Stanislav Ožana

Understanding and optimizing rearing conditions for dragonfly larvae is crucial for ecological research and conservation efforts, yet optimal rearing conditions and general rearing practices are lacking. In this study, we investigated the effect of temperature, amount of oxygen in water, presence of (artificial) plants, and age of eggs on hatchability, survival, and development of dragonfly larvae using the model species Sympetrum striolatum. We conducted three independent experiments and assessed variability between egg clutches of individual females, as well as the occurrence of cannibalism among larvae. Our results showed that egg hatchability varied significantly between individual females and was negatively affected by egg aging and the presence of artificial plants. Larval survival was negatively affected by water temperatures above 24°C, the presence of artificial plants, and egg aging, and positively affected by high feeding frequency, in certain instars. Notably, cannibalism was observed among later instar larvae, especially under higher density conditions. Based on these findings, we provide practical recommendations for optimizing dragonfly larvae rearing protocols, emphasizing the importance of maintaining optimal temperature, appropriate feeding regimes, and managing larval density to reduce cannibalism. This study offers experimental, evidence-based guidelines for dragonfly larvae rearing, contributing to improved research methodologies and conservation efforts.

Freshwater insects, including odonates, have rarely been the target of reintroduction programmes. Furthermore, due to the scarcity of post‐release monitoring, information on factors affecting the long‐term survival of reintroduced populations is lacking. In 2001, the threatened dragonfly Leucorrhinia dubia (Odonata: Libellulidae) was reintroduced into the peatbog in Czechia, and the population had been monitored for fifteen years. The last survey of its demography was conducted in 2017. The present study investigates the current condition of that population by combining exuvial sampling with the capture‐mark‐recapture method for adults. We also focused on the physical features of the habitat and the ability of the population to colonise newly created habitat patches. The current population size is stable (105 exuviae and 96 adults) and comparable to previous monitoring. The acidic bog pools that had been hosting the population since its establishment have undergone succession and disappeared. The remaining single original pool is supporting a considerable proportion of the population (68.6%). In 2016, new pools were created. These alkaline pools with a vegetation composition different from the original pool have been colonised by L. dubia but also predatory newts. Given that their attractiveness to the species is comparable to the original pool, but their reproductive outcome is poorer, the new pools may act as ecological traps. Reintroductions can be effective in preserving threatened odonates. Continuous monitoring and site management, considering the impact of interventions on the entire community, is essential to sustain the reintroduced population over the long term.

Heterospecific interactions are an important phenomenon of animal epigamic behaviour; however, they remain understudied within important groups, such as insects. Dragonflies are an ideal group for research on interspecific mating and possible hybridisation as they are easily identifiable, large insects, with a conspicuous mating process, often striking territorial behaviour and several mating systems. Using the genus Sympetrum as the model group, we examined heterospecific mating at three different levels. In the field, we identified whether species identity, time and weather affected heterospecific mating frequency. One important part of heterospecific mating is whether the process is completed. For dragonflies, this means that flying in tandem is followed by successful copulation, gamete fusion and oviposition (which comprise mating completeness). In a mesocosm experiment, we determined mating completeness (tandems, copulation, oviposition) of hetero‐ and homospecific pairs and the possible role of species density in heterospecific mating. In the laboratory, we compared the viability of the offspring from heterospecific pairs with different epigamous behaviour. We found heterospecific mating to be a relatively common phenomenon unaffected by environmental variables, that was primarily influenced by species identity, temporal distribution and abundance of dragonfly species. Consequently, the presence of counterparts of other species is the main predictor of the frequency of heterospecific mating. The probability of completed epigamic behaviour (copulation and subsequent oviposition) connected with gamete fusion is lower in heterospecific mating. Generally, based on our results we can assume that successful heterospecific mating (leading to gamete fusion) occurs in closely related species (e.g., Sympetrum striolatum and Sympetrum vulgatum). However, as pre‐copulatory barriers are not strongly developed in some dragonfly groups, less closely related species (e.g., Sympetrum sanguineum and S. striolatum) also may mate. This phenomenon requires further study as it may present a threat to the survival of some species in the context of changing environmental conditions, including climate change.

Compositions of partial fuzzy relations dealing with undefined values have been extensively studied in partial fuzzy set theory. Their effectiveness in practical classification problems has been addressed. In general, the compositions relate to three sets of objects, truth-valued features and classes. The aim of compositions is to assign a class to an object by using knowledge of the assignment of features to objects and classes to features. In a classical setting, all features of objects (subjects to the classification) are known in advance. Such an assumption may be indeed inconvenient for some practical applications, e.g., because of the costly determination of features. This paper aims at the development of such framework that allows obtaining results from the composition even if some features are unknown and, more importantly, to select the most appropriate feature to be questioned additionally to maximize the accuracy of the result. For this purpose, the concept of dynamic feature selectors is defined. Based on classification results obtained from the composition on mandatory features, a dynamic feature selector recognizes the most promising optional feature whose knowledge may best improve the accuracy of classification. We propose two distinct dynamic feature selectors: (1) based on the sharpness and maximal truth values of the result, the ability to reach maximal values, and (2) based on the distance between the original and updated result of the composition. A practical experiment shows the performance of the proposed solution.

The use of mitochondrial markers for taxonomic identification and biodiversity monitoring is not without risks or limitations. Most importantly, the natural transfer of DNA from the mitochondria to the nucleus generates nonfunctional nuclear copies of mitochondrial DNA (NUMTs). Their abundance and size vary significantly among taxa, and NUMTs have been reported to complicate molecular studies based on mitochondrial markers in several insect orders, most prominently in Orthoptera. The significance of this phenomenon in Odonata has not yet been properly addressed. Here, we present a complete mitochondrial genome and a draft nuclear genome of Leucorrhinia albifrons (Odonata: Libellulidae), as well as NUMT and cox1 sequences from the related species Leucorrhinia dubia . We document the presence of NUMTs in the L . albifrons nuclear genome and in nuclear genomes of two other Odonata species available in public databases. Our results show that NUMTs can have a serious impact on barcoding, phylogenetic, population and phylogeographic studies of Odonata, especially when the barcode is located in the cox1 gene, the most frequently used molecular marker for Odonata. We suggest that nad1 should be used alone or in combination with cox1 to minimize unintended confusion with NUMTs. Finally, we present a mitophylogenomic analysis of Odonata and document several cases of misidentified mitochondrial genomes belonging to species different from those indicated in public databases. In conclusion, our findings represent an important step for future metabarcoding studies of Odonata based on mitochondrial DNA markers.

Understanding the impact of the changing proportion of land-use patterns on species diversity is a critical issue in conservation biology, and odonates are good bioindicators of these environmental changes. Some freshwater ecosystems that have been modified due to human activities can serve as important secondary habitats for odonate assemblages; however, the majority of studies addressing the value of secondary habitats in industrial and urban areas for adult dragonfly diversity have been limited to the local scale, and the value of such habitats for gamma diversity is still unclear. The aim of this study was to determine the relationship between human transformations of land use/land cover and dragonfly diversity. We interpolated the information based on dragonfly occurrence per grid cell and land cover data, indicating naturalness and degradation in 677 grid cells in the Czech Republic. Species richness did not correspond to habitat naturalness, but the occurrence of endangered species was significantly positively correlated with increasing naturalness; thus, habitat degradation and/or the level of naturalness significantly affected species composition, while species richness remained unchanged. Threatened species that occur predominantly in natural areas and threatened species with a dominant occurrence in degraded squares were also separated, which indicated that the conservation of the latter should be prioritised.

Intrataxonomic differences in terms of angiosperm suitability for herbivorous insects stem from variables such as plant structure, palatability, and chemistry. It has not yet been elucidated whether these differences also occur in terms of the bryophyte’s suitability to bryophages. Hypnum cupressiforme Hedw. is a morphologically variable moss species frequently inhabited or fed by insects. In this investigation, we offered five morphotypes of H. cupressiforme to two bryophagous species of Byrrhidae (Coleoptera) to reveal whether the intrataxonomic variability affects beetles’ preferences. The morphotypes were offered with preserved and removed spatial structures. There were no significant differences in morphotype preferences when spatial structures were preserved, although during the daytime, the beetles moved from the flat morphotype to the usual and turgid morphotypes. The beetles preferred the turgid morphotype when the spatial structures were removed. The results suggest that the spatial structure variations in the H. cupressiforme complex are accompanied by different chemical, physiological, or microscopic morphological profiles that are recognized by the bryophagous insects. Phylogenetic and epigenetic analyses can reveal multiple differences within the H. cupressiforme complex. Their interconnection with information about the preferences of bryophagous insects can help us to elucidate which of these differences are ecologically relevant.

Genetics has been widely used in insect ecology and conservation. To minimise the effect of DNA sampling on organisms as much as possible, it would be ideal to use non‐invasive or non‐lethal DNA sources. Therefore, it is also very important to determine the responses of organisms to DNA sampling. In this study, the quality and quantity of genomic DNA samples from three types of insect tissues (exuvia, mid‐legs and wings) were evaluated. As model organisms, we used two dragonfly species of different sizes ( Leucorrhinia dubia , Anax imperator ). We also tested the regenerative ability of dragonfly larvae as a repair mechanism after mid‐leg cut‐off, with respect to factors such as size and quantity of diet. We found that DNA of sufficient quality for analyses was obtained from all tested tissues. Nonetheless, isolates from exuviae were conclusively less useful for sequencing than those from the mid‐legs and wings. The highest quantity of DNA was obtained from the mid‐legs. The survival of larvae is not affected by removing the legs, which can usually regenerate. All the tested tissues could be a source of adequate DNA; however, we concluded that primarily the legs should be used because they provided the best DNA samples in terms of quantity and quality of DNA. Furthermore, their exploitation would not affect individuals seriously if young larvae with sufficient time (at least 6 months) for regeneration are sampled. The exuviae should be used for absolutely non‐invasive studies involving endangered or protected species.