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Identifying the various factors that influence complex signal evolution is a difficult task, yet it is fundamental to understanding the evolution of animal communication. Here we explore the evolution of complex courtship signaling by taking advantage of a system in which sexual selection on male courtship traits has driven the diversification of geographically isolated populations of the jumping spider Habronattus pugillis Griswold. Using 2 populations (Santa Rita [SR] and Atascosa [AT]) in which SR females show xenophilic mating preferences for foreign (AT) over local males (SR), we examine the mechanisms driving this preference. Both AT and SR males produce multimodal signals (visual + seismic), and while SR and AT signals share certain seismic components, AT seismic signals are more complex and contain novel components. We conducted mate choice trials where SR females were presented with AT or SR males that were either muted or nonmuted. SR females preferred to mate and mated more quickly with foreign AT males over local SR males only if AT males could produce seismic signals (nonmuted treatment). In addition, we found that SR females spent a higher proportion of time attentive to foreign AT males only if they could produce seismic signals. This evidence suggests that SR females have a bias for complex and/or novel forms of seismic signals.