Hybridization in the Diploid-Tetraploid Treefrogs Hyla chrysoscelis and Hyla versicolor

Gerhardt, H. Carl; Ptacek, Margaret B.; Barnett, Louise K.; Torke, Kenneth G.

doi:10.2307/1446670

Cited by 45 publications

(33 citation statements)

References 20 publications

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“…Such an error would be biologically costly if females were to make it in nature due to low hybrid viability (Johnson, 1963). While our experimental set-up did not mimic the natural spatial distributions of signals and noise in real choruses (e.g., Schmidt and Römer, 2011), we would note that female gray treefrogs sometimes (though quite infrequently) make the mistake of mating with males of the wrong species in natural settings (Gerhardt et al, 1994). We suggest that in particularly dense, mixed-species choruses, high levels of background noise and acoustic clutter might contribute to these rare but costly mate choice errors (Bee, 2008; Marshall et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

Spatial release from masking improves sound pattern discrimination along a biologically relevant pulse-rate continuum in gray treefrogs

2013

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Frogs form large choruses during the mating season in which males produce loud advertisement calls to attract females and repel rival males. High background noise levels in these social aggregations can impair vocal perception. In humans, spatial release from masking contributes to our ability to understand speech in noisy social groups. Here, we tested the hypothesis that spatial separation between target signals and ‘chorus-shaped noise’ improves the ability of female gray treefrogs (Hyla chrysoscelis) to perform a behavioral discrimination task based on perceiving differences in the pulsatile structure of advertisement calls. We used two-stimulus choice tests to measure phonotaxis (approach toward sound) in response to calls differing in pulse rate along a biologically relevant continuum between conspecific (50 pulses s−1) and heterospecific (20 pulses s−1) calls. Signals were presented in quiet, in colocated noise, and in spatially separated noise. In quiet conditions, females exhibited robust preferences for calls with relatively faster pulse rates more typical of conspecific calls. Behavioral discrimination between calls differing in pulse rate was impaired in the presence of colocated noise but similar between quiet and spatially separated noise conditions. Our results indicate that spatial release from energetic masking facilitates a biologically important temporal discrimination task in frogs. We discuss these results in light of previous work on spatial release from masking in frogs and other animals.

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Section: Discussionmentioning

confidence: 99%

Spatial release from masking improves sound pattern discrimination along a biologically relevant pulse-rate continuum in gray treefrogs

2013

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“…In contrast, H. versicolor reportedly does not occur as far south in Indiana as the populations where Morris and Yoon (1989) studied H. chrysoscelis , though the two species do occur in relatively close proximity (e.g., ≤ 75 km) and the precise distributions of the two species in the state are still somewhat poorly known (Minton 1972, 2001). One hypothesis for the pattern of results depicted in Figure 4 is that in H. chrysoscelis , female selectivity favoring about average or higher-than-average calls in Minnesota and Missouri has evolved in response to selection against costly hybrid matings (Gerhardt et al 1994) with H. versicolor. To the extent that Morris and Yoon’s (1989) populations in Indiana have been historically isolated from contact with H. versicolor , females in their study may pay little or no costs associated with choosing heterospecific males with low-frequency calls and instead receive whatever benefits might accrue from mating with larger conspecific males.…”

Section: Discussionmentioning

confidence: 99%

Female preferences for spectral call properties in the western genetic lineage of Cope's gray treefrog (Hyla chrysoscelis)

Schrode

Ward

Vélez

et al. 2012

Behav Ecol Sociobiol

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Female frogs discriminate among potential mates based on individual variation in male advertisement calls. While considerable data have accumulated allowing comparisons of female preference functions among species, we still lack fundamental knowledge about how and why the shapes of preference functions for particular call properties vary among populations within all but a few species. Here, we report results from a study aimed at describing female preference functions for spectral call properties in Cope’s gray treefrog (Hyla chrysoscelis). Widespread throughout the eastern half of North America, Cope’s gray treefrog is the diploid member of the cryptic diploid-tetraploid Hyla versicolor species complex, and its populations are divided into two distinct genetic lineages (eastern and western). In this study of a western lineage population, we recorded and analyzed the spectral properties of 1000 advertisement calls from 50 males and conducted two-choice phonotaxis experiments to estimate a population-level preference function. Females preferred calls with average frequencies over calls with frequencies that were 2 or 3 semitones (1.4 or 2.1 standard deviations, respectively) lower than the population mean. We observed no behavioral discrimination between calls with average and higher-than-average frequencies. Preferences discriminating against low-frequency calls were weak and were abolished by attenuating the preferred average call by 3 dB. We discuss these results in light of previous studies of eastern lineage populations, geographic variation in female preference functions, and the potential adaptive value of discriminating against calls with low frequencies.

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“…Evidence from field studies indicates such errors sometimes do, in fact, occur in nature. In mixed-species choruses of the two gray treefrogs, H. chrysoscelis and H. versicolor , for example, females occasionally mate with a male of the wrong species, a mistake that results in infertile or inviable offspring (Gerhardt et al, 1994). Chorus noise can also increase the time females require to choose a mate and decrease the directness of the path she takes to approach him, thereby increasing potential exposure to various predators in the natural environment (Caldwell and Bee, submitted).…”

Section: Brief Primer On Frog Hearingmentioning

confidence: 99%

Treefrogs as animal models for research on auditory scene analysis and the cocktail party problem

Bee

2015

International Journal of Psychophysiology

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The perceptual analysis of acoustic scenes involves binding together sounds from the same source and separating them from other sounds in the environment. In large social groups, listeners experience increased difficulty performing these tasks due to high noise levels and interference from the concurrent signals of multiple individuals. While a substantial body of literature on these issues pertains to human hearing and speech communication, few studies have investigated how nonhuman animals may be evolutionarily adapted to solve biologically analogous communication problems. Here, I review recent and ongoing work aimed at testing hypotheses about perceptual mechanisms that enable treefrogs in the genus Hyla to communicate vocally in noisy, multi-source social environments. After briefly introducing the genus and the methods used to study hearing in frogs, I outline several functional constraints on communication posed by the acoustic environment of breeding “choruses”. Then, I review studies of sound source perception aimed at uncovering how treefrog listeners may be adapted to cope with these constraints. Specifically, this review covers research on the acoustic cues used in sequential and simultaneous auditory grouping, spatial release from masking, and dip listening. Throughout the paper, I attempt to illustrate how broad-scale, comparative studies of carefully considered animal models may ultimately reveal an evolutionary diversity of underlying mechanisms for solving cocktail-party-like problems in communication.

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Hybridization in the Diploid-Tetraploid Treefrogs Hyla chrysoscelis and Hyla versicolor

Cited by 45 publications

References 20 publications

Spatial release from masking improves sound pattern discrimination along a biologically relevant pulse-rate continuum in gray treefrogs

Spatial release from masking improves sound pattern discrimination along a biologically relevant pulse-rate continuum in gray treefrogs

Female preferences for spectral call properties in the western genetic lineage of Cope's gray treefrog (Hyla chrysoscelis)

Treefrogs as animal models for research on auditory scene analysis and the cocktail party problem

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