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Unidirectional response to bidirectional selection on body size. I. Phenotypic, life history and endocrine response.
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  • Clémentine Renneville,
  • Alexis Millot,
  • Simon Agostini,
  • David Carmignac,
  • Gersende Maugars,
  • Sylvie Dufour,
  • Arnaud Le Rouzic,
  • Eric Edeline
Clémentine Renneville
Sorbonne Université
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Alexis Millot
Ecole normale supérieure
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Simon Agostini
CNRS
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David Carmignac
Sorbonne Université
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Gersende Maugars
Museum National d'Histoire Naturelle
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Sylvie Dufour
Museum National d'Histoire Naturelle
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Arnaud Le Rouzic
CNRS
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Eric Edeline
INRAE
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Abstract

Anthropogenic perturbations such as harvesting often select against a large body size, and are predicted to induce rapid evolution towards smaller body sizes and earlier maturation. However, the evolvability of body size and size-correlated traits remains seldom evaluated in wild populations. Here, we use a laboratory experiment over 6 generations to measure the ability of wild-caught medaka fish (Oryzias latipes) to evolve in response to bidirectional size-dependent selection mimicking opposite harvest regimes. Specifically, we imposed selection against a small body size (Large line), against a large body size (Small line) or random selection (Control line), and measured correlated responses across multiple phenotypic, life-history and endocrine traits. As expected, the Large line evolved faster somatic growth and delayed maturation, but also evolved smaller body sizes at hatch, with no change in average levels of pituitary gene expressions of luteinizing, follicle-stimulating or growth (GH) hormones. In contrast, the Small medaka line was unable to evolve smaller body sizes or earlier maturation, but showed marginally-significant signs of increased reproductive investment, including larger egg sizes and elevated pituitary GH production. Natural selection on medaka body size was too weak to significantly hinder the effect of artificial selection, indicating that the asymmetric body-size response to size-dependent selection reflected an asymmetry in body-size evolvability. Our results show that trait evolvability may be contingent upon the direction of selection, and that a detailed knowledge of trait evolutionary potential is needed to forecast population response to anthropogenic change.

Peer review status:ACCEPTED

18 Mar 2020Submitted to Ecology and Evolution
19 Mar 2020Submission Checks Completed
19 Mar 2020Assigned to Editor
20 Mar 2020Review(s) Completed, Editorial Evaluation Pending
27 Apr 2020Editorial Decision: Revise Minor
15 Jul 20201st Revision Received
17 Jul 2020Submission Checks Completed
17 Jul 2020Assigned to Editor
17 Jul 2020Review(s) Completed, Editorial Evaluation Pending
17 Jul 2020Editorial Decision: Accept