The primary objective of the December 2019 expedition was to investigate arboreal species and other carabids that overwinter under bark or at the base of tree trunks, habitat structures that have been largely neglected in previous surveys. Conducted from December 9 to 19, the team visited 28 localities across central and eastern Georgia, ranging from the low-lying Alasani floodplain to high-altitude spruce stands near Bakuriani. The survey aimed to contribute to a new checklist of Georgian ground beetles and to enhance the ecological knowledge base for the country’s main natural areas. By focusing on winter quarters, the researchers sought to capture species that are difficult to detect during the active summer months, providing a more comprehensive picture of the local fauna.

The methodology employed during the excursion was tailored to the specific behaviors of overwintering beetles. Researchers primarily loosened and examined parts of bark and moss at the base of trunks, typically up to a height of 1.5 meters, using insect aspirators to capture individuals hiding between bark layers. In some instances, larger detached pieces of bark and moss were sifted on white cloth or through beetle sieves. The team also investigated soil substrates and litter close to the trunks, as well as other habitat structures such as reed beds, dead wood, and grassland ecotones. Although the survey was not standardized by plot size or time, at least one hour of collecting was conducted by two people at each location, ensuring a thorough assessment of the available microhabitats.

The results of the expedition were substantial, with 227 specimens recorded at 22 of the 28 investigated localities, leading to the identification of 43 taxa at the species or subspecies level. Among these, nine species were found to be new records for Georgia, significantly expanding the known faunistic range of the country. These new records include the arboreal Dromius agilis, the plant-dwelling Demetrias imperialis, and Paradromius suturalis, along with six other species from the genera Microlestes and Pterostichus. The discovery of these species underscores the importance of winter surveys in detecting species that aggregate in specific microhabitats during hibernation, such as under moss or between bark scales.

One of the most notable findings was the presence of Dromius agilis, a European and Siberian-distributed species previously unrecorded in Georgia. The researchers found this species at five locations, exclusively on conifers such as Caucasian fir, pine, and spruce, at altitudes above 1200 meters. The individuals observed were monochromatic red-brown to brown, a coloration that differs from many central European specimens but aligns with descriptions of the taxon formerly known as Dromius caucasicus. The abundance of Dromius agilis increased with altitude, suggesting a preference for cooler and moister conditions. This finding highlights the specific ecological niches occupied by arboreal beetles in the Georgian landscape, where they hibernate in the lower trunk areas after their summer activity phase.

Another significant new record was Demetrias imperialis, a Turano-European species found in a shallow siltation zone with a well-structured reed bed at Lake Bazaleti. This species, which is mostly absent in northern Europe, was previously recorded in the Greater Caucasus but had not been mentioned for Georgia in recent checklists. Its discovery in a semiarid landscape type indicates the adaptability of certain carabid species to diverse environmental conditions. Similarly, Paradromius suturalis, a transpalaearctic species, was found sympatric with Demetrias imperialis at the same location. The habitat of Paradromius is described variably in the literature, ranging from river floodplains and wetlands to mesophilous forests, but its presence in the reed belt of Lake Bazaleti adds to the understanding of its ecological flexibility in the Caucasus region.

The genus Microlestes also yielded several new records, including Microlestes corticalis, M. fissuralis, M. fulvibasis, and M. luctuosus. These species were found in dry grassland and steppe-like habitats, particularly at sites near Lake Kumisi and the salt lake at Jvari Monastery. The determination of these species relied heavily on the examination of genitalia, specifically the aedeagus and paramers, which were prepared using standard taxonomic techniques involving maceration in potassium hydroxide and embedding in a water-soluble medium. The presence of multiple Microlestes species in a single dry grassland site at Lake Jvari demonstrates the high species richness and potential for cryptic diversity in these habitats. These findings emphasize the need for detailed morphological analysis to accurately identify species that may appear similar externally.

In addition to the new species records, the study provided insights into the winter behavior of ground beetles in Georgia. The number of specimens detected under bark or in litter was often low, likely due to specific climatic conditions such as very low humidity. It is hypothesized that in these areas, most individuals reside deeper in the soil during periods of low activity or hibernation. The research also highlighted the importance of using diverse survey methods, as different species occupy different microhabitats. For instance, while Dromius species were found under bark, Syntomus and Olisthopus were more abundant in grassland sites, and Carabus varians was found in cells under loose bark of dead logs. This variability underscores the necessity of a multi-faceted approach to faunistic studies, combining hand catching, sieving, and bark peeling to capture the full spectrum of species present.

The implications of this study extend beyond mere taxonomic updates; it provides a foundation for future conservation and ecological planning in Georgia. The identification of new species and the documentation of their habitats contribute to the ongoing effort to create a comprehensive checklist of Georgian ground beetles. The collaboration between international researchers and local institutions, such as Ilia State University, ensures that the findings are integrated into the broader scientific community. Furthermore, the study highlights the value of winter excursions in revealing aspects of beetle ecology that are invisible during the summer. As surveys are set to resume from 2023 onwards, with further winter trips planned, the data collected will continue to refine the understanding of biodiversity in the Southern Caucasus, a region of immense ecological significance.

Subject of Research: Ground beetles (Coleoptera, Carabidae) from a winter excursion to Georgia, Southern Caucasus ecoregion

Article Title: Ground beetles ( Coleoptera , Carabidae ) from a winter excursion to Georgia, Southern Caucasus ecoregion

Article References: Trautner, J., Fritze, M.-A., Schröter, A., & Chaladze, G. (2023). Ground beetles (Coleoptera, Carabidae) from a winter excursion to Georgia, Southern Caucasus ecoregion. Caucasiana, 2, 113-125. https://doi.org/10.3897/caucasiana.2.e102280

Image Credits: AI Generated

DOI: 10.3897/caucasiana.2.e102280

Keywords: Ground, beetles, Coleoptera, Carabidae, winter, excursion, Georgia, Southern, Caucasus, ecoregion, scientific research