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Learning and experience shape mate preferences in many species. My thesis investigates the role of experience on mating behavior of male and female sailfin mollies (Poecilia latipinna). In the first chapter I explore whether adult experience influences male sailfin molly mate preference for their sexual parasite, the Amazon molly (Poecilia formosa), and whether experience could account for reproductive character displacement (RCD) of male mate preference in this species. Sailfin males from sympatric populations show a stronger preference for conspecific females over Amazon mollies than do males from allopatric populations. I exposed males from sympatric and allopatric populations to either a sailfin female or an Amazon prior to a mating trial with an Amazon. For the allopatric population, males with recent experience with an Amazon directed fewer mating behaviors towards an Amazon during mating trials than did males with recent experience with a sailfin. Males from the sympatric population, however, performed the same amount of mating behaviors towards an Amazon regardless of experience. Thus adult experience influences mating preferences and suggests that experience may play a role in RCD in this species. In the second chapter I investigate whether a learned sensory bias could influence female mate preferences. Sensory biases that influence mate preferences can arise through selection on the sensory system in foraging and predator detection domains. I tested whether a learned preference originating outside of the mating domain, specifically a color-based food preference, can be transferred to a color-based preference for a male trait. I trained female sailfin mollies to associate either green or blue with food and then tested their preference for animated male sailfins featuring either a blue or green spot. I found that females did not prefer the male with the same color spot to which they had been conditioned. I discuss the problem of learned preference transfer and suggest directions for future research into the role of learning in sensory bias. / text

Mate choice plays an important role in sexual selection and speciation. The evolution of mate choice is intriguing in cases where choosy individuals gain little except for genetic material from the mate and where the trait used as a criterion for the choice is costly to its bearer. The sensory exploitation hypothesis is an interesting idea that applies to such cases because it suggests that sexual preferences may arise as side-effects of preferences that are under selection in other contexts. The role of mate choice in speciation is strong but is debated because the reasons for population divergence in mate preferences and sexual traits are sometimes hard to explain. Also in this context sensory exploitation offers a potential explanation in that a link between natural and sexual selection may result in divergence in sexual selection whenever populations differ in natural selection. In this thesis, I test several aspects of this hypothesis in a species of fish, the swordtail characin (Corynopoma riisei). In this species males display a flag-like ornament that grows from the operculum. Because females respond to this ornament by biting at it, it has been proposed to act as a food-mimic. By manipulating female food type and quantity, and testing the resulting female preference for the male ornament, I find support for the theory that the preference has evolved through sensory exploitation and that females indeed appear to relate the ornament to a food item. Furthermore, I show that sensory exploitation can lead to morphological divergence among natural populations in this species. Apart from the flag-ornament, other courtship signals are also investigated. The results show that the relative importance of different signals may vary depending on receiver motivation. This suggests that various aspects of both male courtship signals and the conditions during which they are being signalled should be considered to gain a full understanding of mate choice and its role in sexual selection and speciation.