THE IMPORTANCE OF BEING LARGER - PARASITOID INTRUDER-OWNER CONTESTS AND THEIR IMPLICATIONS FOR CLUTCH SIZE

One of the most important relationships in parasitoid behavioural ecol ogy is that between adult female size and fitness. However, surprising ly few studies have attempted to assess size-related components of fit ness beyond fecundity and longevity. This paper provides a more comple te appraisal of the size-fitness relationship in the bethylid wasp Gon iozus nephantidis by investigating the influences of female size and o wnership-status on the outcome of owner-intruder contests for paralyse d hosts. Both influenced contest outcomes: larger females tended to wi n, but outcome was modified in favour of owners when intruders were on ly moderately larger. Aggressive behaviour during contests is describe d. The size-fitness relationship, based on fecundity and longevity as correlates of fitness, has previously been used to estimate optimal cl utch size in G. nephantidis and a large discrepancy was found between observed and predicted clutch sizes. Here it is argued that because fe male fitness is determined, at least in part, by body size relative to competitors, an evolutionarily stable strategy approach is required t o calculate optimal clutch size when host ownership contests occur. Cl utch sizes could be influenced greatly and this provides a candidate e xplanation for the previously reported discrepancy. (C) 1996 The Assoc iation for the Study of Animal Behaviour