Conservation implications for endangered Euhadra murayamai, restricted to a large-scale limestone cliff: Insights from genome-wide SNP and morphological analyses

Rapid biodiversity loss necessitates accurate taxonomic classification and the definition of conservation units for effective management. Here, we investigated the genetic and morphological distinctiveness of the endangered land snail Euhadra murayamai, endemic to Mt. Myojo, Japan, and its relationship with the closely related species E. quaesita. Genome-wide SNPs from double digest restriction site-associated DNA sequencing (ddRAD-seq) and detailed morphological measurements were obtained. Our analyses revealed clear genetic differentiation between E. murayamai and E. quaesita, challenging previous inferences based solely on mitochondrial markers. Moreover, we detected significant genetic differentiation within E. murayamai populations across low and middle elevations, as evidenced by distinct clustering in fastStructure, a phylogenetic network and principal component analysis, as well as a high FST value. Morphological results aligned with these findings, showing significant differences in shell width and morphology between elevational populations. Approximate Bayesian computation analysis supported a scenario without gene flow after divergence and estimated interspecific divergence at approximately 85,000 generations ago and intraspecific divergence at approximately 35,000 generations ago. These results indicate that limited dispersal and elevational isolation have promoted local adaptation, underscoring the necessity for elevation-specific conservation units. Furthermore, the urgency of incorporating comprehensive genetic and morphological data into conservation planning is emphasised, thereby providing crucial insights for resolving taxonomic uncertainties and guiding effective strategies. Overall, we underscore the importance of integrating high-resolution genetic markers with morphological data to inform conservation strategies for species with restricted distributions and complex evolutionary histories.