Multivariate Geographic Variation of Mating Call in Populations of the Pacific Tree Frog (Hyla regilla)

Three major calls characteristic of Hyla regilla are described and categorized as diphasic, monophasic, and possibly, territorial. Tape recordings of 295 calls from 37 geographically isolated populations ranging from Vancouver, British Columbia, to Las Lagunas, Baja California, and from sea level to 7,000 ft elevation, were made. The midpoints of dominant frequencies of the first and second diphase, the first and second diphase durations, interphase duration, total duration, call repetition rate, and water temperature were analyzed. Multivariate statistics (discriminant functions) were used in the analysis. Discrimination tests of 13 gravid female Hyla regilla established the high degree (11 of 13, 85%, P < 0.01) of female response to calls of Hyla regilla rather than to those of Hyla californiae. High correlations between call duration and repetition rates and water temperature were found (P < 0.01); the relationships may be curvilinear. Dominant frequencies were highly correlated with each other (+ 0.82) but showed low although significant correlations with time-dependent characters. The dominant frequency of the first diphase and the snout-vent length of the animal were negatively correlated (r = -0.81; P < 0.01). Vectors of the dominant frequency characters were relatively shorter than other vectors and consistently linear with population dispersion patterns, indicating these characters to be more significantly different between populations than are other characters.