Distinct cold tolerance traits independently vary across genotypes inDrosophila melanogaster

Abstract

Cold tolerance, the ability to cope with low temperature stress, is a critical adaptation in thermally variable environments. An individual's cold tolerance comprises several traits including minimum temperatures for growth and activity, ability to survive severe cold, and ability to resume normal function after cold subsides. Across species, these traits are correlated, suggesting they were shaped by shared evolutionary processes or possibly share physiological mechanisms. However, the extent to which cold tolerance traits and their associated mechanisms covary within populations has not been assessed. We measured five cold tolerance traits—critical thermal minimum, chill coma recovery, short‐ and long‐term cold tolerance, and cold‐induced changes in locomotor behavior—along with cold‐induced expression of two genes with possible roles in cold tolerance (heat shock protein 70 and frost)—across 12 lines of Drosophila melanogaster derived from a single population. We observed significant genetic variation in all traits, but few were correlated across genotypes, and these correlations were sex‐specific. Further, cold‐induced gene expression varied by genotype, but there was no evidence supporting our hypothesis that cold‐hardy lines would have either higher baseline expression or induction of stress genes. These results suggest cold tolerance traits possess unique mechanisms and have the capacity to evolve independently.

Chill coma onset and recovery fail to reveal true variation in thermal performance among populations ofDrosophila melanogaster

“…In this study, we confirmed that chill tolerance traits can vary independently in Drosophila melanogaster. Similar results have emerged in laboratory selection experiments (Garcia et al, 2020;Gerken et al, 2016) where selection pressure is controlled, but never, to our knowledge, in wild-derived populations like those used here. We were surprised to find that this was the case even in populations that are known to differ significantly in one chill tolerance trait (Pool et al, 2017) -in a way that matched the climatic conditions where their ancestors were collected.…”

“…We were surprised to find that this was the case even in populations that are known to differ significantly in one chill tolerance trait (Pool et al, 2017) -in a way that matched the climatic conditions where their ancestors were collected. In some ways, this finding is not surprising: it is increasingly clear that the underlying mechanisms of several commonly measured chill tolerance traits differ (M. K. Andersen & Overgaard, 2019;Overgaard & MacMillan, 2017), and it is also possible to select on such traits separately (Garcia et al, 2020;Gerken et al, 2016). However, it remains unclear why some wild-derived populations from colder regions display greater chill tolerance across a range of traits (A.…”

“…Since multiple organ systems are involved, chill tolerance traits can vary independently (Garcia, Littler, Sriram, & Teets, 2020;Gerken, Mackay, & Morgan, 2016) -but in practice, they often don't. After cold acclimation or rapid cold hardening (i.e.…”

Characterization of Cold Tolerance of Immature Stages of Small Hive Beetle (SHB) Aethina tumida Murray (Coleoptera: Nitidulidae)

“…Phenotypic plasticity of insects is also used to determine thermal limits in addition to inherent genetic mechanisms. Acclimation is an adaptive phenotypic plasticity [ 5 ], and according to the beneficial acclimation hypothesis [ 6 , 7 ], it depends on species and duration of exposure. Acclimation to lower sub-lethal temperatures for days to several weeks increases cold tolerance of insects by depressing their SCPs [ 8 , 9 ].…”

Multiple paths to cold tolerance: the role of environmental cues, morphological traits and the circadian clock genevrille

“…Even though the ability to resist chill coma and recover from it are thought to be somewhat of a continuum, they are affected by different physiological and molecular mechanisms (e.g. [16, 19]). The onset of chill coma is associated with depolarisation of muscle resting membrane potential due to low temperature (e.g.…”