We surveyed four spring sites of the Edwards Aquifer to determine current distribution and abundance of spring and cave-adapted invertebrates, including three that are federally listed as endangered. We found 18 species from 12 families of endangered and stygobiontic fauna, similar to other surveys completed 10 years prior, and recorded new localities for Tethysbaena texana, Cirolanides texensis, Lirceolus hardeni, Lirceolus smithii, Stygobromus longipes, Stygobromus flagellatus, and Artesia subterranea. We also report discovery of new species of Bogidiellidae (near Parabogidiella), Ingolfiella, and Almuerzothyas. Resumen Examinamos cuatro sitios de nacimento de aguas del acuífero Edwards para determinar las distribuciones y abundancias de invertebrados adaptados a manantiales y cuevas, incluyendo 3 especies que están en peligro de extinción a nivel federal. Encontramos 18 especies de 12 familias de fauna estigobiónticas parecidas a muestreos realizados hace 10 años. Reportamos nuevas localidades para Tethysbaena texana, Cirolanides texensis, Lirceolus hardeni, Lirceolus smithii, Stygobromus longipes, Stygobromus flagellatus y Artesia subterranea. Tambien reportamos el descubrimento de nuevas especias de Bogidiellidae (similar a Parabogidiella), Ingofiella y Almuerzothyas.

The Edwards Aquifer and related Edwards-Trinity Aquifer of Central Texas, USA, is a global hotspot of stygobiont biodiversity. We summarize 125 years of biological investigation at the San Marcos Artesian Well (SMAW), the best studied and most biodiverse groundwater site (55 stygobiont taxa: 39 described and 16 undescribed) within the Edwards Aquifer Groundwater Ecosystem. Cluster analysis and redundancy analysis (RDA) incorporating temporally derived, distance-based Moran’s Eigenvector Mapping (dbMem) illustrate temporal dynamics in community composition in 85 high-frequency samples from the SMAW. Although hydraulic variability related to precipitation and discharge partially explained changes in community composition at the SMAW, a large amount of temporal autocorrelation between samples remains unexplained. We summarize potential mechanisms by which hydraulic changes can affect community structure in deep, phreatic karst aquifers. We also compile information on 12 other Edwards and Edwards-Trinity Aquifer sites with 10 or more documented stygobionts and used distance-based RDA to assess the relative influences of distance and site type on three measures of β-diversity. Distance between sites was the most important predictor of total dissimilarity and replacement, although site type was also important. Species richness difference was not predicted by either distance or site type.

A new stygobitic groundwater amphipod species, Stygobromus bakerisp. nov., is described from 4 central Texas limestone karst springs; John Knox Spring (Comal County), Jacob’s Well (Hays County), Mormon Spring (Travis County) and Salado Springs (Bell County). This species belongs to the predominately western Nearctic hubbsi species group of Stygobromus and differs from other species in the group by gnathopod 1 with row of 4 to 5 setae posterior to the defining angle, pereopods 6 and 7 with broadly expanded bases and distinct distoposterior lobes, gnathopods 1 and 2 with 2 rows of 3 singly inserted setae on the inner palm, and uropod 3 with single, slightly distal peduncular seta. Habitat, sympatric groundwater species, and conservation issues are discussed.

There are eight described species in Phreatodrobia, minute, phreatic (subterranean aquatic) snails, all stygobitic and endemic to the Edwards-Trinity Aquifer System of Texas. Two species were described from river drift (Pilsbry & Ferriss 1906) and the others more recently by sampling the water flowing from wells or springs (Hershler & Longley 1986b; Hershler & Longley 1987). Recent sampling from spring orifices and the hyporheic zone of streams have extended the known ranges of the phreatic snails of the region and encountered unknown snails (Alvear et al. 2020). Here we describe Phreatodrobia spica n. sp., a rarely encountered species with a large range of about 400 km (Figure 1). We find P. spica in samples with a diverse assemblage of phreatic animals including other species of Phreatodrobia, isopods, amphipods, coleopterans, and mites. Phreatodrobia spica is distinguished from congeners using morphological and molecular evidence and is characterized by an elevated, trochiform shell with unique sculpture that include spikes and pustules. It has an open umbilicus and a complete, reflected lip that is sometimes appressed to the body whorl.

A phylogenetic analysis of Hydroporinae (Coleoptera; Dytiscidae) is conducted with emphasis on placement of the North American subterranean diving beetles Psychopomporus felipi Jean, Telles & Miller, Ereboporus naturaconservatus Miller, Gibson & Alarie, and Haedeoporus texanus Young & Longley. Analyses include 49 species of Hydroporinae, representing each currently recognized tribe except Carabhydrini Watts. Data include 21 characters from adult morphology and sequences from seven genes, 12S rRNA, 16S rRNA, cytochrome c oxidase I, cytrochrome c oxidase II, histone III, elongation factor Iα, and wingless. The combined data were analyzed using parsimony and mixed-model Bayesian tree estimation, and the combined molecular data were analyzed using maximum likelihood. Less inclusive branches (genera, genus-groups, and tribes) are well-supported under each criterion, but relationships among tribes are not. These branches are short, poorly supported and in conflict among the estimation methods. Because of certain anomalous relationships in the parsimony and likelihood results, and greater consistency of the Bayesian results with morphological data, this is our preferred phylogenetic estimate. Haedeoporus Young & Longley is related to Neoporus Guignot, Heterosternuta Guignot, and other members of the Hydroporus-group of genera of Hydroporini sensu lato. Psychopomporus Jean, Telles & Miller and Ereboporus Miller, Gibson & Alarie are nested within the Graptodytes-group of genera of Hydroporini sensu lato, and are the only North American members of this otherwise Mediterranean group. Congruent results between optimality criteria indicate that Hydroporini sensu lato is conspicuously non-monophyletic.

The adult and larva of Typhloelmis Barr, a new genus of eyeless, stygobiontic elmid from springs in west-central Texas, and the adults of three new species, Typhloelmis caroline Barr, Typhloelmis finegan Barr, and Typhloelmis sanfelipe Barr, are described, diagnosed, and illustrated. Taxonomic couplets are provided for the insertion of the new genus into existing adult elmid generic keys, and an adult key to the species of Typhloelmis is included. Stygobiontic elmids are reviewed, and the uniqueness of Typhloelmis is discussed. Typhloelmis is the first stygobiontic elmid genus reported from the Nearctic ecozone and is the seventh described worldwide. It is only the second elmid genus known to be anophthalmic (completely eyeless). The Edwards-Trinity Aquifer and the spring habitat in which the genus and species occur are described in detail, and potential threats are discussed.