Trade-offs in phenotypic traits: endurance at birth, growth, survival, predation and susceptibility to parasitism in a lizard, Lacerta vivipara

1. Considerable within-population variability of locomotor performance trai ts has been shown to exist in several species of squamate reptiles. In gene ral, high values for speed and endurance are thought to have positive effec ts on the ability to capture prey, escape from predators, compete with cons pecifics and acquire mates. On the other hand, variation in performance mig ht trade-off with other components of fitness such that the net effect on D arwinian fitness is unpredictable. 2. Gravid females of the common lizard (Lacerta vivipara) were captured and several phenotypic traits of their offspring measured immediately followin g birth. These were endurance, body length and body mass. Offspring were ma rked for individual identification, released into the field, and correlatio ns between the phenotypic traits and their subsequent growth, activity and survival rate over the next months were then tested for. Parasitism by hema tozoa was monitored and predation risk by tail losses estimated. 3. It was found that individuals with a low endurance at birth tended to ha ve reduced activity and growth rate, and higher parasite load; on the posit ive side, however, they experienced lower predation risk as assessed by tai l losses. Conversely, individuals with a high endurance at birth had high a ctivity and growth rates, low parasite load, but higher incidence of broken tails. Finally, endurance at birth was not correlated with survivorship up to the age of sexual maturity. Thus, individuals with varying locomotor en durance seem to exhibit behaviours that may result in the same level of Dar winian fitness. 4. The possibility that our results reveal a trade-off between the risk of becoming infected with parasites when lizards are less active (which is rel ated to having lower endurance) vs the risk of being predated when the liza rds are more active (higher endurance) is discussed.