Aerial images of the high summits of the Spanish Central Range reveal significant changes in vegetation over the period 1957 to 1991. These changes include the replacement of high-mountain grassland communities dominated by Festuca aragonensis, typical of the Cryoro-Mediterranean belt, by shrub patches of Juniperus communis ssp. alpina and Cytisus oromediterraneus from lower altitudes (Oro-Mediterranean belt). Climatic data indicate a shift towards warmer conditions in this mountainous region since the 1940s, with the shift being particularly marked from 1960. Changes include significantly higher minimum and maximum temperatures, fewer days with snow cover and a redistribution of monthly rainfall. Total yearly precipitation showed no significant variation. There were no marked changes in land use during the time frame considered, although there were minor changes in grazing species in the 19th century. It is hypothesized that the advance of woody species into higher altitudes is probably related to climate change, which could have acted in conjunction with discrete variations in landscape management. The pronounced changes observed in the plant communities of the area reflect the susceptibility of high-mountain Mediterranean species to environmental change.

Aim  Biological invasions are a major component of global change with increasing effects on natural ecosystems and human societies. Here, we aim to assess the relationship between plant invader species attributes and the extent of their distribution range size, at the same time that we assess the association between environmental factors and plant invader species richness. Location  Spain, Mediterranean region. Methods  From the species perspective, we calculated the distribution range size of the 106 vascular plant invaders listed in a recently published atlas of alien plant species in Spain. Range size was used as an estimation of the degree of invasion success of the species. To model variation in range size between species as a function of a set of species attributes, we adopted the framework of the generalized linear mixed models because they allow the incorporation of taxonomic categories as nested random factors to control for phylogenetic relationships. From the invaded site perspective, we determined invader plant species richness as the number of species for each 10 × 10 km Universal Transverse Mercator (UTM) grid. For each grid cell, we estimated variables concerning landscape, topography, climate and human settlement. Then, we performed a generalized linear mixed model incorporating a defined spatial correlation structure to assess the relationship between plant invader richness and the environmental predictors. Results  From the species perspective, wind dispersal and minimum residence time appeared to favour invasion success. From the invaded site perspective, we identified high anthropogenic disturbance, low altitude, short distance to the coastline and dry, hot weather as the main correlates to UTM grid cell invader richness. Main conclusions  According to these results, an increasing importance of man‐modified ecosystems and global warming in the Mediterranean region should facilitate the expansion of plant invaders, especially wind‐dispersed species, leading to the accumulation of invasive species in some sites (i.e. invasion hot spots).

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The increasing number of invasive species and their effects on wildlife conservation, together with a lack of public resources, make it necessary to prioritize management actions. In practice, management decisions are often reached on the basis of subjective reasoning rather than scientific evidence. To develop a more evidence-based and efficient management of biological invasions, decision tools (e.g. multi-criteria frameworks) that help managers prioritize actions most efficiently are key. In this paper we review to what degree such decision tools are currently available. We used a literature search to identify relevant studies. Our analysis indicates that available studies are largely biased towards risk analysis and that only a few authors have proposed cost-benefit or multi-criteria frameworks for decision making. Until now, these frameworks have only been applied at limited regional scales but they could be applied more widely. Our review also shows critical biases in the geographical focus, habitats, and taxonomic groups of available studies. Most studies have focused on Europe, North America or Australia; other continents have largely been ignored. The majority of studies have focused on terrestrial plants; other habitats and taxonomic groups have been poorly covered. Most studies have focused on a single invasive species but practical management tools should consider a wide variety of invaders. We conclude with suggestions for developing improved decision tools.

The alien plant species and the ecological factors that facilitate their invasion to a coastal strip in the Baix Camp region (Tarragona, NE Spain) were studied. A detailed inventory of the area showed that 20% of the plant species, most of them from the American Continent, were aliens, many of which were strongly invasive.At the habitat level, the relationships between the invasive behaviour and a number of autecological, ecological and habitat variables were analysed by means of logistic analyses. In the best model five variables were related to alien plant invasions: climatic affinity, disturbance of the invaded habitat, route of introduction, soil moisture during summer, and life form. To elucidate the environmental factors that could be responsible for alien plant invasions at a regional scale, the number of alien taxa and the environmental features at 13 localities of the western Mediterranean area were analysed. The warm lowlands, subjected to low annual rainfall and high population density, exhibited the greatest reception capacity for alien plants.It is concluded that various specific environmental features -high mean temperatures, the abundance of riparian systems, the existence of biotopes with favourable water balance which harbour a great richness of alien species and the high human pressure to which the enclave is subjected, combined with the ecological requirements of the alien species and certain species attributes (biotype) can interact at different scales and have caused the over-representation of alien plants.

Aim  The aims of this study are: (1) to explore the relationships between the Ellenberg indicator values (light, temperature and moisture) recently developed for two Mediterranean regions (Italy and Greece); and (2) to evaluate the possibility of using these values in other Mediterranean areas. Location  Southern Greece and the Mediterranean part of Italy. Methods  A global matrix containing 966 items of information (161 species × 3 indicator variables × 2 values assigned in each study, one in Italy and one in Greece) was constructed. A test of the accuracy of the values in predicting actual environmental conditions was provided using a detrended correspondence analysis (DCA) on published vegetation relevés from the Mediterranean region. The gamma statistic was used to express relationships of ecological indicator values between the two regions, and pairs of indicator values calculated for each species were compared using Wilcoxon matched pairs tests. Results  The results showed that indices developed for Greece and Italy were not similarly correlated to sample scores along DCA axis 1. Species’ indicator values for Italy and for Greece were highly significantly correlated for light and moisture and significantly correlated for temperature, but the correlations were weak (0.20 ≤ gamma ≤ 0.31). Pairwise testing gave significantly different indicator values for the two regions. Discrepancies below or equal to 2 units on 9‐point scales (12 points for moisture) were found for 88%, 70% and 54% of the species respectively for light, temperature and moisture indices. A substantial number of species showed higher discrepancies, from 3 up to 6 units. Main conclusions  In the light of the present work, it seems clear that the indicator values developed for Italy and for Greece should not be used outside the region for which they were defined. This constitutes additional evidence that indicator values can be influenced by the identity of potential competitors. It also underlines the need to use standardized methods for calibrating indicator values against measured variables in such a way that indicator systems can serve as general reference systems.

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