The advertisement call of Hyla intermedia and H. sarda

Abstract

The advertisement calls of two closely related treefrog species, Hyla intermedia and H. sarda were analysed. Calls from seven populations of the former and four populations of the latter were recorded and nine temporal and two spectral acoustic properties were compared. In both species, temporal parameters were influenced by body-temperature, whereas spectral properties were influenced by body-size. Independent of temperature, H. sarda showed longer calls, with a higher number of pulses and higher pulse-rate but with a lower call rate than H. intermedia. Males of H. sarda were smaller than males of H. intermedia and called at higher frequencies, however, differences in call frequency were still significant when the effect of body size was removed. The discriminant function analysis performed on call characters assigned all specimens to the correct species. In allopatry, the advertisement calls of the two species seem to have diverged markedly, and the possibility that these differences may act as a pre-mating barrier in case of future secondary contact is discussed.