Data from: Strength of female mate preferences in temperature manipulation study supports the signal reliability hypothesis

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 the mc4r gene on the Y-chromosome that influences male size in Xiphophorus multilineatus allowed us to use a split-sibling design to determine if male size is more likely to provide information about male genotype (i.e., dam) when males were reared in a warm as compared to a cold environment. We then examined strength of preference for male size by females reared in the same two environments. We found that males were larger in the cold environment, but male size was more variable across dams and therefore a more reliable indicator of dam in the warm environment. Females reared in the warm environment had stronger mate preferences for male size, in addition to a relationship between their strength of preference and growth rates that was not detected in the cold reared females. These results suggest that female preference for male size was influenced by the temperature in which they were reared, with the direction of the difference across treatments supporting the reliability hypothesis. 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 with this species of swordtail fish hypothesizing disassortative mating in relation to growth rates to mitigate a documented growth-mortality tradeoff.