EXPERIMENTAL EXCURSIONS ON ADAPTIVE LANDSCAPES: DENSITY-DEPENDENT SELECTION ON EGG SIZE

摘要: Theories of density-dependent natural selection suggest that intraspecific competition will favor juveniles high competitive ability. Empirical evidence has been provided from laboratory experiments, but field studies are lacking due to the logistical difficulties experimentally manipulating population densities in settings. Here, we present data a decade-long experimental study side-blotched lizards, Uta stansburiana overcomes these difficulties. We tested hypothesis causes egg size increase early late clutches this and many other species. Using novel combination environmental manipulations hatchling density phenotypic size, demonstrate nature on changes dramatically absence older competitors. The strength among later-clutch hatchlings released areas without competitors became almost doubled magnitude, compared presence These findings size; however, they contradict classical idea increases during reproductive season because between hatchlings. results indicate age or asymmetries can override within-cohort size. could be an important mediator oscillating pressures systems. Finally, discuss utility "double-level," simultaneous manipulation both traits targets (e.g., size) as well agents density).