Background Male seminal fluid protein (SFPs) used in females during mating are essential reproductive protein which have multifarious results on feminine reproductive physiology which often show remarkably rapid and divergent evolution. model taxa experimental obstruction of SFPs are known to affect a range of important reproductive phenotypes such as sperm survival male fertility sperm usage WAY-100635 by females female ovulation/egg production male competitive fertilization success and female life span and receptivity to remating [3-5]. Third some of the genes encoding SFPs evolve very rapidly to the point where they are some of the most rapidly evolving genes known [6-8] and a sizeable proportion of these WAY-100635 genes show indicators of positive Darwinian selection [9-14]. Finally because SFPs are ubiquitous affect reproductive success and often evolve divergently genes encoding SFPs are key candidate speciation genes in several taxonomic groups [6 15 16 An understanding of the divergent evolution of SFPs requires an understanding of the mechanism WAY-100635 of selection that acts upon SFP variation. Here the primary paradigm says that strong postmating sexual selection among males generates evolution of SFPs and that male-female coevolution then sparks divergent evolution in both SFPs and the female molecules that interact with SFPs [6 17 This tenet has received comparative support for example from correlations across species between the inferred degree of sperm competition and the rate of evolution of SFPs in primates [11 20 rodents [21 22 and insects . A large body of detailed experimental work involving for example removal or ectopic expression of single SFPs using mutants or RNAi has unveiled the function of key SFPs in model Tnf taxa . However virtually all of what we know about SFP evolution is based on comparisons between species . Although the interspecific approach has been very illuminating it also suffers from limitations. For example the fact that this seminal fluid is usually such a multivariate phenotype/genotype makes it difficult to evaluate patterns of covariation or indeed the lack thereof between specific SFPs and species WAY-100635 characteristics . Moreover the strength and nature of selection for a given SFP can differ among species given that these proteins may have different effects in different species. Finally interspecific approaches generally do not allow functional assays where the reproductive effects of particular SFPs are assessed experimentally simply because species are more or less reproductively isolated. Therefore studies concentrating on within-species variant allows us to check for selection also to characterize divergence which is essential to unveil the procedures of SFP advancement [6 19 24 The intimate selection paradigm of SFP advancement makes at least three important intraspecific predictions. Initial reproductive attributes under intimate selection are usually being among the most quickly and divergently changing attributes during incipient speciation . This predicts that ejaculate composition should differ between allopatric populations markedly. Second as the ejaculate is certainly such a multivariate phenotype haphazardous mutation-order occasions  should render intimate selection and male-female coevolution to steer populations along different multivariate coevolutionary trajectories . This predicts that diversification among populations shall itself be multidimensional. Third because intimate selection works on traits linked to reproductive achievement we anticipate interpopulation divergence in SFP great quantity to become useful in the feeling that it impacts essential reproductive phenotypes. This essential prediction is exclusive to the intimate selection paradigm. Sadly there have become few within-species in-depth studies of SFP variance. Within have successfully associated allelic variance in a few candidate SFP genes with important reproductive phenotypes [29-31]. However we currently lack integrative within-species studies that use quantitative proteomic methods which allow rich multivariate descriptions of the SFP phenotype to relate variance in SFP large quantity to functional divergence or SFP effectiveness . A few previous studies have revealed differences in expression level of specific SFPs across populations [26.