Call variation and vocalizations of the stealthy litter frog <em>Ischnocnema abdita</em> (Anura: Brachycephalidae)

Ischnocnema abdita is a small-sized litter frog belonging to the I. verrucosa species series and only known for mountainous areas of southeastern Espírito Santo State, Brazil, in the Municipalities of Santa Teresa (type locality), Cariacica and Mimoso do Sul. In this paper, we describe the calls and provide estimates of within-male variation of I. abdita from its type locality and from a recently discovered population in the region of Alto Caparaó, Municipality of Espera Feliz, Minas Gerais State, Brazil. Additionally, we also performed a GMYC analysis of molecular assignment that recovered the haplotypes of I. abdita from its type locality and from the new record (Alto Caparaó) under the same taxonomical entity. Our bioacoustical analysis revealed two distinct types of calls, herein referred as A and B calls. The A call was observed in both populations, whereas the B call was only recorded at Alto Caparaó. Despite the apparent similarity in the A calls from both localities, we observed differences in all traits analyzed. Moreover, each call trait expressed variation within males. The peak frequency never exceeded 5% variation and it was classified as static in both populations. Temporal parameters, such as call duration and interval between calls were classified either as dynamic or intermediate, with variations ranging from 1.8-66.1% within males. Although number of pulses per note was a dynamic trait at the type locality, it did not vary in both types of call recorded at Alto Caparaó.