Mode of evolution and protein abundance in seminal fluid
Data from several previous studies that have identified the most abundant proteins in the seminal fluid of domestic animals allow testing hypotheses about the evolution of relevant genes. Our recent study that showed a particularly high proteome diversity of seminal fluid between species suggested this diversity was potentially associated with attributes of male reproductive physiology (Druart et al., 2013). Our negative results concerning the possible correlation between the abundance of proteins in the seminal fluid and the presence of positive selection in the gene encoding it in the same species (obtained by multivariate phylogenetic pairwise comparisons) should be viewed with caution because of the low power of our test, itself resulting from the low number of genes, taxa, and the limited variability of the relevant characters in our dataset. Nevertheless, our results do not lend any support to the hypothesis that both characters are positively correlated. The apparent absence of correlation between the predominance of a protein in seminal fluid in one species and its evolution under positive selection, which is confirmed by visual inspection of the data (Figs 5-6), is compatible with the ‘translational robustness hypothesis’ proposed before (Drummond et al., 2005). According to this hypothesis, genes with high expression evolve slowly, which avoids protein misfolding.