Evaluierung intrinsischer und extrinsischer Gefährdungsursachen heimischer Libellenarten auf unterschiedlichen räumlichen Skalen

Biodiversity can be divided in the three facets: taxonomic, functional, and phylogenetic diversity. The loss of biodiversity as well as its drivers and the organisms most affected by these processes are intensely recognized and discussed in recent decades (Butchart et al., 2010; Newbold et al., 2015; Sala et al., 2000). Insects are an important part of the world’s terrestrial and freshwater biodiversity (Mora, Tittensor, Adl, Simpson, & Worm, 2011; Stork, 2018). Insects provide crucial ecosystem services, such as decomposition and pollination (Cardoso et al., 2020; Macadam & Stockan, 2015; Santos et al., 2020). Especially in densely populated areas of the northern hemisphere insect declines are well documented (Montgomery et al., 2020). Insect extinctions and declines do not solely mean the loss of species but e.g. biomass, unique ecological functions, and fundamental parts of extensive networks of biotic interactions (Cardoso et al., 2020). The concept of ecosystem services raised the awareness of human beings for the importance of insects in our surroundings (Ari, Hortal, Azcárate & Berg, 2018; Reilly et al., 2020), but insects are still underrepresented in the scientific literature. As a consequence, the development and implementation of conservation measures is still hampered (Basset & Lamarre, 2019). In recent years, many strategies were developed to halt the global decline of biodiversity (Butchart et al., 2010). Essential tools are for instance international or national red lists, the Habitats Directive or long-term monitoring programs, which try to assess all kind of threats to species (Gruber et al., 2012; Lindenmayer, Piggott & Wintle, 2013). Knowing these threats potentials helps to develop approaches and methods for the species´ protection (Primack, 2014). The causes of species threats can be separated into extrinsic and intrinsic factors. Extrinsic factors in terrestrial habitats include agricultural intensification, habitat loss, reduced connectivity, and nitrogen influx (Jan C. Habel et al., 2019; Seibold et al., 2019). Intrinsic factors refer to functional traits, meaning any morphological, physiological, behavioural, and phenological feature measurable at the individual level of species determining their interaction with the environment (McGill, Enquist, Weiher, & Westoby, 2006; Violle et al., 2007; Wong, Guénard, & Lewis, 2019). Conservation strategies mainly focus on the protection of biotopes (e.g. Special Protection Areas) and processes (e.g. natural forest development). Due to the availability of range-size data for species these strategies are taxonomically shaped and evaluated, mainly by the number of species (Mammides, 2019; Miller, Jolley-Rogers, Mishler, & Thornhill, 2018; Zupan et al., 2014). These strategies ignore functional or phylogenetic aspects of biodiversity (Vane-Wright, Humphries, & Williams, 1991; Veron, Davies, Cadotte, Clergeau, & Pavoine, 2015). But these differences or variability between the species are essential for future adaptations to changing environments (Faith, 1992; Vane-Wright et al., 1991). One obvious example is the high taxonomic diversity found in urban areas, but the respective assemblages are composed of closely related species and thus represent a reduced phylogenetic diversity (Knapp, Kühn, Schweiger, & Klotz, 2008; Riedinger, Müller, Stadler, Ulrich, & Brandl, 2013). The importance of such places for the protection of biodiversity therefore depends on the phylogenetic context of the resident species (Ibáñez-Álamo, Rubio, Benedetti, & Morelli, 2017). Thuiller et al. (2015b) demonstrated that a random choice of protected areas would have been more expedient in protecting the functional and phylogenetic diversity for many mammals, birds, amphibians, and reptiles than the existing Natura 2000 network. The discipline of phylogenetical and functional studies is steadily developing and improving. During the last decades the availability of e.g. phylogenetic data as well as standardized trait data increased in availability for different taxa as well as in their quality. A similar link exists for trait data or trait-based approaches (Wong et al., 2019). Their availability for and comparability between different taxa is still improving, which is in line with the growing demand for comparative studies e.g. in the relation of traits and extinction risk (Chichorro, Juslén, & Cardoso, 2019). The basis for comparative studies is a standardized measurement of e.g. traits (Moretti et al., 2017) and a comparable level of the respective phylogenetic tree data. Odonates and butterflies are well-studied insect orders. Consequently, a huge amount of available species data and complete phylogenetic trees exist. Odonates have a highly specialized lifecycle. Their larval stages solely develop in lentic (e.g. lakes) or lotic (e.g. streams) water (Corbet, 1999). Their flying imagos depend on waterbodies for e.g. egg laying and terrestrial habitats for hunting (Corbet, 1999). Freshwater habitats cover just 2.4% of the earth’s terrestrial surface (Allan et al., 2015; Lehner & Döll, 2004), underlining the vulnerability of this habitat. The demand for freshwater is still growing for example due to an increased anthropogenic requirement for drinking water or artificial irrigation. Simultaneously, studies show a fast recovery of populations after an improvement of water conditions due to environmental regulations and restoration measures (Termaat, Van Grunsven, Plate, & Van Strien, 2015) as well as general increase of the abundance of freshwater insects in comparison to terrestrial insects (van Klink et al., 2020). We evaluated intrinsic and extrinsic causes of threat on different spatial scales. The core species for this consideration were odonates. Using surrogate taxa for prioritising conservation measures is a common approach in conservation biology (Larsen, Bladt, & Rahbek, 2009; Margules & Pressey, 2000). Advantages are that e.g. costly and time-expansive species surveys can be avoided (Yong et al., 2018). Different species and their e.g. responses to a certain environment are correlated, but the strength of cross-taxa congruence varies greatly and the responses are complex (Aubin, Venier, Pearce, & Moretti, 2013). This taxon-specific patterns of diversity underpin the necessity of multi-taxa approaches for a successful conversation in the interest of nature and preserving biodiversity. Further, we argue that instead of using species as a surrogate for others, information on different species groups should be combined to guide effective nature protection measures. Therefore, we extended the species spectrum for the paper “Predicting regional hotspots of phylogenetic diversity across multiple species groups” by birds, bats, butterflies, and locust and for the paper “Modelling the extinction risk of European butterflies and odonates” by butterflies. At the county level we analysed the number of species in relation to local habitat parameters and its changes over time expressed by the time passed since excavation of these artificial ponds. At the federal state level, we analysed the standardized phylogenetic diversity of the several species depending on local habitat and climatic variables. Throughout Europe we conducted a comparative, phylogenetic-controlled trait-based study for butterflies and odonates to analyse causes of extinction risk.