Molecular analyses of pseudoscorpions in a subterranean biodiversity hotspot reveal cryptic diversity and microendemism

Nested within the Mediterranean biodiversity hotspot, the Dinaric Karst of the western Balkans is one of the world's most heterogeneous subterranean ecosystems and renowned for its highly diverse and mostly endemic fauna. The evolutionary processes leading to both endemism and diversity remain insufficiently understood, and large-scale analyses on taxa that are abundant in both subterranean and surface habitats remain infrequent. Here, we provide the first comprehensive molecular study on Croatian pseudoscorpions, a lineage of arachnids that is common and diverse in both habitats. Phylogenetic reconstructions using 499 COI sequences derived from 128 morphospecies collected across the Dinaric Karst show that: (i) occurrence in karstic microhabitats boosters speciation and endemism in the most diverse genera Chthonius C.L. Koch, 1843 (37 morphospecies) and Neobisium Chamberlin, 1930 ( 34 morphospecies), (ii) evidence for ongoing diversification is found in many species and species complexes through low optimal thresholds (OTs) and species delineation analyses, and (iii) landscape features, such as mountain ranges, correlate with patterns of genetic diversity in the diverse genus Neobisium. We present two synonymies: Protoneobisium Curcic, 1988 = Neobisium, syn. nov., and Archaeoroncus Curcic and Rada, 2012 = Roncus L. Koch, 1873, syn. nov. Overall, our study suggests that karstic microhabitats promote diversification in soil- and cave-dwelling arthropods at all taxonomic levels, but also provide important refugia for invertebrates in past and present periods of environmental change.

Automated summary

Croatian pseudoscorpions, a common and diverse lineage of arachnids, exhibit both diversity in karstic microhabitats and surface habitats. The discovery of karstic microhabitats enhances speciation and endemism in Croatian pseudoscorpions, providing important refugia for invertebrates in past and present periods of environmental change.