Maternal and social effects during early life on the development and life history traits of the pacific beetle cockroach (Diploptera punctata)

  • Molly F Beastall

Student thesis: Master's ThesisMaster of Science (MSc)


An individual’s early life can be influenced by both their mother and interactions with conspecifics. The impact of these extend to shaping development, phenotype and ultimately fitness. Maternal and social effects have been studied extensively in vertebrates but less so in insects, particularly live-bearing species. Further studies are important for showing the generality of such effects. Here, I studied the viviparous Pacific beetle cockroach (Diploptera punctata). Previous research in this system demonstrated that maternal effects and social interactions influence offspring, yet this is the first to investigate both in the same experiment whilst measuring the role of trade-offs.

Firstly, I aimed to investigate maternal effects on offspring size at birth whilst considering maternal body size and brood size. As predicted, there was a significant interaction between maternal size and brood size impacting offspring size (p=0.024). A trade-off was evident in small and medium sized mothers as larger broods consisted of smaller individual offspring. However, no such trade-off was found in large mothers as size of offspring increased with brood size.

Secondly, I aimed to explore how the early social environment impacts developmental trajectory, body size and reproductive organ size. I hypothesised that males reared in groups would develop faster and become smaller at maturity than those in isolation but with relatively larger gonads due to higher perceived mating competition. There was a difference in time spent in stadium two between the social conditions (p=0.004) with grouped individuals spending more time in this stage of post-natal development. On average, group-reared males emerged as smaller adults (p=0.062) but with significantly larger reproductive organs to those reared in isolation (p=0.012).

Building upon previous work and exploring novel hypotheses, this research demonstrates the effect of maternal traits and trade-offs on offspring phenotype and the impact of social effects on morphology and reproductive biology.
Date of Award23 Mar 2021
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorAntoine M G Barreaux (Supervisor) & Sinead English (Supervisor)

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