Order and disorder in ectoparasite communities: the case of congeneric gill monogeneans (Dactylogyrus spp.)

The measure of order and disorder in the distribution of species in fragmen ted habitats proposed by Atmar and Patterson (Oecologia, 96 (1993) 373-82) was applied to investigate nested patterns of Dactylogyrus species parasiti sing the gills of roach. Organisation in dactylogyrid assemblages was inves tigated at three levels: (1) host populations between localities: (2) local host populations over seasons: and (3) individual hosts over one season wi thin a local host population. Dactylogyrid assemblages showed nested patter ns when analyses were conducted at the level of localities (among host popu lations) and at the level of seasons (among host populations within localit ies). The analysis at the level of hosts (infracommunities of parasites) re vealed that nested pattern is not common. We suggest that nestedness may ha ve a variety of causes and does not necessarily imply competition. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd . All rights reserved.