Effect of oviposition delay on early reproductive effort and offspring fitness in a thrips species

Many insects can decide when and where to lay their eggs. In some species, mature females delay oviposition to optimize their reproductive effort in response to unfavourable environmental conditions, lack of oviposition substrates or lack of mates. This behaviour might be an adaptive decision to gain a higher return on reproductive investment or may occur nonadaptively and result in lower fitness for mothers and their offspring. However, empirical studies investigating consequences of delayed oviposition focus mostly on haplodiploid Hymenoptera, thereby limiting the generalization of findings to other haplodiploid arthropods. Here, we studied this in thrips (Thysanoptera), an insect order that has independently evolved haplodiploidy. We deprived gravid Pezothrips kellyanus females of oviposition substrates for up to 2 days and examined the consequences for early reproductive effort and offspring fitness. Irrespective of a female's mating status, delayed oviposition did not affect egg size, but it increased egg load and number of the first oviposition bout, suggesting that egg development was not interrupted by the oviposition delay and eggs were not reabsorbed. Offspring sex ratio in mated females remained unaffected. Finally, oviposition delay did not affect offspring fitness in terms of survival, development time, adult size and longevity under dehydration stress. This suggests that gravid P. kellyanus females are able to avoid physiological oviposition delay costs in their early reproductive effort. This may be important for the evolution of oviposition behaviour because the capacity to delay oviposition without physiological costs may allow females to search for mates and better oviposition sites.