One measurement unit for nestedness is a system's '
temperature' 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 solves 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. Bastolla
et al. introduced a simple measure of nestedness based on the number of common neighbours for each pair of nodes. They argue that this can help reduce the effective competition between nodes in certain situations. For instance, two insect species might "help" each other by pollinating the same subset of plants, thereby reducing the extent to which they are harmful to each other. The authors suggest that this effect is behind a correlation between nestedness and diversity in plant-pollinator ecosystems. However, Johnson
et al. have shown that this measure does not, in fact, properly account for the desired effect. These authors propose a refined version of the measure, and go on to show how certain network properties affect nestedness. ==References==