Amphibians are suffering dramatic loss of life and one implicated factor is a fungal pathogen Batrachochytrium dendrobatidis (Bd). However, the factors mitigating infection are not well understood. One hypothesis is that skin microbiota influence disease risk. Studies have linked the skin microbiome to disease inhibition, but most have focused on prokaryotic communities and neglected eukaryotes, even though cultivation of host-associated fungi has revealed taxa with the ability to inhibit Bd. Moreover, studies have been limited to species that reside in a limited spatial range. Thus, it is necessary to examine microbial communities within different host assemblages in comparable regions at a global scale.
We aimed to investigate the historical invasion and spread of Bd through two mountain ranges (Pyrenees (PY) and Sierra Nevada (SN)) by swabbing museum specimens and testing for the presence of Bd via extraction and qPCR. Furthermore, the same protocol was used to test for current disease status from swabs taken from wild individuals in varied altitudinal transects in PY, SN, and the Dhofar mountain range in Oman (OM). Using Next Generation Sequencing, we will assess the mitigation potential of cutaneous fungal and bacterial microbiota on Bd in amphibian hosts that inhabit these globally, freshwater mountain ecosystems.
Results/Conclusions
Results of over 1,100 museum samples show invasion of Bd through SN over time, with a sharp increase in prevalence starting in the 1970’s, which peaks at 32% prevalence in samples from the 1980’s. Also, we highlight differences in temporal invasion between Yosemite (YOSE) and Sequoia National Park (SEKI). While disease surveillance detected the arrival of Bd into populations of SEKI in real time, the arrival of Bd in YOSE was not observed, and until now the history of Bd in the region was unknown. The same methods have been used to evaluate museum samples from PY, which speak to the historical Bd invasion of the range.
We have disease results from field data of 2016-2017 in PY, 2017 in OM, and soon to be results from 2018 in SN across host species of those ranges. Analysis of microbiotic life is in the midst of processing. Once finished, further analysis can be made in relation to the two bodies of results, disease and the microbiome, across altitudinal gradients in these ranges around the world. This work is part of a larger body of study that explores common threats to freshwater mountain ecosystems including water pollution, habitat loss, and over exploitation.