Abstract
Local adaptation, where fitness in one environment comes at a cost in another, should lead to spatial variation in trade-offs between life history traits and may be critical for population persistence. Recent studies have sought genomic signals of local adaptation, but often have been limited to laboratory populations representing two environmentally different locations of a species’ distribution. We measured gene expression, as a proxy for fitness, in males of Drosophila subobscura, occupying a 20° latitudinal and 11 °C thermal range. Uniquely, we sampled six populations and studied both common garden and semi-natural responses to identify signals of local adaptation. We found contrasting patterns of investment: transcripts with expression positively correlated to latitude were enriched for metabolic processes, expressed across all tissues whereas negatively correlated transcripts were enriched for reproductive processes, expressed primarily in testes. When using only the end populations, to compare our results to previous studies, we found that locally adaptive patterns were obscured. While phenotypic trade-offs between metabolic and reproductive functions across widespread species are well-known, our results identify underlying genetic and tissue responses at a continental scale that may be responsible for this. This may contribute to understanding population persistence under environmental change.
Highlights
Testing this prediction requires studying gene expression across a thermal gradient in many populations
We found locally adaptive patterns of gene expression across the European range of D. subobscura with all evidence pointing to adjustment of a gene expression trade-off between reproductive and metabolic investment, which favours reproduction in the south and growth/maintenance in the north
The use of more than two populations facilitates describing the shape of clinal variation in gene expression across the landscape to test the extent to which populations are either matching to the local optimum, through polygenic effects, resulting in linear effects or whether selection acts on major differences in expression patterns, resulting in non-linear effects[1]
Summary
Testing this prediction requires studying gene expression across a thermal gradient in many populations. We test for the trade-offs in gene expression predicted to underlie local adaptation in both common garden laboratory conditions and caged field populations, using Drosophila subobscura from six locations, from Valencia Spain, to Uppsala Sweden (see Supplementary Table 1) across its native 20° latitudinal range in Europe, representing an 11 °C difference in mean annual temperature This species has been described as a “microevolutionary weapon” against climate change[26] since it exhibits clinal variation – a hallmark of local adaptation - in both phenotypic (such as body size; Bergmann’s rule27) and genetic (polymorphic chromosomal inversions26,28) traits, replicated across three continents, and in genetic responses to thermal selection both in the laboratory and in the wild[29]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
