For social insects, nutrition can mean the difference between reproductive dominance and a life of subordination. Particularly in their early development (larval stages) the quality of food received by primitively eusocial wasps determines whether individuals choose to invest in their own reproduction, or to help a close relative to reproduce. With increasing evidence linking nutrition to social power, this project aims to investigate a seemingly paradoxical behaviour exhibited by social wasps: larvae donating nutrients back to their adult nestmates. With researchers at Mpala and the University of Bristol, the project forms part of the African Wasp Project, a program using wasps as a model species to study the evolution of cooperation and conflict across the diverse habitats of Africa.
Over a century ago, French biologists were surprised to observe that the larvae of some social wasps regurgitated a portion of the precious nutrients that they received into a salivary secretion for their adult nestmates to drink. Yet, it remains unclear whether generous larval donors experience fitness costs in their adult life. We aim to address this knowledge gap and thus identify whether wasp larvae represent hidden altruists in the evolution of eusociality. This project will combine experimental extractions of larval saliva with behavioural recordings, social network analysis, and physiological measurements to capture a comprehensive range of potential downstream effects associated with saliva donation. Collectively, these metrics will present the first test of whether larval helping behaviour shapes adult power asymmetries. The needle-waist wasp (Belonogaster juncea) will present a useful model species on which to manipulate saliva donation, as they can be found in abundance on buildings and trees in the region surrounding Mpala Research Centre.
Our team, planning to commence this work in Kenya, consists of PhD student Ellie Trelfa-Stewart, her supervisor Dr. Patrick Kennedy and their field assistant Rashid Lebunge. The project is part of a larger team of researchers in the University of Bristol’s Social Strategy Lab, who lend their experience from previous field work with social species across the globe. Most importantly, this project would not be possible without the expertise and generosity of the local Laikipia community, who offer invaluable insights regarding sampling sites and open their communities to our researchers.
This project will be part of the African Wasp Project (AWP), a wider research program led by Patrick Kennedy and Dustin Rubenstein, which, through affiliations with organisations such as Mpala, studies B. juncea wasps across Africa. The species occupies an incredible range of habitats, from aseasonal, tropical Cameroon to temperate, mountainous South Africa. As such, from an evolutionary perspective, B. juncea presents an excellent system on which to study the effects of climate and seasonality on sociality. Using powerful comparisons of behaviour and physiology across ecological gradients, the AWP aims to examine the effects of disparate environmental conditions on the evolution of cooperation and conflict. Ongoing work is investigating how factors like relatedness, inconsistent resource availability and unpredictable climates affect one of the most important strategic choices that individuals in cooperative societies make: whether to accept a life of subordination, or to attempt to attain dominance.
Written by: Ellie Trelfa-Stewart, PhD student, University of Bristol
University: Social Strategy Lab, University of Bristol
Principal Investigator: Dr. Patrick Kennedy
Project Start: 2024