The southern Appalachian Mountains in eastern North America host exceptional diversity, a substantial proportion of which has been generated in place. Yet, beyond broad generalities, bio- and phylogeographical patterns, and the temporal scale of diversification in the region are poorly resolved. Using one mitochondrial and one nuclear marker, we analyze intraspecific diversity patterns in a flightless, litter-inhabiting rove beetle Dasycerus carolinensis Horn. Our goals were to reconstruct the phylogeographical history of this species, producing a dated intraspecific phylogeny, and to examine previous hypotheses of possible cryptic divergence across populations of the species. Samples derive from a mix of old-growth fragments and secondary growth forests, and we also ask whether old-growth remnants host a larger proportion of genetic diversity in the species. We recover a strong primary subdivision among major lineages across the French Broad River basin (dated to ~5.8 MYBP), and a secondary subdivision among western populations dating to ~4.5 MYBP. Most interpopulation uncorrected divergences exceed 5%, strongly suggesting cryptic differentiation. Old-growth populations do not show greater genetic diversity than secondary-growth populations, indicating that most populations have persisted through recent anthropogenic disturbance.

Developing systematic conservation plans depends on a wealth of information on a region's biodiversity. For ‘dark taxa' such as arthropods, such data are usually very incomplete and in most cases left out from assessments. Sky islands are important and often fragile biodiversity hotspots. Southern Appalachian high‐elevation spruce–fir forests represent a particularly threatened sky‐island ecosystem, hosting numerous endemic and threatened species, but their arthropods remain understudied. Here we use voucher‐based megabarcoding to explore genetic differentiation among leaf‐litter arthropod communities of these highlands, and to examine the extent to which they represent dispersed communities of more or less coherent species, manageable as a distributed unit. We assembled a dataset comprising more than 6000 COI sequences representing diverse arthropod groups to assess species richness and sharing across peaks and ranges. Comparisons were standardised across taxa using automated species delimitation, measuring endemism levels by putative species. Species richness was high, with sites hosting from 86 to 199 litter arthropod species (not including mites or myriapods). Community profiles suggest that around one fourth of these species are unique to single sky islands and more than one third of all species are limited to a particular range. Across major taxa, endemicity was lowest in Araneae, and highest in neglected groups like Isopoda, Pseudoscorpionida, Protura and Diplura. Southern Appalachian sky islands of spruce–fir habitat host significantly distinct leaf‐litter arthropod communities, with high levels of local endemicity. This is the first work to provide such a clear picture of peak and range uniqueness for a taxonomically broad sample. Ensuring the protection of a sizeable fraction of high‐elevation litter species richness will therefore require attention at a relatively fine spatial scale.

Previous analyses have revealed deep divergences among populations of the relictual and enigmatic rove beetle, Dasycerus carolinensis Horn. New data from additional populations, molecular markers, and morphology unambiguously reveal this “species” to represent a complex of closely related species, distinguishable by characters of the male genitalia and corresponding closely to geographically coherent clades discovered by molecular analyses. Calibrated dating analyses show Appalachian Dasycerus to have been diverging in the region for more than 10 million years, yet largely respecting important biogeographic barriers in the region, such as the French Broad and Little Tennessee River drainages. In addition to discussing finer scale biogeographic patterns in the group, we formally recognize 9 new species from within what was formerly known as Dasycerus carolinensis: Dasycerus virginiensis sp. nov., Dasycerus tuckasegee sp. nov., Dasycerus pacolet sp. nov., Dasycerus chattooga sp. nov., Dasycerus itseyi sp. nov., Dasycerus unicoi sp. nov., Dasycerus nikwasi sp. nov., Dasycerus egwanulti sp. nov., and Dasycerus gadalutsi sp. nov. It was not, however, possible to assign all samples to one of these species, and specimens from some sparsely sampled outlying areas, northern Alabama and central Tennessee in particular, may represent additional species.

HorologionValentine, one of the rarest and most enigmatic carabid beetle genera in the world, was until now known only from the holotype ofHorologion speokoitesValentine, discovered in 1931 in a small cave in West Virginia. A single specimen of a new species from Virginia was collected in 1991, but overlooked until 2018. DNA sequence data from specimens of this new species,Horologion hubbardisp. nov., collected in 2022 and 2023, as well as a critical examination of the external morphology of both species, allow us to confidently placeHorologionin the supertribe Trechitae, within a clade containing Bembidarenini and Trechini. A more specific placement as sister to the Gondwanan Bembidarenini is supported by DNA sequence data. Previous hypotheses placingHorologionin or near the tribes Anillini, Tachyini, Trechini, Patrobini, and Psydrini are rejected. The existence of two species ofHorologionon opposite sides of the high mountains of the middle Appalachians suggests that these mountains are where the ancestralHorologionpopulations dispersed from, and predicts the discovery of additional populations and species. All specimens ofH. hubbardiwere collected in or near drip pools, and most were found dead, suggesting that the terrestrial epikarst, rather than caves, is the true habitat ofHorologion, which explains their extreme rarity since epikarst has not been directly sampled. We recognize the tribe Horologionini, a relict lineage without any close relatives known in the Northern Hemisphere, and an important part of Appalachian biodiversity.

Thirteen new species of Euconnus Thomson (Staphylinidae: Scydmaeninae: Glandulariini) are described from the southern Appalachian Mts, USA: Euconnus megalopssp. nov., E. vexillussp. nov., E. cumberlandussp. nov., E. vetustussp. nov., E. adversussp. nov., E. astrussp. nov., E. cultellussp. nov., E. falcatussp. nov., E. cataloocheesp. nov., E. kilmerisp. nov., E. dracosp. nov., E. tusquiteesp. nov., and E. attritussp. nov. These share a number of morphological characters with the Old World subgenus Cladoconnus Reitter, representing a diversification of species distinct from anything previously known from the western hemisphere. Most of the species occur at higher elevations, some at the tops of the region’s highest mountains, and a few are single-peak endemics. No females of these species are winged, and in several species neither sex is winged. A preliminary phylogeny suggests the wingless species represent a clade within a clade of wing-dimorphic species.