Journal: Ecology Letters
Article Title: Runaway evolution from male‐male competition
doi: 10.1111/ele.13921
Figure Lengend Snippet: Evolution of a male signal, body size, and aggression in response to male‐male competition. Panels (a) and (b) show evolutionary trajectories for each trait over 200 generations, and panels (c) and (d) show predicted lines of equilibria (heavy line) and their stability (gray arrows). In all panels, all three traits have the same genetic variance ( G = 1 ), benefit ( b A = 0.2 ) and cost of aggression ( c A = 0.05 ), fitness cost deriving from the threat of a male's opponent ( c B = 0.2 ), cost of signal size ( c s = 0.05 ; with naturally selected optimum θ S = 0 ), and a responsiveness of aggression to body size ( δ AS = 0.4 ). The line of equilibria is calculated from Equation using these values. In panels (a) and (c), signal size is weakly correlated with body size ( G SB = 0.4 ), while in panels (b) and (d), the two traits are more strongly correlated ( G SB = 0.8 ). When the genetic correlation between signal size and body size is weak, all three traits reach equilibria (a), with equilibrium aggression predicted solely by costs and benefits. Signal size and body size reach a point on the predicted line of equilibrium (c) that differs depending on their starting values. When the genetic correlation is strong, aggression still reaches an equilibrium, but signal size and body size run away together (b), overshooting the predicted line of equilibria (d). As in Fisherian selection from female mate choice (Lande, ), male‐male competition can drive traits to runaway elaboration or extinction when the line of equilibria is unstable (d)
Article Snippet: This effect is captured in our model as a term in which aggression scales with the magnitude of the size difference between opponents, which is supported by optimality models and empirical studies (Emlen, , ; Huxley, ; Maynard Smith & Harper, ; Parker, ; Riechert, ; Sneddon et al., ).
Techniques: Selection