Torrent frogs have fewer macroparasites but higher rates of chytrid infection in landscapes with smaller forest cover

Abstract

Deforestation can compromise ecological processes and biotic interactions, including the host–parasite relationship. While some parasites infect only one host, others require multiple hosts to complete their complex life cycles. In this context, different parasites may have different demands and traits and may have specific responses to habitat degradation. Here, we tested whether forest cover has different effects on different frogs' parasites, as chytrid (Batrachochytrium dendrobatidis; Bd) and helminths (Platyhelminthes and Nematoda). We collected data on two stream frog species (Crossodactylus caramaschii and Crossodactylus schmidti) from nine sites in the Brazilian Atlantic forest, with forest cover ranging from 20% to 99%. Bd presence and load increased with decreasing forest cover, but the opposite was observed for nematodes. Load of monoxenous and heteroxenous helminths increased with forest cover. We suggest that variations in potential host diversity, microclimate conditions, and host immune response may be responsible for the contrasting patterns found for micro-(Bd) and macroparasites (helminths, except Platyhelminthes). Our work brings evidence of how habitat reduction can affect host–parasite relationships, including infection with the pathogen responsible for hundreds of global species extinctions.