Egg load is a cue for offspring sex ratio adjustment in a fig‐pollinating wasp with male‐eggs‐first sex allocation

Zhang, Xiao‐Wei; Dunn, Derek W.; Wang, Rui Wu

doi:10.1111/jeb.13572

Cited by 8 publications

(5 citation statements)

References 58 publications

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“…If it is the former, it should be considered an adaptation; if the latter, it is an exaptation from the viewpoint of sex ratio adjustment. Even if laying sons first is an exaptation, the number of sons laid first could be a quantity that selection has optimized to obtain an optimal sex ratio [30,38,41] (but see [57]). The predictions of these models are similar to standard LMC models [38,41] because the same selective pressures (reduced competition between brothers [7], relatedness asymmetries [17] and more mating opportunities to brothers [13]) influence the process.…”

Section: Discussionmentioning

confidence: 99%

The efficacy of natural selection in producing optimal sex ratio adjustments in a fig wasp species

2020

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Ever since Darwin's discovery of natural selection, we expect traits to evolve to increase organisms' fitness. As a result, we can use optimization models to make a priori predictions of phenotypic variation, even when selection is frequency-dependent. A notable example is the prediction of female-biased sex ratios resulting from local mate competition (LMC) and inbreeding. LMC models incorporate the effects of LMC and inbreeding. Fig wasp sex ratio adjustments fit LMC predictions well. However, the appropriateness of LMC models to fig wasps has been questioned, and the role that a coincidental by-product plays in creating the apparent fit has been clearly illustrated. Here, we show that the sex ratio adjustments of a fig wasp are the result of a dual mechanism. It consists of a standard facultative LMC response favoured by natural selection, as well as a mechanism that may be the result of selection, but that could also be a coincidental by-product. If it is a by-product, the fitness increase is coincidental and natural selection's role was limited to fine-tuning it for higher fitness returns. We further document a case of an apparent fitness-reducing sex ratio adjustment. We conclude that the use of the adaptationist approach demands that our understanding of traits must be remodelled continually to rectify spurious assumptions.

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Section: Discussionmentioning

confidence: 99%

The efficacy of natural selection in producing optimal sex ratio adjustments in a fig wasp species

2020

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“…That may be because under the circumstance of a longer interval, the second one will not be able to lay her full egg load due to oviposition site limitation or the loss of receptivity. Furthermore, fig wasps first lay a set number of male eggs and then female eggs, or at least mainly male eggs initially [14,39]. We infer that oviposition site limitation would be the reason for sex ratio increasing rather than that the second foundress can perceive the existence of the first foundress according to previous studies [42], so the later foundress probably cannot access the full capacity of oviposition due to the age of female flower changing.…”

Section: Discussionmentioning

confidence: 70%

“…Even so, our study corroborated the findings on another Ceratosolen species and another non-fig wasp that males die more easily [37,38] In this study, we also demonstrated the effect of host quality on offspring sex ratio from another perspective by introducing the foundresses that were pollen-loaded or pollen-free. Previous studies have suggested that active pollinators efficiently fertilize flowers in which they oviposit, and wasps' larvae feed on the nucellar tissue of normally double-pollinated flowers; thus, a lack of pollination increases larval mortality [6,39], and active pollination has probably evolved as a way to improve progeny nourishment [29,40,41]. This idea is supported by larger broods in pollinated F. hispida [31].…”

Section: Discussionmentioning

confidence: 96%

The Effect of Ficus semicordata Fig Quality on the Sex Ratio of Its Pollinating Wasp Ceratosolen gravelyi

Yang,

Guan,

Chen

et al. 2024

Diversity

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The interaction between fig wasps and their host fig trees (Ficus spp.) is a striking example of an obligate pollination mutualism. Male and female fig wasps are confined within their natal patch instead of panmictic; under this circumstance, mating only occurs between individuals of the same patch. This is known as a local mate competition (LMC). It pays foundresses to invest mainly in daughters and to only produce enough sons to ensure that all female offspring can be fertilized, but in nature, pollinating fig wasps may face many problems with host quality, such as limitation of oviposition sites and the nutrition deficiency of the host fig. The sex ratio of wasps can determine the stability of fig–fig wasp mutualistic system and, thus, the stability of other species associated with it. In this study, we controlled the quality of host figs in three ways. The results showed that the host fig age can influence the sex ratio of pollinator offspring, while the foundress numbers and the presence of pollen have no significant effect on it. A compelling explanation for this result is that the sex-dependent mortality occurs. This is a novel finding of how host quality influences the interaction of fig and fig wasps, which can also help us understand the evolution and stability mechanism of this symbiotic system.

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“…Zhang et al [97] introduced another technique. They removed Ceratosolen fusciceps foundresses from figs they entered and let them enter new figs in a species where females do not naturally re-enter figs.…”

Section: Approaches To Study Fig Wasp Sex Ratiosmentioning

confidence: 99%

Pollinating fig wasps’ simple solutions to complex sex ratio problems: a review

Greeff

Kjellberg

2022

Front Zool

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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 fit LMC model assumptions and lay female-biased sex ratios as predicted. These female biased sex ratios increase fitness greatly. In line with predictions, their sex ratios become less female-biased as the number of mothers laying in the same fig increases. However, this variation results in comparatively small fitness benefits 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 coefficient 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 first 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 effect will alter sex ratios in all species once the egg capacity of a fig 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 fitness. 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. Graphical Abstract

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Egg load is a cue for offspring sex ratio adjustment in a fig‐pollinating wasp with male‐eggs‐first sex allocation

Cited by 8 publications

References 58 publications

The efficacy of natural selection in producing optimal sex ratio adjustments in a fig wasp species

The efficacy of natural selection in producing optimal sex ratio adjustments in a fig wasp species

The Effect of Ficus semicordata Fig Quality on the Sex Ratio of Its Pollinating Wasp Ceratosolen gravelyi

Pollinating fig wasps’ simple solutions to complex sex ratio problems: a review

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