Annual life-history variation in the striped plateau lizard, Sceloporus virgatus

Abstract

I studied temporal variation in life-history and demographic traits of a population of striped plateau lizards, Sceloporus virgatus, over 3 years in the Chiricahua Mountains of southeastern Arizona. The 3 years of the study varied in precipitation and arthropod (prey) abundance, but the 2 years for which data were available did not differ in the amount of time potentially available for lizard activity. Individual growth, gain in body mass, and adult survivorship varied among years, the year of lowest precipitation levels (1994) having the slowest growth rates (0.099 mm/d) and gain in body mass (0.008 g/d) and the lowest adult survivorship (0.28), and the year of highest precipitation levels (1992) having the fastest growth rates (0.117 mm/d) and gain in body mass (0.029 g/d) and the highest adult survivorship (0.40). The proportion of first-year females that reproduced, juvenile survivorship, sex ratio, and age structure of the population did not differ among years. Individuals that grew faster (or slower) than expected from their body size in one year grew faster (or slower) than expected the next year. Survivors (both male and female) did not grow faster than nonsurvivors. Precipitation appears to be the strongest proximate factor influencing annual life-history traits in this population, probably because of its influence on arthropod abundance.