Cryptic but direct costs of an epidemic caused by Batrachochytrium dendrobatidis in the endangered Sardinian newt Euproctus platycephalus (Amphibia, Caudata)

Abstract Parasites can directly affect host survival by causing cryptic costs that may occur in species when mortality does not take place or is less evident. Costs can be present in differently life history stages or age cohorts or cause age-dependent effects. Here we investigate the effects of chytridiomycete fungus Batrachochytrium dendrobatidis, (Bd), that causes one of the main infectious diseases implicated in numerous mass mortalities and population declines in the class of Amphibia, including in one of the rarest and most threatened salamander in Europe, the endemic Sardinian brook newt Euproctus platycephalus. This species is known to be infected by Bd since 2006, without evident direct cost or mass mortality events being observed. During 5 years of sampling (2007-2011), we captured 273 newts in the main infected area of the Limbara Mountain in the North of Sardinia, and, through epidemiological and age analyzes, we assess that Bd directly affected juvenile recruitment, and it is related to difficulties in the development of the species, with an impact on the females growth.