Eusocial insects provide special opportunities to elucidate the evolution of ageing as queens have apparently evaded costs of reproduction and reversed the fecundity-longevity trade-off generally observed in non-social organisms. But how reproduction affects longevity in eusocial insects has rarely been tested experimentally. In this study, we took advantage of the reproductive plasticity of workers to test the causal role of reproduction in determining longevity in eusocial insects. Using the eusocial bumblebee Bombus terrestris, we found that, in whole colonies, in which workers could freely 'choose' whether to become reproductive, workers' level of ovarian activation was significantly positively associated with longevity and ovary-active workers significantly outlived ovary-inactive workers. By contrast, when reproductivity was experimentally induced in randomly-selected workers, thereby decoupling it from other traits, workers' level of ovarian activation was significantly negatively associated with longevity and ovary-active workers were significantly less long-lived than ovary-inactive workers. These findings show that workers experience costs of reproduction and suggest that intrinsically high-quality individuals can overcome these costs. They also raise the possibility that eusocial insect queens exhibit condition-dependent longevity and hence call into question whether eusociality entails a truly reversed fecundity-longevity trade-off involving a fundamental remodelling of conserved genetic and endocrine networks underpinning ageing.
ReadMe
ReadMe describing data files
Data of Experiment 1
This is the raw data of Experiment1. Definition of column headings:
- Colony no.: identification number of the mother colonies
- Worker no.: identification number of the workers
- Eclosion date: eclosion date of the workers
- Death date: date at which workers died
- Longevity: age of the workers at death in days
- Worker group: 3 groups of workers, 1 (workers that eclosed pre-queen removal/death and died pre-queen removal/death), 2 (workers that both eclosed and died post-queen removal/death) and 3 (workers that eclosed pre-queen removal/death and died post-queen removal/death)
- Body size: length of the radial cell in a forewing (mm)
- Longest oocyte: length of the longest visible oocyte (mm)
Data_Experiment1.xlsx
Behaviour observed in Experiment2
This is the raw data of the behaviours performed by workers during Experiment2. There are two excel sheets: one for focal workers and one for non-focal workers. Definition of column headings:
- Group no.: identification number of the 3-worker groups
- Treatment: social treatment applied to the workers (F+ or F-)
- Worker no.: identification number of the workers
Behaviour_Experiment2.xlsx
Dissection data of control workers in Experiment2
This is the raw data of dissections performed on control groups of workers in Experiment2. Definition of column headings:
- Group no.: identification number of the 3-worker groups
- Collection time: workers were collected sequentially in three time steps (15, 30 and 60 days after group establishment)
- Colony no.: identification number of the mother colonies
- Treatment: social treatment applied to the workers (F+ or F-)
- Worker no.: identification number of the workers
- Focal/Non-focal: type of worker within the group (focal or non-focal)
- Mean oocyte: mean length of all eight terminal oocytes (mm)
- Body size: length of the radial cell in a forewing (mm)
ControlDissections_Experiment2.xlsx
Longevity data of Experiment2
This is the raw data for workers used in the longevity experiment in Experiment2. Definition of column headings:
- Group no.: identification number of the 3-worker groups
- Colony no.: identification number of the mother colonies
- Treatment: social treatment applied to the workers (F+ or F-)
- Worker no.: identification number of the workers
- Focal/Non-focal: type of worker within the group (focal or non-focal)
- Eclosion date: eclosion date of the workers
- Pre-starting date: date at which the non-focal workers in treatment F- were grouped in the plastic boxes
- Starting date: date at which 3-worker groups were formed
- Death date: date at which workers died
- Longevity: age of the workers at death in days
- Mean oocyte: mean length of all eight terminal oocytes (mm)
- Longest oocyte: length of the longest visible oocyte (mm)
- Body size: length of the radial cell in a forewing (mm)
Longevity_Experiment2.xlsx
Reproduction data of Experiment2
This is the raw data of the egg-laying behaviours observed in Experiment2. There are two excel sheets: “Number of scans” described the number of scans performed on workers during the interval between the first and last observed instances of egg-laying; “Worker egg-laying” described the egg-laying observations and the detailed statistical procedure used to compare the egg-laying activities. Column headings are self-explanatory.
Reproduction_Experiment2.xlsx