PEAK SHIFTS PRODUCED BY CORRELATED RESPONSE TO SELECTION

Trevor Price; Michael Turelli; Montgomery Slatkin

doi:10.1111/j.1558-5646.1993.tb01216.x

PEAK SHIFTS PRODUCED BY CORRELATED RESPONSE TO SELECTION

Evolution. 1993 Feb;47(1):280-290. doi: 10.1111/j.1558-5646.1993.tb01216.x.

Authors

Trevor Price¹, Michael Turelli², Montgomery Slatkin³

Affiliations

¹ Department of Biology 0116, University of California at San Diego, La Jolla, CA, 92093, USA.
² Department of Genetics and Center for Population Biology, University of California, Davis, CA, 95616, USA.
³ Department of Integrative Biology, University of California, Berkeley, CA, 97420, USA.

PMID: 28568090
DOI: 10.1111/j.1558-5646.1993.tb01216.x

Abstract

Traits may evolve both as a consequence of direct selection and also as a correlated response to selection on other traits. While correlated response may be important for both the production of evolutionary novelty and in the build-up of complex characters, its potential role in peak shifts has been neglected empirically and theoretically. We use a quantitative genetic model to investigate the conditions under which a character, Y, which has two alternative optima, can be dragged from one optimum to the other as a correlated response to selection on a second character, X. High genetic correlations between the two characters make the transition, or peak shift, easier, as does weak selection tending to restore Y to the optimum from which it is being dragged. When selection on Y is very weak, the conditions for a peak shift depend only on the location of the new optimum for X and are independent of the strength of selection moving it there. Thus, if the "adaptive valley" for Y is very shallow, little reduction in mean fitness is needed to produce a shift. If the selection acts strongly to keep Y at its current optimum, very intense directional selection on X, associated with a dramatic drop in mean fitness, is required for a peak shift. When strong selection is required, the conditions for peak shifts driven by correlated response might occur rarely, but still with sufficient frequency on a geological timescale to be evolutionarily important.

Keywords: Adaptive surface; correlated response; directional selection; disruptive selection; genetic correlations; peaks and valleys; punctuation; stabilizing selection.