Risking life for nothing? A story about the exploration of extreme thermal landscapes and the evolution of natural daredevils

Abstract

Although in nature organisms face thermal fluctuations in time and space that integratively influence their physiology and behavior, experimental studies have focused mainly in the temporal component of thermal landscapes and neglected the spatial one. In fact, the literature presents contrasting evidence between adaptive patterns found in laboratory vs. natural conditions, probably because classic experimental approaches inform nothing about the consequences for individuals of navigating through complex thermal landscapes, a consequential aspect for behavioral thermoregulation in nature. Considering that natural populations exhibit inter-individual variation in thermoregulatory strategies, it is possible to find a fraction of individuals that are more prone to risk (i.e., natural daredevils), for example to voluntarily explore extreme temperatures. An ongoing investigation is showing so in Drosophila melanogaster, and risky behaviors concerning the exploration of thermal extremes in this species occur even under no evident material, social or psychological rewards. Thereby, this research proposal aims to investigate the evolutionary consequences of the volunteer exploration of extreme temperatures on the behavior and physiology of Drosophila melanogaster, a worldwide model organism. By applying a life-threatening filter in which temperature changes in space and time, we will artificially select the flies that voluntarily cross it to breed natural daredevils for several generations. At each generation we will simultaneously measure key behavioral and physiological traits to determine their heritability and evolvability. Following principles from both thermal biology and evolutionary theory, we propose that: 1) the behavioral drive to explore extreme temperatures is an inheritable trait that 2) do not have an a priori dialog with thermal physiology, but that 3) can influence its evolution through experimental selection. As a major gain, we expect to create a model of natural daredevils to study the underlying basis of risk-taking behaviors, with potential implications for understanding risky behaviors in humans. (AU)