J Exp Biol. 2023 Jan 26:jeb.244676. doi: 10.1242/jeb.244676. Online ahead of print.
ABSTRACT
The standard paradigm of organismal biology views lower-level traits (e.g., aspects of physiology) as determining organismal performance abilities (e.g., maximal sprint speed), which in turn constrain behavior (e.g., social interactions). However, few studies have simultaneously examined all three levels of organization. We used focal observations to record movement behaviors and push-up displays in the field for adult male Sceloporus occidentalis lizards during the breeding season. We then captured animals, measured aspects of physiology, morphology, performance, and counted ecto- and endoparasites as potential predictors of sprint speed and maximal oxygen consumption (VO2max). Field behaviors were statistically repeatable, but not strongly so. Sprint speed and VO2max were repeatable using residuals from regressions on body mass (speed: r=0.70; VO2max: r=0.88). Both calf (standardized partial regression [path] coefficient B=0.53) and thigh (B=-0.37) muscle masses (as residuals from regressions on body mass) were significant predictors of sprint speed; hemoglobin concentration (B=0.42) was a predictor of VO2max. In turn, VO2max predicted the maximum number of 4-legged push-ups per bout (B=0.39). In path analysis, log likelihood ratio tests indicated no direct paths from lower-level traits to behavior, supporting the idea that morphology, in the broad sense, only affects behavior indirectly through measures of performance. Our results show that inter-individual variation in field behaviors can be related to performance abilities, which in turn reflect differences in morphology and physiology, although not parasite load. Given the low repeatability of field behaviors, some of the relationships between behavior and performance may be stronger than suggested by our results.
PMID:36700411 | DOI:10.1242/jeb.244676
