Disentangling the cave centipede Lithobius stygius species complex through molecular phylogenetics and redescription of L. stygius s. str.

Distinguishing species is fundamental for obtaining reliable biological insights, yet due to their morphological similarity many species remain undetected until molecular methods are employed. This work uncovers species diversity in the caves of the Dinaric Karst (Europe), shedding light on the understudied cave centipedes. We focus on the taxonomically challenging species Lithobius stygius Latzel, 1880, the first scientifically described cave centipede from the Balkans. Multi-locus phylogeny and uni-locus species delimitation based on extensive sampling revealed that many morphologically and ecologically similar populations previously reported as L. stygius belong to at least five clades, consisting of numerous molecular operational taxonomic units. We propose some taxonomic changes, including reinstating species Lithobius luciani (Folkmanová, 1935) and Lithobius intermedius Folkmanová, 1946. By providing a detailed redescription of L. stygius based on the type and new material, addressing morphological variability, and providing reliable molecular characterization, we set the baseline for further investigations of taxa concealed under the name L. stygius. The species complex represents an interesting case for the study of its evolutionary history, indicating possible multiple cave colonizations. Although disentangling the species complex requires an appropriate molecular and morphological framework, it is invaluable for reliable species identification and recognition of true species diversity.