Using resistance distance from circuit theory to model dispersal through habitat corridors has been published in Journal of Plant Ecology.
Authors Thiele J, Buchholz S & Schirmel J
Abstract Resistance distance, based on circuit theory, is a promising metric for modelling effects of landscape configuration on dispersal of organisms and the resulting population and community patterns. The values of resistance distance reflect the likelihood of a random walker to reach from a source to a certain destination in the landscape. Although it has successfully been used to model genetic structures of animal populations, where it most often outperforms other isolation metrics, there are hardly any applications to plants and, in particular, to plant community data. Our aims were to test if resistance distance was a suitable metric for studying dispersal processes of plants in narrow habitat corridors (linear landscape elements). This would be the case, if dispersal processes (seed dispersal and migration) resembled random walks. Further, we compared the model performance of resistance distance against least-cost distance and Euclidean distance. Finally, we tested the suitability of different cost surfaces for calculations of least-cost and resistance distance.
We used data from 50 vegetation plots located on semi-natural linear landscape elements (field margins, ditches, road verges) in eight agricultural landscapes of Northwest Germany. We mapped linear landscape elements, including hedges and tree rows, from aerial images in a Geographic Information System, converted the maps into raster layers, and assigned resistance values to the raster cells, where all cells outside of linear landscape elements received infinite resistance and, thus, represented barriers to dispersal. For all pairs of plots within study areas, we calculated Jaccard similarity assuming that it was a proxy (or correlate) of dispersal events between plots. Further, we calculated resistance distance and least-cost distance of the network of linear landscape elements and Euclidean distance between the plots. We modelled the effects of distance metrics on community similarity using binomial Generalized Linear Mixed Models.
Agricultural landscape of Westphalia
Euclidean distance was clearly the least suitable isolation metrics. Further, we found that resistance distance performed better than least-cost distance at modelling Jaccard similarity. Predictions varied markedly between the two distance metrics suggesting that resistance distance comprises additional information about the landscape beyond spatial distance, such as the possible presence of multiple pathways between plots. Cost surfaces with equal cell-level resistances for all types of linear landscape elements performed better than more complex ones with habitat-specific resistances. We conclude that resistance distance is a highly suitable measure of isolation or, inversely, connectivity for studying dispersal processes of plants within habitat corridors. It is likely also suitable for assessing landscape permeability in other landscape types with areal habitats instead of narrow corridors. Resistance distance holds the potential to improve assessments of isolation (or connectivity) for models of regional population and meta-community dynamics.
On the identity of the Palearctic species of the wolf spider genus Trebacosa (Araneae: Lycosidae) has been published in Zootaxa.
Authors Szűts T, Zalai B, Villepoux O, Buchholz S, Eichardt J, Zhukovets E, Oger P & Szinetár C
Abstract In this paper we propose Trebacosa brunhesi Villepoux, 2007 as a junior synonym of Trebacosa europaea Szinetár & Kancsal, 2007 based on the examination of specimens from all the localities from where those species are known. Illustration of the type species of the genus, Trebacosa marxi (Stone, 1890) and specimens from all known localities of T. europaea are given to show both the inter- and the intraspecific differences of the genus. Scanning electron micrographs were used to illustrate the detailed structure of the female’s genitalia.
The German Society of general and applied Entomology (DGaaE) and the German Scientific Society for Plant Protection and Plant Health (DPG) organised a conference on insect diversity in cities (III. Urbane Pflanzen Conferenz). I contributed a talk on habitat function of urban meadows for wild bees with emphasis on urbanisation effects (see Abstract in German). Due to a very diverse audience with many relevant stakeholders and decision-makers (e.g. scientists, gardeners, landscape planners, landscape architects, authorities and NGOs) it was possible to elaborate this topic from different perspectives. At the end we had very interesting – sometimes controverse – discussions to develop recommendations how to make cities more insect friendly and to comment on the new white book „Grün in der Stadt“ which was recently send out for preview. The official presentation of the white book will be in May 2017.
Authors Schirmel J, Thiele J, Entling MH & Buchholz S
Abstract Agricultural intensification is a cause of global biodiversity decline. Seminatural linear landscape elements (LLE) within agricultural landscapes can considerably mitigate these declines, but their effects on functional properties of biodiversity are poorly known. We analyzed trait composition and functional diversity (functional dispersion) of spiders and carabids in woody and herbaceous LLE. We expected that species assemblages of woody LLE are more diverse and K-selected compared to herbaceous LLE, and that effects of environmental parameters vary between LLE types. We selected 58 LLE in an agricultural landscape in Northwest Germany. We sampled carabids and spiders by pitfall trapping and measured landscape connectivity, landscape-wide land-use diversity, local land-use diversity, and local plant richness as explanatory variables. The trait composition of arthropods in woody LLE was more K-selected (lower dispersal ability, a higher food specialization or trophic level) than in herbaceous LLE. Moreover, spider functional diversity was higher in woody LLE. Spider functional diversity and proportion of predatory carabids in woody LLE increased with increasing connectivity of the habitats. In contrast, in herbaceous LLE local plant richness and landscape-wide land-use diversity were most important drivers for spider and carabid diversity and traits. Our results show that species richness and functional diversity of spiders and carabids were differently affected by landscape and local factors. Therefore, the importance of landscape connectivity was higher in woody LLE, suggesting that their inhabitants are more sensitive to habitat fragmentation than the highly mobile generalist species living in herbaceous habitats.
Disentangling urban habitat and matrix effects on wild bee specieshas been published in PeerJ.
Authors Fischer LK, Eichfeld J, Kowarik I & Buchholz S
Abstract In face of a dramatic decline of wild bee species in many rural landscapes, potential conservation functions of urban areas gain importance. Yet effects of urbanization on pollinators, and in particular on wild bees, remain ambiguous and not comprehensively understood. This is especially true for amenity grassland and extensively managed wastelands within large-scale residential housing areas. Using Berlin as study region, we aimed to investigate (a) if these greenspaces are accepted by wild bee assemblages as foraging habitats; (b) how assemblage structure of bees and individual bee species are affected by different habitat (e.g., management, flower density) and urban matrix variables (e.g., isolation, urbanization); and (c) to what extend grassland restoration can promote bees in urban environments. In summer 2012, we collected 62 bee species belonging to more than 20 % of the taxa known for Berlin. Urbanization significantly affected species composition of bees; 18 species were affiliated to different levels of urbanization. Most bee species were not affected by any of the environmental variables tested, and urbanization had a negative effect only for one bee species. Further, we determined that restoration of diverse grasslands positively affected bee species richnesss in urban environments. We conclude that differently structured and managed greenspaces in large-scale housing areas can provide additional foraging habitats and refuges for pollinators. This supports approaches towards a biodiversity friendly management within urban regions and may be of particular importance given that anthropogenic pressure is increasing in many rural landscapes.
Last weekend the conference of the German Arachnological Society took place in Greifswald. I gave a talk on trait-based approaches and functional diversity in arachnology and presented progresses and perspectives within this research topic (see slides). Trait-environmental relationships and functional diversity are very important components within biodiversity research and several studies have successfully applied these concepts to spiders. Unfortunately, a consensus how to select appropriate morpho-physiological, phenological and ecological traits and to define trait categories is missing yet. Therefore, my talk intended to encourage the development of a standardised and expert-based open-access trait database for spiders. It was great to have some fruitful discussions afterwards. We agreed on organising an expert workshop soon to work out a first proposal for a meaningful trait selection.
We finished the grasshopper sampling last week! More than 60 urban dry grasslands had been sampled during summer and we are now happy to have a first extensive dataset for the BIBS project. In all, we acoustically and visually assessed more than 4000 grasshopper individuals with 22 species – including some very interesting species such as Calliptamus italicus. We are looking forward to first functional diversity analyses in the next few weeks.
Several raptor species become more and more urban dwellers and they thrive very well in many different urban habitats now. In Berlin, four species are very common – even in heavily urbanised areas. While the common buzzard (Buteo buteo) mostly inhabits parks and urban woodlands, aeries of the peregrine falcon (Falco peregrinus) and the common kestrel (Falco tinnunculus) can be found in higher buildings all over the city. The latter can be regularly seen at the Tempelhofer Feld (see photo) and a good place to observe the peregrine falcon is the Alexanderplatz and the television tower which is used as raised hide, even during the night.
In the last years, we conducted research on the northern goshawk (Accipiter gentilis). Interestingly, this species spreads more and more into the heavily urbanised areas and while it was breeding in urban parks and large gardens at the beginning, aeries can be found in backyards in isolated tree by now. Sometimes northern goshawks are even hunting in busy roads like the Schlesische Straße in Kreuzberg. Watch out for more findings …
Biodiversity functions of urban cemeteries: evidence from one of the largest Jewish cemeteries in Europe has been accepted for publication in Urban Forestry & Urban Greening.
Authors Kowarik I, Buchholz S, von der Lippe M & Seitz B
Abstract As the world becomes more urbanized, urban cemeteries may become increasingly valuable for biodiversity conservation as cemeteries are ubiquitous elements of the green infrastructure in cities worldwide. By implementing a multi-taxon approach at different spatial extents, we analyzed habitat functions of a large urban cemetery in Berlin (Weißensee Jewish Cemetery) and explored related environmental variables. This cemetery is an outstanding cultural heritage site but it also stands for old urban cemeteries that have progressed to urban woodland, an ecosystem type that exists in many regional and religious contexts. The cemetery provided a habitat for 604 species; species of conservation concern comprised 1.6–100% of total species among different groups of taxa (in decreasing order: bats, birds, lichens, bryophytes, carabids, vascular plants, spiders). Species richness and species composition at the plot level were significantly related to differences in management intensity and resulting vegetation structures but differed among taxonomic groups. In vascular plants, carabids and spiders, the species composition varied significantly with habitat age, and there was a set of characteristic species for different age classes in each species group. Our results thus support the use of differentiated management approaches to maintain habitat heterogeneity by allowing wilderness development in some parts of a cemetery while keeping others more open. Since these aims can be combined with efforts to preserve outstanding grave architectures and allow access to visitors, our study indicates ways of reconciling conflicting aims of heritage preservation and biodiversity conservation, a promising perspective for biodiversity conservation in culturally shaped urban landscapes. We conclude that cemeteries provide important cultural ecosystem services within the urban green infrastructure.
Back in Berlin, I am now working as scientist in the new research project „Bridging in Biodiversity Science (BIBS)“ which is established at the Berlin-Brandenburg Institute of Advanced Biodiversity Research (BBIB) and the TU Berlin. Rapid transitions in land use patterns are often very conspicuous in the process of urbanization: within the central European landscape, large urban areas have emerged within the past two centuries. By ignoring them as islands of unnatural, novel landscapes, traditional research on ecology and biodiversity did not predict that numerous mammalian wildlife species would invade, stay and flourish within urban areas, or that cities would emerge as biodiversity hotspots. Since I am now responsible for the work package „Rural-urban coupling“ I am going to work on the following research topics:
understanding the effect and spatial reach of matrix heterogeneity and configuration,
measuring the temporal dynamics of urban landscapes to reveal effects of landuse legacy, historical connectivity and current land use,
identifying key functional traits of successful species that meet the challenges created by urban environments, and
exploring the consequences of increased contact for both people and wildlife