Social interactions throughout life impair longevity and age-specific mating success in male parasitoids

Abstract

Social interactions among individuals within a species profoundly influence behavioural and life history traits, impacting fitness. While extensively studied in cooperative and eusocial species, the effects of social environment on fitness in non-social species, particularly insects, remain less explored. Our study investigates the impact of social environment, specifically male density, on fitness-related traits in the hymenopteran parasitoid Venturia canescens. The research focuses on longevity, reproductive behaviours (latency before mating, mating probability and duration), and offspring production capacity. Through a lifespan study, males were exposed to either isolation or regular encounters with conspecific males, alternating with periods of female presence or absence. Results show a trend of reduced longevity in socially exposed males and a significant decline in mating success with age in the social context. However, reproductive behaviours and offspring produced by males remain unaffected. This study sheds light on the intricate interplay between social environment, ageing, and reproductive strategies in non-social insect species, emphasizing the need for further exploration of social effects on male behaviour and notably potential influences of interactions between male and females but also between females.

Significance Statement

Impacts of social interactions on individuals were largely explored in social species, but remain little studied in non-social ones. This study aims at testing the impact of male-male interactions before the encounter of a female (past social interactions) on male reproductive behaviours and longevity in a non-social parasitoid wasp. We show that longevity is negatively affected by the past social interactions in this wasp. Those interactions also impose a decline in male mating probability with age (senescence pattern) or mating experience (number of matings). Latency before mating, mating duration and offspring production are not influenced by social environment. On the other hand, offspring production increases with mating experience.