The power of monitoring: optimizing survey designs to detect occupancy changes in a rare amphibian population.

Biodiversity conservation requires reliable species assessments and rigorously designed surveys. However, determining the survey effort required to reliably detect population change can be challenging for rare, cryptic and elusive species. We used a tropical bromeliad-dwelling frog as a model system to explore a cost-effective sampling design that optimizes the chances of detecting a population decline. Relatively few sampling visits were needed to estimate occupancy and detectability with good precision, and to detect a 30% change in occupancy with 80% power. Detectability was influenced by observer expertise, which therefore also had an effect on the sampling design - less experienced observers require more sampling visits to detect the species. Even when the sampling design provides precise parameter estimates, only moderate to large changes in occupancy will be detected with reliable power. Detecting a population change of 15% or less requires a large number of sites to be surveyed, which might be unachievable for range-restricted species occurring at relatively few sites. Unless there is high initial occupancy, rare and cryptic species will be particularly challenging when it comes to detecting small population changes. This may be a particular issue for long-term monitoring of amphibians which often display low detectability and wide natural fluctuations.

A new species of Crossodactylodes (Anura: Leptodactylidae) from Minas Gerais, Brazil: first record of genus within the Espinhaço Mountain Range.

The genus Crossodactylodes comprises three species of Atlantic Rainforest endemic frogs strictly dependent on bromeliads where they spend their entire life cycle. The current geographic distribution of the genus covers highland areas of Atlantic Rainforest in the States of Rio de Janeiro and Espírito Santo, Southeastern Brazil. We describe a new species of the genus from Parque Estadual do Pico do Itambé, at Santo Antônio do Itambé municipality, State of Minas Gerais, Southeastern Brazil. Crossodactylodes itambe sp. nov. is characterized by the following combination of traits: male SVL 16.2 ± 1.3 (14.0-17.6 mm, n = 10), female SVL 16.2 ± 1.0 (13.5-18.0 mm, n = 15); snout short, rounded in dorsal view, sloping in lateral view; absence of vocal sac and vocal slits in males; absence of vomerine teeth; males with upper arms and forearms hypertrophied; cloacal flap prominent, simple; dorsal skin coarsely granular. The new species inhabits rupicolous bromeliads in open areas of rocky fields, and is recorded in altitudes between 1836 and 2062 m above sea level. This record extends the genus distribution for about 325 km northwest from where it was known. Crossodactylodes sp. nov. is the only species of the genus that occurs in open field habitats (campos rupestres), in very high altitudes of a non-costal mountain range (the Espinhaço Range).