Introduction

ECOM offers a range of analytical techniques for visualising and ordering the relationships in multivariate data commonly used by community ecologists including Canonical Correspondence Analysis (CCA), Redundancy Analysis (RA) and Multiple Regression (MR). Researchers in other fields such as palaeontology, archaeology and the social sciences also use many of these methods. At the core of all the methods is the exploration and quantification of the effects of the explanatory or environmental variables on the observed dependent variables. ECOM is focused on the analysis of ecological data so the dependent variables are termed biological variables and would typically be an array of species abundances in different samples. The environmental data set comprises observations of the explanatory variables for these samples and would typically hold information on physical variables such as temperature, salinity, altitude, nutrient status etc. However, it may be that the independent variables are themselves biological variables. For example, the insect community might be determined by a variables that measures the density of the tree canopy.

Data can be organized using Windows programs such as Microsoft Excel and the output from ECOM is displayed, exported and printed using standard Windows techniques. The result is a program that is easily learned and used by both students and professional ecologists. It is particularly useful for ecological teaching because it allows students to quickly enter data, try different transformations and explore a range of methods within a familiar Windows setting.

The user supplies two input data sets holding the biological and physical data for the samples (sites) respectively. These data are arranged as two-dimensional arrays. In ecology, it is usual for the samples, which are normally collected from set localities and may be called, for example, quadrats or stations, to form the columns. The variables for each sample are the rows and, in the case of the biological data, comprise the numbers of each species or other taxon observed. The environmental data may be either continuous variables such as pH, temperature or current speed, or binary variables such as soil or treatment type which are scored as either a 0 or 1. ECOM complements CAP (Community Analysis Package), also produced by PISCES Conservation, which offers a range of techniques that only require biological data to undertake the ordination or classification.

ECOM uses the same data structure as CAP and Species Diversity and Richness II, which calculates a wide range of diversity and species richness measures. Together, ECOM, CAP and Species Diversity and Richness II offer an extensive range of methods for the analysis of ecological communities.