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.

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.

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.

A new subterranean species of Anillinus Casey (Carabidae, Trechinae, Anillini) from Florida

A new species of blind subterranean ground beetle in the genus Anillinus Casey is described from Florida. Anillinus albrittonorumsp. nov. (type locality: 6 miles NW High Springs, Columbia County, Florida) has a unique structure of female genitalia and occupies an isolated position within the genus. This new species is illustrated with images of the habitus, body parts, and male and female genitalia. Relationships of A. albrittonorum to other members of the genus are discussed.

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)

Background Mitochondrial 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. Results We 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. Conclusions Our 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.

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 kilometers 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.

Three new subterranean species of Baezia (Curculionidae, Molytinae) for the Canary Islands

The genus Baezia Alonso-Zarazaga & García, 1999 is endemic to the Canary Islands, where four species were known to date. Based on morphological evidence, three new species of Baezia are described in this study: Baezia aranfaybo García & López, sp. nov. from El Hierro island, and Baezia madai García & Oromí sp. nov. and Baezia tizziri García & Andújar, sp. nov. from La Palma island. Notes on their biology, habitat, and distribution are presented. The number of taxa in this endemic Canarian genus increases to seven eyeless species. One species has been reported from the soil (endogean environment), with the other six associated with caves and the mesovoid shallow substratum (hypogean or subterranean environment). Frequent association with the presence of roots suggests that species of Baezia may inhabit the continuum represented by the endogean and hypogean environments. Identification key to the seven species are provided.

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

(1) 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(2) 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 represent 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 lab experiments.(3) 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.(4) Our over-arching goal is to promote caves as model systems where one can perform standardised 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.