Direct evidence for increased disease resistance in polyandrous broods exists only in eusocial Hymenoptera

Abstract

Background The ‘genetic diversity’ hypothesis posits that polyandry evolved as a mechanism to increase genetic diversity within broods. One extension of this hypothesis is the ‘genetic diversity for disease resistance’ hypothesis (GDDRH). Originally designed for eusocial Hymenoptera, GDDRH states that polyandry will evolve as an effect of lower parasite prevalence in genetically variable broods. However, this hypothesis has been broadly applied to several other taxa. It is unclear how much empirical evidence supports GDDRH specifically, especially outside eusocial Hymenoptera. Results This question was addressed by conducting a literature review and posteriorly conducting meta-analyses on the data available using Hedges’s g. The literature review found 10 direct and 32 indirect studies with both having a strong publication bias towards Hymenoptera. Two meta-analyses were conducted and both found increased polyandry (direct tests; n = 8, g = 0.2283, p = < 0.0001) and genetic diversity generated by other mechanisms (indirect tests; n = 10, g = 0.21, p = < 0.0001) reduced parasite load. A subsequent moderator analysis revealed that there were no differences among Orders, indicating there may be applicability outside of Hymenoptera. However, due to publication bias and low sample size we must exercise caution with these results. Conclusion Despite the fact that the GDDRH was developed for Hymenoptera, it is frequently applied to other taxa. This study highlights the low amount of direct evidence supporting GDDRH, particularly outside of eusocial Hymenoptera. It calls for future research to address species that have high dispersal rates and contain mixes of solitary and communal nesting.

Synthesis of sexual selection: a systematic map of meta-analyses with bibliometric analysis

“…However, note that the actual proportion of species that first or second most popular animal groups represent in taxonomically unrestricted meta-analyses tends to decrease with the total number of species used by a meta-analysis (Figure 5). For instance, Soper, Ekroth & Martins (2021) extracted data from nine species in their study, eight of them being insects and one being a mammal, meaning that the two most abundant animal groups in the study represented all its taxonomic diversity. In contrast, Rios Moura et al (2021) included 341 species, 21.1% birds and 20.8% insects, so that these two groups comprised only less than half of the species represented in the study.…”

Genetic diversity and disease: The past, present, and future of an old idea

“…Although the idea that polyandry reduces disease has primarily been tested in eusocial Hymenoptera (Soper et al 2021), there is some evidence for related phenomena in other taxa. Soper et al (2014) found that female snails increased their mating rate and number of distinct mating partners when exposed to native parasites.…”

Positive selection in cytochrome P450 genes is associated with gonad phenotype and mating strategy in social bees

“…As monandry is the ancestral condition 9 , the multiple mating systems and their associated male traits have drawn attention and generated controversial arguments about the adaptive significance of multiple mating in the highly eusocial Hymenoptera 10 . Among the eight hypotheses proposed for the evolution of polyandry in social insects 11 , the currently most accepted one is that it strengthens the colonies’ resistance against parasite or pathogen infections 12 . Polyandry, however, is not a simple categorical trait that stands in contrast with monandry, but there is a very strong skew in the number of recorded mating events 9 , 13 .…”