Subterranean Species Research Articles

A Hotspot of Arid Zone Subterranean Biodiversity: The Robe Valley in Western Australia

Knowledge of subterranean fauna has mostly been derived from caves and streambeds, which are relatively easily accessed. In contrast, subterranean fauna inhabiting regional groundwater aquifers or the vadose zone (between surface soil layers and the watertable) is difficult to sample. Here we provide species lists for a globally significant subterranean fauna hotspot in the Robe Valley of the Pilbara region, Western Australia. This fauna was collected from up to 50 m below ground level using mining exploration drill holes and monitoring wells. Altogether, 123 subterranean species were collected over a distance of 17 km, comprising 65 troglofauna and 58 stygofauna species. Of these, 61 species were troglobionts and 48 stygobionts. The troglofauna occurs in small voids and fissures in mesas comprised mostly of an iron ore formation, while the stygofauna occurs in the alluvium of a river floodplain. The richness of the Robe Valley is not a localized aberration, but rather reflects the richness of the arid Pilbara region. While legislation in Western Australia has recognized the importance of subterranean fauna, mining is occurring in the Robe Valley hotspot with conditions of environmental approval that are designed to ensure species persistence.

Isolation and endemism in subterranean aquatic snails: unexpected case of Montenegrospeum bogici (Pe\u0161i\u0107 et Gl\xf6er, 2012) (Gastropoda: Truncatelloidea: Hydrobiidae)

The subterranean aquatic snails may serve as a model of endemism and isolation vs. migration in subterranean habitats. The aim of the present paper is to verify the hypothesis that subterranean aquatic snails can migrate through diverse subterranean habitats, applying four molecular markers as well as a RAPD technique and shell morphometry. They were used to estimate the differences and gene flow between populations of the hydrobiid subterranean aquatic species Montenegrospeum bogici, collected in the Dinaric karst region. Three molecularly distinct taxonomic units were distinguished. The mOTU B was found at single locality, mOTU C at two, but the mOTU A at ten localities, scattered along 236 km distance, at two of them in sympatry with either mOTU B or C. Within mOTU A, the estimated levels of the gene flow were high. The pairwise measures of genetic differentiation were statistically significantly associated with geographic distances between the populations. In general, neither the infinite-island model of interpopulation differentiation, expected for isolated populations, nor the stepping-stone one, but rather the isolation-by-distance model explained the observed pattern. Our results suggest that interstitial habitats provide ways of migration for the stygobiont M. bogici, as has been already suggested for other subterranean gastropods.

No room for males in caves: Female-biased sex ratio in subterranean amphipods of the genus Niphargus.

Sex allocation theory predicts that the proportion of daughters to sons will evolve in response to ecological conditions that determine the costs and benefits of producing each sex. All else being equal, the adult sex ratio (ASR) should also vary with ecological conditions. Many studies of subterranean species reported female-biased ASR, but no systematic study has yet been conducted. We test the hypothesis that the ASR becomes more female-biased with increased isolation from the surface. We compiled a data set of ASRs of 35species in the subterranean amphipod Niphargus, each living in one of three distinct habitats (surface-subterranean boundary, cave streams, phreatic lakes) representing an environmental gradient of increased isolation underground. The ASR was female-biased in 27 of 35species; the bias was statistically significant in 12species. We found a significant difference in the ASR among habitats after correction for phylogeny. It is most weakly female-biased at the surface-subterranean boundary and most strongly female-biased in phreatic lakes. Additional modelling suggests that the ASR has evolved towards a single value for both surface-subterranean boundary and cave stream-dwelling species, and another value for 9 of 11 phreatic lake dwellers. We suggest that a history of inbreeding in subterranean populations might lower inbreeding depression such that kin selection favours mating with siblings. This could select for a female-biased offspring sex ratio due to local mate competition among brothers. The observed patterns in sex ratios in subterranean species make them a group worthy of more attention from those interested in sex allocation theory.

The Towakkalak System, A Hotspot of Subterranean Biodiversity in Sulawesi, Indonesia

The Towakkalak System located in the Maros karst of South Sulawesi is currently the richest of Southeast Asia in obligate subterranean species. It comprises several caves and shafts that give access to the subterranean Towakkalak river as well as many unconnected fossil caves, stream sinks, and springs located within its footprint. The total length of the caves linked to the active system is 24,319 m and comprises two of the longest caves of Indonesia, Gua Salukkan Kallang and Gua Tanette. Studies of its fauna began in 1985. There are 10 stygobionts and 26 troglobionts that are known from the system. The smaller adjacent system of Saripa has 6 stygobionts and 18 troglobionts, of which 1 and 3, respectively, are absent from Towakkalak. Like all tropical cave inventories, our dataset has limits due to identification uncertainties, gaps in habitat (waters, guano) and taxonomic coverage (micro-crustaceans, mites), sampling methods (pitfall trapping, Karaman–Chappuis), and problems of ecological assignment. A number of additional species are therefore expected to be found in the future. The Towakkalak and Saripa cave systems are included in the Bantimurung-Bulusaraung National Park and are under efficient protection, but parts of the Maros karst outside the park are under serious threat, mainly from quarrying.

The structure and importance of nest mounds in a tropical ant Diacamma indicum

1. Nest mounds are an integral part of many subterranean insect species, and they aid in thermoregulation, gaseous exchange, and flood prevention. Ants living in subterranean nests are prone to nest flooding particularly during monsoons and this will impact the colonies' fitness.2. Diacamma indicum is a tropical Ponerine ant species that lives in simple, single‐chambered nests with a single entrance. In this study, we characterised the mound architecture and performed field experiments to check functional significance of mounds.3. On examining mound architecture (n = 19 nests), we found that mounds not only elevated the nest entrance by 3.39 cm on average, but they also made the entrance at the top of the mound significantly smaller than the nest entrance at the base of the mound. Both these features are likely to reduce rainwater from falling directly into the nest's entrance tunnel.4. Upon performing partial (n = 18 nests) and complete destruction (n = 20 nests) in two different seasons, colonies were observed to actively rebuilt mounds to pre‐destruction levels within 3 days in all cases.5. Furthermore, examining the amount of water that entered the nest upon flooding in the presence and absence of mounds (n = 18 colonies) revealed that mounds prevented a minimum of 29.2% of water from seeping into the nest from the surrounding area, as mounds could act as a levee. This study highlights the active architectural adaptations to flooding by an organism that dwells in subterranean nests in a tropical habitat.

Ambient Temperature as a Strong Zeitgeber of Circadian Rhythms in Response to Temperature Sensitivity and Poor Heat Dissipation Abilities in Subterranean African Mole-Rats.

Mammals have evolved circadian rhythms in internal biological processes and behaviors, such as locomotor activity (LA), to synchronize to the environmental conditions they experience. Photic entrainment of LA has been well established; however, non-photic entrainment, such as ambient temperature (Ta), has received much less attention. To address this dearth of knowledge, we exposed two subterranean endothermic-homeothermic African mole-rat species, the solitary Cape mole-rat (Georychus capensis [GC]) and social Mahali mole-rat (Cryptomys hottentotus mahali [CHM]), to varying Ta cycles in the absence of light. We showed that the LA rhythms of these two species entrain to Ta cycles and that the majority of LA occurred during the coolest 12-h period. LA confined to the coolest Ta periods may be the direct consequence of the poor heat dissipation abilities of African mole-rats brought about by physiological and ecological constraints. Recently, it has been hypothesized that Ta is only a strong zeitgeber for circadian rhythms in species whose thermoregulatory abilities are sensitive to changes in Ta (i.e., heterotherms and ectotherms), which previously has excluded endothermic-homeothermic mammals. However, this study demonstrates that Ta is a strong zeitgeber or entrainer for circadian rhythms of LA in subterranean endothermic-homeothermic mammals as a consequence of their sensitivity to changes in Ta brought about by their poor heat dissipation abilities. This study reinforces the intimate link between circadian rhythms and thermoregulation and conclusively, for the first time, provides evidence that Ta is a strong zeitgeber for endothermic-homeothermic mammals.

Cave amphipods reveal co‐variation between morphology and trophic niche in a low‐productivity environment

Abstract Identifying the relationships between morphology and trophic niche is at the core of functional morphology. Low resource diversity and fluxes of organic carbon are expected to constrain trophic specialisation of morphological structures because food resources are too scarce to promote trophic differentiation. However, species from low‐productivity habitats often exhibit specialised biological traits such as resistance to starvation and high food‐finding abilities, which may in turn release constraints on trophic and morphological differentiation among species. Groundwaters are food resource‐limited because of the lack of photosynthetic production and limited inputs of organic carbon from surface ecosystems. We tested for co‐variation between morphology and trophic habits in co‐occurring Niphargus amphipods from five groundwater caves of the Dinaric Karst, Europe. We predicted that the size of gnathopods—the accessory feeding appendages—would positively co‐vary with trophic position: species with larger gnathopods should more easily grab and immobilise prey. We quantified gnathopod size and shape by means of morphometric measurements and assessed isotopic niche, trophic position, and carbon signatures using nitrogen (δ15N) and carbon (δ13C) stable isotopes. We tested for correlation between morphological traits and trophic position and δ13C signatures while accounting for phylogenetic relationships among species. All co‐occurring species differed morphologically in at least one gnathopod measurement and all of them differed in their isotopic niches. As predicted, gnathopod size increased with the increasing trophic position. This co‐variation probably reflects differences in detritivorous and predatory habits among species: amphipods with larger gnathopods, hence larger muscle and more powerful grip, could more easily subdue prey. Moreover, we found a significant correlation between gnathopod shape and the normalised δ13C values, indicating that shape of the gnathopods may be related to exploitation of different food resources. We show that low‐productivity subterranean habitat species can exhibit strong trophic specialisation of morphological structures. Gnathopod size and shape of Niphargus amphipods are functional traits that co‐vary with trophic habits. Our findings pave the way for investigating how co‐variation of morphological and trophic traits may control energy flow and species’ coexistence at lower bounds of habitat productivity.

Undara Lava Cave Fauna in Tropical Queensland with an Annotated List of Australian Subterranean Biodiversity Hotspots

The lava tubes at Undara became internationally recognised in the late 1980s, when 24 species of terrestrial cave-adapted invertebrates (troglobionts) were recorded from Bayliss Cave, making it one of the 20 richest known cave communities in the world at the time. Over the last decades, several of the Undara species have been taxonomically described and a great deal of research has been undertaken in other parts of Australia, which has revealed additional subterranean hotspots. It is therefore timely to update the list of Undara cave fauna, and to evaluate the Undara cave system in relation to other subterranean hotspots in Australia. The updated species list was compiled from the published literature and museum databases. Minimally, 78 species of arthropods have been recorded from 17 lava tube caves in the Undara Basalt. Sixteen species have been taxonomically described; 30 identified to genus and/or morpho-species; and 32 remain unidentified to species or genus level. Thirty troglobionts and one stygobiont species were recorded. Seven caves harboured obligate subterranean species; Bayliss Cave harboured the most obligate subterranean species: 23 troglobionts and one stygobiont. All these caves contained deep zone environments with high humidity, of which three also contained ‘bad air’ (CO2). The unique combination of geomorphic structure and environmental parameters (high humidity) and multiple energy sources (tree roots, bats and guano, organic material wash-in) are the main factors responsible for Bayliss Cave’s extraordinary local richness. Further research is needed to investigate CO2 as a factor influencing troglobiont richness and distribution in ‘bad air’ caves. Undara remains the richest subterranean hotspot in humid tropical Australia; however, significantly richer subterranean assemblages are found in arid and semi-arid calcrete aquifers, karst and iron-ore terrains, mostly in Western Australia.

The joint effect of micro- and macro-climate on the thermoregulation and heat dissipation of two African mole-rat (Bathyergidae) sub-species, Cryptomys hottentotus mahali and C. h. pretoriae.

The effect of the macro- and microclimate on small mammal thermoregulation in the past has been studied independently instead of investigating the dual effect of both the components. This study addresses this dearth in knowledge by exploring the dual effect of both micro- and macro-climate on the thermoregulatory responses of two subterranean rodent species belonging to the family Bathyergidae, namely the more arid dwelling Mahali mole-rat (Cryptomys hottentotus mahali) and less arid dwelling Highveld mole-rat (C. h. pretoriae). Open flow through respirometry was used to quantify resting metabolic rates (RMR), evaporative water loss (EWL), core body temperature (Tb), the ratio between the evaporative heat loss and metabolic heat production (EHL/MHP: evaporative cooling capacity) and conductance (Cdry) over a range of increasing ambient temperatures (Ta; 20-42°C). Furthermore, RMR, EWL, Tb, EHL/MHP and Cdry were measured at the mole-rat's thermal maxima (43°C). At cooler temperatures, the arid-dwelling C. h. mahali possesses a broader thermoneutral zone (~5°C; 27.2-32.1°C), while C. h. pretoriae possess a single thermoneutral point (33.6°C). This is in response to the greater selection pressure to conserve energy in the more arid regions inhabited by C. h. mahali. Contrastingly, at hotter temperatures, there were no significant thermoregulatory differences in EWL, EHL/MHP or Cdry responses between the two sub-species, as expected due to the limitations bestowed by the buffered microclimates (burrow systems). Thus, neither macro-climate, nor micro-climate singularly moulds the thermoregulatory adaptations, but rather, it appears to be a combined effect from both climates. Other small endotherms may share this dual response, and therefore, it is crucial to incorporate the effect of both macro- and microclimates into future climate models when determining the ecological capabilities and persistence of a species.

ECOLOGIA DE PEIXES DE RIACHOS DE CAVERNAS E OUTROS HABITAT SUBTERRÂNEOS

Brazil is rich in caves, with more than 20,000 officially registered. In addition to the caves, which develop in different types of rock, there are other subterranean habitats (hypogean) with bodies of water in the form of drainages (level base streams), outcrops of the water table (saturated zone) in flooded caves or in the form of pools and lakes within caves, in addition to upper aquifers formed by infiltration of water in the rock. In some cases, groundwater does not emerge in caves, but in alluviums close to rivers, representing a hyporeic zone. The Brazilian subterranean ichthyofauna is composed of fish restricted to caves and other subterranean habitats (generally categorized as troglobites / stygobites) or species that have well-established populations in these habitats, but which also occur in streams and bodies of water on the surface (categorized as troglophilics). Currently, there are more than 80 species of fish with troglobitic and troglophilic populations in Brazil. Some population studies show estimates of varying population sizes and densities, generally characterized by small populations; a tendency towards a sedentary lifestyle; low condition factor values and life cycle strategies tending to K within the r-K continuum. These characteristics are related to the unique abiotic conditions of these habitats, such as low, infrequent and often unpredictable supply of nutrients, which can represent an accentuated filter. In relation to conservation, subterranean fish are threatened and most of the species formally described are included in lists of threatened fauna in Brazil. Only four species have been included and evaluated globally (Stygichthys typhlops, Pimelodella kronei, Phreatobius cisternarum and Phreatobius sanguijuela).

Caecidotea burkensis, new species, a unique subterranean isopod from Burke’s Garden, with a synthesis of the biogeography and evolution of southwestern Virginia asellids

Caecidotea burkensis, a new species of subterranean asellid isopod, is described and illustrated from material collected from Lawson Cave, in Burke’s Garden, Tazewell County, Virginia. The type-locality in Burke’s Garden is located within the highest mountain basin in the southern Appalachians. Burke’s Garden is a unique, geologically isolated area encompassing one of the headwater streams of the New River basin. Phylogenetically, the isopod is a member of the forbesi Group, a clade comprised primarily of epigean species. The complex mountain valleys and coves of southwestern Virginia are an area of intense speciation among asellids that have produced a bizarre array of cavernicolous species belonging to groups of otherwise epigean isopods. In addition to a few subterranean species of the Caecidotea cannula and stygia Groups, the Lirceus hargeri Group possesses over a dozen species endemic to caves and springs in the region, mostly only now in the process of being discovered and described. With so much species richness, syntopy of two, or even three, asellid species is commonplace in caves and springs in southwestern Virginia.

Mesofauna at the Soil-Scree Interface in a Deep Karst Environment

The community patterns of Collembola (Hexapoda) were studied at two sites along a microclimatically inversed scree slope in a deep karst valley in the Western Carpathians, Slovakia, in warm and cold periods of the year, respectively. Significantly lower average temperatures in the scree profile were noted at the gorge bottom in both periods, meaning that the site in the lower part of the scree, near the bank of creek, was considerably colder and wetter compared to the warmer and drier site at upper part of the scree slope. Relatively high diversity of Collembola was observed at two fieldwork scree sites, where cold-adapted species, considered climatic relicts, showed considerable abundance. The gorge bottom, with a cold and wet microclimate and high carbon content even in the deeper MSS horizons, provided suitable environmental conditions for numerous psychrophilic and subterranean species. Ecological groups such as trogloxenes and subtroglophiles showed decreasing trends of abundance with depth, in contrast to eutroglophiles and a troglobiont showing an opposite distributional pattern at scree sites in both periods. Our study documented that in terms of soil and subterranean mesofauna, colluvial screes of deep karst gorges represent (1) a transition zone between the surface and the deep subterranean environment, and (2) important climate change refugia.

Searching for signatures of positive selection in cytochrome b gene associated with subterranean lifestyle in fast-evolving arvicolines (Arvicolinae, Cricetidae, Rodentia)

BackgroundMitochondrial genes encode proteins involved in oxidative phosphorylation. Variations in lifestyle and ecological niche can be directly reflected in metabolic performance. Subterranean rodents represent a good model for testing hypotheses on adaptive evolution driven by important ecological shifts. Voles and lemmings of the subfamily Arvicolinae (Rodentia: Cricetidae) provide a good example for studies of adaptive radiation. This is the youngest group within the order Rodentia showing the fastest rates of diversification, including the transition to the subterranean lifestyle in several phylogenetically independent lineages.ResultsWe evaluated the signatures of selection in the mitochondrial cytochrome b (cytB) gene in 62 Arvicolinae species characterized by either subterranean or surface-dwelling lifestyle by assessing amino acid sequence variation, exploring the functional consequences of the observed variation in the tertiary protein structure, and estimating selection pressure. Our analysis revealed that: (1) three of the convergent amino acid substitutions were found among phylogenetically distant subterranean species and (2) these substitutions may have an influence on the protein complex structure, (3) cytB showed an increased ω and evidence of relaxed selection in subterranean lineages, relative to non-subterranean, and (4) eight protein domains possess increased nonsynonymous substitutions ratio in subterranean species.ConclusionsOur study provides insights into the adaptive evolution of the cytochrome b gene in the Arvicolinae subfamily and its potential implications in the molecular mechanism of adaptation. We present a framework for future characterizations of the impact of specific mutations on the function, physiology, and interactions of the mtDNA-encoded proteins involved in oxidative phosphorylation.

The Subterranean Fauna of Križna Jama, Slovenia

The karstic cave Križna jama in the South Western part of Slovenia is one of the largest, well known and most beautiful Slovene water caves. The cave consists of more than 8 km of corridors with impressive halls, colossal dripstone formations, a subterranean river and numerous lakes. Considering the subterranean fauna, Križna jama has been identified amongst the richest caves in the world. So far, 60 troglobionts, the obligate subterranean species among them 32 aquatic and 28 terrestrial taxa have been recorded and documented. Križna jama has scientific importance, as well as ten subterranean taxa, which have been described based on specimens from this cave. Despite Križna jama is relatively well-studied, new recent unexpected findings are promising. Thus, further discoveries of specialized subterranean species in the cave are expected.

Vibratory behaviour produces different vibration patterns in presence of reproductives in a subterranean termite species

Vibratory behaviours are widespread in social insects, but the produced vibrations remain poorly explored. Communication using vibrations is an efficient way to transmit information in subterranean environments where visual and odorant signals are less efficient. In termites, different vibratory behaviours are performed in different contexts like reproductive regulation and alarm signalling, but only few studies explored the structure of the produced vibrations (i.e., duration, number of pulses, amplitude). Here, we described several types of vibrations produced by a vibratory behaviour widespread in termites (body-shaking), which can be transmitted through the substrate and detected by other colony members. We analysed the structures of the emitted vibrations and the occurrence of the body-shaking events in presence/absence of reproductives and/or in presence/absence of a stress stimuli (flashlight) in the subterranean termite Reticulitermes flavipes. Interestingly, only the presence of the reproductives did influence the number of pulses and the duration of the emitted vibrations. Moreover, the first part of the emitted vibrations seems to be enough to encode reproductive information, but other parts might hold other type of information. Body-shaking occurrence did increase in presence of reproductives but only briefly under a flashlight. These results show that vibratory cues are complex in termites and their diversity might encode a plurality of social cues.

Ojo Guareña: A Hotspot of Subterranean Biodiversity in Spain

Ojo Guareña Natural Monument in Burgos (Spain) is an important and large karstic system. It consists of more than 110 km of surveyed galleries, and it has rich sources of organic material from the surface and permanent water circulation. It is the fourth largest cave system in the Iberian Peninsula, and one of the 10 largest in Europe. Ojo Guareña also ranks 23rd among the world’s largest caves. To date, only volcanic caves in the Canary Islands, in which between 28 and 38 subterranean species occur, are considered subterranean diversity hotspots in Spain. Here, we provide the first list of subterranean taxa present in Ojo Guareñ, which is comprised of 54 taxa that includes 46 stygobiotic and eight troglobiotic species (some still unidentified at the species level), revealing Ojo Guareña as the largest known subterranean biodiversity hotspot in Spain and Portugal. In addition, we provide a list of an additional 48 taxa, 34 stygophiles and 14 troglophiles, found in the system, whose ecological status could change with detailed biological studies, which may change the number of strictly subterranean species present in the system. Indeed, at present, these numbers are provisional as they correspond to a small part of this sizeable cave system. The biodiversity of large areas of the system remains unknown as these areas have yet to be explored from the biological point of view. In addition, a large number of samples of both terrestrial and aquatic fauna are still under study by specialists. Furthermore, evidence of cryptic species within Bathynellacea (Crustacea) indicates an underestimation of biodiversity in the karstic system. Despite these limitations, the data available reveal the typical uneven distribution of subterranean aquatic fauna, and suggest that the great heterogeneity of the microhabitats in this wide and highly connected karstic extension led to the great richness of aquatic subterranean species.

Collecting eco-evolutionary data in the dark: Impediments to subterranean research and how to overcome them.

Caves and other subterranean habitats fulfill the requirements of experimental model systems to address general questions in ecology and evolution. Yet, the harsh working conditions of these environments and the uniqueness of the subterranean organisms have challenged most attempts to pursuit standardized research.Two main obstacles have synergistically hampered previous attempts. First, there is a habitat impediment related to the objective difficulties of exploring subterranean habitats and our inability to access the network of fissures that represents the elective habitat for the so‐called “cave species.” Second, there is a biological impediment illustrated by the rarity of most subterranean species and their low physiological tolerance, often limiting sample size and complicating laboratory experiments.We explore the advantages and disadvantages of four general experimental setups (in situ, quasi in situ, ex situ, and in silico) in the light of habitat and biological impediments. We also discuss the potential of indirect approaches to research. Furthermore, using bibliometric data, we provide a quantitative overview of the model organisms that scientists have exploited in the study of subterranean life.Our over‐arching goal is to promote caves as model systems where one can perform standardized scientific research. This is important not only to achieve an in‐depth understanding of the functioning of subterranean ecosystems but also to fully exploit their long‐discussed potential in addressing general scientific questions with implications beyond the boundaries of this discipline.

Isolation of Microsatellite Markers from De Novo Whole Genome Sequences of Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae)

Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae) is a subterranean termite species from Southeast Asia which has been unintentionally introduced to many parts of the world through commerce and modern transportation. Known for causing extensive damage to timber used in the built environment, the termite also has a habit of nesting in carton nests in wood and wooden structures in buildings. As so little is known of its breeding system, colony, and genetic structure, we initiated work to sequence its genome with an Illumina HiSeq™ 2000 sequencer. In this publication, we announce our paired-end sequencing data and report the isolation of 119,190 microsatellite markers from our DNA assembly. The microsatellite marker reported in this publication can be used to elucidate the mating system and genetic structure of this highly invasive termite species. Additionally, in this announcement the study authors make the Bio Project sequence accession number SRR13105492 accessible from the Sequence Read Archive database.

Dynamic spatial overlap in a solitary subterranean rodent: the Anillaco tuco-tuco (Ctenomys sp.)

Abstract Despite striking diversity in mammalian social behavior, studies of social organization have often dichotomized species by identifying them as either solitary or social (i.e., group living). This tendency has been particularly pronounced for subterranean rodents, the majority of which have long been assumed to be solitary. As a result, variation in social organization has likely been underestimated for these animals, particularly for species in which patterns of space use suggest limited or temporally dynamic opportunities for interactions among conspecifics. Here, we characterize patterns of space use in a population of tuco-tucos (Ctenomys sp.) from Anillaco, La Rioja Province, Argentina. Although these animals have been the subject of extensive research regarding circadian patterns of activity, spatial and social relationships among free-living individuals have not been documented. Analyses of radiotelemetry data from 17 individuals monitored during the breeding season (December 2015) revealed that partial overlap of individual home ranges was common, occurring between male–female as well as female–female pairs of animals. Spatial relationships, however, were dynamic, with both home range sizes and overlap changing on a daily basis. Although members of the study population did not meet the criteria typically used to identify group living in subterranean species, they were not completely solitary. Instead, the animals displayed an intermediate form of social organization characterized by persistent partial overlap of the areas occupied by different adults. These data add to the growing comparative picture of social variation in Ctenomys and suggest that further studies of these animals should contribute to improved understanding of the factors underlying differences in mammalian social systems.

Using expert knowledge to support Endangered Species Act decision-making for data-deficient species.

Many questions relevant to conservation decision‐making are characterized by extreme uncertainty due to lack of empirical data and complexity of the underlying ecologic processes, leading to a rapid increase in the use of structured protocols to elicit expert knowledge. Published ecologic applications often employ a modified Delphi method, where experts provide judgments anonymously and mathematical aggregation techniques are used to combine judgments. The Sheffield elicitation framework (SHELF) differs in its behavioral approach to synthesizing individual judgments into a fully specified probability distribution for an unknown quantity. We used the SHELF protocol remotely to assess extinction risk of three subterranean aquatic species that are being considered for listing under the U.S. Endangered Species Act. We provided experts an empirical threat assessment for each known locality over a video conference and recorded judgments on the probability of population persistence over four generations with online submission forms and R‐shiny apps available through the SHELF package. Despite large uncertainty for all populations, there were key differences between species’ risk of extirpation based on spatial variation in dominant threats, local land use and management practices, and species’ microhabitat. The resulting probability distributions provided decision makers with a full picture of uncertainty that was consistent with the probabilistic nature of risk assessments. Discussion among experts during SHELF's behavioral aggregation stage clearly documented dominant threats (e.g., development, timber harvest, animal agriculture, and cave visitation) and their interactions with local cave geology and species’ habitat. Our virtual implementation of the SHELF protocol demonstrated the flexibility of the approach for conservation applications operating on budgets and time lines that can limit in‐person meetings of geographically dispersed experts.