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Height distribution of grass species in subfamilies and tribes as per Soreng (2015)’s classification of Poaceae. Species within the black-outlined box have average bloom (inflorescence) heights of ≥ 2 m. Note that not all of these taxa are defined in this paper as tall-statured grasses (TSGs) as some taxa do not maintain their height independently (e.g. climbing species). The area of the black circles is proportional to the number of species. Data were retrieved from Kew’s GrassBase (http://www.kew.org/data/grasses-db.html) for 10,818 species. Species that are unplaced in a tribe are shown as incertae sedis for that subfamily. Woody bamboos (tribes Arundinarieae and Bambuseae) are marked with an asterisk. Figure generated using Tableau V 10.0
Source publication
Species in the grass family (Poaceae) have caused some of the most damaging invasions in natural ecosystems, but plants in this family are also among the most widely used by humans. Therefore, it is important to be able to predict their likelihood of naturalisation and impact. We explore whether plant height is of particular importance in determini...
Citations
... Life form, which is associated with stress resistance and intrinsic growth rate (Guo et al., 2018), was extracted from multiple sources (for details, see Omer et al., 2021), and was available for 10,967 of the 13,718 introduced species. Maximum growth height, which is relevant for competitive ability and seed dispersal distance (Canavan et al., 2019;Thomson et al., 2011), was extracted from multiple sources, including Dave's Garden (one of the largest online encyclopaedias on gardening plants; https:// daves garden. com), the European Garden Flora (Cullen et al., 2012), PLANTATT (Hill et al., 2004), the Flora of the USSR (Cherepanov, 2007) ...
... Tall plants often have a competitive advantage over short ones, and their propagules can be dispersed over longer distances (Canavan et al., 2019;Guo et al., 2018 Propagation mode and height also had indirect effects on naturalization that varied among the three life-form categories (Figure 3). ...
Aims
Most naturalized plants are escapees from cultivation. Inventories of cultivated introduced species thus offer unique, still underutilized, opportunities to assess naturalization drivers of introduced plants. We used a comprehensive inventory of 13,718 introduced species cultivated in China's botanical gardens to test which species characteristics distinguish the 739 species that have naturalized.
Locations
China.
Methods
We used generalized linear models to test whether the naturalization of cultivated introduced plants in China is associated with functional traits, propagule pressure, environmental niche and introduction history. To test direct and indirect effects of those variables and their relative importance in driving naturalization, we used structural equation models.
Results
We showed that species were more likely to naturalize when they originate from the Americas, are more widely cultivated, and have a longer residence time. Moreover, species were more likely to naturalize if they have a good environmental match, are short‐lived herbs, are predominantly propagated from seeds, and, in the case of herbs, are relatively tall compared to other herbs. Part of the latter effects are mediated by how these variables relate to propagule pressure proxies, and this varies among short‐lived herbs, long‐lived herbs and woody plants.
Main Conclusions
Naturalization is partly driven by life‐form‐dependent cultivation biases.
... Some preferred ornamental features are associated with survival advantages. For example, taller plants and larger leaves may permit higher nutrient acquisition (Canavan et al., 2019). Flowers with showy colors and prominent shapes can attract insects such as butterflies and bees to foster reproduction and propagation (Lunau, 2016;Morales and Traveset, 2009). ...
Global ornamental horticulture is a major pathway for plant invasions, while urban parks are key areas for
introducing non-native ornamental plants. To react appropriately to the challenges (e.g., biological invasion
issues) and opportunities (e.g., urban ecosystem services) of herbaceous ornamentals in urban parks, we con-
ducted a comprehensive invasive risk assessment in 363 urban parks in Chongqing, a subtropical city in China.
The results found more than 1/3 of the 119 non-native species recorded in urban parks had a high invasion risk,
and more than five species had potential invasion risk in 96.29% of the study area, indicating herbaceous or-
namentals in urban parks are potentially a pool of invasive species that deserves attention. Moreover, humans
have chosen herbaceous ornamentals with more aesthetic characteristics in urban parks, where exotic species
were more prominent than native species in floral traits, such as more conspicuous flowers and longer flowering
periods. The findings can inform urban plant management, provide an integrated approach to assessing herba-
ceous ornamentals’ invasion risk, and offer insights into understanding the filtering effects of human aesthetic
preferences.
... A key challenge is connecting the magnitude of invasion impacts to particular characteristics of individual invaders, which could facilitate predictions of future impacts. A few such characteristics have been emphasized as fundamental drivers of post-establishment invasion success, including high productivity, rapid growth, tall stature, and the ability to spread clonally (Py sek and Richardson, 2007;van Kleunen et al., 2010;Canavan et al., 2019). However, attempts to explicitly link species characteristics with impact magnitudes are rare and limited to identifying broad categories of high-impact invaders (e.g., annual grasses and Figure 1. ...
... Because nutrient enrichment has increased dramatically in wetlands globally (Zedler and Kercher, 2004), we should expect such conditions to favor invasion by strong competitors (Table 1). This expectation aligns with the fact that some of the most well-known wetland invaderslike Phragmites australis and Arundo donax-are large-statured plants Canavan et al., 2019). Thus, by mere observation, it appears that the robust size of some invaders contributes to their dominance and suppression of other species by potentially reducing their survival, growth, and fitness. ...
... This is in agreement with expectations based on trait comparisons between native and introduced grass species which show higher SLA (Sandel and Low 2019;Broadbent et al. 2020;Monnet et al. 2020), higher LA (Visser et al. 2016) and greater height (Visser et al. 2016;Monnet et al. 2020) for introduced species. Tall grass species with greater than 2 m height are more likely to naturalize than shorter species, but probability of naturalization was only increased when bamboos and nonbamboos were analysed separately (Canavan et al. 2019). In our dataset, differences in height were only found when bamboos were excluded from the native species (no introduced bamboos were included in our analyses), with species averages of 42.8 cm for introduced species vs. 35.6 ...
Background and Aims
Grass species (family Poaceae) are globally distributed, adapted to a wide range of climates and express a diversity of functional strategies. We explored the functional strategies of grass species using the competitor, stress tolerator, ruderal (CSR) system and asked how a species’ strategy relates to its functional traits, climatic distribution and propensity to become naturalized outside its native range.
Methods
We used a global set of trait data for grass species to classify functional strategies according to the CSR system based on leaf traits. Differences in strategies in relation to lifespan (annual or perennial), photosynthetic type (C3 or C4), or naturalisation (native or introduced) were investigated. In addition, correlations with traits not included in the CSR classification were analyzed, and a model was fitted to predict a species’ average mean annual temperature and annual precipitation across its range as a function of CSR scores.
Key Results
Values for competitiveness were higher in C4 species than in C3 species, values for stress tolerance were higher in perennials than in annuals, and introduced species had more pronounced competitive-ruderal strategies than native species. Relationships between the CSR classification, based on leaf traits, and other functional traits were analyzed. Competitiveness was positively correlated with height, while ruderality was correlated with specific root length, indicating that both above- and belowground traits underlying leaf and root economics contribute to realized CSR strategies. Further, relationships between climate and CSR classification showed that species with competitive strategies were more common in warm climates and at high precipitation, whereas species with stress tolerance strategies were more common in cold climates and at low precipitation.
Conclusions
The findings presented here demonstrate that CSR classification of functional strategies based on leaf traits matches expectations for the adaptations of grass species that underlie lifespan, photosynthetic type, naturalization and climate.
... Here, we examined soil seed banks and submersion effects on germination of an emerging, but poorly understood, invading nonnative plant species along the Colorado River system in the southwestern United States. Ravennagrass (Saccharum ravennae), originally from Eurasia, is a tall ($3 m), invasive, C 4 grass capable of forming monoculture, traits frequently associated with high-impact invaders capable of major alterations to habitats (Canavan et al., 2019). In the last 10-30 years, managers of protected areas along the Colorado River and its tributaries, such as in Grand Canyon National Park and Glen Canyon National Recreation Area, have initiated or prioritized efforts to manage ravennagrass using pulling and herbicide (Hill & Ayers, 2009). ...
Soil seed banks along shorelines and the ability of seeds to survive submersion in water are among potential factors that can influence seed supply, a frequent driver of riparian plant invasions. We investigated germinable soil seed banks and the ability of seeds to germinate after different durations of submersion in water for non-native ravennagrass (Saccharum ravennae), an emerging but poorly understood invader of riparian habitats in the American Southwest, including along the Lake Powell section of the Colorado River where we performed the study. We assessed soil seed bank composition in 27 ravennagrass-invaded plots using the emergence technique and evaluated effects on ravennagrass germination of submersion in river water for up to 15 months in a laboratory experiment. Ravennagrass was sparse in soil seed banks, detected in samples from only one of the 27 plots. Instead, soil seed banks were dominated by the non-native annual cheatgrass (Bromus tectorum) and a mixture of native early colonizers (e.g., Pseudognaphalium stramineum) and shrubs (e.g., Baccharis emoryi). Although ravennagrass seed germination was low (<9%) in the submersion experiment, some seeds retained germinability after 15 months of continuous submersion in water. Results suggest that while ravennagrass may have limited on-site, readily germinable soil seed banks, potential implications of its protracted seed viability in water for dispersal along waterways warrants further attention. K E Y W O R D S germination, hydrochory, non-native plants, Saccharum ravennae
... Based on the impacts reported for other species from the same plant family (Poaceae), we can speculate that U. arrecta may decrease light availability, alter nutrient cycling and reduce decomposition rates of invaded ecosystems (Canavan et al., 2019;Song et al., 2017). ...
A growing body of evidence has shown that biological invasions cause shifts in species composition of communities in space and time. Although biological invasions are considered a major driver of biotic homogenisation worldwide, most previous studies were conducted at small spatial scales and over short time periods, which may have underestimated the impacts of exotic species on native communities.
Using a unique dataset of aquatic plants sampled in 235 sites over 12 years (2007–2010 and 2015–2019) in a large reservoir (Itaipu Reservoir; 1350 km ² ), we analysed how the invasion of a non‐native grass Urochloa arrecta affects the species richness, ecological uniqueness (i.e. local contribution to beta diversity—LCBD) and temporal β –diversity of native plant communities.
From 3934 surveyed plant communities, U. arrecta was recorded in 2888 samples and it was absent from 1046 samples. Overall, species richness and ecological uniqueness of native plant communities were markedly lower in sites invaded than non‐invaded by U. arrecta . From 2007 to 2019, the ecological uniqueness of native plants was 60% lower in the invaded than non‐invaded sites. Whereas in invaded sites species loss was the dominant process driving native communities over time, in non‐invaded sites gain of new native species was the primary process underlying community trajectories. Moreover, comparing native plant communities before and after the invasion of U. arrecta , species richness, ecological uniqueness and species gains of native plant communities decreased, whereas species losses increased after the invasion of U. arrecta . Finally, the positive relationship between native biodiversity and precipitation was stronger in non‐invaded than invaded sites.
Synthesis . Our findings provide comprehensive evidence that an invasive plant is decreasing the spatial and temporal β –diversity of native plant communities through declining species richness, rather than simply correlating with them. This suggests that U. arrecta is driving native plants to become less diverse and homogeneous after the invasion, both spatially and temporally. Our findings illustrate that at broad scales, aquatic plant communities may become increasingly homogeneous with the increasing number of biological invasion events taking place worldwide.
... Grasses that are taller than 2 m are more likely to establish following introduction than shorter grasses (Canavan et al., 2019), and Guinea grass grows taller than most of its competitors across a broader ecological niche in its introduced range (Rhodes, Plowes, Martins, et al., 2022). But what other factors drive this variation and allow Guinea grass to achieve competitive dominance outside its native range? ...
Biological invasions are a leading ecological issue of the 21st century because of their worldwide contributions to biodiversity loss and degradation of ecosystem services. Answering general questions about the mechanisms facilitating the spread of successful invasives is key to understanding how to manage them moving forward. The success of introduced primary producers has often been attributed to superior competitive ability or to their release from natural enemies that constrained them in their native range. In contrast, nonnative primary producers can successfully invade and establish in new areas by releasing allelochemical compounds into the environment that are toxic to the native flora. The interactive effects of allelopathy and competition remain underexplored. Here, we evaluated the mechanism of invasion by Guinea grass, a globally distributed tallgrass from tropical and subtropical Africa with known allelopathic effects associated with 2‐hydroxyphenylacetic acid (2HPAA). We asked if allelopathy and light availability interact to give Guinea grass a competitive advantage during seedling establishment in its introduced range. We used a fully factorial greenhouse experiment in which allelochemical concentrations and light availability treatments were based on empirical measurements of these variables at an invaded site in South Texas. Seedling recruitment and growth were assessed for three native species and for Guinea grass itself. We also described the metabolome (the complete set of small molecules) of an invasive grass for the first time to facilitate a comparison of the effect of the known allelochemical 2HPAA with that of the whole‐plant chemical extract. Shading and allelochemistry each reduced recruitment and growth by themselves, and a significant interaction of these stressors exacerbated the negative effects in the shade, resulting in short plants, low biomass, and ultimately decreased seedling recruitment. The whole‐plant metabolomic extract had significantly stronger effects than pure 2HPAA, and these negative effects were intensified in the shade. Moreover, the mechanism showcased here demonstrated that resource competition and biochemical interference are not mutually exclusive mechanisms that facilitate the spread of a globally distributed invasive species.
... both are tall-statured grasses) (Canavan et al., 2019b). ...
... Nitrogen-fixing trees promote improved nutrient availability, shade, and soil moisture (Zitzer et al. 1996;Scholes and Archer 1997) and facilitate Guinea grass invasion (Rhodes et al. 2022). Guinea grass is a tall-statured grass, often apomictic and polyploid, and is highly invasive pantropically (Kaushal et al. 2015;Canavan et al. 2019;Lambertini 2019). Tall-statured invasive grasses generally produce culms over 1.5 m in height and are noted for associating with invasiveness. ...
A significant challenge of global change is the human-mediated movement of pasture grasses and their subsequent impact on ecosystem processes when they become invasive. We must understand invasive grass ecology and their natural enemies in native and introduced ranges to mitigate these impacts. Guinea grass ( Megathyrsus maximus ) is a pantropically introduced pasture grass that escapes intended areas and invades native ecosystems – threatening biodiversity and ecosystem function. The success of invasive plants has often been attributed to ecological release from stressors, including natural enemies and resource availability. Our objective was to assess Guinea grass functional traits across three different habitat types in native and invaded ranges by documenting ungulate and arthropod abundance, diversity, and feeding guilds. Guinea grass functional traits were assessed in three habitat types: grassland, riparian, and woody thickets around nitrogen-fixing Prosopis glandulosa in its introduced range in Texas, USA, and Senegalia mellifera in its native range in Kenya. We characterized Guinea grass functional traits by measuring plant height, cover, biomass, root-to-shoot ratios, and reproductive traits. We then examined the phytophagous arthropod and ungulate abundance and feeding guild diversity across the three habitat types. We hypothesized that functional trait expression related to invasiveness would be associated with Guinea grass in its introduced range. Also, we hypothesized that the abundance and diversity of phytophagous arthropods and ungulates would be lower in the invaded range. Finally, we hypothesized that Guinea grass functional traits would differ between the three habitat types, given the habitat types’ innate differences in resource availability. We found that Guinea grass was 2.5 times taller and 3.3 times more productive and covered 2.5 times more area in its invaded versus native ranges. Introduced Guinea grass had higher reproduction rates with 2.5 times more reproductive tillers, while habitat type drove vegetative reproduction with 15 times more stoloniferous establishment in wooded and riparian sites than grasslands. Texan ungulate communities were less species-rich, less functionally diverse, and less abundant than the Kenyan ungulate community. The phytophagous arthropod diversity on plants was twice as high on Kenyan Guinea grass than on Texan Guinea grass. Total arthropod family richness was nearly double, with 15 families represented in Kenya and 8 in Texas. These results suggest that Guinea grass has escaped a rich assemblage of arthropods and ungulates and likely explains some of its spread in introduced ranges. This study demonstrates how the invasive success of Guinea grass can be understood in terms of its competitive ability and interaction with natural enemies in the introduced and native ranges and may inform future biological control.
... Kaçan and Boz 2015;Uludağ 2015;Üstüner et al. 2015;Sezer and Kolören 2019; Terzioğlu and Ergül Bozkurt 2020; Yazlık and Albayrak 2020; Aksan and Yazlık 2021). Specifically, clonal growth(Bímová et al. 2003), high biomass(van Kleunen et al. 2010;Hejda 2013;Canavan et al. 2019) and a large number of branches/tillerings ...
Most risk analysis studies in invasion biology have focused on the invasiveness of non-native species, even though some native species also can pose a high risk to the environment and human well-being. This is especially true under current global change, which may cause dominant native species to expand their range of distribution and have substantial effects on the ecosystem. In this study, the risk of invasiveness of five non-native and five native plant species in Turkey was evaluated using a standard risk screening protocol. All ten species selected for screening are known to be invasive in several parts of the world, i.e. non-native Ailanthus altissima, Cuscuta campestris, Phytolacca americana, Robinia pseudoacacia and Sicyos angulatus, and native Cirsium arvense, Hedera helix, Onopordum acanthium, Phragmites australis and Sorghum halepense. The Australian Weed Risk Assessment decision-support tool adapted to Turkey's geographical and climatic conditions was used for screening the study species based on their biological traits, ecology and management approaches. All species were classified as high-risk, with R. pseudoacacia among non-natives and P. australis among natives achieving the highest scores followed by S. halepense, C. campestris, C. arvense, O. acanthium, P. americana, S. angulatus, A. altissima and H. helix. Based on their risk scores, all non-native species were classified as invasive and all native species as 'expanding' for Turkey. An ordination based on the risk scores showed similarities between invasive and expanding species. The outcomes of this study indicate that species can have several risk-related traits resulting in high risk scores irrespective of their origin. Such species can modify their environment and interact with other species with severe consequences for biodiversity. It is argued that dominant species with highly negative environmental and socioeconomic impacts in their habitats should be included in priority lists for management measures irrespective of their origin (i.e. native or non-native). More studies are needed to evaluate the magnitude and prevalence of the present findings for other regions worldwide.
