Predictors of abundance of a rare bromeliad-dwelling frog (Crossodactylodes itambe) in the Espinhaço Mountain Range of Brazil

Although tank bromeliads are used by many anuran species, bromeligenous frogs (species strictly dependent on bromeliads for reproduction) occur less frequently and are poorly understood. Crossodactylodes are small frogs confined to bromeliads where they lay their eggs and complete their life cycle without leaving the plant. The genus comprises five species and there is little information on their natural history. We focused on Crossodactylodes itambe – a species confined to a single summit of <0.5 km2 at 1700 m above sea level in the Espinhaço Mountain Range of Brazil. We surveyed frogs in 75 individual bromeliads during two consecutive years and we used a Generalized Linear Model to investigate the drivers of species abundance related to habitat structure and local climate. We recorded 446 adults, 267 tadpoles and 40 juveniles over the two years. Most bromeliads contained one adult frog and the mean number of tadpoles was 2-3. The structure of bromeliads influenced species abundance more than local climate. We found that bromeliad size, volume of central tank, and presence/absence of invertebrates and water influenced abundance of frogs. Abundance increased in larger bromeliads at higher elevation. Changes in the structure and size of bromeliads might therefore affect abundance. We provide the first species assessment and evaluation of threat categories for this poorly known species.