Nestedness
Encyclopedia
Nestedness is a measure of order in an ecological system
, referring to the order in which the number of species
is related to area or other factors. The more a system is "nested" the more it is organized.
Imagine island communities at different distances from the mainland. Then we would expect islands farther away to contain fewer species, and these species to be present on all islands that are closer to the mainland. In this case, the species-island-matrix would be highly nested (the matrix has a lowest nestedness temperature: it is 'cold'). If, on the other hand, all species have the same dispersal ability, population size etc. on the mainland, then island communities might simply be random draws from the mainland pool, and the species-island-matrix would not display any significant nestedness (it is 'hot', i.e. in maximum entropy).
' offered by Atmar and Patterson in 1993. This measures the order in which species' extinctions would occur in the system (or from the other side - the order of colonizing a system). The 'colder' the system is, the more fixed the order of extinction would be. In a warmer system, extinctions will take a more random order. Temperatures go from 0°, coldest and absolutely fixed, to 100° absolutely random.
For various reasons, the Nestedness Temperature Calculator is not mathematically satisfying (no unique solution, not conservative enough. A software (BINMATNEST) is available from the authors on request and from the Journal of Biogeography to correct these deficits In addition, ANINHADO resolves problems of large matrix size and processing of a large number of randomized matrices; in addition it implements several null models to estimate the significance of nestedness and
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
, referring to the order in which the number of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
is related to area or other factors. The more a system is "nested" the more it is organized.
Imagine island communities at different distances from the mainland. Then we would expect islands farther away to contain fewer species, and these species to be present on all islands that are closer to the mainland. In this case, the species-island-matrix would be highly nested (the matrix has a lowest nestedness temperature: it is 'cold'). If, on the other hand, all species have the same dispersal ability, population size etc. on the mainland, then island communities might simply be random draws from the mainland pool, and the species-island-matrix would not display any significant nestedness (it is 'hot', i.e. in maximum entropy).
Measures of nestedness
One measurement unit for nestedness is a system's 'temperatureTemperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
' offered by Atmar and Patterson in 1993. This measures the order in which species' extinctions would occur in the system (or from the other side - the order of colonizing a system). The 'colder' the system is, the more fixed the order of extinction would be. In a warmer system, extinctions will take a more random order. Temperatures go from 0°, coldest and absolutely fixed, to 100° absolutely random.
For various reasons, the Nestedness Temperature Calculator is not mathematically satisfying (no unique solution, not conservative enough. A software (BINMATNEST) is available from the authors on request and from the Journal of Biogeography to correct these deficits In addition, ANINHADO resolves problems of large matrix size and processing of a large number of randomized matrices; in addition it implements several null models to estimate the significance of nestedness and
Software
- Nestedness Temperature Calculator Program
- an Fortran Version correcting some of the initial problems, by Werner Ulrich, Poland
- ANINHADO, a Nestedness Temperature Calculator Program improving NTC for large matrices and implementing additional null models, by Paulo Guimarães and Paulo R. Guimarães Jr., Brazil
- Weighted Interaction Nestedness Estimator. It works with weighted matrices (i.e. species abundance)