Influences of host feeding-niche and foodplant type on generalist and specialist parasitoids

Abstract

• Parasitoids of 185 British herbivorous insect species were classified as being koinobionts (tending to be specialists) or idiobionts (potential generalists) to examine the influences of host feeding-niche and food plant type on the numbers of parasitoid species attacking individual host species. The majority of parasitoid species of exophytic (internally feeding) hosts were koinobionts, whereas endophytic (externally feeding) hosts supported mainly idiobionts. Parasitoid assemblage size increased with host food plant size and complexity; for endophytic hosts this was due to an increase in idiobionts on hosts on large plants, but for exophytic hosts it was the number of koinobionts that increased with food plant size. Comparison of these patterns with those predicted under a competition hypothesis suggested that parasitoid communities associated with endophytic hosts may be commonly limited by interspecific competition, whereas those of exophytic hosts probably are not.