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

Abstract

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.

Auditory brainstem responses in Cope’s gray treefrog (Hyla chrysoscelis): effects of frequency, level, sex and size

“…We chose frequencies of 1.3 and 2.6 kHz for two reasons. First, they are close to the average frequencies present in the bimodal spectrum of male advertisement calls in our study populations (Schrode et al 2012). Second, according to the “matched filter hypothesis” of anuran hearing (Capranica and Moffat 1983), they are presumed to be encoded primarily by the amphibian papilla (AP) and the basilar papilla (BP), respectively (Hillery 1984b; Gerhardt 2005).…”

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

“…By comparison with H. cinerea , spectral sensitivity and frequency selectivity have been less well studied in H. chrysoscelis and H. versicolor . What information is available for these two species, however, is entirely consistent with general patterns demonstrated for H. cinerea and other frogs (Bee, 2010; Gerhardt, 2005; Gerhardt and Huber, 2002; Gerhardt et al, 2007; Hillery, 1984; Schrode et al, 2012; Schrode et al, in review).…”

Spatial hearing in Cope’s gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations

“…Angles of 0° and 180° correspond, respectively, to the rostral and caudal ends of the midline. All frequencies fell within the audible range of H. chrysoscelis (Hillery 1984; Schrode et al 2014), and frequencies of 1,250 and 2,500 Hz correspond to the two peaks present in the bimodal spectrum of male advertisement calls in our study population (Schrode et al 2012). Signal levels between 76 and 94 dB are within the range of call amplitudes likely experienced in breeding choruses (Gerhardt 1975).…”