Meeting Abstract
The ecomorphological paradigm recognizes that lower-level subordinate traits (e.g. enzyme activities at the cellular level, limb proportions) affect organismal performance abilities (e.g., maximal sprint speed), these performance traits constrain behavior, and behaviors impinge on life history traits and hence Darwinian fitness. Few studies aimed at testing these ideas have been able to examine all levels in this hierarchy. As a step towards that goal, we examined key lower-level morphological and physiological traits, two aspects of organismal performance, and indicators of field locomotor behavior in ~40 adult male S. occidentalis from Hampton Buttes, OR, during the breeding season. We measured lower-level traits (blood [hemoglobin] & hematocrit; heart, liver, lung, thigh & calf muscle masses; hind & fore limb spans; tail length; number of ticks), performance (maximal sprint speed, aerobic capacity), and field behavior (displays, distance, moves per minute). Where appropriate, residuals from regressions on body mass were analyzed. Some of the lower-level traits were significantly (P<0.05) intercorrelated, e.g., hematocrit and hemoglobin (r=0.9), and both correlated with heart mass (r=0.6 and 0.5, respectively). Multiple regression revealed residual hemoglobin concentration (b=0.51) and residual calf muscle mass (b=0.37) as significant predictors of residual VO2max and speed, respectively, consistent with previous theoretical and empirical studies. However, neither VO2max nor speed were correlated with any behavioral trait, which suggests that the measured aspects of movement and display intensity are not limited by those performance capacities.
