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INTRODUCTION
Vocalizations are some of the most important means of animal communication, and acoustic signals may convey information about the species, such as physical condition and heritable fitness of a mate (Henderson and Gerhardt, 2013; Fang et al., 2014, 2015). Individuals of one sex (usually male) emit acoustic signals, and individuals of the other sex recognize the signals and use these to choose an appropriate sexual partner (Andersson, 1994; Rosso et al., 2006; Fang et al., 2012). In anurans, the male advertisement calls are the primary mating displays. Male advertisement calls are usually recognized to have follow functions: to facilitate species recognition and to provide females with criteria for choosing their partner among many males and also known to function in male spacing with some species (Castellano and Giacoma, 1998; Gerhardt and Brooks, 2009; Hernández et al., 2010; Wei et al., 2012).
Most species of anurans rely on one or more unique properties of their call (i.e., fundamental frequency, dominant frequency, note duration, etc.) to facilitate conspecific recognition (Bickford et al., 2007; Kohler et al., 2017). Several factors can influence the properties of an anuran's call, including air temperature, body size and geographic variation (Márquez, 1995; Márquez and Bosch, 1997; Cui et al., 2011; Baraquet et al., 2015). However some anurans may alter their calling patterns and the temporal properties of their calls to meet the female preference. Many researchers suggest that the female preference may affect the male call behaviour (Gerhardt and Huber, 2002), and that it is related to the female's reproductive condition (Lynch et al., 2005).
Preference functions describe how female preferences vary as a function of male call trait values, and define a form of selection for male signals (Gerhardt, 1991; Wagner, 1998; Murphy and Gerhardt, 2000; Rosso et al., 2006). These functions take several shapes, and the overall shapes of preference functions have important consequences (Murphy and Gerhardt, 2000). Ample evidence supports the notion that female anurans prefer certain advertisement call properties over others and use these calls to evaluate prospective mates (Ryan and Keddy-Hector, 1992; Gerhardt and Huber, 2002; Tárano and Herrera, 2003; Martinez-Rivera and Gerhardt, 2008; Fang et al., 2014; Velásquez et al., 2015). Female anurans show preferences based on call duration, call rate, and dominant frequency (Tárano...