Meeting Abstract
Climate change is increasingly exposing populations to rare and novel environmental conditions. Theory suggests that extreme conditions will expose ‘hidden’ phenotypes, with a concomitant increase in trait variation. Although some empirical support for this exists, it is also well established that physiological mechanisms change when organisms are exposed to constant vs. fluctuating temperatures (most experiments to date have been conducted under constant conditions). To determine the effect of normal, rare, and novel temperatures on the release of hidden variation, we exposed fathead minnows, Pimephales promelas, to five fluctuating and four constant temperature regimes. We then measured each individual’s length-at-age (weekly over 60 days), critical thermal maximum, 5 morphometric traits, and fluctuating asymmetry. Length-at-age for both constant and fluctuating conditions decreased with temperature, and variance decreased with temperature under fluctuating conditions but increased and then decreased in constant temperatures. CTmax in both treatments increased with increasing water temperature, while variance decreased in warmer waters. No consistent pattern in mean or variance was found across morphometric traits or fluctuating asymmetry. Our results suggest that variance can decrease as the environment becomes more stressful, so it may be difficult to establish comprehensive rules for the effects of rarer environments on trait variation.
