Beyond Composition: Network Topology Reveals Batrachochytrium Dendrobatidis -Linked Changes in Salamander Skin Microbiomes

Chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) continues to threaten amphibian biodiversity; however, Bd-associated microbiome signatures in salamanders remain inconsistent across studies. Here, we tested whether Bd detection is linked to shifts in salamander skin bacterial communities and, critically, whether it alters the architecture of microbial associations. We reanalyzed publicly available 16S rRNA amplicon data from Eurycea bislineata, Notophthalmus viridescens, and Desmognathus monticola, comparing Bd-detectable (Bd+) and Bd-non-detectable (Bd−) samples. Standard diversity and compositional analyses (alpha/beta diversity, PERMANOVA) showed no significant Bd-associated differences at broad community scales, and the dominant phyla were conserved across conditions. In contrast, differential abundance approaches (LEfSe and ANCOM-BC) identified the targeted Bd-associated taxa. Network inference and community detection revealed pronounced reorganization of the modular structure, with minimal overlap in module membership between Bd+ and Bd− networks and strong condition-specific turnover in stringent “core” networks. Modularity and robustness patterns were host-dependent and highlighted clearer contrasts between tolerant and susceptible hosts under targeted node removal. Together, these results show that Bd detection may leave the overall composition largely intact while reshaping the microbial association structure, supporting network topology as a sensitive complementary lens for detecting disease-linked community changes in amphibian skin microbiomes.