title: Intraspecific competition and high food availability are associated with insular gigantism in a lizard.
abstract: Resource availability, competition, and predation commonly drive body size evolution. We assess the impact of high food availability and the consequent increased intraspecific competition, as expressed by tail injuries and cannibalism, on body size in Skyros wall lizards (Podarcis gaigeae). Lizard populations on islets surrounding Skyros (Aegean Sea) all have fewer predators and competitors than on Skyros but differ in the numbers of nesting seabirds. We predicted the following: (1) the presence of breeding seabirds (providing nutrients) will increase lizard population densities; (2) dense lizard populations will experience stronger intraspecific competition; and (3) such aggression, will be associated with larger average body size. We found a positive correlation between seabird and lizard densities. Cannibalism and tail injuries were considerably higher in dense populations. Increases in cannibalism and tail loss were associated with large body sizes. Adult cannibalism on juveniles may select for rapid growth, fuelled by high food abundance, setting thus the stage for the evolution of gigantism.
authors.affiliation: School of Natural Resources & Environment, University of Michigan, Dana Building, 440 East University, Ann Arbor, MI 48109-1041, USA. pafman@umich.edu
authors.forename: Panayiotis
authors.initials: P
authors.lastname: Pafilis
authors.forename: Shai
authors.initials: S
authors.lastname: Meiri
authors.forename: Johannes
authors.initials: J
authors.lastname: Foufopoulos
authors.forename: Efstratios
authors.initials: E
authors.lastname: Valakos
mesh_terms: D000374:Aggression / Q000523:psychology; D000821:Animal Feed; D000818:Animals; D049628:Body Size; D003163:Competitive Behavior / Q000502:physiology*; D017753:Ecosystem; D005260:Female; D005877:Gigantism / Q000503:physiopathology / Q000523:psychology; D006115:Greece; D008116:Lizards / Q000033:anatomy & histology* / Q000502:physiology*; D008297:Male; D026684:Personal Autonomy; D011156:Population Density