Niche separation in coprophagous beetles: A comparison of two multivariate approaches

Coprophagous beetles (endocoprid and paracoprid Scarabaeidae, Hydrophili- dae, and Staphylinidae) were extracted from 698 sheep droppings from a pasture in southwest Germany. To quantify the pairwise niche overlap of these species, pairwise discriminant function analysis was used to calculate the overlap of the discriminant distributions in a four-dimensional niche space. Niche separation was studied considering the following four factors: season (month) and macrohabitat when and where the dropping was deposited, dropping size, and water content of the dropping. Multiple discriminant function analysis was used to describe the distribution of species in a space defined by four discriminant functions. The first discriminant function was mostly influenced by the factor ‘season'. The importance of different factors for niche separation in different functional groupings of dung beetles is compared with results from the literature. Advantages and disadvantages of pairwise and multiple discriminant function analysis, and univariate evaluation methods are compared. The following problems and restrictions of discriminant function analyses are emphasized: (i) the usage of non-numerical variables; (ii) the calculation of niche breadths; (iii) failures, when bimodally distributed variables are considered; and (iv) the ecological interpretation of statistical significances.