Taxonomy and Distribution of the genus Merodon (Meigen, 1803) (Diptera: Syrphidae) in Palaeartic

Predmet ovog istraživanja su vrste iz  Merodon  aureus,  M.  nanus  i  M. ruficornis  grupe i  M.  avidus  kompleksa sa područja Palearktika. Usled izuzetne morfološke sličnosti pomenutih vrsta, korišćene su tri različite metode u cilju utvrđivanja  prisustva skrivenih taksona i definisanja granica vrsta. Komparativnom geometerijsko-morfometrijskom analizom su obuhvaćene vrste iz  M.  aureus  i  M.  nanus  grupe i  M.  avidus  kompleksa. Interspecijska varijabilnost  M.  aureus  grupe i  M.  avidus  kompleksa je analizirana sa dva geometrijsko-morfometrijska pristupa: analiza oblika krila -  zasnovana na specifičnim tačkama (landmarks) i analiza oblika genitalnog aparata mužjaka  -  zasnovana na pomoćnim tačkama (semilandmarks). Sredinske niše su kvantifikovane i poređene “Point base” metodom i njome su obuhvaćene sve istraživane vrste. Uslovljenost razlika u obliku krila i surstila analiziranih vrsta geografskom distribucijom i klimatskim faktorima je testirana upotrebom Mantel testa. Dobijeni rezultati analize oblika krila i genitalnog aparata mužjaka ukazuju na veliki potencijal geometrijske morfometrije u detekovanju morfološke  varijabilnosti, odnosno kriptičnih vrsta kod sirfida. Na osnovu oblika krila i genitalnog aparata mužjaka, unutar svih istraţivanih grupa vrsta prepoznato je 45 nezavisnih evolucionih jedinica (M. aureus grupa - 36;  M. nanus grupa - 5,  M. avidus  kompleks  -  4). Sve kriptične vrste iz 12 analiziranih kompleksa vrsta su uspešno razdvojene, sa visokim procentom korektne klasifikacije jedinki. Rezultati ukazuju na veću moć diskriminacije oblika genitalnog aparata mužjaka u odnosu na krila. Razlike u obliku krila se odnose prvenstveno na promene u apikalnom delu krila što utiče na promene u dužini i širini ovog dela, dok su razlike u obliku genitalnog aparata mužjaka najvećim delom koncentrisane u posteriornom delu posteriornog lobusa surstila, delu genitalnog aparata mužjaka koja igra ključnu ulogu u pridržavanju ženki tokom kopulacije. Razlike u obliku krila nisu posledica geografske udaljenosti, kao ni razlika u ekološkim nišama vrsta. Uticaj abiotičkih parametara na razlike u obliku genitalnog aparata mužjaka nije zabeležen ni kod jedne od analiziranih vrsta, dok je uticaj geografske distribucije na razlike u obliku surstila zabeležen samo u jednom slučaju, kod  M. luteomaculatus kompleksa vrsta. Ovi rezultati ukazuju da je izolacija putem distance imala glavnu  ulogu u diverzifikaciji oblika genitalnog aparata mužjaka kod vrsta ovog kompleksa. Rezultati su pokazali da se klimatski profili svih analiziranih parova vrsta razlikuju u makar jednoj sredinskoj niši (PC osi), osim para vrsta  M. rojoi - M. puniceus  i  M.  loewi  -  M. ovaloides. Faktori koji najviše doprinose divergenciji klimatskih profila analiziranih vrsta predstavljaju esktreme tj. limitirajuće faktore poput niskih vrednosti padavina i temperature i fluktuacija temperaure tokom godine. Za razliku od široko rasprostranjenih vrsta, endemske vrste imaju uzak opseg nadmorskih visina na kojima se javljaju i uglavnom su vezane za planinska staništa. Takođe, imaju niske vrednosti standardne devijacije za većinu izdvojenih PC osa što ukazuje na njihovu striktnu klimatsku adaptibilnost. Prema rezultatima analize distribucije i specijskog diverziteta, Balkansko poluostrvo odlikuje najveći divezitet analiziranih vrsta. On predstavlja centar biodiverziteta za M. aureus grupu, a zajedno sa severnim delom Apeninskog poluostrva za M. ruficornis grupu, dok je najveći diverzitet vrsta M. nanus grupe zabeležen na jugozapadu i severoistoku Anadolije. Analize klimatskih profila i specijskog diverziteta zajedno sa rezultatima geometrijske morfometrije ukazuju da je geološka istorija, tj. kontrakcije areala tokom glacijacija i interglacijacija, značajno uticala na diverzifikaciju istraživanih grupa u refugijumima zapadnog Palearktika.The objects of this study are species from Merodon aureus, M. nanus and M.  ruficornis groups, and M. avidus complex in Palaearctic. These species are characterised by great morphological  similarity, and three different approaches were used to detect cryptic species and establish species boundaries. Species from M. aureus and M.  nanus groups, and M. avidus complex were analysed using geometric morphometry. Interspecific variability of M. aureus group and M. avidus complex were studied using two approaches: landmark based wing shape analysis and semilandmark analysis of male genitalia.  Ecological niche analysis were conducted for all analyzed species.  Correlation between Squared Mahalanobis  distances of both wing and surstylus, and geographic and environmental distances were addressed using  the two tailed Mantel test. Geometric morphometric results indicate that wing and especially surstylus shape, have meaningful interspecific discriminatory power. Based  on these characters 45 evolutionary independent units are recognized (M. aureus group - 36; M. nanus group - 5, M. avidus complex - 4). All cryptic species from 12 analysed species complexes were successfully distinguished with high overall  classification success. Results showed that geometric morphometry of surstylus had a higher classification rate than wing geometric morphometry. The main wing shape differences are connected with apical part of the wing which influences his length and width. The main differences in surstylus shape are connected to the posterior margin of the posterior part of the surstylus lobe, involved in gripping the female during copulation. Mantel tests revealed that geographic and environmental distances exhibited no association with wing and  surstylus shape distance among investigated species, except in M. luteomaculatus  complex. In this complex, Mantel test results suggested that isolation by distance had a major role in the diversification of male genitalia. Ecological niche analysis contributed to the species delimitation. These results demonstrated that among all related species, with the exception of species pairs M. rojoi - M. puniceus and M. loewi - M. ovaloides, overall or partial divergence in environmental  space is present. Distribution patterns of all analyzed species are mainly affected by the limiting effects such as low temperature and precipitation values,  as well as the temperature fluctuation during the year. Endemics and species with a narrow range had smaller altitudinal ranges and were mainly connected with mountainous areas. Additionally, low standard deviation values for endemic species reflect their narrow geographic distribution and very strict climatic adaptations, whereas large values for widely distributed species reflect their broad adaptability. According to the results of distribution and species diversity analysis, the Balkan Peninsula is characterized with highest diversity. It is a centre of biodiversity for M. aureus group, together with the northern part of the Apennine peninsula for M. ruficorn is group, while the largest species diversity of M. nanus group is recorded in the southwest and northeast Anadolia. Distribution and species diversity analyses, together with  the results of geometric morphometry indicate that geological history, i.e. range contraction during glaciations and interglaciations had a significant impact on the diversification of the studied groups in refuges in the Western Palaearctic

An integrated approach to delimiting species borders in the genus Chrysotoxum Meigen, 1803 (Diptera: Syrphidae), with description of two new species

Integrative taxonomy tests the validity of taxa using methods additional to traditional morphology. The existence of two different morphotypes in specimens identified as Chrysotoxum vernale Loew (Diptera: Syrphidae) prompted their taxonomic study using an integrative approach that included morphology, wing and male-surstylus geometric morphometrics, genetic and ecological analyses. As a result, a new species is recognised, Chrysotoxum montanum Nedeljković & Vujić sp. nov., and C. vernale is re-defined. A lectotype and paralectotypes are designated for C. vernale to stabilize this concept. An additional species, Chrysotoxum orthostylum Vujić sp. nov., with distinctive male genitalia is also described. The three species share an antenna with the basoflagellomere shorter than the scape plus pedicel and terga with yellow fasciae not reaching the lateral margins. This study confirms the value of integrative approach for resolving species boundaries.Financial support was provided by the Serbian Ministry of Education, Science and Technological Development (projects OI173002 and III43002), the Provincial Secretariat for Science and Technological Development (project ‘Genetic resources of agro-ecosystems in Vojvodina and sustainable agriculture’), the Transnational Access to Research Infrastructures activity in the FP7 of the EC (ExpeER project, TA visit ‘STEPS’) and the FP7 EU project, Innosense

Functional groups of hoverflies in Southeast Europe across different vegetation types

To better understand the relationship between biodiversity and ecosystem functioning, it is increasingly accepted that the focus of study needs to shift from taxonomic identity to the diversity of functional traits displayed by species within a community. Such an approach allows species to be grouped according to particular functional characteristics. Increasingly viewed as an extremely important group of model organisms, hoverflies have been the focus of a variety of ecological studies. Based on data regarding selected functional traits of hoverflies registered in Southeast Europe, the main aims of our study were to define hoverfly functional groups according to the similarity of these traits, as well as to compare the representation of delineated hoverfly functional groups among these vegetation types. We used fuzzy clustering to classify 568 SE European hoverfly species into five functional groups. The principle trait separating these functional groups was larval feeding type, followed by size of species range, flight ability, number of generations, inundation tolerance, and tolerance to human impact. For 9 of 11 vegetation types, the dominant functional group was characterized by species with good flight ability, having high human impact tolerance and more annual generations. The remaining two vegetation types, South-west Balkan sub-Mediterranean mixed oak forests and Mediterranean mixed forests, showed disparate dominance patterns, indicating that richness of functional groups is dependent on vegetation. Further investigation of whether and how established conservation measures enable recovery of the functional richness affected by habitat disturbance would help elucidate the importance of functional diversity in preserving biodiversity.Peer reviewe

MERODON NATANS AND M. PULVERIS (DIPTERA: SYRPHIDAE): DELIMITATING CRYPTIC HOVERFLY SPECIES USING THE GEOMETRIC MORPHOMETRIC METHOD

A landmark-based geometric morphometric method was employed to delimitate two morphologically closely-related species of the hoverfly Merodon natans species group based on wing parameters. The studied species, Merodon natans and M. pulveris, were successfully determined using this method. Analyses revealed a significant difference in wing size and shape between individuals of the two species, thereby proving that these are two distinct species, even though, morphologically very similar. Discriminant and cluster analyses also uncovered a subtle difference in wing shape between M. pulveris populations, indicating intraspecific differentiation with potential conservation implications. The results of the morphological study were supplemented with known distribution data of the investigated species

Phylogeographic patterns of Merodon hoverflies in the Eastern Mediterranean region: revealing connections and barriers

We investigated the phylogeographic patterns of Merodon species (Diptera, Syrphidae) in the Eastern Mediterranean. Ten species were sampled on five different islands and mainland sites as a minimum. All samples were screened for their mtDNA COI barcode haplotype diversity, and for some samples, we additionally generated genomic fingerprints. The recently established zoogeographic distribution categories classify these species as having (1) Balkan distribution; (2) Anatolian distribution; (3) continental areas and large islands distribution; and (4) with wide distribution. The ancestral haplotypes and their geographical localities were estimated with statistical parsimony (TCS). TCS networks identified as the ancestral haplotype samples that originated from localities situated within the distributional category of the species in question. Strong geographical haplotype structuring was detected for many Merodon species. We were particularly interested to test the relative importance of current (Aegean Sea) and past Mid-Aegean Trench) barriers to dispersal for Merodon flies in the Aegean. We employed phylogenetic β-diversity (Pβ total) and its partition in replacement (Pβ repl) and richness difference (Pβ rich) to test the importance of each explanatory variable (interisland distance, MAT, and island area) in interisland differences using partial Mantel tests and hierarchical partitioning of variation. β-Analyses confirmed the importance of both current and past barriers to dispersal on the evolution of group. Current interisland distance was particularly important to explain the replacement of haplotypes, while the MAT was driving differences in richness of haplotypes, revealing the MAT as a strong past barrier whose effects are still visible today in the phylogenetic history of the clade in the Aegean. These results support the hypothesis of a highly restricted dispersal and gene flow among Merodon populations between islands since late Pleistocene. Additionally, patterns of phylogeographic structure deduced from haplotype connections and ISSR genome fingerprinting data revealed a few putative cases of human-mediated transfers of Merodon spp

The Genus Heterogynis Rambur, 1866 (Heterogynidae, Lepidoptera): Congruence of Molecular, Morphological and Morphometric Evidence Reveal New Species in Serbia

The Heterogynidae are a small family of moths consisting of a single genus Heterogynis and sixteen described species distributed in the Mediterranean region. A species new to science, Heterogynis serbica sp. nov., is described from the locality of Srebrenac, Mt. Kopaonik, Republic of Serbia, Balkan Peninsula, by applying an integrative taxonomic approach using morpho-anatomical characteristics, wing morphometics and DNA barcoding. Male genitalia, scanning electron micrographs of adult male head anatomy, abdominal tergites/sternites, cocoons and habitats of the closely related species H. serbica sp. nov. and H. zikici are discussed and illustrated. Photographs of adult males and females, cocoons, plants in which the cocoons were found and habitats are shown. Importantly, marked differences in genital structure and other morphological characters were noted. These differences were confirmed with forewing morphometrics and COI-based DNA barcoding results. Additionally, DNA barcodes for H. serbica sp. nov. and H. zikici were compared against previously available data for the genus to evaluate the phylogenetic relationships. We conclude that deep, previously unknown and unexpected intrageneric morphological diversity exists in the genus Heterogynis.The authors wish to express their gratitude to Goran Anaˇckov, a Director of The Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, for his support; he enabled the usage of the equipment in the University Center for Electronic Microscopy (UCEM-NS), at the University of Novi Sad for this research. The authors are also very grateful to the Director and the Executive Director of the National Park “Kopaonik” Bojan Milovanovi´c and Predrag Šumarac for their long-term cooperation and support in this research. Finally, the authors deeply appreciate the support from Vladimir Žiki´c, from the University of Niš, Faculty of Sciences and Mathematics, Department of Biology and Ecology, who has kindly provided the analysed samples of H. zikici

Characterization of preimaginal developmental stages of two cryptic South African species of the Merodon planifacies complex (Diptera: Syrphidae: Eristalinae: Merodontini), with differentiation through morphometry analysis

Merodon capi Vujić et Radenković, 2020 and Merodon roni Radenković et Vujić, 2020 are two cryptic species belonging to the Merodon planifacies Bezzi, 1915 species complex that have recently been described, with the differences between them being revealed by molecular and geometric morphometry studies of adult specimens. In the present study, the preimaginal morphology of both species is described and displayed, with the material used corresponding to samples taken from bulbs of Merwilla plumbea (Lindl.) Speta plants at two locations in KwaZulu-Natal province (South Africa). The preimaginal stages were compared, looking for morphological evidence supporting species divergence. Linear and geometric morphometric analyses of the larval posterior respiratory process were conducted for the first time and the results of these analyses support the separation of the two taxa. Information about the life cycle and the relation with the host plant is also provided. In addition, we carried out a preliminary study of the adult feeding requirements of the species, based on the description of the mouthparts and an analysis of the pollen present in the gut and on the integument of adults. The results of the study supports a close relationship between the preimaginal stages and plant species of the Hyacinthaceae family.The study was mainly funded by the European Union project: Horizon 2020, Marie Skłodowska-Curie Actions, Research and Innovation Staff Exchange (RISE) Programme: FlyHigh – “Insect–plant relationships: insights into biodiversity and new applications” (project 645636). The study was partly supported by the Ministry of Education, Science and Technological Development, Republic of Serbia, Grant No. 451-03-68/2022–14/200125 and Grant No. 451-03-68/2022–14/200358. It was also supported by the research department of the University of Alicante in the framework of a predoctoral grant (UAFPU2019-03). This manuscript was written as a part of a PhD project conducted by Andrea Aracil at the University of Alicante (Spain)

Review of the Merodon natans group with description of a new species, a key to the adults of known species of the natans lineage and first descriptions of some preimaginal stages

Merodon natans group (Diptera, Syrphidae) taxa are reviewed using an integrative taxonomic approach combining morphological, morphometric and molecular techniques. The approach substantiates recognition of the three species: M. calcaratus (Fabricius, 1794), M. natans (Fabricius, 1794) and M. pulveris Vujić & Radenković in Radenković et al. 2011, and reveals the existence of a new species, M. makrisi Vujić, Radenković & Tot sp. nov., which is described. It also highlights the existence of a series of natans group populations, especially on some of the Mediterranean islands, in the Levant and in the Afrotropical Region, for which more comprehensive data are required to clarify their status. A key is provided to the natans lineage species currently recognised, and preimaginal stages of some natans-group species are described for the first time. Redescriptions for M. calcaratus and M. natans are provided. A neotype is selected for M. natans. Lectotypes are designated for M. annulatus (Fabricius, 1794) and M. melancholicus (Fabricius, 1794). Merodon annulatus is recognised as a synonym of M. natans.The authors acknowledge financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant No. 451-03-9/2021-14/200125 and Grant No. 451-03-9/2021-14/200358). André van Eck was financially supported for research in Cyprus by the Dutch Uyttenboogaart-Eliasen Foundation (UES), with grant nrs. SUB.2016.12.12 and SUB.2018.12.03

Taxonomy and Distribution of the genus Merodon (Meigen, 1803) (Diptera: Syrphidae) in Palaeartic

Predmet ovog istraživanja su vrste iz  Merodon  aureus,  M.  nanus  i  M. ruficornis  grupe i  M.  avidus  kompleksa sa područja Palearktika. Usled izuzetne morfološke sličnosti pomenutih vrsta, korišćene su tri različite metode u cilju utvrđivanja  prisustva skrivenih taksona i definisanja granica vrsta. Komparativnom geometerijsko-morfometrijskom analizom su obuhvaćene vrste iz  M.  aureus  i  M.  nanus  grupe i  M.  avidus  kompleksa. Interspecijska varijabilnost  M.  aureus  grupe i  M.  avidus  kompleksa je analizirana sa dva geometrijsko-morfometrijska pristupa: analiza oblika krila -  zasnovana na specifičnim tačkama (landmarks) i analiza oblika genitalnog aparata mužjaka  -  zasnovana na pomoćnim tačkama (semilandmarks). Sredinske niše su kvantifikovane i poređene “Point base” metodom i njome su obuhvaćene sve istraživane vrste. Uslovljenost razlika u obliku krila i surstila analiziranih vrsta geografskom distribucijom i klimatskim faktorima je testirana upotrebom Mantel testa. Dobijeni rezultati analize oblika krila i genitalnog aparata mužjaka ukazuju na veliki potencijal geometrijske morfometrije u detekovanju morfološke  varijabilnosti, odnosno kriptičnih vrsta kod sirfida. Na osnovu oblika krila i genitalnog aparata mužjaka, unutar svih istraţivanih grupa vrsta prepoznato je 45 nezavisnih evolucionih jedinica (M. aureus grupa - 36;  M. nanus grupa - 5,  M. avidus  kompleks  -  4). Sve kriptične vrste iz 12 analiziranih kompleksa vrsta su uspešno razdvojene, sa visokim procentom korektne klasifikacije jedinki. Rezultati ukazuju na veću moć diskriminacije oblika genitalnog aparata mužjaka u odnosu na krila. Razlike u obliku krila se odnose prvenstveno na promene u apikalnom delu krila što utiče na promene u dužini i širini ovog dela, dok su razlike u obliku genitalnog aparata mužjaka najvećim delom koncentrisane u posteriornom delu posteriornog lobusa surstila, delu genitalnog aparata mužjaka koja igra ključnu ulogu u pridržavanju ženki tokom kopulacije. Razlike u obliku krila nisu posledica geografske udaljenosti, kao ni razlika u ekološkim nišama vrsta. Uticaj abiotičkih parametara na razlike u obliku genitalnog aparata mužjaka nije zabeležen ni kod jedne od analiziranih vrsta, dok je uticaj geografske distribucije na razlike u obliku surstila zabeležen samo u jednom slučaju, kod  M. luteomaculatus kompleksa vrsta. Ovi rezultati ukazuju da je izolacija putem distance imala glavnu  ulogu u diverzifikaciji oblika genitalnog aparata mužjaka kod vrsta ovog kompleksa. Rezultati su pokazali da se klimatski profili svih analiziranih parova vrsta razlikuju u makar jednoj sredinskoj niši (PC osi), osim para vrsta  M. rojoi - M. puniceus  i  M.  loewi  -  M. ovaloides. Faktori koji najviše doprinose divergenciji klimatskih profila analiziranih vrsta predstavljaju esktreme tj. limitirajuće faktore poput niskih vrednosti padavina i temperature i fluktuacija temperaure tokom godine. Za razliku od široko rasprostranjenih vrsta, endemske vrste imaju uzak opseg nadmorskih visina na kojima se javljaju i uglavnom su vezane za planinska staništa. Takođe, imaju niske vrednosti standardne devijacije za većinu izdvojenih PC osa što ukazuje na njihovu striktnu klimatsku adaptibilnost. Prema rezultatima analize distribucije i specijskog diverziteta, Balkansko poluostrvo odlikuje najveći divezitet analiziranih vrsta. On predstavlja centar biodiverziteta za M. aureus grupu, a zajedno sa severnim delom Apeninskog poluostrva za M. ruficornis grupu, dok je najveći diverzitet vrsta M. nanus grupe zabeležen na jugozapadu i severoistoku Anadolije. Analize klimatskih profila i specijskog diverziteta zajedno sa rezultatima geometrijske morfometrije ukazuju da je geološka istorija, tj. kontrakcije areala tokom glacijacija i interglacijacija, značajno uticala na diverzifikaciju istraživanih grupa u refugijumima zapadnog Palearktika.The objects of this study are species from Merodon aureus, M. nanus and M.  ruficornis groups, and M. avidus complex in Palaearctic. These species are characterised by great morphological  similarity, and three different approaches were used to detect cryptic species and establish species boundaries. Species from M. aureus and M.  nanus groups, and M. avidus complex were analysed using geometric morphometry. Interspecific variability of M. aureus group and M. avidus complex were studied using two approaches: landmark based wing shape analysis and semilandmark analysis of male genitalia.  Ecological niche analysis were conducted for all analyzed species.  Correlation between Squared Mahalanobis  distances of both wing and surstylus, and geographic and environmental distances were addressed using  the two tailed Mantel test. Geometric morphometric results indicate that wing and especially surstylus shape, have meaningful interspecific discriminatory power. Based  on these characters 45 evolutionary independent units are recognized (M. aureus group - 36; M. nanus group - 5, M. avidus complex - 4). All cryptic species from 12 analysed species complexes were successfully distinguished with high overall  classification success. Results showed that geometric morphometry of surstylus had a higher classification rate than wing geometric morphometry. The main wing shape differences are connected with apical part of the wing which influences his length and width. The main differences in surstylus shape are connected to the posterior margin of the posterior part of the surstylus lobe, involved in gripping the female during copulation. Mantel tests revealed that geographic and environmental distances exhibited no association with wing and  surstylus shape distance among investigated species, except in M. luteomaculatus  complex. In this complex, Mantel test results suggested that isolation by distance had a major role in the diversification of male genitalia. Ecological niche analysis contributed to the species delimitation. These results demonstrated that among all related species, with the exception of species pairs M. rojoi - M. puniceus and M. loewi - M. ovaloides, overall or partial divergence in environmental  space is present. Distribution patterns of all analyzed species are mainly affected by the limiting effects such as low temperature and precipitation values,  as well as the temperature fluctuation during the year. Endemics and species with a narrow range had smaller altitudinal ranges and were mainly connected with mountainous areas. Additionally, low standard deviation values for endemic species reflect their narrow geographic distribution and very strict climatic adaptations, whereas large values for widely distributed species reflect their broad adaptability. According to the results of distribution and species diversity analysis, the Balkan Peninsula is characterized with highest diversity. It is a centre of biodiversity for M. aureus group, together with the northern part of the Apennine peninsula for M. ruficorn is group, while the largest species diversity of M. nanus group is recorded in the southwest and northeast Anadolia. Distribution and species diversity analyses, together with  the results of geometric morphometry indicate that geological history, i.e. range contraction during glaciations and interglaciations had a significant impact on the diversification of the studied groups in refuges in the Western Palaearctic

Does population density influence fluctuating asymmetry of Sitophilus oryzae laboratory populations?

The rice weevil, Sitophilus oryzae, is one of the most pernicious pests of stored grain. It is a primary pest and causes a reduction in weight, quality, seed viability and commercial value of various cereals. For this study, we reared S. oryzae on wheat grains under two different adult densities, low and high, with an aim to assess the influence of population density on fluctuating asymmetry of the adult’s ventral body. Fluctuating asymmetry represents slight and random deviations from bilateral symmetry normally distributed around a 0 mean, and its level is usually higher under a disturbed developmental process. Accordingly, we expected that environmental stress caused by higher density would increase its level. Opposite to our hypothesis, the study showed that population density did not influence fluctuating asymmetry of S. oryzae adults. Both experimental populations exhibited a similar, non-significant level of fluctuating asymmetry.The work has been carried out within the Centre of Excellence for Innovations in Breeding of Climate-Resilient Crops – ClimateCrops