Understanding how populations adapt to rising temperatures has been a challenge in ecology. Research often evaluates multiple populations to test whether local adaptation to temperature regimes is occurring. Space-for-time substitutions are common, as temporal constraints limit our ability to observe evolutionary responses. We employed a resurrection ecology approach to understand how thermal tolerance has changed in a Daphnia pulicaria population over time. Temperatures experienced by the oldest genotypes were considerably lower than the youngest. We hypothesized clones were adapted to the thermal regimes of their respective time periods. We performed two thermal shock experiments that varied in length of heat exposure. Overall trends revealed that younger genotypes exhibited higher thermal tolerance than older genotypes; heat shock protein (hsp70) expression increased with temperature and varied among genotypes, but not across time periods. Our results indicate temperature may have been a selective factor on this population, although the observed responses may be a function of multifarious selection. Prior work found striking changes in population genetic structure, and in other traits that were strongly correlated with anthropogenic changes. Resurrection ecology approaches should help our understanding of interactive effects of anthropogenic alterations to temperature and other stressors on the evolutionary fate of natural populations.
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Data accessibility. Our data are deposited at Dryad: https://dx.doi.org/10.5061/dryad.f30r1 . Authors’ contributions. A.M.Y. conceived and designed the overall study with considerable input from P.D.J. and L.J.W.; N.B. conceived, designed and conducted the first experiment with input from P.D.J. and P.R.C.; A.M.Y. conceived, designed and conducted the second experiment with input from L.J.W.; A.M.Y. coordinated data analyses for the overall study with input from P.D.J. and L.J.W.; P.R.C. and J.H.S. carried out the molecular laboratory work and measured heat shock protein expression; A.M.Y., P.D.J. and L.J.W. wrote the paper with input from all authors. All authors gave final approval for publication. Competing interests. We declare we have no competing interests. Funding. Funding for this study was provided by the US National Science Foundation (NSF-IOS-OEI) collaborative grant nos. 0924289 and 1256881 to L.J.W. and grant no. 0924401 to P.D.J. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Acknowledgements. We thank the staff at the University of Minnesota LacCORE facility for assisting with the collection and provisioning of core samples, in particular, R. O’Grady. We thank B. Culver, D. Frisch, R. Hartnett, C. Henpita, P. Morton and R. Yorks for their assistance. We thank I. Schlupp, J. Urabe and C. Vaughn for critical input on earlier drafts of the manuscript, and J.P. Masly for his contribution towards the statistical analyses. This manuscript constitutes a portion of A. Yousey’s MS thesis at the University of Oklahoma.
© 2018 The Authors.
Copyright 2018 Elsevier B.V., All rights reserved.
- Climate change
- Local adaptation
- Resurrection ecology
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