• Fecundity;
  • geographic variation;
  • phenotypic plasticity


  • 1
     Previous experiments showed that Checkered Garter Snakes (Thamnophis marcianus) from south Texas, USA (an environment subject to high seasonal and annual variation in environmental conditions), demonstrated marked phenotypic plasticity in clutch size and clutch mass in response to experimental changes in prey availability.
  • 2
     In this study, the extent of phenotypic plasticity in life-history traits in Checkered Garter Snakes from south Texas was experimentally compared with a population of the same species from south-eastern Arizona, where the environment may be more constant.
  • 3
     Unlike results from south Texas, Checkered Garter Snakes from Arizona showed no significant phenotypic plasticity in clutch size, clutch mass or any other life-history trait in response to changes in food availability, at least within the boundaries of our experimental conditions.
  • 4
     The data indicate that the degree of phenotypic plasticity in life-history traits differs among populations within the same species. However, these differences are subject to both adaptive and non-adaptive explanations.