Supplemental Information 4: Text for supplementary tables and files

Invasive allergenic plant species may have severe health-related impacts. In this study we aim to predict the effects of climate change on the distribution of three allergenic ragweed species (Ambrosia spp.) in Europe and discuss the potential associated health impact. We built species distribution models based on presence-only data for three ragweed species, using MAXENT software. Future climatic habitat suitability was modeled under two IPCC climate change scenarios (RCP 6.0 and RCP 8.5). We quantify the extent of the increase in ‘high allergy risk’ (HAR) areas, i.e., parts of Europe with climatic conditions corresponding to the highest quartile (25%) of present day habitat suitability for each of the three species. We estimate that by year 2100, the distribution range of all three ragweed species increases towards Northern and Eastern Europe under all climate scenarios. HAR areas will expand in Europe by 27–100%, depending on species and climate scenario. Novel HAR areas will occur mostly in Denmark, France, Germany, Russia and the Baltic countries, and overlap with densely populated cities such as Paris and St. Petersburg. We conclude that areas in Europe affected by severe ragweed associated allergy problems are likely to increase substantially by year 2100, affecting millions of people. To avoid this, management strategies must be developed that restrict ragweed dispersal and establishment of new populations. Precautionary efforts should limit the spread of ragweed seeds and reduce existing populations. Only by applying cross-countries management plans can managers mitigate future health risks and economical consequences of a ragweed expansion in Europe

Warmer and less variable temperatures favour an accelerated plant phenology of two invasive weeds across sub-Antarctic Macquarie Island

The great plasticity and diverse reproductive strategies of invasive alien plants are widely assumed to contribute to invasion success, even in extreme areas, often displacing native species. In this context, climate change creates new opportunities for biological invasions. Environmental variability and global warming are two of the climatic processes that may promote invasiveness, since alien species modulate their phenology to succeed under these circumstances. We monitored the phenological development (phenological stage advancement) of the two main invasive alien species: Poa annua L. and Cerastium fontanum Baumg. in the sub-Antarctic Macquarie Island during the austral summer period along an altitudinal gradient. We found that higher temperatures lead to increased plant height and accelerated phenological development than lower temperatures in P. annua but found no direct evidence of the latter in C. fontanum. However, increased temperature variability negatively affected the phenological development of both species. Interestingly, despite their different reproductive strategy (rapid and impromptu in P. annua, and more synchronic and gradual in C. fontanum), both species prolifically succeeded in producing seeds at all sites showing the great acclimation of these two alien species even in limiting conditions. Since both alien species in Macquarie Island showed larger size and faster phenology at lower altitudes (i.e. milder conditions), this would indicate a great influence of ameliorating abiotic extremes on alien plant invasive capabilities at environmental extremes. Thus, our results warn of the increasing capabilities under climatic warming scenarios for alien plants to reproduce even at such remote ranges. This highlights the need to reinforce calls for special attention to prevent the spread of these kinds of species to other similar sub-polar areas, where intensive post-introduction management may be difficult or expensive.Field research of LRP was supported by AAS 4158 project of the Australian Antarctic Science Program.LRP was also recipient of a SCAR fellowship. MMS was supported by a FPI PhD Grant (BES-2013-062910) that was funded by the Spanish Ministry of Economy and Competitiveness