Browsing by Person "Krogmann, Lars"

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Ecosystem services and insect decline: The role of parasitoid Hymenoptera
(2024) Haas-Renninger, Maura; Krogmann, Lars
Parasitoid Hymenoptera provide essential ecosystem services, as they consume their arthropod hosts during their development, controlling host populations and thus contributing to the resilience of ecosystems. However, information on their taxonomic diversity, distribution and population trends are scarce even in well-studied regions such as Central Europe, making it difficult to understand how they are affected by insect decline. Reasons for this knowledge gap are the enormous diversity in contrast to their small size (microhymenoptera), which is why they are referred to as ‘dark taxa’. In recent years, many monitoring projects have been launched to study insect population trends in the context of insect decline and climate change, with a focus on well-studied target groups, such as wild bees, butterflies or beetles. However, parasitoid wasps, which are probably the most species rich group of all insects, are totally neglected although Malaise traps, which are widely used in monitoring studies, catch large numbers of parasitoid Hymenoptera and can therefore serve as a starting point to assess diversity and abundance of this important group. The present work aims to establish a baseline for parasitoid Hymenoptera diversity and abundance in semi-arid meadows in southwestern Germany in a conservational and applied context. It consists of three research papers, each of which contribute to fulfil this goal. The first research paper deals with the efficiency of the fractionator to separate microhymenoptera families from Malaise trap samples and discusses its potential for long-term monitoring studies. The fractionator is an affordable and user-friendly apparatus based on a plastic tub with a sieve that is placed on an orbital shaker. When the complete sample is poured in, it can be separated by shaking into two size fractions. In this study it was used to separate microhymenoptera families from a Malaise trap sample. The results show that 24 out of 34 Hymenoptera families (71 %) were separated into one of the two size fractions, which proves that the fractionator can be a helpful tool to make microhymenoptera from bulk samples accessible for further taxonomic work. In the second research paper, Malaise trap samples from an ongoing insect monitoring program were used to study the relationship of total insect biomass to abundance and diversity of microhymenoptera, as well as to assess the phenology of microhymenoptera families. Microhymenoptera abundance and diversity were positively correlated with total insect biomass, suggesting that insect biomass can be a valuable proxy for abundance trends even for small-sized insects such as microhymenoptera. Further, 90,452 specimens from 26 families belonging to 10 superfamilies of Hymenoptera were counted in total. Microhymenoptera showed two main activity periods during the year, reaching a first peak between June and July and a second between July and August. We could not find any evidence for a negative impact of mowing or grazing on the abundance of microhymenoptera. The families showed different phenological patterns, with varying numbers of activity peaks, and with some families being abundant very early (e.g. Platygastridae) or very late in the season (e.g. Figitidae, Trichogrammatidae). This is the first baseline for microhymenoptera occurrence patterns in Central Europe. The third research paper assesses the effect of mowing on microhymenoptera and how this effect can be reduced through arthropod-friendly mowing techniques, such as an adapted mowing head and a flushing bar. The results show that mowing with a conventional mulching mower has a detrimental effect on microhymenoptera with a loss of up to 64 % of individuals. The adapted mowing head had an effect only on Chalcidoidea, sparing 38 % of individuals compared to the conventional mower. The flushing bar had only a limited positive impact, because it showed a significant effect on total number of microhymenoptera with a significant reduction of 30 % on Chalcidoidea and a tendency for Ichneumonoidea with a reduction of 47 %. This shows that the conventional mowing head can have serious effects on microhymenoptera and that the effect can only be partially mitigated by insect-friendly mowing techniques. I presented the benefits and the limitations of implementing the fractionator in a monitoring workflow. As a positive example, using the fractionator enabled me to create the dataset of research paper 2, which together with research paper 3 can be a valuable reference for adapting schedules for plant protection measures and mowing dates. Insect biomass is strongly correlated with microhymenoptera abundance (research paper 2), which implies that microhymenoptera follow similar negative trends as other insects, but more meadows would need to be included to support our findings. I sorted microhymenoptera from Malaise trap samples as well as suction samples, resulting in different dominating families. Therefore a variety of collecting methods are necessary to assess the whole diversity of parasitoid Hymenoptera. All 103,312 specimens that I processed during my doctoral work are assessed in a digital database, and available for further morphological and molecular work. By linking an insect monitoring initiative with the taxonomically focused GBOLIII: Dark Taxa project, I was able to bring together the best of two worlds, and these combined efforts supported the discovery of a new wasp species. In conclusion, this work lays the foundation for the long-term assessment of parasitoid Hymenoptera in meadow ecosystems and thus contributes to a better understanding of how they are affected by insect decline. It highlights the ecological importance of parasitoid Hymenoptera and serves as a resource for their conservation. In the future, focus must be laid on studying the complex species interaction networks of parasitoid Hymenoptera and associated species. Automated systems such as the DiversityScanner using AI in combination with molecular techniques can help to gain knowledge on this highly important insect group.
Elucidating the megadiversity of Chalcidoidea (Hymenoptera) with a multi-taxonomic approach
(2022) Haas, Michael; Krogmann, Lars
With over 22,500 described and up to 500,000 estimated species, the jewel wasps (Chalcidoidea: Hymenoptera) are among the most species-rich insect lineages. Their evolutionary success is tightly linked to their parasitoid biology, having evolved to utilize a wide array of different arthropod hosts. Additionally, secondary phytophagy evolved several times within this superfamily. Although new approaches are employed in integrative taxonomic research, progress to decipher the megadiversity of this taxon, including their evolution, is still limited. With this work, the diversity of the superfamily is studied at two evolutionary key points in time. The evolutionary origin of Chalcidoidea is investigated in the Cretaceous and the resulting diversity since then is examined in the present. Different systematic levels will be elucidated with the help of integrative taxonomic methods. In the first chapter, the fossil origins of jewel wasps are addressed, around the middle of the Cretaceous period 110 million years ago. The morphology of a putative early chalcidoid specimen is studied, as it is highly informative for chalcidoid evolution due to its age. Based on those results, its phylogenetic placement is critically examined. The specimen is assumed to be one of the oldest described chalcidoid fossils, Parviformosus wohlrabeae Barling et al., 2013. It is a key fossil because of its age and putative assignment to the polyphyletic family Pteromalidae and could therefore be a valuable voucher for dating modern phylogenies. A precise redescription of the fossil was conducted and its morphology and phylogenetic position was discussed. No synapomorphic characters could be identified, warranting an inclusion in an already established chalcidoid family. In fact, none of the autapomorphies for Chalcidoidea could be recognized, necessitating a revised systematic placement in the Proctotrupomorpha. In the second chapter, several fossils in amber are described that grant insights in the early evolution of Chalcidoidea and the morphological diversity of Cretaceous lineages. Morphological characters are studied to answer the question of plesiomorphic character states in Chalcidoidea, aiding to understand their early evolution. The phylogenetic placement of these fossils is discussed, to provide hypotheses on the diversification of the superfamily, which so far has only few fossil representatives described from this time. Four fossils are made scientifically available that were found in 99 million year old Burmese amber. Those specimens are described in a new, extinct family, the Diversinitidae. This family exhibits a unique combination of plesiomorphic characters, not present in any other chalcidoid taxon, but lacks apomorphic characters. In total, three new genera and three new species are delimited and described. Phylogenetically relevant characters like the fully developed funicular segments, possessing multiporous plate sensilla, or the peg like cerci that improve our understanding of the early evolution of Chalcidoidea, are discussed based on the newly established family. A phylogenetic analysis based on morphological characters was performed. This analysis supported the monophyly of Diversinitidae, but left its exact systematic position within Chalcidoidea open. In the third chapter the focus shifts from the early evolution of Chalcidoidea towards the extant fauna, representing the diversity evolved since the Cretaceous. Exemplary, in the speciose family Pteromalidae the unknown diversity is examined to better understand the undiscovered species richness of parasitoid wasps. DNA barcoding is used to record and help identify previously unknown genera and species in Germany. Compared to the already known pteromalid fauna, 17 genera and 41 species are added as new records for Germany and the males of two species are described anew. The identified DNA barcodes were made available to enable the genetic identification of those species that have a high potential as indicators for nature conservation efforts due to their high host specificity. In the fourth chapter, the pertinent problem of cryptic diversity in Chalcidoidea is investigated. Via an extensive integrative taxonomic approach, the morphological species hypothesis is tested for one of the most abundant pteromalid species in Europe, Spintherus dubius. In this example, the benefit of combining different methods for species discovery and delimitation is highlighted. Genetic analyses of S. dubius reveal discrepancies between the morphological species concept and molecular data, indicating two potential species instead of one. The usage of an advanced morphological method, the multivariate ratio analysis, results in a confirmation of the molecular results, also exposing distinctive morphological characters per taxonomic unit. The examination of the host spectrum through rearing experiments further substantiates these findings, by revealing different host parasitoid affiliations. Altogether, this thesis showed that it is necessary to combine methods and examine different evolutionary points in time, to better understand the diversity of parasitoid lineages. Fossil taxa are important study subjects to examine the character evolution of any taxon, laying the base for phylogenetic research. The study of Diversinitidae highlights the plasticity of character states in Chalcidoidea, also providing evidence for plesiomorphic states. Their encompassing description and the redescription of P. wohlrabeae allow their incorporation into phylogenetic studies, to serve as solid anchor points in dating lineages and morphological evolution on the way towards extant diversity. Examining the extant fauna of Pteromalidae revealed the amount of diversity of species, for which the biology is often unknown. It is shown that molecular methods aid in the discovery of this diversity, opening possibilities for further research. It is affirmed that hidden diversity is even pertinent in abundant, well known species, with S. dubius being an example of cryptic diversity unveiled by integrative taxonomy.
Integrative taxonomy of platygastrine wasps of Germany
(2023) Awad, Jessica; Krogmann, Lars
In the context of the sixth mass extinction, our understanding of insect decline is severely limited by a lack of information on biodiversity. Many highly abundant and diverse insect groups remain unidentifiable to species or even to genus. The parasitoid wasp superfamily Platygastroidea is one such “dark taxon”. The taxonomic impediment is especially severe in the Palearctic Platygastrinae due to the proliferation of names with vague concepts. Platygastrine wasps parasitize the hyper-diverse Cecidomyiidae (Diptera), suggesting that their species richness may be correspondingly high. Revisionary work is needed to identify named species and to discover new ones. This work applies integrative taxonomic methods to address the most pressing problems within the subfamily. The research presented in this dissertation focuses on Europe, particularly Germany, which is the current center of insect decline research as well as a historical center of platygastrine taxonomy. As part of this work, historical descriptions and their associated type material were examined and clarified so that further revisionary work can occur. The dissertation is structured in five chapters, of which two are published and three are unpublished. The first chapter reviews 18 genera of Platygastridae described by Arnold Förster (1856), most of which represent distinct and recognizable lineages. The study provides their taxonomic history, diagnostic remarks, English translations, and illustrations of important specimens from the Förster collection in the Natural History Museum Vienna. The collection also includes original exemplar specimens of European species whose types have been lost. Potential neotypes and lectotypes from this material are noted, with the aim of improving nomenclatural stability in the group. Potential neotypes were found for Amblyaspis forticornis (Nees, 1834), Isocybus grandis (Nees, 1834), Platygaster striolata Nees, 1834, and Trichacis tristis (Nees, 1834). Lectotypes will be designated for Platygaster spinigera Nees, 1834, which will be transferred to Leptacis, and for Platygaster corvina Förster, 1861, with Platygaster henkvlugi Buhl, 1996 treated as a junior synonym. Synopeas mutica (Nees, 1834) should be transferred back to Platygaster. The second chapter addresses generic concepts within Platygastrinae sensu Ashmead. Part of Platygastrinae (former Inostemmatinae sensu Ashmead) was reviewed and keyed by Masner & Huggert (1989). However, more than half of the genera in the subfamily, including the vast majority of species, have not been revised. A working key to 14 major world genera, the first of its kind, is provided. An additional six genera and three subgenera of uncertain placement are discussed. The third chapter focuses on nomenclatural problems in the genus Platygaster Latreille, which is the type genus for its subfamily, family, and superfamily. It is also the largest genus in Platygastroidea with nearly 700 species, and recent evidence indicates that it is not monophyletic. It is necessary to establish the identity of the type specimen, as well as the identities of the 13 generic junior synonyms and four subgenera, in order to proceed with taxonomic divisions. The type specimen Scelio ruficornis Latreille, 1805, lost to science for 192 years, was rediscovered. However, it does not belong to the prevailing concept of Platygaster, but to Isocybus Förster, which has extreme taxonomic ramifications. The proposed solution would replace the type species of each genus in order to retain prevailing usage and prevent widespread confusion. A petition is presented to designate Epimeces ensifer Westwood as the type of Platygaster and Scelio ruficornis as the type of Isocybus. In the fourth chapter, the genus Trichacis Förster is revised for Europe. Examination of historical and modern collections combined with DNA barcoding revealed the presence of only a single species in Europe, Trichacis tristis (Nees, 1834), redescribed here. The results suggest that T. tristis has 14 junior synonyms: T. abdominalis (Thomson, 1859); T. bidentiscutum Szabó, 1981; T. didas (Walker, 1835); T. fusciala Szabó, 1981; T. hajduica Szabó, 1981; T. illusor Kieffer, 1916; T. nosferatus Buhl, 1997; T. pisis (Walker, 1835); T. persicus Asadi & Buhl, 2021; T. pulchricornis Szelényi, 1953; T. quadriclava Szabó, 1981; T. remulus (Walker, 1835); T. vitreus Buhl, 1997; and T. weiperti Buhl, 2019. Four species should be transferred to Amblyaspis Förster: T. afurcata Szabó, 1977, T. hungarica Szabó, 1977, T. pannonica Szabó, 1977, and T. tatika Szabó, 1977. Intraspecific variation, biological associations, and taxonomic history are discussed. DNA barcodes are provided and analyzed in the context of worldwide Trichacis and its sister genus Isocybus Förster. The fifth chapter examines platygastrid diversity in Germany in the context of insect decline. DNA barcodes indicate the presence of 178 observed species, with an estimated total of 290. GBOL sampling captured an estimated 93.7% of total species richness, but only 45.8% of rare species. A case study from Isocybus compares historical specimens, DNA barcode vouchers, and ecological data to illustrate the possible decline of a wetland parasitoid species. Altogether, the research demonstrates the importance of historical material, especially type specimens, in understanding biodiversity through time, and provides an essential taxonomic foundation for much-needed modern identification resources for Platygastrinae in the western Palearctic and beyond.
Integrative taxonomy, systematics and biogeography of geometrid moths in a Middle Eastern biodiversity hotspot
(2023) Wanke, Dominic; Krogmann, Lars
Iran is an important biodiversity hotspot in the world. Recent studies have shown that two of the 36 global biodiversity hotspots are located in Iran: The Irano-Anatolian and the Caucasian hotspots. These two hotspots include parts of the two mountain ranges in Iran, the Alborz Mountains and the Zagros Mountains, which are crucial for the biodiversity, hosting a large number of endemic species. However, climate change and anthropogenic activities threaten its diversity. This study uses geometrid moths as a model group to better understand general patterns of biodiversity and zoogeography in Iran. Geometridae are suitable for such studies and scientifically interesting for several reasons: The family is species-rich with nearly 24,000 known species worldwide (539 known species in Iran), the species have short life-cycles and thus react quickly to environmental changes, and they occupy specialized ecological niches. Knowledge of Palearctic geometrid moths is rather advanced compared to other regions. The Western Palearctic, in particular, has been the target of considerable research. However, this is not the case for regions in the Middle East and Central Asia, where much is still unknown and further research is crucial. To fill this gap for geometrid moths in this region, data on their species richness and distribution patterns were collected to reveal regions with special faunal elements. Therefore, this dissertation consists of three parts, each of which contributes an essential element to achieve these goals. The first part deals with the taxonomic problems of partially species-rich and morphologically very difficult genera within the three subfamilies Sterrhinae (Problepsis, Scopula, Cinglis, Pseudocinglis, Scopuloides, Glossotrophia, Zygophyxia); Geometrinae (Xenochlorodes); and Ennominae (Nychiodes, Synopsia, Synopsidia, Eumera). Type specimens and original descriptions were used for critical revisions to understand the diagnostic characters of the species. Additionally, large series of specimens from many different museums and private collections were examined to highlight morphological variations. Using an integrative taxonomic approach that includes morphological and molecular data, a total of one new genus and four new species were described and 37 taxonomic changes (e.g., new synonyms, new combinations) were made. The second part addresses genera with uncertain tribal affiliation or questionable taxonomic status, which were also partially targets of the taxonomic revisions. A multi-gene phylogenetic analysis was performed using one mitochondrial gene and up to nine nuclear genes, sequences generated as part of this work and sequences from published phylogenetic studies were taken to run the analyses. As a result, the genus Eumera was determined to belong to the tribe Prosopolophini, the genera Cinglis and Scopuloides were removed from synonymy with Scopula, two genera were synonymized (Glossotrophia, Pseudocinglis), and two species were transferred to a different genus (Problepsis wiltshirei, Aphilopota tyttha). In the third part, distribution data of Iranian Geometridae was used to identify biodiversity hotspots and regions of high endemism. In addition, a network-based method was used to divide the country into unique bioregions and highlight areas with specific faunal elements. As a result, an exceptional species richness was found along the two main mountain ranges, Zagros in the west and south and Alborz in the north. Considering only the endemic species, the southern mountain areas were identified as the most species-rich regions. The bioregionalization analysis also identified six main bioregions. Most of these bioregions reflect specific faunal structures and are in accordance with previous studies. This highlights the complex species composition in Iran and demonstrates the exceptional biodiversity of the country. In addition, our results indicated two transition zones between zoogeographical realms. Of the six zoogeographical realms defined by Wallace, three occur in Iran meeting in the south of the country: The Palearctic and Saharo-Arabian along the foothills of the Zagros Mountains and the Palearctic and Oriental in southeastern Iran. At these transition zones, Iran has very specific faunal elements of the Geometridae, which makes these zones important for conservation. Overall, this work contributes to a better understanding of the biodiversity of geometrids in Iran and neighboring countries. It serves as a resource for the identification of species, their distribution and habitats, which are of great interest for conservation efforts in Iran and neighboring countries.