Data from: Variation in the strength of female mate preference for male size supports the signal reliability hypothesis

<p>Both sexually selected traits and mate preferences for these traits can be condition dependent, yet how variation in preferred traits could select for condition dependent preferences has rarely been examined. The signal reliability hypothesis predicts that mate preferences vary across environments in relation to the reliability of the information preferred traits provide in those environments. Extensive variation in copy number of the <em>mc4r</em> gene on Y chromosome is correlated with adult male size in <em>Xiphophorus multilineatus</em>, when males stop growing. This genetic variation allowed us to use a split-sibling design to show that male size is more variable, and thus likely to provide reliable information about male genotype, when males were reared in a warm as compared to cold environment. Females reared in the warm environment had stronger mate preferences for male size. Understanding how the reliability of male traits can select for conditional variation in the strength of the female mate preferences will further our discovery of adaptive mate preferences. For example, the relationship between the strength of a female's mate preference and their growth rates supports previous work hypothesizing disassortative mating in relation to growth rates to mitigate a documented growth-mortality tradeoff in this species.</p>