Figure 3.

Sperm traits of the invasive round goby (Neogobius melanostomus) sampled from the ancestral range (Sozopol, far left, and the Danube, far right on x-axes) and compared against previously published data (all other sites on x-axes) [35,38,39] and across different salinities (facets). Panel (a) shows sperm velocity and panel (b) shows sperm motility. Facets show different sperm treatment salinities corresponding to freshwater (0–1 PSU), brackish (15–16 PSU), marine (30–32 PSU) and local with varying salinity for each site (see Table 1 for local salinity measurements and estimates). Asterisks indicate significant differences between sites and a mean value (indicated by the dashed line) using a linear model (see Supplementary Table S2 for full statistics). Means for model tests are: freshwater: the Danube (ancestral freshwater site); brackish: Sozopol (ancestral brackish site); marine: global mean across all sites; local: global mean across all sites. “A” denotes sites of ancestral origin in each respective salinity condition. * = p < 0.05, ** = p < 0.01, *** = p < 0.001.