Stefan Dullinger

Mountains host highly diverse biota that are increasingly threatened by anthropogenic pressures around the globe. Although biological invasions are a well-recognized driver of global change, the available information on the distribution of alien species in mountains remains fragmented. To advance in filling this gap, we present a comprehensive dataset focused on alien vertebrates that contain roughly 320,000 records of over 700 species reported across ~3,000 mountains of the World. The dataset can be downloaded or visualized through interactive maps that facilitate access to species-specific occurrence records, mountain-specific lists of alien vertebrate species and mountain characterizations based on environmental and anthropogenic features. A workflow for the customized compilation of alien species records for specific taxonomic groups or study areas is also available at the RAVeM repository. Ours is a dynamic dataset open to continuous development based on user feedback, that has the potential to facilitate and support future studies and monitoring efforts of alien vertebrates in mountains worldwide.

Reconciling food production and biodiversity conservation requires socio-ecologically viable agroecosystems. To meet this goal, tropical agroforestry must balance yield-biodiversity trade-offs through local and landscape-level management. By integrating assessments of multi-taxa diversity, biocontrol, pollination, crop pests, soil fertility, microclimate, and yield in Amazonian cacao agroforests, we identified ecological-economic synergies. Yield gains were not associated with species loss. Instead, agroforests with high spatial and vertical shade-tree heterogeneity embedded in landscapes combining 30–35% forest cover and 40–45% of other arboreal habitats (e.g., orchards/agroforests) achieved the highest biodiversity and yields. In these landscapes, flying-vertebrate-mediated arthropod suppression doubled cacao yields. Increasing agroforest shade-tree cover from ≈15% to ≈80% yielded a four-fold rise in cacao fruit-set, tripled soil potassium and enhanced thermal buffering. But light limitation, rather than pest pressure, reduced harvestable yields above 30% shade-tree cover. Our findings demonstrate that combined agroforest-level and landscape-scale management can align biodiversity conservation and economic returns in tropical landscapes.

The peri‐Antarctic islands have largely been shielded from alien plant species due to low human pressure, limited introduction pathways, and local harsh climates. However, climate change is expected to lower these barriers. We assess the vulnerability of 12 peri‐Antarctic islands to invasion by 2220 plant species invasive in at least one region of the globe by projecting their climatic suitability under recent climate (1981–2010) and three future (2071–2100) climate change scenarios, ranging from mild to severe. We use three general circulation models (GCMs) and predictor sets, and account for widespread non‐analog climatic conditions by excluding projections outside the clamping mask. Our results reveal that eight islands are already climatically suitable for at least 100 invasive species. Climate change will generally increase climatic suitability for alien plants, particularly under moderate (+39% species on average across GCMs and islands) and severe climate change (+36% species). Nevertheless, under one GCM, suitability declines (−9.3% species) on eight islands under the most severe scenario. Currently, forbs and graminoids dominate native and alien plant communities, with woody species largely absent from colder islands. Our projections suggest that, if introduced, more woody alien species could establish, with all islands becoming suitable for at least one alien tree species even under moderate climate change. The greatest increases in alien species richness averaged across all scenarios and GCMs are projected for the Kerguelen (206 species) and Falkland Islands (175 species), whereas Signy (31 species), King George (72 species), and the Prince Edward Islands (54 species) will remain relatively resistant to plant invasion, despite strong proportional increases. These findings highlight an increasing vulnerability of the peri‐Antarctic island ecosystems to plant invasions and the need for strong biosecurity measures to limit further propagule introductions. Proactive management strategies are essential to mitigate risks and preserve the ecological integrity of these unique ecosystems.

Polyploidy, the possession of more than two sets of chromosomes in somatic cells, is a major driver in the diversification of flowering plants. Whereas an association between the occurrence of polyploids and latitude suggests a major impact of temperature on their global distribution, it remains unknown how polyploid frequency varies at regional spatial scales, leaving unclear the overall robustness of such relationship and its major determinants. Here, we present a flora-wide dataset of newly sampled, georeferenced ploidy occurrence data for ca. 42,000 samples of angiosperms collected along 101 elevational transects across the Eastern European Alps. Based on these data, we find that on a regional level polyploid frequency decreases with elevation, in contrast to expectations derived from global latitudinal distribution patterns. Moreover, polyploid frequency increases with distance from glacial refugia for samples below the timberline, particularly for plants with limited dispersal abilities. These results suggest that range dynamics associated with Pleistocene climatic fluctuations rather than current temperature may have played a predominant role for the current distribution of polyploids in temperate mountain ranges. In sum, our systematic fine-scale survey identified a complex interplay between historical processes and current environments on polyploid distribution that have remained undetected at the global scale.

Shrubification (i.e., increasing shrub abundance) and thermophilisation (i.e., increasing dominance of warmth-demanding species) are among the most widely documented imprints of climate change on mountain ecosystems. Still, it remains insufficiently quantified how increasing shrub cover alters the near-ground microclimate and snow duration, and in turn, how this interacts with the climate-change responses of alpine plant communities. To this end, we leveraged 21 years of vegetation resampling data and soil temperature time-series from 576 permanent plots positioned on European mountaintops and covering the treeline ecotone up to the middle alpine belt. Snow duration decreased faster in plots with stronger macroclimate warming, which in turn led to a rise in minimum soil temperatures of 0.28°C per decade across all plots. Overall thermophilisation rates were higher in sheltered habitats with snow accumulation, while habitats with higher shrub cover showed faster loss of cold-adapted species. Further research is needed to disentangle the joint effects of shrubs, snow and microclimates, yielding more accurate projections of climate-induced plant community reshuffling in alpine habitats.

Climate change increases plant species richness in alpine ecosystems. However, to what extent this diversity enrichment masks extinction dynamics of resident species remains elusive. In this study, we used floristic resurvey data from 896 permanent vegetation plots across 62 European mountain summits to show that local extinctions have increased over the past 21 years. Extinction rates rose with the magnitude of warming, and species were more likely to go extinct toward their low-elevation range margins and in communities undergoing stronger thermophilization. Moreover, local extinctions were significantly related to preceding abundance declines, which can serve as an early warning signal. These findings suggest that despite increasing plant species richness, plant assemblages above the treeline face an accelerating but so far neglected loss of their most characteristic species.

Summary: Impacts of alien fungal and fungus‐like plant pathogens depend on host interactions, including novel associations with native plants and co‐xenic associations with alien plants that do not share the same area of origin, both largely unquantified globally. Combining global distribution and association data, we characterised associations across pathogens' introduced regions, calculated host species richness (SR) and phylogenetic divergence, and examined predictors of novel/co‐xenic associations. Novel/co‐xenic alien pathogen–plant association records were common (53%) and dominated by widespread generalists. They were found in about one‐third of alien pathogens examined, mostly within their known phylogenetic host range. However, 46% of associations remained unclassified due to limited knowledge of pathogen biogeography. Novel/co‐xenic associations were more likely for pathogens with larger introduced ranges, wider phylogenetic host range, economically used hosts co‐occurring in the region, and host communities phylogenetically similar to the recipient regions' plant community. They were also more likely for host plants with no economic use and restricted native ranges, and in regions with higher plant SR. Novel/co‐xenic associations are common and shaped by contact opportunity, phylogenetic host range, and regional community composition. Unravelling fungal and fungus‐like pathogen biogeography is key to assessing their full magnitude.

Aim: Evaluating whether host plants can constrain the current distribution of host‐specialized butterflies as well as their ability to adapt ranges to climate change at cold and warm range margins. Location: Continental Europe. Time Period: Current to end of 21st century. Major Taxa Studied: Butterflies. Methods: We determined thermal niche margins of host‐specialized, Europe‐centred butterflies and their hosts from occurrence records and defined butterflies as potentially range‐limited by hosts if these limits differed by ≤ 0.1°C, ≤ 1°C or ≤ 2°C between the butterfly and its host collective. We used future temperatures under mild and pronounced climate change scenarios to evaluate whether a static host distribution could constrain butterflies' range adaptations at the cold margin or trigger co‐extinctions at the warm margin. Finally, we assessed relations between current host limitations and range size, mobility, phylogenetic host‐niche breadth, and red‐list status of the butterflies. Results: Of the 118 butterfly species studied, 48/33 (cold/warm margin) were potentially host‐limited, when using the ≤ 2°C as criterion, 29/11 species under the ≤ 1°C criterion, but only 15/5 species using the ≤ 0.1°C criterion. Expansion at the cold margin was potentially hampered by host immobility in 22 and 59 species under mild and pronounced climate change, respectively, while we detected risk of co‐extinction at the warm range margin in 14 and 55 species. Current host limitation at the cold margin increased with larger butterfly ranges. No consistent relations with other variables were detected. Main Conclusions: The distribution of several specialized Europe‐centred butterflies is at least co‐constrained by their hosts already today, and the impact of these constraints may intensify in the future. This is not only true at cold, but also at warm range limits, implying a risk of yet understudied future co‐extinctions. Understanding and prediction of climate‐change effects on insects thus need increased consideration of simultaneous host plant dynamics.

Recent changes in alpine vegetation are often attributed to climate warming, particularly community composition shifts towards more warmth-associated species, or thermophilization. Here we assess the link between thermophilization and warming across 53 European mountain summits. We combine long-term macroclimatic and microclimatic temperature time series with vegetation surveys in 724 permanent plots, monitored over 21 years, to evaluate a possible thermophilization signal and relate it to rates of change in 10 temperature metrics. We find evidence of both thermophilization of alpine plant communities and an increase in temperatures. However, although these two trends are related when averaged across mountain regions, their relationship is weak at the individual plot scale, especially when considering microclimatic temperature metrics. Instead, substrate conditions and particularly the availability of thermophilic colonizers in the surrounding vegetation have a major influence on plot-level thermophilization rates. We conclude that the response of plant communities to climate change strongly depends on the abiotic and biotic context, and intensified monitoring efforts are needed to reduce the resulting uncertainties.