Tree Lizard Territory and Adaptation

Territoriality, shaped by intraspecific competition, often depends on population density, yet empirical evidence for this relationship is inconsistent. Using eight populations of Swinhoe’s tree lizards, we examined how male density influences multiple combat-related traits. Males in high-density populations displayed less aggressive tactics, lower immobilization and wounding rates, weaker bite forces, and smaller body sizes, whereas the opposite pattern occurred at low density. Additionally, the association between body size and bite force weakened as density increased. These coordinated shifts in behavior, performance, and morphology along a density gradient demonstrate how density-dependent selection can drive adaptive polymorphism within species.