Data from: Sneaker males affect fighter male body size and sexual size dimorphism in salmon

Large male body size is typically favored by directional sexual selection
through competition for mates. However, alternative male life-history
phenotypes, such as "sneakers," should decrease the strength of
sexual selection acting on body size of large "fighter" males.
We tested this prediction with salmon species; in southern populations,
where sneakers are common, fighter males should be smaller than in
northern populations, where sneakers are rare, leading to geographical
clines in sexual size dimorphism (SSD). Consistent with our prediction,
fighter male body size and SSD (fighter male∶female size) increase with
latitude in species with sneaker males (Atlantic salmon Salmo salar and
masu salmon Oncorhynchus masou) but not in species without sneakers (chum
salmon Oncorhynchus keta and pink salmon Oncorhynchus gorbuscha). This is
the first evidence that sneaker males affect SSD across populations and
species, and it suggests that alternative male mating strategies may shape
the evolution of body size.