A new Pristimantis (Anura: Strabomantidae) of the P. unistrigatus species group from open ombrophilous forests of Southwestern Amazonia

In the present study, we describe a new species of Pristimantis inhabiting open ombrophilous forests of Southwestern Amazonia. We describe this new species combining mitochondrial (16S and COI) and nuclear (RAG1) loci, external morphology, bioacoustic and natural history data. The new species is phylogenetically related to other Southwestern Amazonian lowland species of the P. unistrigatus species group (P. croceoinguinis, P. lirellus, P. okmoi and P. carvalhoi).

It differs from its closest relatives mainly by its body size (male SVL of 17.7–20.4 mm, n = 29; female SVL of 24.6–26.5 mm, n = 2) and the presence of tympanum, extensive tuberculation (i.e., scapular, ulnar, heels, tarsal and eyelid tubercles), tarsal folds and dentigerous processes of vomers. Moreover, the new species differentiates from its relatives by presenting a yellow groin and gray iris, and by its two types of advertisement calls, consisting of either by a single-note call with duration of 130–254 ms, with three well-defined harmonics, or in three-note call with duration of 421–459 ms, with a single harmonic.

The new species is very inconspicuous in its natural habitat due to its small body size, dull coloration, low intensity call, short call activity at dusk (lasting about 20 minutes) and shy behavior. Although open ombrophilous forests of Southwestern Amazonia are still poorly studied, recent studies have revealed a great number of undescribed anuran species under their canopy. Concerningly, the region is the main western route for the expansion of the Amazonian arc of deforestation, which strongly threatens endemic amphibians.