Aim: Alien plants with certain characteristics may have been introduced earlier and more frequently than others. Such introduction bias may cause spurious associations between plant characteristics ...and naturalization (the establishment of self-sustaining populations in the wild). We aimed to disentangle direct and indirect (i.e. mediated by introduction history) effects of species characteristics on the naturalization success of alien plants introduced for horticulture. Location: Germany (non-native range); rest of the world (native range). Methods: We compiled a dataset of 435 alien plant species introduced in cultivation in Germany, including data on their year of introduction, the number of botanical gardens where they are planted, native range, biological traits and naturalization success. We used path analysis to estimate the direct effects of geographical origin and biological traits on naturalization, and their indirect effects mediated by year and/or frequency of introduction. Results: We found significant direct positive effects of native range size and winter hardiness on naturalization. Alien species native to other parts of Europe and species with a large native range were brought to the country earlier than other species. In addition, woody species, winter-hardy species and tall species were planted more frequently than others. Because the number of botanical gardens where a species is planted increased naturalization success directly, and residence time did so indirectly through a significant positive association with the number of botanical gardens, most of the species characteristics had indirect effects on naturalization. Main conclusions: Our approach allowed us to show that apparent effects of species characteristics on naturalization success can be at least partly indirect, due to introduction biases. This indicates that failure to recognize such introduction biases could impair our ability to explain the success of alien plant species.
We demonstrate how native and nonnative plant taxa used as ornamentals in private and public urban green spaces can significantly strengthen plant conservation in time of extinctions by expanding the ...capacity for ex situ living collections and raising awareness among professional and private gardeners and plant collectors. Based on global databases, we document the current representation of threatened plant taxa in horticulture compared to collections in botanical gardens. A substantial number of threatened taxa are already used in gardening, however, there is great unused potential—especially to reach high enough representation of genetic diversity and plant material for reintroduction and restoration programs. Considering urban greening as an integral part of ex situ conservation strategies can provide critically needed additional space and human resources for ex situ collections, while increasing the often low genetic, species and phylogenetic diversity of many newly established plantings that make them vulnerable to climate change and disease risks.
•82.3 % of woody species in Spanish urban parks are non-native.•Socioeconomic and climatic variables explain the trait composition of parks.•Proportion of non-native species increases with older ...human population and bigger homes.•Proportion of established species decreases with higher annual thermic range.•Our study provide new ways of predicting establishment of non-native plant species.
Urban parks and gardens provide cultural and aesthetic services critical for human well-being. Yet, they represent one of the main reasons for the intentional introduction of ornamental species, some of which can escape and establish in natural ecosystems. Besides aesthetic reasons, climate and socioeconomic factors can also modulate which species are planted in urban parks. Here, we evaluate the relationship between traits of 486 ornamental woody species from 46 Spanish urban parks and climatic and socioeconomic variables. We specifically assessed how plant traits, climatic, and socioeconomic factors are related to the proportion of non-native species and, among them, to the proportion of established non-native species in Spain. Overall, we found clear associations between species traits and climatic variables. Most notably, parks with warmer winters have more plant species with conspicuous flowers, whereas parks with colder winters and a more continental climate have more species with higher tolerances to cold and shade. Most of the species recorded in our study are non-native (82 %). Higher proportions of non-native species in urban parks were positively associated with towns with large size homes and inhabitants with higher median age but negatively related to parks with species with a higher hardiness-zone range. Moreover, a greater proportion of non-native species that can establish in the natural ecosystems was found in parks with lower continentality conditions. Our results show that Spanish urban parks have an overwhelming proportion of non-native woody species, some of which have the potential to establish, and that the variation in their proportions can be explained by climatic, and socioeconomic factors.
Abstract
Humans cultivate thousands of economic plants (i.e. plants with economic value) outside their native ranges. To analyze how this contributes to naturalization success, we combine global ...databases on economic uses and naturalization success of the world’s seed plants. Here we show that naturalization likelihood is 18 times higher for economic than non-economic plants. Naturalization success is highest for plants grown as animal food or for environmental uses (e.g. ornamentals), and increases with number of uses. Taxa from the Northern Hemisphere are disproportionately over-represented among economic plants, and economic plants from Asia have the greatest naturalization success. In regional naturalized floras, the percentage of economic plants exceeds the global percentage and increases towards the equator. Phylogenetic patterns in the naturalized flora partly result from phylogenetic patterns in the plants we cultivate. Our study illustrates that accounting for the intentional introduction of economic plants is key to unravelling drivers of plant naturalization.
Aim: A major challenge in ecology is to understand how multiple causal factors, which may interact, drive success of non-native plants in new ranges. In this study we addressed the role of ...introduction history, climatic suitability, native range size, species traits and their interactions in the establishment of Chinese woody species in Europe. Location: China (native range), Europe (new range). Methods: We tested whether establishment of 449 Chinese woody species in Europe was associated with residence time (time since earliest planting), planting frequency, climatic suitability, native range size and species traits. We also considered possible nonlinear effects and interactions among these variables. For the 38 species that have established in Europe, we further tested whether these variables and interactions explained their establishment in multiple European countries. Results: Establishment of the 449 species in Europe was positively associated with residence time, planting frequency and climatic suitability. Except residence time, these factors were also positively associated with establishment of the 38 species in multiple countries. None of the traits tested had statistically significant main effects on establishment in Europe, but, for the established species, longer flowering period and having compound leaves were positively associated with establishment in multiple countries. The positive association between establishment in Europe and residence time was stronger for evergreen than for deciduous species. In addition, evergreens, unlike deciduous species, showed a positive association between establishment in Europe and fruiting duration. Moreover, establishment in multiple countries was positively associated with planting frequency for species with compound leaves but not for species with simple leaves, and the association between the establishment and fruiting duration changed from negative to moderately positive as climatic suitability increased. Main conclusions: Introduction history and climatic suitability explain most of the variation in establishment, and modulate the role of species traits, such as leaf retention, leaf type and fruiting duration.
Urban biotic homogenization is one of the foremost challenges for conservation of biodiversity in urban green areas. Urban gardening is a common practice in many industrialised and developing ...countries. The ability of urban vegetable gardens to support biodiversity, however, has yet to be studied in depth. To investigate the responses of flora and soil fauna to urbanization, we surveyed the taxonomic and functional composition of plant and collembolan communities, in addition to soil parameters, in 15 urban vegetable gardens across three large French cities. The vegetation was identified in six plots of 1 × 1 m in each urban vegetable garden and collembolan were extracted from one intact soil core sampled in the center of each plot (5 cm depth, 6 cm diameter). We found contrasting effects of urbanization on plants and Collembola biodiversity. The taxonomic and functional composition of the soil fauna was more similar within cities than among cities, which was driven by similarities in soil parameters. In contrast, plant communities were functionally similar among cities. Understanding the effects of urbanization on soil biodiversity could have implications for the management of urban ecosystems, in particular that of urban soils.
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Butterfly fitness strongly depends on larval development, and selection should thus favour butterflies that can detect high-quality host plants for oviposition. In myrmecophilic ...butterflies, which need plants for initial larval development, but rely on ants for completing the larval stage, selection may also favour butterflies that can detect plants in the vicinity of host ants. However, the ability of butterflies to detect host ant presence is still under debate.
In this paper, we study the factors that determine oviposition of the specialist butterfly Phengaris alcon rebeli on its obligate host plant Gentiana asclepiadea. The factors considered include gentian traits, vegetation descriptors and host ant abundance (P. alcon larvae can only complete their lifecycle when nursed by Myrmica host ants). Using (generalised) linear models, we found that both oviposition probability and egg number increased with increased gentian flower number per branch and with increased abundance of the host ant Myrmica scabrinodis. In turn, M. scabrinodis abundance increased with gentian flower number per branch and decreased with gentian density. Path analysis confirmed that the positive effects of M. scabrinodis abundance on oviposition probability and egg number are not spurious, i.e., they did not arise simply because flower number per branch has a positive effect on host ant abundance and oviposition. While not proving causality, our findings suggest that oviposition preference of P. alcon butterflies is affected both by host plant traits and by abundance of the host ant. We discuss our findings within the context of the long-standing debate on whether or not ant-dependent oviposition occurs in the genus Phengaris, and the potential underlying mechanisms.
Invasive plants are recognised as a major threat to biodiversity. Although they are well-established in natural areas, the supposed negative impacts of invasive plants upon communities and ecosystems ...have so far been poorly investigated in urban areas, where invasions are a main issue for ecologists and for urban planners and managers. We propose to assess the effects of an invasive species along an invasion gradient in a typical urban habitat. We focused on the Japanese knotweed (
Reynoutria japonica
Houtt.), a widespread invasive species in Europe and North America. We considered eight urban wastelands invaded by this species in the heart of the Greater Paris Area, France. On each site, we ran four transects from the centre of the Japanese knotweed patch towards the uninvaded peripheral vegetation. We recorded the flora using the line intercept method, and several soil parameters (thickness of A horizon, abundance of earthworm casts, topsoil Munsell value, pH) every metre along each transect. The A horizon was thicker and the topsoil darker under
R. japonica
canopy. Thus, this invasive plant species seemed to influence soil organic matter pool. However, our results also steadily showed that
R. japonica
locally excluded and/or severely reduced the cover of many plant species through competition. Our study clarified the local effects of
R. japonica
: an influence on the soil organic matter, and a severe negative impact on wasteland plant communities. We suggest implications in both conservation and restoration ecology.
Many plant species have established self-sustaining populations outside their natural range because of human activities. Plants with selfing ability should be more likely to establish outside their ...historical range because they can reproduce from a single individual when mates or pollinators are not available. Here, we compile a global breeding-system database of 1,752 angiosperm species and use phylogenetic generalized linear models and path analyses to test relationships between selfing ability, life history, native range size and global naturalization status. Selfing ability is associated with annual or biennial life history and a large native range, which both positively correlate with the probability of naturalization. Path analysis suggests that a high selfing ability directly increases the number of regions where a species is naturalized. Our results provide robust evidence across flowering plants at the global scale that high selfing ability fosters alien plant naturalization both directly and indirectly.
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