Local adaptation and ecological differentiation under selection, migration, and drift in Arabidopsis lyrata*

Tuomas Hämälä, Tiina M. Mattila, Outi Savolainen

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23 Scopus citations

Abstract

How the balance between selection, migration, and drift influences the evolution of local adaptation has been under intense theoretical scrutiny. Yet, empirical studies that relate estimates of local adaptation to quantification of gene flow and effective population sizes have been rare. Here, we conducted a reciprocal transplant trial, a common garden trial, and a whole-genome-based demography analysis to examine these effects among Arabidopsis lyrata populations from two altitudinal gradients in Norway. Demography simulations indicated that populations within the two gradients are connected by gene flow (0.1 < 4Nem < 11) and have small effective population sizes (Ne <6000), suggesting that both migration and drift can counteract local selection. However, the three-year field experiments showed evidence of local adaptation at the level of hierarchical multiyear fitness, attesting to the strength of differential selection. In the lowland habitat, local superiority was associated with greater fecundity, while viability accounted for fitness differences in the alpine habitat. We also demonstrate that flowering time differentiation has contributed to adaptive divergence between these locally adapted populations. Our results show that despite the estimated potential of gene flow and drift to hinder differentiation, selection among these A. lyrata populations has resulted in local adaptation.

Original languageEnglish (US)
Pages (from-to)1373-1386
Number of pages14
JournalEvolution
Volume72
Issue number7
DOIs
StatePublished - Jul 2018

Bibliographical note

Funding Information:
TH and OS devised the study and wrote the manuscript. TH conducted the field experiments and analyzed the sequence data with TMM. We thank H. Sten?ien for sharing information about the Arabidopsis lyrata growing sites in Norway and seeds from the T2 population; D. Remington for sharing seeds from the NC population; T. Toivainen, U. Kemi, and J. Tyrmi for sample collections; N. Aryamanesh and S. Alatalo for sequencing library preparations; S. Alatalo, H. Parkkinen, A. H?m?l?inen, T. Huhtakangas, R.-P. Apuli, E. Haataja, and M. Takou for assistance with the field trials; B. Hansson, L. Rose, and two anonymous reviewers for their constructive comments on the manuscript. We are especially grateful for the Bakkom family for lending us their land and for their invaluable help throughout the experiment. IT Center for Science (CSC) provided computational resources. This work was financially supported by Biocenter Oulu (to TH and OS), Eemil Aaltonen Foundation (to TH and TMM), and Academy of Finland's Research Council for Biosciences and Environment (decision 132611 to OS). Phenotype data and R scripts (Dryad): https://doi.org/10.5061/dryad.3gc6nj6. DNA sequences (NCBI SRA): https://www.ncbi.nlm.nih.gov/sra/SRP144592.

Funding Information:
We thank H. Stenøien for sharing information about the Arabidopsis lyrata growing sites in Norway and seeds from the T2 population; D. Remington for sharing seeds from the NC population; T. Toivainen, U. Kemi, and J. Tyrmi for sample collections; N. Aryamanesh and S. Alat-alo for sequencing library preparations; S. Alatalo, H. Parkkinen, A. Hämäläinen, T. Huhtakangas, R.-P. Apuli, E. Haataja, and M. Takou for assistance with the field trials; B. Hansson, L. Rose, and two anonymous reviewers for their constructive comments on the manuscript. We are especially grateful for the Bakkom family for lending us their land and for their invaluable help throughout the experiment. IT Center for Science (CSC) provided computational resources. This work was financially supported by Biocenter Oulu (to TH and OS), Eemil Aaltonen Foundation (to TH and TMM), and Academy of Finland’s Research Council for Biosciences and Environment (decision 132611 to OS).

Publisher Copyright:
© 2018 The Author(s). Evolution © 2018 The Society for the Study of Evolution.

Keywords

  • Arabidopsis
  • demography simulations
  • gene flow
  • genetic drift
  • local adaptation
  • reciprocal transplant

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