Temperature adaptation and its impact on the shape of performance curves in Drosophila populations

Understanding how species adapt to different temperatures is crucial to predict their response to global warming, and thermal performance curves (TPCs) have been employed recurrently to study this topic. Nevertheless, fundamental questions regarding how thermodynamic constraints and evolution interact to shape TPCs in lineages inhabiting different environments remain unanswered. Here, we study Drosophila simulans along a latitudinal gradient spanning 3,000 km to test opposing hypotheses based on thermodynamic constraints (‘hotter-is-better’) versus biochemical adaptation (‘jack-of-all-temperatures’) as primary determinants of TPCs variation across populations. We compare thermal responses in metabolic rate and the egg-to-adult survival as descriptors of organismal performance and fitness, respectively, and show that different descriptors of TPCs vary in tandem with mean environmental temperatures, providing strong support to hotter-is-better. Thermodynamic constraints also resulted in a..., Animal collection and maintenance
The study collected D. simulans adult flies from eight locations in Chile, spanning almost 3,000 km from North to South, during summer 2018 and 2019. The flies were caught using nets over banana or decomposing fruit traps and brought to the laboratory for taxonomic identification. Separate laboratory lines were established from each location and maintained in plexiglass cages under controlled conditions for at least three generations before experiments. Two replicate subcultures per line were maintained in separate cases, and populations were pooled every generation to minimize genetic drift. Maternal and grand maternal effects were removed by maintaining individuals under common garden conditions for at least three generations prior to experiments.
Metabolic rate
The study measured the standard metabolic rate (SMR or VCO2) in adult D. simulans flies using CO2 production through a flow-through respirometry design. Individual female and male flies were m..., R-software is required to open and analyse the data files.Â