Species diversity refers to the measure of diversity in an ecological community. A book on biodiversity and community ecology analysis is available for free download from the website. Such indices include species richness, the shannon index, the simpson index, and the complement of the simpson index also known as the ginisimpson index when interpreted in ecological terms, each one of these indices corresponds to a different thing, and their. Species diversity indices take two aspects of a community into account, namely species richness and evenness or equitability the distribution of abundance among the species. The term simpsons diversity index can actually refer to any one of 3 closely related indices. Indices of association and species diversity indices. In order to evaluate each communitys structure and the interactions among them, several population indices are used as key. Species density or the number of species per m 2 is most commonly used to measure species richness.
C the more species you have, the more diverse the area. A diversity index is a mathematical measure of species diversity in a community. As a measure of species diversity, we will calculate the shannon index. Species richness an index based on the number of species i. Simpsons diversity index is a measure of diversity which takes into account the number of species present, as well as the relative abundance of each species. Species diversity and richness 4 is designed for professional ecologists and their students. Diversity indices as you have probably figured out, the choice of a particular index is chosen with respect to the goals of the study emphasis on abundant vs rare species and to what.
Informationstatistic indices can take into account rare species in a community. Usually used as biodiversity as in species, but can apply to other data where you count the number of times a particular category occurs e. The may 2018 issue of the american biology teacher vol. B based on the species richness the number of species present and species abundance the number of individuals per species. There has been a proliferation of indices and models for measuring diversity followed by many critiques of these indices. The smallest sample size may be 1 km and the largest may be the entire region or country. This function also features plots of empirical and estimated continuous diversity profiles. Species diversity species diversity differs from species richness in that it takes into account both the numbers of species present and the dominance or evenness of species in relation to one another. Responses of taxonomic distinctness and species diversity. Chaoshared estimating the number of shared species between two communities. However, at the same time, weeds are major interacting components of the agroecosystems. Addition of menhinick, gini and strongs alpha diversity indices. Then each participant will determine a simplified version of the biodiversity index for their ecosystem. Teaching diversity indices the american biology teacher.
The question of how many different species exist in a particular environment is central to the understanding of why it is important to promote and preserve species diversity. D however, there are two types of indices, dominance indices and information. The species abundance distribution is a very simple and powerful tool for describing and comparing the species diversity from different sampling stations. In table 1, species diversity is calculated for the two communities using the formula h. Since evenness and dominance are simply two sides of the same coin, their measures are complimentary. The present article extends that work by having students collect authentic ecological field data and utilize diversity indices to quantify biodiversity. Diversity estimating a continuous diversity profile and various diversity indices in one community including species richness, shannon diversity and simpson diversity. Comparative evaluation of species diversity indices in the. In this habitat the number of species is rather low, which greatly simplifies the analysis, and we hope that the statistical behaviour of the indices we find will hold for other, especially other low diversity communities as in polluted environments, as well.
Different authors have used different indices to measure species diversity and the whole subject. Species richness, as measure of diversity, has been used by ecologists. It was proposed that the simpson, pielou and shannonwiener indices, which are widely used as plant species diversity indicators, can be precisely estimated through hyperspectral indices at. Of the major environmental gradients analysed, biodiversity indices showed the strongest relationships with catchment area, lending further support to the. The methods on offer range from the familiar, such as the calculation of various diversity indices and the fitting of common distributions, to more recentlydeveloped techniques such as total species complement estimators. Whittaker 1972 described three terms for measuring biodiversity over spatial scales. For example, if we are monitoring the effect that british farming practices have on the. For biological diversity, these items are organized at many levels. Frontiers weedspecies abundance and diversity indices. Initially thought that more diversity more stable ecosystem now used to. According to the encyclopedia of earth, species diversity is a measurement of an ecosystems species richness and species evenness. This is the total number of species divided by the total number of organisms. The simplest of these indices was proposed by berger and parker, has an analytical relationship with the geometric series of the species abundance model may 1975.
Explicit formulas for these diversity indices, as a. Simpsons diversity index a community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance. Speciesarea relations life on earth is diverse at many levels, beginning with genes and extending to the wealth and. A comparison between diversity, similarity and biotic.
Species diversity takes into consideration species richness, which is the total number of different species in a community. Pdf functional diversity may be summarized using indices based on trait values and species importance in the community, like abundance, cover and. Comparing species diversity and evenness indices journal. Lepidoptera, diversity, pakistan, peshawar introduction diversity can be defined as the number of different items and their relative frequency. This suggests that, at least very generally, relationships between richness and evenness of these traits are similar to those seen in species diversity. Southwood 1978 and southwood and henderson 2000 give good accounts of this topic and provide numerous references to ecological papers, while pielous 1975 book on mathematical approaches to species diversity remains. Information statistic indices are based on the rationale that diversity in a natural system can be measured in a way that is similar to the way information contained in a code or message is measured. Often researchers have used the values given by one or more diversity indices to quantify species diversity. A diverse species assemblage also contributes to ecosystem diversity.
Species diversity, abundance and distribution of fish. Species richness variety of species or the number of different species or genera, families, etc. The idea was that the total species diversity in a landscape. Diversity indices usually used as biodiversity as in species, but can apply to other data where you count the number of times a particular category occurs e. Difficult to define because definition consists of two distinct components. Diversity indices provide more information about community composition than simply species richness i. Species richness is the number of species present in a sample, ecological community, ecosystem, landscape, region, or any defined spatial unit. Indices n1 and hadj have not been included in the dendrogram. It also takes into account evenness, which is the variation of abundance in individuals per species in a. The importance of species diversity to the ecosystem. Species richness the number of species that live in a certain location. Alpha, beta, and gamma diversity biology libretexts.
The resultant diversity indices are a key feature of communities which can throw light on many aspects of conservation. A second advantage of hill numbers is that they are all expressed in units of effective numbers of species. In our example, we had complete equitability, therefore, hbmax hb 1. C the more species you have, the more diverse the area, right. Part of the biodiversity counts curriculum collection. The shannonweiner diversity index of three different sampling indicated a strong relationship with overall species richness, showed variation and ranged from 0. Mcintosh 1967 coined the name species richness to describe this concept. If an ecosystem has poor species diversity, it may not function properly or efficiently. This study was conducted to search the point where only a few more species were increased via species area curve, to understand stand structure through importance value, rank abundance curve, and species abundance curve, and to compare seven di.
The term diversity is quite complex and attempts have been there to confine it within the definitons and mathematical equations. Indices of species diversity part ii biotech articles. Alpha diversity refers to the diversity within a particular area or ecosystem, and is usually expressed by the number of species i. Explain that the closer the biodiversity index is to 1, the more diverse the ecosystem is. As for the measures of species diversity, the compound diversity indices d 1, d 2, h outperformed others when differentiating sites based on molecular and chemical diversity data. Third, key diversity indices proposed in the literature.
Weeds pose a major threat to world agriculture by reducing detrimentally crop yield and quality. The variability of the species diversity indices is extremely low for sib. The aim of the study was to measure bird species diversity at taunsa. However, species density, rarefied species richness, shannons diversity and taxonomic diversity showed higher index values in streams draining mineral as opposed to peatland catchments. A a diversity index is a mathematical measure of species diversity in a given community. Outline lecture class room exercise to calculate diversity indices 3. Diversity and evenness indices 561 diversity all species diversity indices show a significant degree of positive kurtosis, but no skewness except for sib. A uniform population of a single species of plants adapted to a.
Speciesarea curves, diversity indices, and species. How to calculate a biodiversity index main content. An overview is given of the different indices used, since their. It is between 20 and 30% for the number of species sand margalevs index ma, both indices which. Abundance and diversity of weeds vary significantly among the several communities. Relative to other diversity indices, such as simpsons index, it is considered sensitive to the addition of rare species krebs, 1989. Correlation r between species richness, diversity and evenness on the one hand, and. Simpsons index measures the probability that any two individuals drawn at random from an infinitely large community will belong to same species. However, species richness increases with sample size. The highest fish diversity was recorded at siteiii followed by siteii and sitei. The article presents a brief overview of the commonest indices used in ecological studies. Different diversity indices apportion different relative weights to these properties, and the definition of evenness itself varies. As a result, many different measures or indices of biodiversity have been. Species and biological diversity choices of diversity indices and.
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