Response to joint selection on germination and flowering phenology depends on the direction of selection

Laura F. Galloway, Ray H.B. Watson, Holly R. Prendeville

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5 Scopus citations


Flowering and germination time are components of phenology, a complex phenotype that incorporates a number of traits. In natural populations, selection is likely to occur on multiple components of phenology at once. However, we have little knowledge of how joint selection on several phenological traits influences evolutionary response. We conducted one generation of artificial selection for all combinations of early and late germination and flowering on replicated lines within two independent base populations in the herb Campanula americana. We then measured response to selection and realized heritability for each trait. Response to selection and heritability were greater for flowering time than germination time, indicating greater evolutionary potential of this trait. Selection for earlier phenology, both flowering and germination, did not depend on the direction of selection on the other trait, whereas response to selection to delay germination and flowering was greater when selection on the other trait was in the opposite direction (e.g., early germination and late flowering), indicating a negative genetic correlation between the traits. Therefore, the extent to which correlations shaped response to selection depended on the direction of selection. Furthermore, the genetic correlation between timing of germination and flowering varies across the trait distributions. The negative correlation between germination and flowering time found when selecting for delayed phenology follows theoretical predictions of constraint for traits that jointly determine life history schedule. In contrast, the lack of constraint found when selecting for an accelerated phenology suggests a reduction of the covariance due to strong selection favoring earlier flowering and a shorter life cycle. This genetic architecture, in turn, will facilitate further evolution of the early phenology often favored in warm climates.

Original languageEnglish (US)
Pages (from-to)7688-7696
Number of pages9
JournalEcology and Evolution
Issue number15
StatePublished - Aug 2018
Externally publishedYes

Bibliographical note

Funding Information:
We thank W. Crannage for plant care; M. Garino, D. Attia, J. Cahoon, B. Cottrell, A. Greenlee, K. Kubow, J. O'Brien, R. Slotter, Z. Spires, and B. Sutherland for assistance; and E.D. Brodie III for comments on an earlier version. This work was supported by NSF DEB 1020717 and 1457686.

Publisher Copyright:
© 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.


  • Campanula americana
  • Campanulastrum americanum
  • artificial selection
  • bivariate selection
  • correlated response
  • flowering time
  • germination time
  • life history evolution
  • maternal effects
  • realized heritability
  • reproductive phenology


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