Sexually Antagonistic Inversions Can Accumulate in Drosophila melanogaster Populations

Alapfogalmak

Inversions can maintain balanced polymorphisms by linking alleles that contribute antagonistically to male reproductive success and survival, generating frequency-dependent disruptive selection.

Kivonat

The content explores a model for the maintenance of inversion polymorphisms in populations, where some variants contribute antagonistically to two phenotypes - one with negative frequency-dependent fitness. This generates a form of frequency-dependent disruptive selection, favoring two predominant haplotypes segregating alleles that favor opposing antagonistic phenotypes.

The key insights are:

1. Inversions can reduce the fitness load incurred by generating recombinant offspring, reinforcing their linkage to haplotypes with antagonistic variants and enabling the accumulation of more antagonistic variants than expected otherwise.

2. Simulations demonstrate that this model can generate stable balanced polymorphisms, with inversions maintained at predictable frequencies and linked to haplotypes exhibiting opposing sex-specific fitness effects.

3. Experiments with Drosophila melanogaster populations provide evidence that some common inversions show tradeoffs between male reproductive success and survival, consistent with the proposed model of sexually antagonistic balancing selection.

4. The sex-specific fitness effects implied by the model can also explain deviations from Hardy-Weinberg genotype frequencies observed for polymorphic inversions in natural populations.

Statisztikák

"Larger effect sizes are plotted in the left panels, with values incrementing by 0.025, and smaller effect sizes (a subset of the larger) are plotted in greater detail in the right panels, with values incrementing by 0.005."
"Values given are the mean of 1000 replicate simulations of 1000 diploid individuals run for 20N generations."
"Ranks are normalized to be relative to the median arrangement value, to better account for rare arrangements and ties."

Idézetek

"Inversions can reduce the fitness load incurred by generating recombinant offspring, reinforcing their linkage to haplotypes with antagonistic variants and enabling the accumulation of more antagonistic variants than expected otherwise."
"Simulations demonstrate that this model can generate stable balanced polymorphisms, with inversions maintained at predictable frequencies and linked to haplotypes exhibiting opposing sex-specific fitness effects."
"Experiments with Drosophila melanogaster populations provide evidence that some common inversions show tradeoffs between male reproductive success and survival, consistent with the proposed model of sexually antagonistic balancing selection."

Főbb Kivonatok

Inversions Can Accumulate Balanced Sexual Antagonism: Evidence from Simulations and Drosophila Experiments

by McAllester,C... : www.biorxiv.org 10-03-2023

https://www.biorxiv.org/content/10.1101/2023.10.02.560529v3

Mélyebb kérdések

How might the dynamics of this model change if the antagonistic effects were not symmetric between the sexes, but instead one sex experienced a much stronger cost

In the model presented, if the antagonistic effects were not symmetric between the sexes and one sex experienced a much stronger cost, it would likely lead to a shift in the equilibrium frequencies of the inversions. Specifically, the inversion associated with the sex experiencing the stronger cost would be expected to decrease in frequency compared to the other inversions. This asymmetry in the antagonistic effects would result in a more pronounced selection pressure on the inversion linked to the sex with the stronger cost, leading to a decrease in its frequency over time. Conversely, the inversion associated with the sex experiencing the milder cost would likely increase in frequency or remain stable. This imbalance in selection pressures would disrupt the equilibrium of the system, potentially leading to shifts in inversion frequencies and the overall maintenance of balanced polymorphism.

What other types of antagonistic tradeoffs, beyond survival and male display, could generate similar patterns of balanced polymorphism maintained by inversions

Beyond survival and male display, there are several other types of antagonistic tradeoffs that could generate similar patterns of balanced polymorphism maintained by inversions. One common example is the tradeoff between fecundity and longevity. Variants that enhance reproductive success may come at the cost of reduced lifespan, creating a sexually antagonistic relationship where the optimal genotype differs between males and females. Another example is the tradeoff between immunity and reproductive success. Alleles that confer enhanced immune function may have negative effects on reproductive traits, leading to a balance between pathogen resistance and mating success. Additionally, tradeoffs related to resource allocation, stress tolerance, or competitive ability could also generate similar patterns of balanced polymorphism when linked to inversions.

Could this model of sexually antagonistic inversions be extended to explain patterns of inversion polymorphism in other species beyond Drosophila melanogaster

The model of sexually antagonistic inversions proposed in the study could potentially be extended to explain patterns of inversion polymorphism in other species beyond Drosophila melanogaster. Many species exhibit chromosomal inversions that are maintained at intermediate frequencies within populations, suggesting the presence of balancing selection. By considering the tradeoffs between different fitness components, such as survival, reproduction, immunity, or stress tolerance, it is possible to apply similar models to understand the maintenance of inversion polymorphisms in diverse taxa. The key lies in identifying the specific antagonistic relationships between traits that are linked to the inversions and understanding how these tradeoffs shape the genetic diversity and evolutionary dynamics of inversion polymorphisms in different species.