Conflict, compensation, and plasticity: Sex-specific, individual-level trade-offs in green anole (Anolis carolinensis) performance.

Abstract

Trade-offs in performance expression occur because animals must perform multiple whole-organism performance tasks that place conflicting demands on shared underlying morphology. Although not always detectable within populations, such trade-offs may be apparent when analyzed at the level of the individual, particularly when all of the available data are taken into account as opposed to only maximum values. Detection of performance trade-offs is further complicated in species where sexual dimorphism drives performance differences between males and females, leading potentially to differing patterns of trade-offs within each sex. We tested for within- and between-individual trade-offs among three whole-organism performance traits (sprint speed, endurance, and bite force) in adult male and female Anolis carolinensis lizards using all of the measured performance data. Sprinting and endurance did not trade-off among individuals in either sex, but we found a significant negative among-individual relationship between sprint speed and bite force in females only, likely driven by the mechanical burden of larger than optimal heads imposed on females through intralocus sexual conflict. We also found evidence for marked within-individual plasticity in male bite force, but no within-individual trade-offs between any traits in either sex. These data offer new insight into the sex-specific nature of performance trade-offs and plasticity and, ultimately, into the constraints on multivariate performance evolution.