Acoustics of parental and hybridogenetic water frogs (Pelophylax: Amphibia: Ranidae): a tool for monitoring an invasive species

Abstract

The Pelophylax genus comprises two main hybridogenetic systems resulting from hybridization between Pelophylax ridibundus and other species: the P. lessonae-esculentus (LE) system and the P. perezi-grafi (PG) system, whose distribution ranges lie partly (LE) or entirely (PG) outside the natural distribution of P. ridibundus. The introductions and subsequent expansions of P. ridibundus in many areas naturally inhabited by these hybridogenetic systems have led to their decrease or local extinction. One of the major impediments to efficient population surveys and conservation measures for these systems is the difficulties of reliable species identification due to their similar morphology and poorly documented vocalizations, especially for the PG system. Our aim in this work was to design a reliable method of acoustic identification to distinguish the taxa composing the hybridogenetic systems from P. ridibundus and to assess the possibility of separating the PG and LE systems by their vocalizations. Our acoustic identification methods proved highly accurate to separate the PG and LE systems from P. ridibundus but only a fraction of the PG and LE calls can be identified.