Abstract
Simple SummaryThe two sexes of a species usually exhibit phenotypic differences, such as in behavior, body size or color. They, however, share most of their genomes, preventing fixation of distinct alleles for genes coding for those traits in each sex. The different optima between the sexes on these loci lead to genomic conflicts, called sexually antagonistic selection (SAS). Under SAS, distinct alleles are therefore selected in each sex. In the invasive tawny crazy ant, Nylanderia fulva, a genomic region is under SAS, while the rest of the genome is randomly selected in males and females. Here, we provide a suite of 15 polymorphic microsatellite markers located in the SAS genomic region to study the origin and evolution of SAS in N. fulva. These markers have allelic frequencies that are highly different between males and females. All males carry only a subset of the alleles present in the population, while females are reliably heterozygous, with one allele from the male gene pool and a different allele inherited from their mother. The SAS markers may be used to test for the strength and the extent of the genomic regions under SAS in both the native and introduced ranges of N. fulva. These markers may serve to answer similar questions in other introduced species of the Nylanderia genus, yielding insights into the origin and evolution of SAS within and among species of the genus Nylanderia.Sexually antagonistic selection (SAS) occurs when distinct alleles are differentially selected in each sex. In the invasive tawny crazy ant, Nylanderia fulva, a genomic region is under SAS, while the rest of the genome is randomly selected in males and females. In this study, we designed a suite of 15 microsatellite markers to study the origin and evolution of SAS in N. fulva. These SAS markers were polymorphic, with allelic frequencies that are highly different between males and females. All haploid males carry only a subset of the alleles present in the population, while females are reliably heterozygous, with one allele from the male gene pool and a different allele inherited from their mother. In addition, we identified six polymorphic markers not associated with SAS and six markers yielding consistent, yet monomorphic, amplification in the introduced range of this species. Reaction condition optimizations allowed all retained markers to be co-amplified in four PCR mixes. The SAS markers may be used to test for the strength and the extent of the genomic regions under SAS in both the native and introduced ranges of N. fulva, while the set of non-SAS loci may be used to assess the invasion route of this species. Overall, the application of these microsatellite markers will yield insights into the origin and evolution of SAS within and among species of the genus Nylanderia.
Highlights
Within a sexually reproducing species, males and females share a common optimum for most of their traits. They may differ in their optima for some specific traits, leading to sexually antagonistic selection (SAS) [1,2]
Sexually antagonistic selection (SAS) was thought to be resolved through the evolution of sex chromosomes, enabling the sexes to overcome the constraint of a shared genome by allowing each sex to separately fix beneficial alleles in distinct sex chromosomes, preventing deleterious recombination between them [5,6]
The invasive tawny crazy ant Nylanderia fulva represents a unique case of SAS, as it occurs in a sexually reproducing haplodiploid species lacking sex chromosomes [7]
Summary
Within a sexually reproducing species, males and females share a common optimum for most of their traits. For two of these markers, all males carried a single allele (arbitrarily called allele A), while almost all females were heterozygous, with allele A and another allele (B or C), resulting in either A/B or A/C genotypes These three microsatellite markers allow for the identification of complex DNA inheritance between the sexes, their weak polymorphism (respectively, 2, 3 and 3 alleles for L02, L06 and L07) prevents any further analyses. Overall, developing a robust set of microsatellite markers is required to properly answer these questions These findings may provide insights into the strength of the selective pressures acting upon the male and female gene pools and illuminate the origin and evolution of SAS in this haplodiploid species. In this study, we aimed to design microsatellite markers informative to study SAS in Nylanderia fulva For this purpose, these SAS markers are not randomly spread throughout the genome but instead located in the SAS region(s). Insects 2021, 12, 643 markers located in randomly inherited scaffolds (i.e., scaffolds showing no deviation from the Hardy–Weinberg equilibrium)
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