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Diversification under sexual selection: the relative roles of mate preference strength and the degree of divergence in mate preferences.

Rodríguez RL, Boughman JW, Gray DA, Hebets EA, Höbel G, Symes LB - Ecol. Lett. (2013)

Bottom Line: To ask how this disparity in focus may affect the conclusions of evolutionary research, we relate the amount of diversification in mating displays to quantitative descriptions of the strength and the amount of divergence in mate preferences across a diverse set of case studies of mate choice.We find that display diversification is better explained by preference divergence rather than preference strength; the effect of the latter is more subtle, and is best revealed as an interaction with the former.Adopting this view will enhance tests of the relative role of natural and sexual selection in processes such as speciation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA. rafa@uwm.edu

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Preference functions relate variation in sexual response to variation in display traits. (a) Closed preference functions rise to peak response at the preferred display trait value (‘peak preference’; arrow) and then decline. (b) Open preference functions continue to rise or level off, although a peak may be defined (arrows) if further display investment brings diminishing returns. (c) In relation to display trait distributions (histograms), preference functions make predictions about the form of selection (see text). Here, black vs. grey functions predict stabilising vs. directional selection (closed preferences) or varying directional selection (open preferences). Note that a closed preference may predict stabilising or directional selection according to the position of the display trait distribution relative to peak preference. (d) Preference functions may vary in strength (grey is weaker), according to the extent of the decrease in attractiveness as displays deviate from peak preference.
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fig02: Preference functions relate variation in sexual response to variation in display traits. (a) Closed preference functions rise to peak response at the preferred display trait value (‘peak preference’; arrow) and then decline. (b) Open preference functions continue to rise or level off, although a peak may be defined (arrows) if further display investment brings diminishing returns. (c) In relation to display trait distributions (histograms), preference functions make predictions about the form of selection (see text). Here, black vs. grey functions predict stabilising vs. directional selection (closed preferences) or varying directional selection (open preferences). Note that a closed preference may predict stabilising or directional selection according to the position of the display trait distribution relative to peak preference. (d) Preference functions may vary in strength (grey is weaker), according to the extent of the decrease in attractiveness as displays deviate from peak preference.

Mentions: We tested two hypotheses about the action of sexual selection through mate choice by relating changes in display traits to changes in mate preferences: (1) The amount of divergence in displays is explained by the strength of mate preferences. This hypothesis predicts that stronger preferences will be associated with greater divergence in display traits. (2) The amount of divergence in display traits is explained by the amount of divergence in mate preferences. This hypothesis makes two predictions: First, greater preference divergence will be associated with greater divergence in display traits. Second, this relationship will be stronger for closed preferences than for open preferences – because the display–preference match should be tighter for closed preferences, which select against deviation from peak preference in both directions, whereas open preferences select against deviation from the peak in only one direction (Rodríguez et al. 2006) (see Fig. 2). When possible, we also tested a prediction that relates the two hypotheses above. In some cases, the effect of preference divergence should be greater with stronger preferences (Fig. 1), so that these variables interact in a positive way. However, if the amount of preference divergence determines how much display divergence can occur, there will be a point at which stronger preferences cannot result in any greater Δt (Fig. 1) and the interaction may be negative. Alternatively, with enough time, large preference divergence can result in large display divergence even if preferences are weak (Fig. 1) and the interaction may again be negative. These considerations predict an interaction between the effects of preference strength and preference divergence, which we tested whenever the sample size for each case study allowed constructing a model with the interaction term (see below). Because the interaction can be complex, we focused on testing for its presence, rather than on its sign. We tested these predictions for each case study, and then conducted an overall analysis of effects and effect sizes.


Diversification under sexual selection: the relative roles of mate preference strength and the degree of divergence in mate preferences.

Rodríguez RL, Boughman JW, Gray DA, Hebets EA, Höbel G, Symes LB - Ecol. Lett. (2013)

Preference functions relate variation in sexual response to variation in display traits. (a) Closed preference functions rise to peak response at the preferred display trait value (‘peak preference’; arrow) and then decline. (b) Open preference functions continue to rise or level off, although a peak may be defined (arrows) if further display investment brings diminishing returns. (c) In relation to display trait distributions (histograms), preference functions make predictions about the form of selection (see text). Here, black vs. grey functions predict stabilising vs. directional selection (closed preferences) or varying directional selection (open preferences). Note that a closed preference may predict stabilising or directional selection according to the position of the display trait distribution relative to peak preference. (d) Preference functions may vary in strength (grey is weaker), according to the extent of the decrease in attractiveness as displays deviate from peak preference.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3757319&req=5

fig02: Preference functions relate variation in sexual response to variation in display traits. (a) Closed preference functions rise to peak response at the preferred display trait value (‘peak preference’; arrow) and then decline. (b) Open preference functions continue to rise or level off, although a peak may be defined (arrows) if further display investment brings diminishing returns. (c) In relation to display trait distributions (histograms), preference functions make predictions about the form of selection (see text). Here, black vs. grey functions predict stabilising vs. directional selection (closed preferences) or varying directional selection (open preferences). Note that a closed preference may predict stabilising or directional selection according to the position of the display trait distribution relative to peak preference. (d) Preference functions may vary in strength (grey is weaker), according to the extent of the decrease in attractiveness as displays deviate from peak preference.
Mentions: We tested two hypotheses about the action of sexual selection through mate choice by relating changes in display traits to changes in mate preferences: (1) The amount of divergence in displays is explained by the strength of mate preferences. This hypothesis predicts that stronger preferences will be associated with greater divergence in display traits. (2) The amount of divergence in display traits is explained by the amount of divergence in mate preferences. This hypothesis makes two predictions: First, greater preference divergence will be associated with greater divergence in display traits. Second, this relationship will be stronger for closed preferences than for open preferences – because the display–preference match should be tighter for closed preferences, which select against deviation from peak preference in both directions, whereas open preferences select against deviation from the peak in only one direction (Rodríguez et al. 2006) (see Fig. 2). When possible, we also tested a prediction that relates the two hypotheses above. In some cases, the effect of preference divergence should be greater with stronger preferences (Fig. 1), so that these variables interact in a positive way. However, if the amount of preference divergence determines how much display divergence can occur, there will be a point at which stronger preferences cannot result in any greater Δt (Fig. 1) and the interaction may be negative. Alternatively, with enough time, large preference divergence can result in large display divergence even if preferences are weak (Fig. 1) and the interaction may again be negative. These considerations predict an interaction between the effects of preference strength and preference divergence, which we tested whenever the sample size for each case study allowed constructing a model with the interaction term (see below). Because the interaction can be complex, we focused on testing for its presence, rather than on its sign. We tested these predictions for each case study, and then conducted an overall analysis of effects and effect sizes.

Bottom Line: To ask how this disparity in focus may affect the conclusions of evolutionary research, we relate the amount of diversification in mating displays to quantitative descriptions of the strength and the amount of divergence in mate preferences across a diverse set of case studies of mate choice.We find that display diversification is better explained by preference divergence rather than preference strength; the effect of the latter is more subtle, and is best revealed as an interaction with the former.Adopting this view will enhance tests of the relative role of natural and sexual selection in processes such as speciation.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53201, USA. rafa@uwm.edu

Show MeSH