Factors determining diversity in diet composition: multivariate analysis of a guild of epiphytic predators fig: 7 tab: 3
published: Dec 9, 2002
ArtNo. ESP141015502006, Price: 29.00 €
The diet composition of five species of epiphytic predators (the larval damselfly Enallagma cyathigerum, larval midge Ablabesmyia monilis, larval caddisfly Cyrnus flavidus and leeches Erpobdella octoculata and E. nigricollis), inhabiting Stratiotes aloides in the shallow littoral of three Polish lakes, was analysed using multivariate methods. The gut contents of individuals living in experimental mesocosms were also analysed to test the behavioural effects of the stimuli released by larger predators - fish and aquatic insects. The main aims of the study were: to deterxnine the most important interactions between particular members of the guild of epiphytic predators, to explain interactions between the above and their feeding resources and to characterize the effects of experimentally simulated predatory pressure. A further aim was also to test if the diversity in dietary composition caused by intrinsic, species-specific feeding preferences is higher or lower than that caused by anti-predator changes in their feeding behaviour. To design the data matrix, the dietary composition of each of 595 individuals was characterised by 28 variables, designing at the numbers or percentage of prey taxa and prey ecological groups as well as the cumulative metrics and indices. Data were explored using Discriminant Analysis, Principal Components Analysis, Multidimensional Scaling and Index of Diet Diversity. Individual dietary composition has customarily been seen as depending more markedly on the presence of stimuli from larger predator than on taxonomic specifics. The dietary compositions of the three insect species studied were more similar in natural conditions than in experimental habitats. The dietary composition of E. nigricollis was more distinct from the diets of the other species, and significantly different even from that of the congeneric species E. octoculata. Diets of leeches diverged more significantly in various feeding habitats than those of insect larvae. Moreover, the diversity to the dietary compositions of particular species feeding in natural lake conditions was lower than that to the composition noted for conspecifics feeding in different habitats.