ИСТИНА

Contribution analysis is a tool that enables one to disentangle the effects of several input variables on the response variable which is a function of the input variables. Technically, the contribution of a given input variable to a resulting change in the response variable is the product of the partial derivative of the function with respect to the input variable times a shift in that variable. The sum of the contributions of all input variables can be made equal to the resulting change in the response variable, precisely as the word ‘contribution’ implies. Originally, contribution analysis was proposed by Hal Caswell in 1989 to interpret the results of life-table response experiments. Here, I would like to show a wide range of its applications both within and outside demography. In demography, we applied it to study birth rate in zooplankton in order to assess the relative strength of top-down and bottom-up effects (Polishchuk L.V. et al. 2013. Oikos 122: 1177–1186). Outside demography, it was used in such different areas as species diversity in phytoplankton in relation to the frequency and intensity of disturbance (Polishchuk L.V. 1999. Ecology 80: 721–725) and body mass dynamics in Daphnia in relation to individual somatic mass, clutch size and individual egg mass (Polishchuk L.V., Vijverberg J. 2005. Oecologia 144: 268–277). These multiple uses of contribution analysis will be reviewed, and its potential in regard to some very general issues of ecology such as identifying a single limiting factor (Liebig’s law) will be discussed.