Johnstone’s whistling frog outside Prague: A report on the distribution and historical spread of Eleutherodactylus johnstonei (Anura: Eleutherodactylidae) in the Czech Republic

The Caribbean frog Eleutherodactylus johnstonei has been increasingly reported as an introduced species in tropical greenhouses and pavilions of numerous institutions across Europe. Despite this trend, its distribution and ecology in Central Europe remain poorly documented. Here we report its occurrence in eight previously undocumented institutions across the Czech Republic, in addition to earlier records from Prague and Kostelní Lhota. Based on field surveys, curator interviews, and historical records, we reconstructed the introduction history and current distribution of E. johnstonei . All Czech populations originate from Venezuela and were introduced via two independent, human-mediated events in the early 1990s. These populations likely merged in the Fata Morgana greenhouse in Prague, which later served as a source for further spread. The species forms stable populations in tropical facilities, showing nocturnal activity, flexible habitat use, and reduced male vocalization activity under cold conditions. Occasionally, these frogs were also observed outside greenhouses, suggesting potential interactions with native fauna. While E. johnstonei may provide ecosystem services such as invertebrate pest control in the facilities, where it occurs, it also poses biosecurity concerns due to its ability to carry and transmit diverse skin microbiota and fungal pathogens, including Batrachochytrium dendrobatidis . Given these risks, we strongly discourage further deliberate introductions within the Czech Republic and across Europe. We recommend future research focusing on pathogen screening and dietary analysis to better understand the ecological impact of this species in artificial environments. • Eleutherodactylus johnstonei has been surviving for decades in various tropical greenhouses and zoological exhibits within temperate climatic zone of the Czech Republic, outside Prague • E. johnstonei was spread mainly through deliberate introduction but also via tropical plant transports across the Czech Republic • E. johnstonei could pose a serious environmental risk to the local amphibian fauna due to its ability to transmit dangerous pathogens such as the chytrid fungus