Estimates of genetic diversity and evidence of weak population structure in the range-restricted Jiangxi giant salamander (Andrias jiangxiensis)

The Jiangxi giant salamander ( Andrias jiangxiensis ) is a recently described endemic species restricted to a small montane stream system in the upper Beiliao River, Jiangxi Province, China. Extreme range restriction is generally expected to intensify genetic drift and inbreeding risk and reduce genetic diversity, yet the population genetic status of this species remains poorly understood. We assessed genetic diversity, spatial genetic structure, and demographic signals using 11 microsatellite loci and mitochondrial COI and Cyt b sequences from 49 individuals sampled at two wild localities and one conservation-breeding unit. Microsatellite expected heterozygosity ranged from 0.591 to 0.669 across the three sampling units, whereas mitochondrial haplotype diversity was 0.655 and nucleotide diversity was 0.001313. Wild-only analyses of Beigang (BG) and Daqishan (DQ) revealed weak but statistically detectable nuclear differentiation ( Φ ST = 0.0468, P = 0.0027; F ST = 0.0481), although STRUCTURE and PCoA did not support discrete genetic clustering. No detectable mitochondrial differentiation was found between BG and DQ, and the dominant haplotypes were shared. Tajima’s D was significantly negative in DQ and the pooled wild dataset, whereas Fu’s Fs was non-significant and the sudden-expansion models failed to converge. Together, these results did not provide robust support for a simple sudden-expansion scenario. Microsatellite-based tests detected no recent bottleneck signal, although inference was constrained by the limited number of loci and the small sample size of BG. Overall, A. jiangxiensis retains standing genetic variation across both nuclear and mitochondrial markers despite its extremely restricted distribution. Conservation should prioritize watershed-scale habitat protection, preservation of local genetic composition, careful management of captive breeding and releases, and long-term genetic monitoring.