The Tadpole, Bioacoustics, Natural History, Morphological Variation, and Conservation of Isthmohyla debilis (Hylidae: Hylinae: Hylini)

Abstract

The description of the tadpole of Isthmohyla debilis by Duellman (1970) revealed a distinctive morphology that deviated from closely related stream-breeding species within the I. tica group in several important aspects, including the size of the oral disc, configuration of submarginal papillae on both labia, body shape, and jaw sheath morphology. These character states complicated the identification of phenotypic synapomorphies for the clade composed by I. debilis, I. rivularis, I. tica, and tentatively, I. pictipes and I. xanthosticta. We collected adults and tadpoles of I. debilis in the Reserva Forestal Fortuna, western Panama. Our findings indicate that the previously described tadpoles assigned to I. debilis were misidentified and likely correspond to the Panamanian lineage associated with I. lancasteri. We show that the larvae of I. debilis indeed share all the character states present in their closely related species, including a depressed body with a sloping snout and an enlarged oral disc that is nearly as wide as the body, deep angular folds, complete marginal papillae, three or more rows of submarginal papillae in the upper and lower labia, an M-shaped upper jaw sheath and LTRF 2/3, with complete tooth rows. Moreover, we provide information on vocalizations, natural history, and adult coloration patterns across the known geographic range of I. debilis. Additionally, we report a currently extant population of I. debilis from Boquete, western Panama, complementing a previous, tentative record of the species from the same area.