Contrasting Responses of Rhizosphere Bacterial and Fungal Communities of Paeonia ludlowii to Habitat Transition.

Habitat transition can reorganize plant-associated microbial communities, yet whether rhizosphere bacteria and fungi respond similarly to the transition from native to introduced habitats remains unclear. Here, we investigated this question in the endangered plant Paeonia ludlowii by comparing rhizosphere bacterial and fungal communities across three native and two introduced sites in Xizang. Both bacterial and fungal communities showed significant site-associated differentiation and strongly concordant spatial patterns. However, their responses differed markedly: bacterial richness remained relatively stable despite compositional turnover, whereas fungal communities showed reduced richness at the Lhasa introduction site, lower OTU sharing among habitats, and significantly greater divergence from native assemblages than bacterial communities. Soil pH and available phosphorus were the environmental variables most consistently associated with differentiation in both microbial groups. These findings demonstrate that rhizosphere bacteria and fungi exhibit concordant spatial differentiation but contrasting responses to habitat transition, with fungal communities showing greater departure from native states. This contrast highlights the importance of considering bacterial and fungal communities jointly when evaluating rhizosphere reorganization during the introduction and ex situ conservation of endangered plants.