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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.

We compared the species composition, relative abundances and life form structure of subterranean Collembola (Hexapoda) captured by two different methods along a depth gradient of five forested scree sites in the Western Carpathians, Slovakia: (1) high-gradient extraction of soil samples, and (2) collection using subterranean traps. Our results showed that the soil samples were more efficient in covering species richness at the majority of the sites. The body size of the captured animals depended remarkably on the sampling method. Extraction was more effective in collecting smaller, less active hemi- and euedaphic forms of Collembola, while collection by subterranean traps favoured both motile ground-dwelling as well as relatively large, active euedaphobionts. Additionally, different trends in the vertical stratification of Collembola life forms and their relative abundances were detected by the two methods. Atmobionts and epigeonts, forming the greater part of the communities in traps compared to soil samples, were distributed along the entire scree profiles, but their relative abundance and species numbers had a strongly decreasing trend with depth. Moreover, motile, large hemi- and euedaphic forms had high relative abundances in traps in the middle and deeper scree levels at three sites. In contrast, in soil samples the hemi- and euedaphobionts with small body size were abundant on the surface of the MSS sites. Thus, soil sampling applied before installation of subterranean traps may serve as an appropriate complementary technique to obtain a more complete pattern of Collembola diversity in forested scree habitats.

IntroductionUsing an integrative taxonomic approach, we investigated the morphological and molecular characters to identify the species of the genus Pseudosinella occurring in caves of the Western Carpathians and to clarify their phylogenetic relationships. Based on morphological characters, we hypothesized that Pseudosinella aggtelekiensis (Stach, 1929) and Pseudosinella paclti (Rusek, 1961) originated from different phyletic lineages.MethodsWe used the barcoding fragment of the mtDNA COI gene from 87 individuals from 16 caves to reconstruct the phylogenetic history of the genus Pseudosinella.ResultsThe molecular phylogenetic tree revealed two distinct species groups with allopatric distributions. The first group consisted of P. aggtelekiensis populations from the Slovak Karst and three undescribed species from fragmented and isolated karst areas in southeastern Slovakia. The second group, P. paclti populations in the Central Western Carpathians, was merged. This group included Pseudosinellamuranensis, a new species taxonomically described in this work. It is characterized by highly developed troglomorphic features and is restricted to a small karst area, the Muranska planina Plateau. The phylogeny of the genus Pseudosinella from the caves of the Western Carpathians revealed a Miocene diversification. According to molecular calibration, the two distinct Pseudosinella lineages were separated in the Middle Miocene, about 14.51 Mya, followed by further diversification in the P. paclti lineage 10.89 Mya and in the P. aggtelekiensis lineage 11.14 Mya.DiscussionThis phylogeny is consistent with the uplift of Triassic limestones during the early formation of the Western Carpathians in the Paratethys region and the initial development of caves during this period. The study provides further important evidence that the Western Carpathians played a significant role as an independent speciation center of the obligate cave fauna in Europe.

The observations from the recent period revealed that the Western Carpathians, a part of the Carpathian mountain chain, is the northernmost region in Europe with the occurrence of the obligate cave fauna. The collembolan genus Pseudosinella Schäffer, 1897 is a polyphyletic taxon derived from the genus Lepidocyrtus Bourlet, 1839 from which it differs in reduced number of eyes. It covers about 350 species with predominantly Holarctic distribution of which about 39% are confined to caves. We studied the morphology and molecular traits to identify cave species of the genus Pseudosinella occupying the Western Carpathian caves and clarify their phylogenetic relationships. Based on morphological traits we hypothesized that Pseudosinella aggtelekiensis (Stach, 1929) and P. paclti Rusek, 1961 are descendants of the different phyletic lineages, the former species lacking morphologically related edaphic species. On the other hand, several species related to P. paclti were found in caves, superficial subterranean habitats and in the soil. Molecular phylogeny analysis has shown two distinct groups of cave species following pattern of allopatric distribution. The first group consisted of populations of P. aggtelekienis from the Slovak Karst and an undescribed species from fragmented and isolated karst in eastern Slovakia. In the second group different populations of P. paclti occupying caves of the central karst regions were incorporated together with a new highly troglomorphic species confined to a small karst area. After an approximate estimate of the geological timing of the species isolation (RelTime), the two distinct Pseudosinella lineages separated approx. 9.54 mya followed by subsequent diversification in P. paclti lineage 8.36 mya, and in P. aggtelekiensis lineage 6.99 mya. This study contributed to assumption that the Western Carpathian Mts played an important role as speciation centre of the obligate cave fauna in Europe.