Aim
Common species contribute more to species richness patterns (SRPs) than rare species in most studies. Our aim was to test this hypothesis using a novel model system, species living exclusively in ...subterranean habitats. They consist of mainly rare species (small ranges), only a few of them being common (large ranges), and challenge whether rare species are less important for the development of SRPs in this environment. We separately analyzed aquatic and terrestrial species.
Location
Western Balkans in southeastern Europe.
Methods
We assembled two datasets comprising 431 beetle and 145 amphipod species, representing the model groups of subterranean terrestrial and aquatic diversity, respectively. We assessed the importance of rare and common species using the stepwise reconstruction of SRPs and subsequent correlation analyses, corrected also for the cumulative information content of the subsets based on species prevalence. We applied generalized linear regression models to evaluate the importance of rare and common species in forming SRPs. Additionally, we analyzed the contribution of rare and common species in species‐rich cells.
Results
Patterns of subterranean aquatic and terrestrial species richness overlapped only weakly, with aquatic species having larger ranges than terrestrial ones. Our analyses supported higher importance of common species for forming overall SRPs in both beetles and amphipods. However, in stepwise analysis corrected for information content, results were ambiguous. Common species presented a higher proportion of species than rare species in species‐rich cells.
Main Conclusion
We have shown that even in habitats with the domination of rare species, it is still common species that drive SRPs. This may be due to an even spatial distribution of rare species or spatial mismatch in hotspots of rare and common species. SRPs of aquatic and terrestrial subterranean organisms overlap very little, so the conservation approaches need to be habitat specific.
We studied whether species richness patterns develop due to rare or common species, using a novel model system, subterranean species. Subterranean species with extremely high endemism, challenge the view that common species constitute a backbone of species richness patterns. Although subterranean aquatic and terrestrial species differ in degrees of endemism and spatial patterns, our analyses consistently imply that also in such systems common species backbone the patterns.
We tested three hypotheses (productive energy, habitat heterogeneity, historical climate stability) to explain regional species richness patterns in subterranean habitats, which have less ...habitat/climatic variability than surface habitats. For the first time, we investigated the pattern of two species richness hotspots in the world's richest region in subterranean biodiversity in southeast Europe. We used distribution records for 388 species of beetles, the most species rich group of terrestrial subterranean fauna, belonging to subfamilies Trechinae (Carabidae) and Leptodirinae (Cholevidae), and mapped them onto a 20Â ÃÂ 20Â km grid. We applied spatial and nonâspatial multiple regression, using generalised linear models and spatial eigenvector mapping. The relative importance of each hypothesis, and of the spatial versus the environmental components, was assessed with variation partitioning. We analysed the total dataset as well as each subfamily separately. Our results show that although the relative importance of species richness drivers differed among taxonomic groups, in most cases habitat heterogeneity had the biggest influence. It was followed by historical climate stability, while productive energy had a neglecting effect. This proves that even though habitat variability is smaller in subterranean than in surface habitats, its gradient is still strong enough to explain species richness patterns better than the other two hypotheses. Identification of the drivers shaping the two regional species richness hotspots within a global hotspot of highly endemic subterranean fauna is important for conservation practices. Additionally, we contribute to the general understanding of species richness patterns of insects, by providing the first detailed analyses on a regional scale for subterranean systems.
Species richness patterns (SRP) emerge due to overlap in species distributions. They critically depend on two parameters of species ranges: geographic position and size. An important question is ...which species contribute more to the observed SRP, range restricted or widespread species. Most studies concluded that the widespread species tend to influence SRP more. However, the relative importance of either may strongly depend on the study system. Here we investigated how subterranean species of different range sizes contribute to SRP in the Western Balkans. We studied spatially defined datasets of terrestrial and aquatic troglobionts, represented by beetles (Cholevidae, Carabidae, 425 species) and amphipod crustaceans (Niphargidae, 150 species), respectively. The two groups differ in dispersal capacities, and indeed distribution of their range sizes differed. The proportion of single site species reached 30% in beetles, and 21% in niphargids. Maximum linear extent (MLE) of the range exceeded 200 km in only 1% of beetles, but in nearly 20% of niphargids. SRP of both taxonomic groups only partly overlapped. To assess the contribution of species with different ranges on SRP, we created different subsets and compared their SRPs with full dataset SRP. Subsets were first formed by adding species one-by-one, in ascending and descending order according to range size. We used correlation analysis, with significance assessed using null models generated from randomly generated subsets. In the second analysis, we assigned species info four classes according to range size, and modelled which size class best explains SRP. The results showed certain differences among the two taxonomic groups, which make generalizations difficult. We find it important to evaluate the contribution of species with different ranges to overall SRP, but also to identification of local hotspots.
Biokovo Mountain in Croatia is a Dinaric hotspot of subterranean biodiversity and its area of 196 km 2 is protected as a nature park. Until now, more than 400 caves have been registered here, ...however, only in about 30% of them biospeleological research has been carried out. It is hypothesized that over 1000 caves exist in highly karstified Biokovo Mt. Biospeleological research of the area started at the beginning of 20th century and deep caves were infrequently explored after the year 1980. Previous research recorded more than 90 troglobiotic species in this area and most of them are endemic. The primary goal of the Expedition was a systematic survey of eight deep caves (depth over 250 m), one of which was never before biospeleologically surveyed. We also surveyed other caves from which material for detailed faunistic analysis was missing. The main part of the expedition took place from 17 th to 25 th June 2017, with 52 participants. Fauna was collected by hand and by pitfall traps with baits, in the total of 26 caves. Five deep caves were completely surveyed (depth up to 710 m), the topographic map was made when missing, and fauna was photographed. Microclimatic conditions were measured and in two caves data loggers were placed. According to preliminary results, around 10 new species for science have been found from following groups: leeches (Hirudinea), spiders (Araneae), harvestmen (Opiliones), woodlice (Isopoda), centipedes (Chilopoda), springtails (Collembola), two-pronged bristletails (Diplura) and beetles (Coleoptera). These results confirm that deep caves of Biokovo Mt are still underexplored and that detailed and systematic research is needed.
Due to increasing human activities with negative impacts on wildlife and natural habitats, it has become necessary to establish conservation policies protecting at least parts of natural diversity. ...Subterranean fauna presents a challenge for conservation as species with small ranges or single site occurrences are common. In addition to the high level of strict endemism, the concealed lifestyles in habitats that are difficult to access make it challenging to establish the conservation status of subterranean species. Conservation approaches have different practical implications, but they should: i) include a sufficient number of important sites or proportion of species populations, and ii) involve monitoring of target species and habitats to check the effectiveness of conservation efforts.
We evaluated both aspects in two study cases on subterranean fauna from Slovenia, which is known as one of the global biodiversity hotspots in the Western Balkans. In the first case, we investigated to what extent current conservation schemes cover single site species. In the second case, we studied a region in Southern Slovenia and evaluated to what extent the EU legislation, namely EU Habitats directive, has been successfully implemented. In the frame of the latter, Sites of Community Importance were designated also due to the presence of important cave habitats and subterranean species. Our results suggest that the inclusion of important subterranean sites in conservation schemes is considerable. But, the apparent lack of research and monitoring of both subterranean habitats and species hampers the conclusions on effectiveness of different conservation approaches.
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