Post-spawning sexual selection and reproductive fitness in fishes

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Until recently, sexual selection theory assumed most taxa were monogamous and selection was thought to operate mainly via processes prior to copulation (i.e. pre-copulatory selection), namely mate choice (typically females choosing amongst males) and competition for mates (typically males vs. males for access to females). However, genetic and behavioural studies have recently shown that sexual promiscuity is common among most taxa. Multiple mating by females creates the potential for sexual selection to continue after copulation through (i) the competition between sperm of different males for the fertilization of a set of ova (sperm competition) and (ii) the differential use of sperm from one male over another, with a presumed genetic benefit to offspring fitness (cryptic female choice). As a result, reproductive fitness is now understood to be determined by the complex interactions of traits (at both the phenotypic and genotypic level) selected in males and females during episodes of selection before and after copulation. Thus, a central question emerging in sexual selection theory is how do males and females interact in terms of sexual conflict (i.e. due to different reproductive interests) in this post-copulatory selection arena. My long-term objective is to quantify the relative importance of post-copulatory selection on reproductive fitness (from a male and female perspective) in order to gain a better understanding of the evolutionary consequences of sexual selection by building on my previous work and move into innovative new areas of research focusing on Chinook salmon (Oncorhynchus tshawytscha) and redside dace (Clinostomus elongatus) mating systems to examine: (1) whether post-spawning selection reinforces or counteracts pre-spawning selection using experimental crosses (in a wild setting), (2) post-spawning mechanisms that include all ejaculate components for males (sperm, seminal plasma) and females (ovarian fluid and eggs), (3) broad-scale evolutionary patterns of post-spawning sexual selection across populations and species. The research will involve several approaches to test hypotheses including (among others) field research, in-vitro fertilization trials, genomics and microscopy techniques to assess sperm quality. Overall, this research program promises to (i) produce high quality peer-reviewed publications, (ii) create innovative research tools for those who study intrasexual and intersexual selection and (iii) train highly qualified personnel for academia, the private sector or government.