Physiological phenotypes differ among color morphs in introduced populations of the common wall lizard, Podarcis muralis

Many species exhibit color polymorphisms which have distinct physiological and behavioral characteristics. However, the consistency of morph trait covariation patterns across species, time, and ecological contexts remains unclear. This trait covariation is especially relevant in the context of invasion biology and urban adaptation. Specifically, physiological and behavioral traits pertaining to energy maintenance are crucial to fitness, given their immediate ties to individual reproduction, growth, and population establishment. We investigated the physiological and behavioral traits of Podarcis muralis, a versatile color polymorphic species that thrives in urban environments (including invasive populations in Ohio, USA). We measured five physiological and behavioral traits (circulating corticosterone and triglycerides, hematocrit, body condition, and field body temperature) which compose an integrated multivariate phenotype. We then tested variation among stable color polymorphisms in the context of establishment in an urban environment. We found that the traits describing physiological status and strategy shifted across the active season in a morph-dependent manner-the white and yellow morphs exhibited clearly different multivariate physiological phenotypes, characterized primarily by differences in circulating corticosterone. This suggests that morphs have different strategies in physiological regulation, the flexibility of which is crucial to urban adaptation. The white-yellow morph exhibited an intermediate phenotype, suggesting an intermediary energy maintenance strategy. Orange morphs also exhibited distinct phenotypes, but the low prevalence of this morph in our study populations precludes clear interpretation. Our work provides insight into how differences among stable polymorphisms exist across axes of the phenotype and how this variation may aid in establishment within novel environments. O_QDEpigraph: "If you are only moved by color relationships, you are missing the point." - Mark Rothko, Latvian-American abstract painter C_QD