Ornamentation, age, and survival of female striped plateau lizards, Sceloporus virgatus.

Abstract

Individuals with greater expression of secondary sexual traits are often older and have higher survivorship than individuals with lower expression; if so, assessment of such indicator traits may provide genetic and/or direct benefits to potential mates. I examined the relationship between ornament expression, age, and survival in the striped plateau lizard, Sceloporus virgatus, a species with female-specific ornamentation that honestly signals reproductive quality. I followed a group of females from 2008 to 2013, examined ornament color and size as females aged, and compared ornamentation of survivors versus non-survivors. In addition, I explored whether other (non-ornamental) phenotypic characters predicted survival. I found that peak ornament expression (both color and size) of individual females changed year to year but appeared to be a weak signal of age due to high among-female variation in ornament expression that occurred independent of age and a non-linear pattern of change for ornament color. However, both absolute and relative ornament size did increase significantly as an individual aged and therefore may provide some age-related information such as reproductive investment, which is expected to increase as residual reproductive value declines with age. Individual survival was unrelated to peak ornament expression and to other phenotypic variables measured, providing no support for the ornament as a viability indicator and suggesting that individual survival prospects are affected by stochastic and environmental factors.