A gradient of sexual selection and sexual conflict: parental investment and sex-role reversal and their genomic footprints

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Selection acts differently on males and females and drives their phenotypic dissimilarities. Most research has focused on males and how sexual selection shapes their ornaments and weaponry in the context of gaining access to female mates. This is not least due to the fact that humans, as most other vertebrates, show "conventional", "Darwinian" sex roles concentrating our perception on competitive males and caring mothers. In several seahorse, seadragon and pipefish species (family Syngnathidae), however, females compete for access to mates, while males are the choosy sex and provide the parental care during male pregnancy. Our project will investigate how these species evolved under intensified sexual selection on females and how the evolution of sex-specific traits from a genome shared between the sexes and hence with sexual conflict is impacted by increasing paternal care. To this aim we will identify sex-specific sequences (sex chromosomes) as well as sex-biased gene expression in tissues with strong or little sex differences in species with varying degrees of sexual conflict. We will analyze if genes mediating sex roles are derived from sex-determining genes. Benefitting from the repetitive evolution of sex-role reversal, we will test for patterns of novel and convergent sequence evolution within syngnathids but also to other vertebrate groups that also evolved pregnancy. Not only is male pregnancy a unique reproduction strategy of syngnathids but the structure sustaining embryonic attachment to the father´s body, the brood pouch, also evolved increased complexity several times within syngnathids. We will use this repetitive evolutionary pattern for comparative studies of genome and transcriptome evolution as well as their physiological impacts along repeated gradients of ascending paternal investment. The afore mentioned "sex-role reversal" accompanied by the evolution of sexual dimorphism manifested with beautiful and sometimes spectacular ornaments in the female sex has independently evolved in several phylogenetic subgroups of syngnathids. We will investigate how sex-specific phenotypes are built upon sex-biased gene expression and how this might lead to sexual antagonistic conflict in their common genome. In addition, we will scrutinise the role of hormones in regulating gene expression and sexual phenotypes including behaviour. This project will characterise the genetic and endocrinological network of female- and maleness and distinguish it from the sex-role network building upon generating of high-quality reference genomes, genome resequencing data of males and females, multi tissue transcriptomics as well as endocrinological manipulations.