Hormonal modulation of brood allocation underlying evolutionary conflicts in the supercolonial ant Tapinoma darioi
Description
This repository contains the datasets and R script for the article "Hormonal modulation of brood allocation underlying evolutionary conflicts in the supercolonial ant Tapinoma darioi", published in the journal Behavioral Ecology and Sociobiology. It contains three datasets, one regarding queen survivorship, one related to methoprene and precocene effect on larvae cannibalization, and one containing data for queen number effect on larvae cannibalization. Additionally, a file containing metadata information for the three datasets is supplemented. Finally, the R script file utilised for statystical analysis in this publication is also present. In social insects, caste fate is typically determined by larval feeding, but in several species juvenile hormone (JH) also regulates caste development, with elevated JH levels biasing brood towards queens. In some ants, queens influence the caste fate of their offspring by depositing higher JH levels into eggs. We hypothesized that in polygynous societies, individual queens could gain fitness advantages over co-nesting reproductives by increasing JH deposition, thereby producing more sexuals that are reared by workers with low relatedness. To test this, we conducted a bioassay in the supercolonial ant Tapinoma darioi, experimentally altering queens’ circulating JH levels via topical application of methoprene (a JH analogue) and precocene II (a JH synthesis inhibitor), while monitoring brood production. Our results show that workers detect and cull the excessive production of reproductive brood, revealing for the first time the precise moment at which this occurs. These findings support the hypothesis that maternal control of JH deposition into eggs can bias caste fate to the queen’s advantage, particularly in supercolonial species where sexual larvae are often reared by unrelated workers. At the same time, our data indicate that workers are not at a loss in this evolutionary conflict of interests, since they can detect and cannibalize excess queen larvae, likely adjusting the queen/worker ratio towards the colony’s optimum from their own evolutionary perspective. Overall, our study highlights the dynamic interplay between maternal control and worker counter-adaptation in shaping caste determination, providing new insights into the mechanisms and evolutionary conflicts underlying social insect reproduction.
Files
Steps to reproduce
To test the effect of experimentally manipulating queen JH levels in brood production, experimental colonies were prepared by placing five queens and approximately 100 workers from the same source nest into a plastic box (20 x 10 x 5 cm) previously coated in Fluon to prevent escape. Workers were sampled from unearthed nests, ensuring a mix of nurses and foragers were present equally in all colonies. Worker number was maintained throughout the experiment; if any colony experienced a noticeable decline, workers from the same source colony were added to restore initial colony size. Individuals were carefully transferred to avoid introducing eggs, larvae or pupae from the original nest, ensuring that all brood observed during the experimental period was laid after treatment. The experiments were conducted in two separate trials using a matched experimental design, with each trial including its own control group corresponding to the various treatment concentrations. Colonies were fed with 1:3 sugar water solution, mealworms and water ad libitum, and maintained at room temperature (~25ºC). Queen JH levels circulating in the hemolymph were experimentally increased via the topical application of the JH analogue methoprene, while precocene II was used to decrease circulating JH levels. Treatment groups consisted of the three concentrations used in the toxicity tests, each with five replicates, and followed the same application protocol. Brood developmental stage and number were documented three times a week, on Mondays, Wednesdays, and Fridays for a total duration of three months. To ensure accurate quantification, brood counts were restricted to larvae and pupae, beginning at the first larval instar, as eggs deposited in brood piles could not be reliably quantified under our experimental setup. Queen numbers were established weekly to assess long-term survivorship during the experiment. All observations were conducted by the same researcher, who was not blind to treatment condition. However, because the study relied on objective quantitative measures obtained through numerical counts, observer bias was unlikely to affect the results.
Institutions
- Universitat Autonoma de Barcelona Departament de Biologia Animal de Biologia Vegetal i d'EcologiaCatalunya, Bellaterra