Jonathan M. Jeschke’s research while affiliated with Freie Universität Berlin and other places

Aim The enemy release hypothesis states that the invasion success of non‐native species is partly due to their escape from natural enemies, e.g., herbivores. Large‐scale studies of herbivory using multiple species across multiple sites are needed to test the generality of herbivory release in non‐native plants. Location Europe. Methods We carried out leaf‐herbivory surveys from 2007 to 2021 in 15 botanical gardens ranging in latitude from 47°N (Switzerland) to 63°N (Norway) to investigate how herbivory levels differed between (i) native and non‐native species, and (ii) native and non‐naturalised or naturalised species. Results Overall, we found that herbivory levels were lower on non‐native than native species. In addition, we found that non‐naturalised plants suffered less herbivory than natives and that naturalised plants showed similar levels of herbivory to native plants. Main Conclusions We find broad support for lower herbivory of non‐native plant species compared to natives. However, the stronger reduction in herbivory for non‐naturalised plants suggests that herbivore release may be transient and less pronounced for naturalised non‐native species that have become abundant and integrated into resident communities. This has implications for the management of naturalised non‐native plants, which are performing well in their non‐native ranges despite suffering comparable herbivory levels to native species.

In this contribution of the Hypothesis Description series, we provide an overview of one of the longest-standing hypotheses in invasion science: Darwin's naturalization hypothesis. We present a brief summary of past definitions and propose the revised definition “low phylogenetic similarity between non-native species and the recipient community increases invasion success”. This formulation follows the basic form ‘subject – relationship – object’, enabling clarity for future research and computational applications in invasion biology. We also provide formalized definitions for previous formulations of the hypothesis and identify both related and opposite hypotheses to Darwin’s naturalization hypothesis.

In the era of big data and global biodiversity decline, there is a pressing need to transform data and information into findable and actionable knowledge. We propose a conceptual classification scheme for invasion science that goes beyond hypothesis networks and allows to organize publications and data sets, guide research directions, and identify knowledge gaps. Combining expert knowledge with literature analysis, we identified five major research themes in this field: introduction pathways, invasion success and invasibility, impacts of invasion, managing biological invasions, and meta-invasion science. We divided these themes into 10 broader research questions and linked them to 39 major hypotheses forming the theoretical foundation of invasion science. As artificial intelligence advances, such classification schemes will become important references for organizing scientific information. Our approach can be extended to other research fields, fostering cross-disciplinary connections to leverage the scientific knowledge needed to address Anthropocene challenges.

Wildlife in cities divides people, with some animals bringing positive benefits and others causing conflict, for example due to property damage. Urban wildlife professionals from municipal administration, nature conservation, and hunting associations have a crucial role in shaping human‐wildlife relationships in cities and fostering conflict‐free coexistence. While many studies on urban wildlife have focused on the views of citizens, few have investigated the perspectives of experts to date. To address this knowledge gap, we interviewed 36 urban wildlife professionals giving guidance in the context of urban wildlife management, either in one of the four largest German cities by population (Berlin, Hamburg, Munich and Cologne) or at the national level. Red foxes, wild boars, raccoons, stone martens and Eurasian beavers were the five mammal species most frequently highlighted in interviews to cause human‐wildlife conflicts. The interviewees saw wild boars and raccoons as the most controversial urban wild mammals but emphasized the need to create refuges for beavers and better inform the public about foxes. Management in terms of public outreach, urban planning and population control, as well as establishing official contact points and stricter fines of activities violating regulations were highlighted as important elements of a toolkit to manage urban wildlife conflicts. Read the free Plain Language Summary for this article on the Journal blog.

Cemeteries are key urban green spaces with multifaceted societal and ecological importance. Their biodiversity is shaped by unique environmental and cultural factors. They can potentially protect rare and endangered species, yet their conservation value compared with other urban green spaces remains largely unexplored. We sought to fill this gap by systematically reviewing literature to investigate the conservation value of cemeteries relative to other urban green spaces (botanical gardens, institutional premises, natural remnants, and parks) by comparing species richness and proportions of native and unique species. We analyzed data from 70 papers covering 50 cities in 27 countries with linear and binomial mixed‐effects models at both site and city level. Cemetery conservation value was similar to urban parks, except for the proportion of unique species, for which parks had significantly higher proportions (21.9% vs. 14.2%, p < 0.001). Cemeteries hosted slightly higher proportions of native species at the city level than botanical gardens (99.7% vs. 99.6%, p < 0.001) and institutional green spaces (96.3% vs. 94.1%, p = 0.034) and proportions comparable to parks and natural remnants (p > 0.05). They also had similar or higher values than institutional premises in species richness and unique species proportions (p > 0.05) and a higher site‐level proportion of native species (p < 0.001). In contrast, species richness (slopes = −0.11 and −0.25, respectively) and unique species proportions (4.4% and 6.9%, respectively, p < 0.001 for both) were lower in cemeteries than in remnants of natural areas and in botanical gardens. The conservation value of cemeteries and parks was similar for animals, but parks had a higher value for plants. Overall, cemeteries were generally at least as valuable as some other green spaces for urban biodiversity and mostly native biota. Their religious and cultural significance suggests they will remain intact in the long term; thus, it is essential to prioritize and further promote their biodiversity in conservation and sustainable urban design plans.

Hypotheses are critical components of scientific argumentation. Knowing established hypotheses is often a prerequisite for following and contributing to scientific arguments in a research field. In scientific publications, hypotheses are usually presented for specific empirical settings, whereas the related general claim is assumed to be known. Prerequisites for developing argumentation machines for assisting scientific workflows are to account for domain-specific concepts needed to understand established hypotheses, to clarify the relationships between specific hypotheses and general claims, and to take steps towards formalization. Here, we develop a framework for formalizing hypotheses in the research field of invasion biology. We suggest conceiving hypotheses as consisting of three basic building blocks: a subject, an object, and a hypothesized relationship between them. We show how the subject-object-relation pattern can be applied to well-known hypotheses in invasion biology and demonstrate that the contained concepts are quite diverse, mirroring the complexity of the research field. We suggest a step-wise approach for modeling them to be machine-understandable using semantic web ontologies. We use the SuperPattern Ontology to categorize hypothesized relationships. Further, we recommend treating every hypothesis as part of a hierarchical system with 'parents' and 'children'. There are three ways of moving from a higher to a lower level in the hierarchy: (i) specification, (ii) decomposition , and (iii) operationalization. Specification involves exchanging subjects or objects. Decomposition means zooming in and making explicit assumptions about underlying (causal) relationships. Finally, operationalizing a hypothesis means providing concrete descriptions of what will be empirically tested.

While reintroductions of regionally extinct native species usually benefit ecosystems, reintroduced animals often struggle to locate appropriate habitats where they can establish themselves without conflict with humans. European beavers (Castor fiber) were successfully reintroduced to Germany almost 60 years ago and have reached high abundances again. As beavers can damage trees and change landscapes, they are increasingly in conflict with humans. We investigated human perceptions of beavers in Germany using an online survey, as they are an example of a reintroduced species with an expanding population and potential conflicts with humans. We asked participants about their emotions (anger, fear, interest, joy) towards beavers and what they consider to be acceptable beaver habitats. Of nearly 1500 survey participants, 803 (53%) were from the general public, 475 (32%) from the agricultural sector and 219 (15%) from forestry. People in these sectors had very different perspectives: beavers were positively perceived by the general public, but negatively by stakeholders working in agriculture and forestry. Independently of stakeholder groups, we also found regional differences, as participants from Bavaria—the German state with the highest beaver densities—viewed beavers more negatively than those from the rest of Germany. Zoos and wildlife parks, as well as urban and nature conservation areas, were considered to be the most acceptable habitats for beavers, whereas survey participants did not accept private gardens and cultivated areas as beaver habitats. We discuss the sources of negative emotions towards beavers and how ecologically suitable habitats differ from those that appear acceptable by humans. Even 60 years after their reintroduction, beavers in Germany are still being recognized as both a novelty and a nuisance. Our findings highlight the need for active beaver management and increased public engagement to enable positive coexistence between beavers and humans in Germany. Read the free Plain Language Summary for this article on the Journal blog.

Urbanisation alters biodiversity patterns and threatens to disrupt mutualistic interactions. Aside from pollination, however, little is known about how mutualisms change in cities. Our study aimed to assess how urbanisation affects the protective mutualism between ants and aphids, investigating potential behavioural changes in mutualistic ants and their implications for aphids in urban environments. To do so, we studied the protective mutualism between the pink tansy aphid (Metopeurum fuscoviride) and the black garden ant (Lasius niger) along an urbanisation gradient in Berlin, Germany. In nine locations along this gradient, we measured aphid colony dynamics and proxies for parasitism, quantified the investment of ants in tending aphids and conducted behavioural assays to test the aggressiveness of ant responses to a simulated attack on the aphids. We found that aphid colonies flourished and were equally tended by ants across the urbanisation gradient, with a consistent positive density dependence between aphid and ant numbers. However, ants from more urbanised sites responded more aggressively to the simulated attack. Our findings suggest that this protective mutualism is not only maintained in the city, but that ants might even rely more on it and defend it more aggressively, as other food resources may become scarce and more unpredictable with urbanisation. We thereby provide unique insights into this type of mutualism in the city, further diversifying the growing body of work on mutualisms across urbanisation gradients.

A branch of island biogeography has emerged to explain alien species diversity in the light of the biogeographic and anthropogenic context, yet overlooking the functional and phylogenetic facets. Evaluating alien and native birds of 407 oceanic islands worldwide, we built structural equation models to assess the direct and indirect influence of biotic, geographic, and anthropogenic contexts on alien functional diversity (FD) and phylogenetic diversity (PD). We found that alien taxonomic richness was the main predictor of both diversities. Anthropogenic factors, including colonization pressure, associated with classic biogeographical variables also strongly influenced alien FD and PD. Specifically, habitat modification and human connectivity markedly drove alien FD, especially when controlled by taxonomic richness, whereas the human population size, gross domestic product, and native PD were crucial at explaining alien PD. Our findings suggest that humans not only shape taxonomic richness but also other facets of alien diversity in a complex way.