Transcriptomics of Intralocus Sexual Conflict: Gene Expression Patterns in Females Change in Response to Selection on a Male Secondary Sexual Trait in the Bulb Mite

Abstract

Intralocus sexual conflict (IASC) prevents males and females from reaching their disparate phenotypic optima and is widespread, but little is known about its genetic underpinnings. In Rhizoglyphus robini, a mite species with alternative male morphs, elevated sexual dimorphism of the armored fighter males (compared to more feminized scramblers males) was previously reported to be associated with increased IASC. Because IASC persists if gene expression patterns are correlated between sexes, we compared gene expression patterns of males and females from the replicate lines selected for increased proportion of fighter or scrambler males (F- and S-lines, respectively). Specifically, we tested the prediction that selection for fighter morph caused correlated changes in gene expression patterns in females. We identified 532 differentially expressed genes (FDR < 0.05) between the F-line and S-line males. Consistent with the prediction, expression levels of these genes also differed between females from respective lines. Thus, significant proportion of genes differentially expressed between sexually selected male phenotypes showed correlated expression levels in females, likely contributing to elevated IASC in F-lines reported in a previous study.

Keywords: alternative reproductive tactics (ARTs); differential gene expression; ontogenetic conflict; polyphenism; sexual selection.

Fig. 1.—

Boxplot for differences in expression between F-line and S-line females for genes biased in males (positive difference represents higher expression in F-line females). Y-axis depicts difference in mean over replicate lines for log transformed expression values (FPKM) in F-line and S-line females. Diamonds represent means. F-male-biased genes (MF), S-male-biased genes (MS).