A tale of two species: recent discovery of a cryptic leopard frog species from the New York City region

Background/Question/Methods

Here, we review the recent discovery and pending taxonomic description of a previously undescribed leopard frog (genus Rana [=Lithobates]). This species was first detected in the New York City metropolitan area and is morphologically similar to two regional congeners; the southern leopard frog (R. sphenocephala) and northern leopard frog (R. pipiens). This new and currently unnamed species remained undocumented until recently despite occupying one of the most heavily developed and well-inventoried regions on earth. Its long-term concealment and recent elucidation from this part of the world is both intriguing and illustrative of the potential for new species discoveries even in locales rarely associated with undocumented vertebrate biodiversity or endemism. This discovery also carries several potential conservation concerns and implications. The new species was initially elucidated in a previous study through molecular methods; we follow here in the present study with bioacoustic and morphological comparisons between closely related taxa. We also examine differences in behavioral ecology.

Results/Conclusions

Our results reveal a species that is acoustically distinct from all other closely related species. The primary (‘advertisement’) call exhibits a single-noted, unpulsed structure that is unique compared to its congeners, all of which have pulsed calls that are easily distinguished in a waveform display. The new species also exhibits at least one apparent patterning diagnostic, and other potential diagnostic features warrant additional investigation. We also found differences in behavioral ecology, in terms of both breeding activity and habitat use, between the new species and its most morphologically similar congener, R. sphenocephala, the species within which it was formerly included.