Describing mate preference functions and other function-valued traits.

Mate preferences are important causes of sexual selection. They shape the evolution of sexual ornaments and displays, sometimes maintaining genetic diversity and sometimes promoting speciation. Mate preferences can be challenging to study because they are expressed in animal brains and because they are a function of the features of potential mates that are encountered. Describing them requires taking this into account. We present a method for describing and analysing mate preference functions, and introduce a freely available computer program that implements the method. We give an overview of how the program works, and we discuss how it can be used to visualize and quantitatively analyse preference functions. In addition, we provide an informal review of different methods of testing mate preferences, with recommendations for how best to set up experiments on mate preferences. Although the program was written with mate preferences in mind, it can be used to study any function-valued trait, and we hope researchers will take advantage of it across a broad range of traits.