The first comprehensive population size estimations for the highly endangered largest diving beetle Dytiscus latissimus in Europe

Funding Information: Work in Latvia was supported by the LVAF project Nr. 1/27/2020–8/27/2020 "Improvement and approbation of the methodology for monitoring and estimating the population size of three EU protected invertebrate species—Dytiscus latissimus, Graphoderus bilineatus and Hirudo medicinalis". Work in Germany was supported by the "University of Applied Science Neubrandenburg and the Ministry of Climate Protection, Agriculture and Environment Mecklenburg-Vorpommern". The second author would like to say a special word of thanks to Prof. Dr. Grünwald (†) for his invaluable encouragement and academic stimulus. Publisher Copyright: © 2023, The Author(s).Dytiscus latissimus (Coleoptera Dytiscidae) is an endangered diving beetle throughout its range. It is one of the two species of Dytiscidae listed in Annex II of the Habitats Directive, IUCN red list and in many national level legislations and therefore strictly protected. The conservation of endangered species first of all requires an assessment of their population size. Until now, a method has not been developed for estimating the size of D. latissimus populations. The article summarizes the results of two studies carried out independently in Germany and Latvia. Both studies were carried out in one water body used recapture method but with a different spatial placement of traps, which, according to our data, is an important factor in population estimation. We evaluated Jolly-Seber and Schnabel approaches of estimating aquatic beetle's populations and found that confidence intervals obtained by different methods in our research do not differ significantly, but combination of both models provide the most accurate estimates of population dynamics. As part of the study, we concluded that the populations of Dytiscus latissimus are relatively closed, so we accept that the Schnabel estimate shows more accurate data. By fixing the places of capture of each individual, it was found that females live mainly locally, and males actively move within the water body. This aspect indicates the advantage of the spatial placement of traps compared to the use of transects. The results of our study show a significantly higher number of both captured and recaptured males Such a sex ratio may indicate both a greater activity of males and differences in the sex ratio in the population. The study confirmed that environmental changes, such as the water level in a water body, can also significantly affect the result of a population assessment. In the frame of D. latissimus monitoring, to obtain an objective estimation of the species population size we recommend using four traps for each 100 m of water body shoreline with 4–8 censuses, dependently on the recapture rate.publishersversionPeer reviewe

Evidence for geographic substructuring of mtDNA variation in the East European Hermit beetle (Osmoderma barnabita)

The genus Osmoderma is a flagship taxon of invertebrate conservation in Europe and encompasses a complex of four accepted species. While species limits amongst Osmoderma have been intensively studied, patterns of intraspecific variation are poorly known. In this paper, the authors focus on clarifying the phylogeographic structure of the East European Osmoderma barnabita using samples from Croatia to Finland. Samples of hind legs were collected from populations in Latvia and Finland (n=186) and combined with previously-published sequences from GenBank and museum specimens (n=10). In a partial sequence of the mitochondrial COI gene (759 bp), 26 closely related haplotypes were found. Beetle samples from different parts of Europe were distinct and showed no overlap in haplotype composition. The solitary population of Finland proved to be monomorphic and all 97 individuals sampled here belonged to a single haplotype unique to this region. The results suggest the Northern parts of Eastern Europe to be dominated by a single COI haplotype to which most of the other haplotypes are linked by one or two mutations. The pattern seems to reflect a founder effect or a strong bottleneck event. While O. barnabita is widely distributed over Eastern Europe, current patterns of mitochondrial genetic diversity appear influenced by population history and little homogenisation by ongoing gene flow. From a conservation perspective, the patterns suggest that regional populations might need to be managed as subunits and that the population of Finland may be affected by low genetic diversity