PS 40-115
Fire salamander developmental plasticity facilitates virulent pathogen transmission and persistence
Risk of pathogen extinction can be avoided by exploiting multiple life stages of a primary host, adopting alternative hosts, or by utilizing life history strategies that enable environmental persistence outside of a host. Furthermore, the ecological setting can also provide opportunities for virulent pathogens and highly susceptible hosts to coexist. In amphibians, different cohorts of larvae can temporally overlap in the same environment, offering pathogens the opportunity to be transmitted across age classes. The role that delayed maturation of larvae stages has in pathogen maintenance is uncertain. The fire salamander (Salamandra salamandra) commonly delays metamorphosis and overwinters in rearing sites with permanent water, whereas in ephemeral sites they are obligated to complete metamorphosis within a season. In Central Spain, the lethal amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd) infects S. salamandra larvae and causes post-metamorphic mortality. We conducted a comparative study of Bd infection dynamics in larvae from multiple populations of S. salalmandra in Peñalara Natural Park, Spain. We used qPCR to estimate Bd infection intensity of field collected larvae (total N= 364), and addressed whether infection in cohorts of new larvae was predicted by the presence of overwintered larvae, and whether this interaction varied among permanent and ephemeral breeding sites.
Results/Conclusions
Overall, we found that the highest prevalence of Bd infection was associated with permanent rearing sites and the presence of overwintered larvae, while ephemeral rearing sites had no Bd infection. In addition, among permanent rearing sites mean Bd infection prevalence was higher in ponds (62%) than in streams (5%). Disease incidence varied over the course of the season and between larval stages, with an increase in prevalence of infection in the new year larval stage in permanent rearing sites. Our results show that intraspecific infection with Bd can be maintained without alternative hosts, and that interactions between different larval age classes can contribute to the maintenance of the infection within populations over time. This can, in turn, influence host population persistence and recovery. Our results also suggest that when developing strategies for mitigating pathogens in nature we should think carefully about the species and life stages on which we will focus our efforts.