Green, charismatic, microendemic, and threatened: breeding biology of the leaf frog Pithecopus rusticus (Anura: Hylidae: Phyllomedusinae)

Abstract

ABSTRACT Pithecopus rusticus is a small and charismatic leaf frog species known only from the type locality, in the Brazilian Subtropical Highland Grasslands of the Atlantic Forest, southern Brazil. In this study, we describe aspects of the reproductive biology and populational size of P. rusticus, encompassing the characterization of breeding season, microhabitat use for vocalization and spawning, the variation in body size of males and females and operational sex ratio, as well as explore the influence of climate variables on the abundance of individuals. We collected information from 2015 to 2021, mainly in the breeding seasons of 2015/16 and 2017/18. We recorded 91 individuals of P. rusticus, with a recapture rate of 61% in the 2015/16 breeding season and 57% in the 2017/18 breeding season. The estimated population size was 28.9 individuals for the 2015/16 breeding season and 21 individuals for the 2017/18 breeding season. The temporal reproductive pattern was intermediate, being concentrated in spring to early summer months (October to January), and the male calling activity differed throughout the night, increasing from 9pm onwards. The abundance of P. rusticus was significantly related with relative air humidity. We found sexual size dimorphism, with females larger than males, and a male-skewed operational sex ratio. Males and females used Poaceae and Cyperaceae leaves located close to water. Spawns contained 43 ± 5 eggs, with a diameter of 3.26 ± 0.45 mm, and were deposited on leaves of Senecio (Asteraceae) and Eriocaulon (Eriocaulaceae). Information on natural history is essential to support the implementation and success of in situ and ex situ conservation strategies for this endangered species.