively-logged forest from canopy level. Share this: Tweet. Like this: Like Loading And Vice-Versa! Pingback: Functional diversity assessment — traits! The Waterthrush Blog. Leave a Reply Cancel reply Enter your comment here Fill in your details below or click an icon to log in:. Email required Address never made public.
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Login processing Estimating Biodiversity The differences in richness and evenness between two communities can be visualized by rank-abundance curves.
Threats to Biodiversity and their Implications Biodiversity around the world is threatened by pollution, climate change, and invasive species. References Knowlton, Nancy. The future of coral reefs. Andrea S. Downing, Egbert H. Mooij, Marten Scheffer. PLoS One. Wall, Monroe E. Camptothecin and taxol: Discovery to clinic. Med Res Rev. Yuh Fen Pung, Peter T.
Wong, Prakash P. Kumar, Wayne C. Hodgson, R. Manjunatha Kini. J Biol Chem. Estes, J. Bulletin of Marine Science, Volume. Please enter your institutional email to check if you have access to this content. Please create an account to get access.
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