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Across the globe, invasive alien species cause severe environmental changes, altering species composition and ecosystem functions. So far, mountain areas have mostly been spared from large-scale invasions. However, climate change, land-use abandonment, the development of tourism and the increasing ornamental trade will weaken the barriers to invasions in these systems. Understanding how alien species will react and how native communities will influence their success is thus of prime importance in a management perspective. Here, we used a spatially and temporally explicit simulation model to forecast invasion risks in a protected mountain area in the French Alps under future conditions. We combined scenarios of climate change, land-use abandonment and tourism-linked increases in propagule pressure to test if the spread of alien species in the region will increase in the future. We modelled already naturalized alien species and new ornamental plants, accounting for interactions among global change components, and also competition with the native vegetation. Our results show that propagule pressure and climate change will interact to increase overall species richness of both naturalized aliens and new ornamentals, as well as their upper elevational limits and regional range-sizes. Under climate change, woody aliens are predicted to more than double in range-size and herbaceous species to occupy up to 20% of the park area. In contrast, land-use abandonment will open new invasion opportunities for woody aliens, but decrease invasion probability for naturalized and ornamental alien herbs as a consequence of colonization by native trees. This emphasizes the importance of interactions with the native vegetation either for facilitating or potentially for curbing invasions. Overall, our work highlights an additional and previously underestimated threat for the fragile mountain flora of the Alps already facing climate changes, land-use transformations and overexploitation by tourism., (© 2017 John Wiley & Sons Ltd.)

Coastal dunes worldwide harbor threatened habitats characterized by high diversity in terms of plant communities. In Italy, recent assessments have highlighted the insufficient state of conservation of these habitats as defined by the EU Habitats Directive. The effects of predicted climate change could have dramatic consequences for coastal environments in the near future. An assessment of the efficacy of protection measures under climate change is thus a priority. Here, we have developed environmental envelope models for the most widespread dune habitats in Italy, following two complementary approaches: an "indirect" plant-species-based one and a simple "direct" one. We analyzed how habitats distribution will be altered under the effects of two climate change scenarios and evaluated if the current Italian network of protected areas will be effective in the future after distribution shifts. While modeling dune habitats with the "direct" approach was unsatisfactory, "indirect" models had a good predictive performance, highlighting the importance of using species' responses to climate change for modeling these habitats. The results showed that habitats closer to the sea may even increase their geographical distribution in the near future. The transition dune habitat is projected to remain stable, although mobile and fixed dune habitats are projected to lose most of their actual geographical distribution, the latter being more sensitive to climate change effects. Gap analysis highlighted that the habitats' distribution is currently adequately covered by protected areas, achieving the conservation target. However, according to predictions, protection level for mobile and fixed dune habitats is predicted to drop drastically under the climate change scenarios which we examined. Our results provide useful insights for setting management priorities and better addressing conservation efforts to preserve these threatened habitats in future.

The Mediterranean Basin has historically been subject to alien plant invasions that threaten its unique biodiversity. This seasonally dry and densely populated region is undergoing severe climatic and socioeconomic changes, and it is unclear whether these changes will worsen or mitigate plant invasions. Predictions are often biased, as species may not be in equilibrium in the invaded environment, depending on their invasion stage and ecological characteristics. To address future predictions uncertainty, we identified invasion hotspots across multiple biased modelling scenarios and ecological characteristics of successful invaders. We selected 92 alien plant species widespread in Mediterranean Europe and compiled data on their distribution in the Mediterranean and worldwide. We combined these data with environmental and propagule pressure variables to model global and regional species niches, and map their current and future habitat suitability. We identified invasion hotspots, examined their potential future shifts, and compared the results of different modelling strategies. Finally, we generalised our findings by using linear models to determine the traits and biogeographic features of invaders most likely to benefit from global change. Currently, invasion hotspots are found near ports and coastlines throughout Mediterranean Europe. However, many species occupy only a small portion of the environmental conditions to which they are preadapted, suggesting that their invasion is still an ongoing process. Future conditions will lead to declines in many currently widespread aliens, which will tend to move to higher elevations and latitudes. Our trait models indicate that future climates will generally favour species with conservative ecological strategies that can cope with reduced water availability, such as those with short stature and low specific leaf area. Taken together, our results suggest that in future environments, these conservative aliens will move farther from the introduction areas and upslope, threatening mountain ecosystems that have been spared from invasions so far. [ABSTRACT FROM AUTHOR]

Question: Vegetation around the alpine–treeline ecotone faces changes in both climate and land use (i.e. grazing abandonment). Broad‐scale shrub encroachment is considered an effect of these changes, but it remains unclear how this process is mediated by local‐scale environmental heterogeneity. Our goal is to determine which local‐scale environmental factors shape the spatial distribution and temporal trends of alpine dwarf shrub vegetation dominated by Juniperus communis in Mediterranean mountains. Location: Three sites in the Central Apennine Mountain Range (Italy): Mt. Terminillo, Mt. Duchessa and Mt. Ernici. Methods: Combining a set of environmental variables obtained at a fine scale (25‐m resolution) from multi‐year remote sensing imagery and field‐collected vegetation data, we modelled the occurrence and cover of Juniperus communis‐dominated dwarf shrubland, as well as its change over time, as a function of local climate, topography and land use, using linear and generalized mixed effects models. Results: Over a period of almost 60 years (1954–2012) shrubland occurrence increased by 12% and shrubland cover by 10% in our study sites. Its current distribution and change over time appear to be strongly shaped by the joint influences of fine‐scale topography, above‐ground biomass, land use and microclimate. Shrublands have been favoured locally in areas with harsher alpine environmental constraints and stronger resource limitations. Conclusions: Our study shows that in the Mediterranean high‐mountain environment J. communis dwarf shrubland acts as a stress‐tolerant pioneer vegetation, occurring in areas that are otherwise sparsely vegetated. Contrary to our expectations, at fine scales, warmer temperatures and the regional decline in grazing did not favour shrub encroachment. Despite increasing overall, J. communis shrubs have little competitive ability to successfully encroach grasslands, and remain restricted to less‐productive areas. Our results confirm that fine‐scale environmental heterogeneity can strongly influence shrub distribution and dynamics, thereby modulating future responses in evolving alpine ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Invasive species provide an opportunity to study biogeography in action, allowing us to observe how species adapt and fill their environmental niche when introduced to new ecological settings. Here we use sea spurge—a foredune specialist plant species native to Europe which has recently spread across Australia's southern coasts—as a model system to explore species' environmental niches adaptations and potential for future spread following introduction outside their native range. Location: Europe and Australia. Taxon: Sea spurge, Euphorbiaparalias, Euphorbiaceae. Methods: We compiled presence‐absence data of E.paralias from >190,000 vegetation surveys in the native and invaded range. We combined presence‐absence data with information on climate, soil, coastal morphology and human pressure, to test whether E.paralias' environmental niche has shifted following invasion and used species distributions models (SDMs) to map its invasion potential under current and future climatic conditions. Results: The environmental niche of E.paralias has shifted since reaching Australia, expanding into areas further away from people, closer to the shoreline and with higher temperatures. SDMs revealed that alongside broad‐scale gradients in temperature and rainfall, the distribution of E.paralias is also constrained by soil substrate and dune morphology—highlighting the importance of these fine‐scale drivers in shaping invasion dynamics in coastal environments. Moreover, SDMs suggest that future expansion in Australia will result from continued niche filling, not changes in climatic suitability. Main conclusions: Despite its impressive dispersal ability, E.paralias has not yet reached equilibrium in its invaded range and is likely to continue to expand its distribution in Australia regardless of climate change. E.paralias' key to success has been its ability to suit novel environments. We provide one of the first examples of how to leverage distribution data and SDMs to test hypotheses about niche conservatism and expansion in coastal dune invasive plant species. [ABSTRACT FROM AUTHOR]

Aim: Seasonal germination is critical in synchronizing seedling emergence with optimal conditions for survival but will be disrupted by climate change. Understanding how germination of threatened species with complex dormancy patterns will be affected by climate change is a priority for their management. By exploring the effects of temperature on germination for six Persoonia species ranging in rareness, this study aims to improve ex situ plant production and better understand the probable impacts of climate change on persistence of local populations. Location: South‐eastern Australia. Methods: The role of temperature on seed dormancy was explored using generalized additive models to predict germination probabilities for six Persoonia species ranging in rarity. Embryos were exposed to 24‐hr cycles of alternating 12‐hr warmer/light and 12‐hr cooler/dark combinations of temperatures between 8°C and 45°C. Optimal temperature conditions for germination were determined, and spatiotemporal changes in germination probability were predicted in response to expected temperatures under future climate change scenarios. Results: Unique germination niches representing complex responses across diurnal regimes were identified for each species. Germination probability was predicted to decline in four species in response to warmer day or night temperatures and in two species in response to cooler day or night temperatures. Across bioregions, areas of likely germination largely aligned with species‐specific temperature sensitivity, with suitable germination niche declining in four species, one staying roughly the same and one increasing in physical range under predicted climate warming. Main conclusions: In response to increased temperatures associated with climate change, germination probability varied from current rates. These changes were quantified both spatially and temporally and highlight expected challenges for persistence of some populations, particularly range restricted and rare species. Current understanding of extinction threat must consider future conditions, and these results highlight the urgent need to protect populations of these six Persoonia species that are currently threatened by habitat destruction and encourage future population persistence through restoration efforts. [ABSTRACT FROM AUTHOR]

ABSTRACT: The number of alien plants escaping from cultivation into native ecosystems is increasing steadily. We provide an overview of the historical, contemporary and potential future roles of ornamental horticulture in plant invasions. We show that currently at least 75% and 93% of the global naturalised alien flora is grown in domestic and botanical gardens, respectively. Species grown in gardens also have a larger naturalised range than those that are not. After the Middle Ages, particularly in the 18th and 19th centuries, a global trade network in plants emerged. Since then, cultivated alien species also started to appear in the wild more frequently than non‐cultivated aliens globally, particularly during the 19th century. Horticulture still plays a prominent role in current plant introduction, and the monetary value of live‐plant imports in different parts of the world is steadily increasing. Historically, botanical gardens – an important component of horticulture – played a major role in displaying, cultivating and distributing new plant discoveries. While the role of botanical gardens in the horticultural supply chain has declined, they are still a significant link, with one‐third of institutions involved in retail‐plant sales and horticultural research. However, botanical gardens have also become more dependent on commercial nurseries as plant sources, particularly in North America. Plants selected for ornamental purposes are not a random selection of the global flora, and some of the plant characteristics promoted through horticulture, such as fast growth, also promote invasion. Efforts to breed non‐invasive plant cultivars are still rare. Socio‐economical, technological, and environmental changes will lead to novel patterns of plant introductions and invasion opportunities for the species that are already cultivated. We describe the role that horticulture could play in mediating these changes. We identify current research challenges, and call for more research efforts on the past and current role of horticulture in plant invasions. This is required to develop science‐based regulatory frameworks to prevent further plant invasions. [ABSTRACT FROM AUTHOR]

Climate change and extreme events, such as drought, threaten ecosystems world-wide and in particular mountain ecosystems, where species often live at their environmental tolerance limits. In the European Alps, plant communities are also influenced by land-use abandonment leading to woody encroachment of subalpine and alpine grasslands., In this study, we explored how the forest-grassland ecotone of Alpine tree lines will respond to gradual climate warming, drought events and land-use change in terms of forest expansion rates, taxonomic diversity and functional composition. We used a previously validated dynamic vegetation model, FATE- HD, parameterized for plant communities in the Ecrins National Park in the French Alps., Our results showed that intense drought counteracted the forest expansion at higher elevations driven by land-use abandonment and climate change, especially when combined with high drought frequency (occurring every 2 or less than 2 years)., Furthermore, intense and frequent drought accelerated the rates of taxonomic change and resulted in overall higher taxonomic spatial heterogeneity of the ecotone than would be expected under gradual climate and land-use changes only., Synthesis and applications. The results from our model show that intense and frequent drought counteracts forest expansion driven by climate and land-use changes in the forest-grassland ecotone of Alpine tree lines. We argue that land-use planning must consider the effects of extreme events, such as drought, as well as climate and land-use changes, since extreme events might interfere with trends predicted under gradual climate warming and agricultural abandonment. [ABSTRACT FROM AUTHOR]