Dimensions of invasiveness: Links between local abundance, geographic range size, and habitat breadth in Europe's alien and native floras

Understanding drivers of success for alien species can inform on potential future invasions. Recent conceptual advances highlight that species may achieve invasiveness via performance along at least three distinct dimensions: 1) local abundance, 2) geographic range size, and 3) habitat breadth in naturalized distributions. Associations among these dimensions and the factors that determine success in each have yet to be assessed at large geographic scales. Here, we combine data from over one million vegetation plots covering the extent of Europe and its habitat diversity with databases on species' distributions, traits, and historical origins to provide a comprehensive assessment of invasiveness dimensions for the European alien seed plant flora. Invasiveness dimensions are linked in alien distributions, leading to a continuum from overall poor invaders to super invaders - abundant, widespread aliens that invade diverse habitats. This pattern echoes relationships among analogous dimensions measured for native European species. Success along invasiveness dimensions was associated with details of alien species' introduction histories: earlier introduction dates were positively associated with all three dimensions, and consistent with theory-based expectations, species originating from other continents, particularly acquisitive growth strategists, were among the most successful invaders in Europe. Despite general correlations among invasiveness dimensions, we identified habitats and traits associated with atypical patterns of success in only one or two dimensions - for example, the role of disturbed habitats in facilitating widespread specialists. We conclude that considering invasiveness within a multidimensional framework can provide insights into invasion processes while also informing general understanding of the dynamics of species distributions.Deutsche Forschungsgemeinschaft (264740629) Grantová Agentura České Republiky (19-28491X) Grantová Agentura České Republiky (19-28807X) Grantová Agentura České Republiky (RVO 67985939) Austrian Science Fund (I 2086 - B29) Bundesministerium für Bildung und Forschung (01LC1807A) Eusko Jaurlaritza (IT299-10) National Research Foundation of Korea (2018R1C1B6005351) University of Latvia (AAp2016/B041//Zd2016/AZ03) Villum Fonden (16549

Analyzing landscape diversity in time: The use of Rènyi's generalized entropy function

This paper analyses the use of Re`nyi’s generalized entropy function to identify landscape temporal transformation. In order todemonstrate its application we analyze recent historic landscape diversity changes focusing on the evolution of boundariesbetween patches in the town of Isernia (central Italy).Firstly, three 1:25,000 land cover/vegetation raster maps (1954, 1981 and 1992) were selected. Next, changes in landscapediversity were measured analyzing the variation in the extension of boundary types between adjacent land cover categories(patches) from 1954 to 1992. To do this, Re`nyi’s diversity curves for each year were built and compared.The major advantage in applying the Re`nyi generalized parametric diversity function to analyze landscape changes in time isthat diversity profiles do not display a single index. In fact, a family of indexes is shown, many of which are currently applied andwidely used in landscape ecology

Are there habitats that contribute best to plant species diversity in coastal dunes ?

This paper describes patterns of diversity across major habitat typesin a relatively well preserved coastal dune system in central Italy. The research addressesthe following questions: (a) whether different habitats defined on the base of a land covermap support similar levels of biodiversity in terms of vascular flora richness and number ofrare and endangered species, and (b) how each habitat contributes to the total speciesdiversity of the coastal environment. A random stratified sampling approach based on adetailed land cover map was applied to construct rarefaction curves for each habitat typeand to estimate total species richness. In addition, the number of exclusive, rare andendangered species was calculated for each habitat type. Results highlight the importanceof the coastal dune zonation (embryo-dune, main dune, transition and stabilized dune) inspecies conservation because they harbour progressively higher species richness. However,differences among these habitats were not significant, so no particular species rich ‘‘hotspots’’could be evidenced. On the contrary, rarefaction curves show that the upper beach(strand) habitat sustains significantly smaller number of species, but surprisingly, it showsthe highest rarity values and highest proportion of endangered species. Therefore, for theestablishment of successful biodiversity conservation programs in these coastal environments,it is imperative not only to conserve biologically rich hotspots but also to includespecies poor habitats containing endangered or unique elements. Thus, the completecoastal vegetation mosaic including all coastal habitats is important to adequately characterizethe plant species diversity of coastal dune ecosystems

Assessing conservation status on coastal dunes: A multiscale approach

Coastal dune systems are particularly fragile and threatened environments, which, however, providefundamental ecosystem services to nearby urban areas acting for example as protective buffers againsterosion. Correctly assessing their conservation status is a priority in order to manage them adequately andto plan urban development in coastal regions. In this paper we propose a practical multiscale method forthe assessment of the conservation status of sandy coastal environment. The proposed method is articulatedin two stages, one focusing on the landscape and the other on the plant community level. In the firstphase mosaic structure and composition of the coastal landscape are analyzed using a series of indicators:natural coastal surface, richness of land cover typologies, landscape diversity and eveness, numberand average size of habitat patches, and mean shape index. At a detailed scale, floristic, vegetational andstructural aspects of the dune plant communities are analyzed along the main environmental gradient bymeasuring: spatial connectivity and richness of boundaries, species diversity, eveness and chorologicalindex. In this work we apply and test the method in an experimental area on the Tyrrhenian coast of Italy(Latium region), comparing the conservation status of two study sites

Assessing Carpobrotus invasion effects on coastal dune soils. Does the nature of the invaded habitat matter?

We investigate the modifications of soil factors in Carpobrotus invaded sites by evaluating differences between non-invaded and highly invaded plots in three habitats of coastal dune ecosystems in Central Italy. Nitrogen content, organic matter content, pH and salinity were measured in three coastal habitats: shifting dunes along the shoreline with Ammophila arenaria, Crucianellion maritimae fixed beach dunes and fixed coastal dunes with Juniperus spp. Soil variables of the invaded plots were compared to non-invaded ones using two-way factorial ANOVAs and post-hoc Tukey HSD tests. We found significant differences between invaded and non-invaded plots for nitrogen content, organic matter content and pH in both foredune habitats. On the other hand, no differences were revealed on fixed dunes. Thus, we found distinct responses of soil factors to Carpobrotus invasion depending on the habitat. Pioneer habitats with very poor soils are more sensitive to invasion probably because the production of litter by Carpobrotus is considerably higher than for native species. Therefore, for the establishment of efficient alien control programs of those habitats of conservation interest, it is imperative to take into account the relationship between invasive species presence and the top soil characteristics. For instance, particular attention is required in the foredune zone (pioneer habitats), where Carpobrotus invasion is more likely to affect the parameters of the soil

Habitat selection by invasive alien plants: a bootstrap approach

Even though there is no doubt that an invasion of a landscape by plants is a function of the abundance and spatial arrangement of different types of habitat, to the best of our knowledge, there has been no analysis of the relation between the patterns of plant invasion and the availability of specific habitats within landscapes invaded. The application of habitat selection functions (HSFs) provides a quantitative measure for determining if specific habitats are more likely to be invaded by a given species. The remarkable dynamics of spread of invasive alien plants makes them an ideal species pool for applying HSFs. This paper discusses the possible application of a bootstrap test of significance for identifying habitat types where the incidence of alien species is higher (preferred) or lower (avoided) than would be expected from a random null model for which all habitat types are invaded in proportion to their availability. In order to demonstrate the usefulness of the proposed approach we explored the habitat selection of a coastal alien plant, Carpobrotus aff. acinaciformis, in the Tyrrhenian coastal dunes of central Italy. According to this bootstrap test of significance, some important habitats of European conservation interest were more readily invaded by Carpobrotus than expected. From an applied research perspective, the use of an HSF approach can help identify the most invasion-prone habitats and, therefore, may facilitate the development of a clear and targeted prevention policy to control the introduction and spread of alien species in a landscape, for example, coastal dune habitats