Data from: Sex allocation conflict between queens and workers in Formica pratensis wood ants predicts seasonal sex ratio variation

Sex allocation theory predicts parents should adjust their investment in
male and female offspring in a way that increases parental fitness. This
has been shown in several species and selective contexts. Yet, seasonal
sex ratio variation within species and its underlying causes are poorly
understood. Here we study sex allocation variation in the wood ant Formica
pratensis. This species displays conflict over colony sex ratio as workers
and queens prefer different investment in male and female offspring, owing
to haplodiploidy and relatedness asymmetries. It is unique among Formica
ants because it produces two separate sexual offspring cohorts per season.
We predict sex ratios to be closer to queen optimum in the early cohort
but more female-biased and closer to worker optimum in the later one. This
is because the power of workers to manipulate colony sex ratio varies
seasonally with the availability of diploid eggs. Consistently more
female-biased sex ratios in the later offspring cohort over a three-year
sampling period from 93 colonies clearly support our prediction. The
resulting seasonal alternation of sex ratios between queen and worker
optima is a novel demonstration how understanding constraints of sex ratio
adjustment increases our ability to predict sex ratio variation.