Bromeligenous anuran species in the Northern Atlantic forest: bromeliad selection and assessment of Batrachochytrium dendrobatidis infection

Abstract

The chytrid fungus, Batrachochytrium dendrobatidis (hereafter Bd), is a pathogen that infects amphibians and may cause amphibian mass die-offs and populations declines in some regions. This disease was described from dying anurans from Australia and Panama in 1999. For almost a decade, the chytrid was thought to be genetically homogenous with a virulent strain (Bd-GPL) distributed worldwide. However, recent discoveries of chytrid ancient lineages, endemism, constant prevalence, oldest records and apparently non-declining populations suggest that the Atlantic forest might be the local of its origin. High diversity and endemism of many taxa occur in the Atlantic forest, and both amphibian and bromeliad diversity are not an exception. Tank bromeliads seem to be an ideal microhabitat for the chytrid fungus: many anuran species are bromeliad-dependent to complete their life cycle and bromeliad water reservoirs may help chytrid fungus to endure environmental constraints. A qPCR assay for detecting Bd in anurans was used to quantify the presence and infection loads of Bd. Specifically, three bromeligenous anurans in the Estação Ecológica de Murici, Alagoas State, Brazil were tested for Bd. Furthermore, bromeliad characteristics (phytotelm water temperature and pH, canopy closure, phytotelm diameter, leaf number and size, bromeliad maximum column depth to store water, phytotelm relative water volume) were measured and associated with Phyllodytes edelmoi occurrence. We performed a Logistic Generalized Linear Model (GLM) approach to analyze bromeliad variables selected by P. edelmoi adults, presence of tadpoles and the chytrid presence. Current knowledge on B. dendrobatidis in north Atlantic forest was added. Specifically, three bromeligenous species (Phyllodytes acuminatus, P. edelmoi, and P. gyrinaethes) tested positive for Bd. High prevalence on two of those species (P. edelmoi 31.8 % n=22; P. gyrinaethes 20.8 % n=24) were detected. Nevertheless, relative low intensity of zoospores infection was found. Phyllodytes edelmoi individuals selected smaller diameter bromeliads with more leaves and relative more volume of water. The chytrid presence was more frequent on individuals that inhabit smaller bromeliads with maximum capacity to store water. Bromeliad traits chosen by this bromeligenous frog showed that P. edelmoi optimum microhabitat may be related to a higher probability of presence of the chytrid fungus due to the higher number of individuals that prefer this trait.