Local mate competition (LMC) favours female biased clutch sex ratios because it reduces competition between brothers and provides extra mating opportunities for sons. Fig wasps seem to ft LMC model assumptions and lay femalebiased sex ratios as predicted. These female biased sex ratios increase ftness greatly. In line with predictions, their sex
ratios become less female-biased as the number of mothers laying in the same fg increases. However, this variation
results in comparatively small ftness benefts compared to just biased ratios and data suggest substantial mismatches
with LMC theory. The mismatches are due to several factors. (1) Multiple foundresses typically lay too many daughters.
(2) Single foundress sex ratios are explained by sequential oviposition and ladies-last models. (3) Mortality that typically exceeds 10% may decouple the link between primary sex ratios, the focus of model predictions, and secondary
sex ratios of adult wasps that are counted by researchers. (4) Model assumptions are frequently violated: (a) clutch
sizes are unequal, (b) oviposition may not be simultaneous (c) cryptic/multiple wasp species inhabit the same host,
(d) foundress numbers are systematically undercounted, (e) inbreeding coefcient calculations are inaccurate, and (f )
male wasps sometimes disperse. These data and calculations suggest that alternative explanations must be considered seriously. Substantial data show that wasps typically lay most of their male eggs frst followed by mostly female
eggs require a new approach. These “slope” strategies result in more accurate sex ratios that are automatically adjusted
to foundress number, own and relative clutch sizes and to sequential clutches. This efect will alter sex ratios in all
species once the egg capacity of a fg is crossed or when interference reduces clutch sizes. In addition to this passive
response, the females of about half the studied species have a conditional response that reduces female bias under
higher foundress numbers by laying more sons. Therefore, wasps seem to use a very simple strategy that increases
their ftness. Natural selection could have optimized parameters of the slope strategy and possibly the existence
of the slope strategy itself. Variation in the slope strategy that is the result of natural selection is adaptive. Research
should therefore focus on quantifying variables of this slope strategy. Currently, it is unclear how much of the variation
is adaptive as opposed to being coincidental by-products.SUPPLEMENTARY INFORMATION: ADDITIONAL FILE 1. Supplementary text and figures. Explanation of methods, derivation of ESS sex ratio, analysis of wasp size and supplementary
figures.
ADDITIONAL FILE 2. Figure 4 data. Observed (± 95% CI) and expected sex
ratios in 36 studies of 25 species.
ADDITIONAL FILE 3. Figures 8 and 9 data. Clutch composition in 33 studies
on 25 species.
ADDITIONAL FILE 4. Figure 10 data. Single Foundress sex ratios, fraction of
single foundress figs and clutch size of 39 species.https://frontiersinzoology.biomedcentral.com/dm2022BiochemistryGeneticsMicrobiology and Plant Patholog
