INFLUENCES OF HOST FEEDING-NICHE AND FOODPLANT TYPE ON GENERALIST AND SPECIALIST PARASITOIDS

Abstract. 1. We classified the parasitoids of 185 British herbivorous insect species as being koinobionts (which should tend to be specialists) or idiobionts (potential generalists) to examine the influences of host feeding‐niche and foodplant type on the numbers of parasitoid species attacking individual host species. 2. The majority of parasitoid species of exophytic hosts are koinobionts, whereas endophytic hosts support mainly idiobionts. 3. Parasitoid assemblage size increases with host foodplant size and complexity; for endophytic hosts this is due to an increase in idiobionts on hosts on large plants, but for exophytic hosts it is the number of koinobionts that increases with foodplant size. 4. Comparison of these patterns with those predicted under a competition hypothesis suggests that parasitoid communities associated with endophytic hosts may be commonly limited by interspecific competition, whereas those of exophytic hosts probably are not. Copyright © 1990, Wiley Blackwell. All rights reserved