Sexual Selection in Female Perceptual Space: How Female Tungara Frogs Perceive and Respond to Complex Population Variation in Acoustic Mating Signals

Abstract

Abstract. Female preferences for male mating signals are often evaluated on single parameters in isolation or small suites of characters. Most signals, however, are composites of many individual parameters. In this study we quantified multivariate traits in the advertisement call of the tú ngara frog, Physalaemus pustulosus. We represented the calls in multidimensional scaling space and chose nine test calls to represent the range of population variation. We then tested females for phonotactic preference between calls in each pair of the nine test calls. We used statistics developed for paired comparisons in such ''round robin'' competitions to evaluate the null hypothesis of equal attractiveness, and to examine the degree to which females responded to calls as being different from or similar to one another in attractiveness. We then examined the attractiveness of each test call relative to all other test calls as a function of their location in multivariate acoustic space (the acoustic landscape) to visualize sexual selection on calls. Finally, we used methods from cognitive psychology to illustrate the females' perception of call attractiveness in multivariate space, and compared this perceptual landscape to the acoustic landscape of quantitative call variation.We show that correlations between individual call characters are not strong and thus there are few biomechanical constraints on their independent evolution. Most call variables differed among males, and there was high repeatability of call characters within males. Females often discriminated between pairs of calls from the population, and there were significant differences among calls in their attractiveness. Female preferences for calls were not stabilizing. The region of the acoustic landscape that was most attractive to females included the mean call but was not centered around it. The females' perceptual or preference landscape did not correlate with the call's acoustic landscape, and female perception of calls decreased rather than enhanced call differences. Jang and Greenfield 1998). Some of these studies have measured preference functions for single traits or pairs of traits and show how the strength of preference, which is sometimes translated to a selection gradient, covaries with the stimulus (Ritchie 1996;Wagner 1998;Murphy and Gerhardt 2000;Schul and Bush 2002).The approaches used above have been invaluable in elucidating how female mating preferences (and sometimes male mating preferences) can generate selection on individual or small suites of signal traits. There are several limitations to these approaches, however. One limitation is that the female preferences for individual traits might not predict how females respond to comparisons of entire signals. The interaction effect of individual traits on female preference might not be additive, and it could even reverse signs. As a specific example, studies of jungle fowl show that females attend to a suite of characters but the relative importance of each character can vary with time (Zuk et ...

Mate choice in response to dynamic presentation of male advertisement signals in túngara frogs

“…Ryan & Rand (2003b) studied female mate choice in response to recorded natural calls from males in the study population (Gamboa, Panamá ) and showed that the complex calls of some males are consistently more attractive than those of others. Here we use this natural variation in attractiveness to examine how such intrinsic differences influence the extent to which females commit to a given male in the face of dynamic changes in call complexity.…”

“…system. Other studies have addressed signal variation within the population (Ryan 1985;Ryan & Rand 2003b). In addition to using the mean synthetic call, we also conducted choice tests with six natural advertisement calls (three whine-chucks, Wc (n1), Wc (n2) and Wc (n3), and the identical three whine-chucks with the chuck digitally excised to leave just the whine, W (n1), W (n2) and W (n3)) recorded from three males in Gamboa, Panamá ( Fig.…”

“…1; also see Results, Table 1). These stimuli have been used previously to explore female preferences in the Gamboa tú ngara population and the relative attractiveness of these calls for females has been determined (Ryan & Rand 2003b). Natural whine-chucks Wc (n1) and Wc (n3) are equivalently attractive, while Wc (n2) is significantly more attractive than Wc (n1).…”

The effect of signal complexity on localization performance in bats that localize frog calls

“…Calls were recorded by M. J. Ryan in July 1996 in Gamboa, Panama, with a Marantz PMD 420 cassette recorder and a Sennheiser ME 80 microphone with K3U power module. These calls were also used in the study of Ryan & Rand (2003b).…”

On the distinctive call of a threatened phenotype of Allobates femoralis (Anura: Aromobatidae) and its recognition by allopatric conspecific males

“…duration, bandwidth, peak frequency) of elements that constitute the acoustic signal, or more obvious shifts in composition of elements of call repertoire (Bee et al, 2001;Ryan & Rand, 2003;Boul et al, 2007;Guerra & Ron, 2008;Rodríguez et al, 2010). Although intraspecifi c variation of discrete elements occurs to some extent among acoustic signals of sympatric males of Neotropical anurans (e.g., Guerra & Ron, 2008;, fi xed diff erences have also been reported among allopatric groups of individuals, and these diff erences have been generally attributed to evolutionary eff ects of isolation by distance or vicariance, potentially reinforced by sexual selection (Boul et al, 2007;Guerra & Ron, 2008;Amézquita et al, 2009).…”