Territoriality and behavioural strategies at the natal host patch differ in two microsympatric Nasonia species

Territoriality occurs in a wide variety of animal taxa. The defence of valuable resources, which in the case of territoriality are bound to a specific location, gives the defender priority of access to these resources. Males often defend areas in which the chance to meet females is high and territoriality frequently includes pheromonal marking. When closely related species co-occur within the same environment, different behavioural strategies frequently evolve to avoid reproductive interference. Males of the gregarious parasitoid wasp Nasonia vitripennis exhibit territorial behaviour on the host from which they emerge. However, descriptions of territorial behaviour have been for the most part anecdotal and quantitative standardized observations in an experimental set-up are lacking. In addition, studies of the behaviour of the other Nasonia species that frequently occur in microsympatry, that is, within the same host individual, have rarely been conducted. We investigated and compared territoriality in two species of Nasonia by extensive video recording of emerging wasps in a microcosm approach. We show that males of N. vitripennis meet the concept of territoriality whereas males of Nasonia giraulti do not. Although N. giraulti females are already mated when emerging from the host and males do not show territoriality, N. giraulti males mark the substrate with their abdominal sex pheromone as often as males of N. vitripennis . For N. vitripennis we further show that, although larger males were more often territorial, experience of being in the territorial position was particularly important for winning territoriality contests. Finally, we investigated differences in the pattern of emergence and dispersal between the two species and discuss how the different behavioural strategies may help them avoid reproductive interference.