Measuring thermal behavior in smaller insects: A case study in Drosophila melanogaster demonstrates effects of sex, geographic origin, and rearing temperature on adult behavior

Abstract

Measuring thermal behavior in smaller insects is particularly challenging. In this study, we describe a new horizontal thermal gradient apparatus designed to study adult thermal behavior in small insects and apply it using D. melanogaster as a model and case study. Specifically, we used this apparatus and associated methodology to examine the effects of sex, geographic origin, and developmental rearing temperature on temperature preferences exhibited by adults in a controlled laboratory environment. The thermal gradient established by the apparatus was stable over diurnal and calendar time. Furthermore, the distribution of adult flies across thermal habitats within the apparatus remained stable following the period of acclimation, as evidenced by the high degree of repeatability across both biological and technical replicates. Our data demonstrate significant and predictable variation in temperature preference for all 3 assayed variables. Behaviorally, females were more sensitive than males to higher temperatures. Flies originating from high latitude, temperate populations exhibited a greater preference for cooler temperatures; conversely, flies originating from low latitude, tropical habitats demonstrated a relative preference for higher temperatures. Similarly, larval rearing temperature was positively associated with adult thermal behavior: low culture temperatures increased the relative adult preference for cooler temperatures, and this response was distinct between the sexes and for flies from the temperate and subtropical geographic regions. Together, these results demonstrate that the temperature chamber apparatus elicits robust, predictable, and quantifiable thermal preference behavior that could readily be applied to other taxa to examine the role of temperature-mediated behavior in a variety of contexts.

Wolbachia modifies thermal preference in Drosophila melanogaster

“…T p can vary significantly between populations of the same species (Matute et al ., ; Rajpurohit and Schmidt, ) and can have profound effects on immune function, fitness, and fecundity (Huey and Berrigan, ; Martin and Huey, ; Hoffmann, ). Recent population analyses of Wolbachia and mitochondria from D. melanogaster have provided evidence that over the past few thousand years, the w MelCS variant is being globally replaced by the w Mel‐variant (Riegler et al ., ; Nunes et al ., ; Richardson et al ., ; Early and Clark, ).…”

“…Uninfected D. melanogaster flies preferred an average temperature of 24.4 C, whereas wMel-infected flies preferred 23.2 C and both wMelCS-and wMelPop-infected flies preferred 20.6 C and 20.5 C respectively. T p can vary significantly between populations of the same species (Matute et al, 2009;Rajpurohit and Schmidt, 2016) and can have profound effects on immune function, fitness, and fecundity (Huey and Berrigan, 2001;Martin and Huey, 2008;Hoffmann, 2010). Recent population analyses of Wolbachia and mitochondria from D. melanogaster have provided evidence that over the past few thousand years, the wMelCS variant is being globally replaced by the wMel-variant (Riegler et al, 2005;Nunes et al, 2008;Richardson et al, 2012;Early and Clark, 2013).…”

“…Ectotherms, such as terrestrial insects, depend on ambient conditions to maintain their body temperature within a thermoregulatory range (Angilletta et al, 2004). For example, thermal preference (T p ) in Drosophila melanogaster, a dipteran model species of world-wide distribution, varies with geography and elevation, and is thus potentially shaped by selection (Martin and Huey, 2008;Dillon et al, 2009;Garrity et al, 2010;Hoffmann and Sgrò, 2011;Huey et al, 2012;Rajpurohit and Schmidt, 2016). In addition, variation in temperature can have fundamental effects on ecological interactions among organisms and their symbiotic microbes.…”

“…S2. Schematic of the thermal gradient apparatus used for thermal gradient assays as adapted from Rajpurohit and Schmidt (). The polycarbonate tube and length of aluminium gradient within the tube were 58.76 cm and temperature was recorded with K‐type thermocouples.…”

Spatiotemporal dynamics and genome‐wide association analysis of desiccation tolerance in Drosophila melanogaster

“…Instead, the significant decrease in in the more resistant ME females as they settled to the dry metabolic chamber environment, and absence of this response for HFL females, suggests a difference in behavioural response. Both males and females in these populations do exhibit very distinct behaviour in response to thermal variation as well (Rajpurohit & Schmidt, ).…”