First biological data, associated fauna, and microclimate preferences of the enigmatic cave-dwelling beetle Dalyat mirabilis Mateu, 2002 (Coleoptera, Carabidae)

Abstract

Dalyat mirabilis is an extraordinary troglobite carabid described in 2002 from the cave Simarrón II in the southeast of the Iberian Peninsula (Spain). A new subfamily Dalyatinae was erected to accommodate this species with remarkable morphological characters and adaptations to live underground. In addition to the former original descriptions, there is only one more study and it aimed to elucidate its evolutionary history. Its closest living relative belongs to the genus Promecognathus in North America and both groups seem to have diverged sometime in the late Jurassic to early Cretaceous. In this work, the phenology of D. mirabilis, its associated invertebrate fauna and the environmental conditions of the cave Simarrón II were studied for a full year cycle. This carabid is not evenly distributed in the cave, in time or space. It is most abundant during the winter months, wet season, and it disappears from the top layer of the substrate in the summer. A positive correlation was found between the number of carabids captured per trap and the distance to the entrance of the cave; most specimens were captured in traps farthest from the entrance and located in the chamber known as Vias Salas Negras. Furthermore, several spatially-resolved analyses integrating relative humidity, temperature, and the number of captures per trap showed that D. mirabilis prefers Vias Salas Negras for having a higher and more stable relative humidity than other chambers in the cave. Larvae were never captured, regardless of intense efforts to collect them for years. Finally, 30 other invertebrate species belonging to 12 different Orders were captured in the cave and are listed here, 25.8% are troglobites, 29.0% troglophiles and 45.2% troglexenes. The data from this study was used for an initiative to protect this cave and its remarkable fauna. Some of the measures taken by the Administration include the control of human visits to the cave, the installation of a perimetral fence surrounding the entrance, and the installation of an informative panel at the exterior of the cave describing the endemic entomological fauna it contains.