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Coefficient plots for establishment (a) and tiller count (b). Each coefficient represents positive or negative treatment effects as compared to a reference level of one propagule with one node in the sun. We consider coefficients with confidence intervals (95 %) excluding zero to be significantly positive or negative, with those above zero being positive and below being negative

Coefficient plots for establishment (a) and tiller count (b). Each coefficient represents positive or negative treatment effects as compared to a reference level of one propagule with one node in the sun. We consider coefficients with confidence intervals (95 %) excluding zero to be significantly positive or negative, with those above zero being positive and below being negative

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Propagule pressure is commonly considered a primary driver of invasive plant establishment and spread. However, the physical size or condition (i.e., quality) of propagules may also affect establishment, particularly under unfavorable habitat conditions such as low light environments. We used an outdoor mesocosm experiment to test the relative cont...

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... 3)(2004), 16 of the 24 in the recorded areas (Ren et al. 2009) of introduction were located in the latitudinal zone from Shenzhen (22°46′ N) to Zhanjiang (21°27′ N) (Fig. 3a), which was also the main area of S. apetala distribution in China in this study. The biology of propagules plays a crucial role in plant dispersal (Williamson and Fitter.1996;Estrada et al., 2016). Propagule characteristics of mangroves are particularly critical in the colonization of new habitats (Stocken et al. 2019). In our previous study, we conducted a systematic study of fruit and seed features of S. apetala at different latitudes in China, and found the fruit properties with significant variation in latitudinal gradients ( ...
Article
The non-native mangrove species, Sonneratia apetala, was widely planted in coastal restoration projects of China in the past three decades, and dispersed in mangrove habitats in some introduction areas, which aroused wide attention from scientists and forest managers. Therefore, it is an urgent need to investigate their distributing patterns and build a dataset with basic information for natural mangrove conservation and restoration. The techniques combined field survey and visual interpretation based on sub-meter spatial resolution imagery from Google Earth (GE). The results showed that the boundary of stable S. apetala populations was ranged from 18°15′ N to 25°36′ N, with a total area of 3,804.86 ha in China in 2020. Guangdong had the largest distribution area of 3,217.34 ha, accounting for 84.56% of the total S. apetala populations in China, within which Zhanjiang (20°35'-21°30' N) took the largest amount. The spatial distribution of S. apetala in China followed the following three characteristics, 1) S. apetala was concentrated in the mid-latitude region (20°00'-23°00' N) of the southeast coast of China, especially along the coasts of Leizhou Bay (20°35'-21°30' N) in Guangdong; 2) S. apetala populations were commonly found in the middle to low tidal zones and at the seaward edges of native mangroves; 3) the dispersal S. apetala populations were found along rivers, tidal creeks, and other water systems, which also concentrated in estuaries or bays with freshwater inflow, on the coastal zones with low salinity, and in bare mudflat or low-shading forest edges, and forest gaps as well.
... seedlings grown in plastic tubes) 2.5 weeks before the experimental fires (Southern Habitats, LLC) because these species often resprout from below-ground buds after fires. Cogongrass rhizome fragments, each with three nodes (Estrada et al., 2016), were planted the day before fires. The number of seeds sown ranged from 13 to 40 seeds for species with larger seeds and 175 to 350 seeds for species with smaller seeds (Table S2). ...
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Non‐native invasive grasses are driving intense fires across the globe but the impacts of native versus invader‐fuelled fires on community assemblages are poorly understood. By increasing fire intensity, grass invasions might increase below‐ground mortality of heat‐sensitive seeds and buds, thereby shifting community composition. We compared fuel loads in native and non‐native invasive (cogongrass, Imperata cylindrica) plant‐dominated areas of pine savannas in Florida. Then, we conducted a field experiment to examine how fuel loads and native and invasive fuel types affected soil heating and seedling emergence or resprouting of native and invasive plant species. Average fuel loads in invaded communities were 152% greater than that in native communities. Soil heating, including heating duration >60°C, maximum temperature and heat flux >60°C, increased, and seedling emergence and resprouting decreased with greater fuel loads; these relationships were similar across the overlapping range of native and invasive fuel loads. However, longer durations of soil heating at the higher average fuel loads of invaded communities resulted in 23% lower predicted probability of seedling emergence compared to average fuel loads of native communities. Invasive cogongrass resprouting was not affected by fuel loads, indicating that cogongrass tolerates the intense fires it generates. In contrast, seedling emergence and resprouting of most other species was reduced by greater fuel loads. Synthesis and applications. By increasing fuel loading and soil heating, grass invasions may alter post‐fire community assemblages and facilitate invasive grass dominance at the expense of native species via an invasion‐fire cycle. Fuel loads can be used to predict soil heating duration and depth, and these data, combined with information on species tolerances to heating, can be used to forecast the impacts of invasions on post‐fire community composition. To maintain fire regimes that promote native communities and resist invader dominance, it is critical to manage invasive species that increase fuel loads.
... Many of the world's most invasive macrophytes spread vegetatively via asexual fragmentation (Wright, 2005;Williams and Smith, 2007). The recruitment success of macroalgal fragments (i.e., propagules) can be influenced by their quality (van Kleunen et al., 2015;Estrada et al., 2016), the recipient environment Gribben et al., 2018), and the interaction between the two (Bulleri et al., , 2019. For example, larger, more intact fragments such as those with intact rhizoid structures generally show higher recruitment potential (Khou et al., 2007;Wu et al., 2007;Uyà et al., 2018). ...
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A species’ ability to spread is in part governed by the extent to which recipient habitats either resist, tolerate or promote the species’ recruitment. In disturbed marine environments, there is a general trend for the loss of algal canopies, thought to resist invasion, toward algal turf or rock barrens habitat. This study tested whether the spread of the range-expanding native macroalga Caulerpa filiformis was resisted by algal canopies but facilitated by algal turf or barrens habitats. Large-scale field surveys generally supported the predicted recruitment patterns, with C. filiformis recruits being most abundant on turf (but not barrens) and absent under kelp canopies. However, a discrepancy existed between different structural forms of turf, with the positive association holding true only for geniculate corallines, not filamentous turf. Secondly, a laboratory experiment tested whether the physical structure and/or the sediment-trapping properties of coralline turf influenced the recruitment success of C. filiformis. Whilst the structural complexity of turf aided overall recruitment performance (i.e., increased rhizoid production, attachment speed, success, and strength), a positive influence of turf-derived sediment on recruits’ growth was less obvious, at least over 10 days. The high morphological plasticity of C. filiformis propagules resulted in possible benefits of faster or stronger attachment of more developed propagules being only temporary, and that recruitment may be regulated in accordance with habitat preference. Finally, a field experiment confirmed the observed positive role of turf and the negative influence of algal canopies in the short-term, however, adverse environmental conditions in the longer-term resulted in the loss of most fragments. In conclusion, this study demonstrated the importance of both positive and negative species interactions for the recruitment success of a native alga, suggesting that a shift from kelp to turf algae can initiate further community change.
... Cogongrass is a highly invasive, rhizomatous C 4 grass that is of management concern throughout much of the Southeast US due to its impacts on biodiversity and ecosystem processes (see Estrada and Flory 2015). While there are a variety of explanations for the invasive success of cogongrass, the ability to reproduce and spread rapidly via rhizomes is a commonly cited mechanism (Patterson 1980, Lippincott 2000, Holzmueller and Jose 2012, Estrada et al. 2016. Additionally, it has been suggested that cogongrass invasion in low resource environments (e.g., shade) is augmented by photosynthate transfer (Estrada et al. 2017). ...
... 'This article is protected by copyright. All rights reserved.' a size that elicits high emergence rates (Estrada et al. 2016). Rhizome fragments were grown in the greenhouse until new rhizome formation was noted (~ 4 weeks). ...
Article
While many clonal plants are highly successful invaders, the contribution of clonal integration (i.e., the translocation of resources among ramets) to invasion is often unknown. We used model simulations to ask if clonal integration would facilitate photosynthate translocation, if the performance of daughter ramets might be enhanced by clonal integration, and if shaded ramets benefited relatively more from transferred photosynthate. Then, to test if photosynthate translocation augmented performance of emerging daughter ramets for a globally invasive grass (Imperata cylindrica ), we combined a ¹³CO2 pulse‐chase experiment with a greenhouse experiment manipulating light levels and rhizome attachment. We found that acropetal photosynthate transfer occurred between all sampled parent‐daughter ramet pairs and that this resource sharing led to higher biomass and tiller production when rhizomes between parent and daughter ramets were intact. We also found that the benefits of integration to recipient clones outweighed the costs to donors, since there was no reduction in parent plant performance due to sharing. Additionally, our data analyses show that photosynthate transfer was likely of greater benefit in overcoming growth constraints in shade than in full sun (posterior probability ~ 96.5%), a result that is further supported by our numerical simulations from a basic growth model. Thus, resource sharing among clonal plants may be a critical but underappreciated trait of invasive species. More generally, photosynthate transfer is a probable mechanism that explains why clonal integration can be particularly beneficial in heterogeneous resource environments. This article is protected by copyright. All rights reserved.
... The reproductive traits of plants are positively correlated with their invasive ability (Williamson and Fitter 1996;Estrada et al., 2016), and the biological characteristics of propagules play a crucial role in the successful colonization of invasive plants (Estrada et al., 2016). Normally, higher quantities of propagules increase the possibility of survival during transport (Kolar and Lodge 2001;Lockwood et al., 2005). ...
... The reproductive traits of plants are positively correlated with their invasive ability (Williamson and Fitter 1996;Estrada et al., 2016), and the biological characteristics of propagules play a crucial role in the successful colonization of invasive plants (Estrada et al., 2016). Normally, higher quantities of propagules increase the possibility of survival during transport (Kolar and Lodge 2001;Lockwood et al., 2005). ...
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High reproductive and dispersal capacity allow invasive plant species to spread and establish, out-compete and occupy new niches. Sonneratia apetala, a species used in afforestation projects in southern China, was introduced from Bangladesh in 1985. This species has the capacity to colonize in mangrove mudflats and invade natural mangrove community of China. However, its effectiveness to do so may change with latitude. Aiming to provide reproduction evidence on S. apetala invasiveness from the perspective of fruit and seed properties, we conducted in situ observations of fruit and seed properties of 12 S. apetala populations across the latitudinal gradient from Haikou (19.60°N) to Quangang (25.25°N, current latitudinal limit for this species). Fruits per tree decreased with increasing latitude (R² = 0.47; p < 0.0001); fruit weight (R² = 0.28; p < 0.0001) and volume (R² = 0.27; p < 0.0001) varied quadratically relative to latitude. However, seed quantity per fruit, weight and volume were not correlated with latitude. The relationship between fruit and several climatic factors showed that mean annual precipitation, mean annual low temperature and mean annual irradiance had significant effects on these properties. Fruit floating percentages suggested decreases with time but was markedly site specific. Accordingly, the dispersing potentials were high in low latitude regions with small and light fruits but with big quantity; while they were weak in high-latitude regions where medium size fruits might resist the cold in winter. The mid-latitude sites with large fruits and great germination percentage resulted in good performance and establishment, where the species invasiveness should be noted.
... their quality). For example, establishment success of rhizome fragments of the invasive cogongrass, Imperata cylindrica, increased with fragment size (Estrada, Wilson, NeSmith, & Flory, 2016). Similarly, shoot height and survival of the invasive giant cane, Arundo donax, in Southern California riparian habitats were positively correlated with the weight of transplanted rhizomes (Quinn & Holt, 2008). ...
... For example, fragments of the clonal seaweed, Caulerpa cylindracea, lacking rhizoids performed as well as intact fragments and better than fragments lacking fronds, but only when sediments were enriched in organic matter . Likewise, in the cogongrass, positive effects of increased fragment size on tiller production and growth were modulated by light levels (Estrada et al., 2016). As a consequence of disturbance, land-or seascapes often consist of mosaics of habitats differing in environmental conditions and resource availability. ...
... This mechanism may explain the greater ability of −F+R fragments in regenerating fronds in bare sediments, but not on sediments from which both below-and above-ground Z. growth, but only when exposed to full sun light (Estrada et al., 2016). ...
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Propagule pressure is acknowledged as a key determinant of invasion success. Nonetheless, the role of morphological or physiological attributes of propagules (i.e. their quality) in regulating invader establishment has been little explored. In particular, no study has investigated how the presence of propagules differing in quality within an inoculum influences establishment across heterogeneous landscapes. We experimentally tested the hypothesis that the quality (+Fronds+Rhizoids; +Fronds−Rhizoids; −Fronds+Rhizoids) and the diversity (1, 2 and 3 fragment types) of vegetative fragments of the seaweed Caulerpa taxifolia determine their establishment success across seascapes consisting of bare sediments and patches of the seagrass Zostera muelleri exposed to different disturbance intensities (control, seagrass canopy clipping and total removal). After 6 weeks, seaweed biomass, stolon and frond length, frond and rhizoid number were generally greater in unvegetated habitats (bare sediments and total seagrass removal) than full or reduced seagrass canopies. The type and the diversity of types of fragments inoculated had significant effects on the final biomass and morphological features of C. taxifolia only in vegetated habitats. In control plots, inocula of fragments retaining both fronds and rhizoids achieved higher biomass, developed longer stolons and more fronds. In canopy clipping plots, mixed inocula of +Fronds+Rhizoids and −Fronds+Rhizoids fragments had the greatest biomass and stolon length. Synthesis. Assessing how propagules differing in quality perform in different habitats might be not sufficient to draw a comprehensive picture of invasion risk, as their establishment can be modulated by both negative and positive interactions among them. Propagule composition should be, therefore, considered as a further dimension of propagule pressure. Our results also suggest that the relevance of specific propagule traits for invader establishment decreases from intact to degraded habitats. Considering propagule size in terms of amount of competent propagules, rather than an absolute measure, would refine our ability of predicting invasion risk across habitats differing in biotic or abiotic conditions.
... Each growth cycle entailed 3 months of growth, where newly formed rhizomes were harvested and used for the next growth cycle. Rhizomes from the third growth cycle were introduced directly into the experiment as three-node rhizome segments, a propagule size shown to have high emergence rates (Estrada et al., 2016). ...
... Phenotypic plasticity may contribute to the establishment or spread of Imperata by enhancing phenotype-environment matching across heterogeneous resource conditions. For example, a plastic Imperata population that establishes along a forest edge in full sun conditions could also spread into nearby forests with shaded conditions by altering functional traits such as (plant height, increasing LMR, and/or increasing SLA) (Estrada et al., 2016;Estrada et al. 2017;this study). Under such a scenario, a plastic population would ultimately occupy a larger area and would, therefore, be considered to have greater invasiveness than a less plastic population that is restricted to full sun conditions. ...
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Phenotypic plasticity can promote plant invasions and enhance impacts on native species, but little is known about variation in plasticity among invader populations compared with native species. Variation in plasticity among invader populations could inform more precise predictions of invader spread and impacts across heterogeneous resource environments. We used a common garden experiment with sun and shade treatments to test for variation in plasticity among 12 populations of an invasive grass (Imperata cylindrica), and to determine whether the invader exhibited greater plasticity than six native species that co‐occur in the Southeast USA. Principal component analysis revealed that invader populations from different native ranges consistently varied from each other and native species in traits linked to more favorable phenotypes under resource limitation. Overall, the invader exhibited greater plasticity than native species did, as demonstrated by higher plasticity index values for traits such as plant height, leaf mass ratio, and root : shoot ratio. Variation in phenotypic plasticity among invader populations suggests the potential for evolution of plasticity, and greater plasticity of invader populations than native species may underlie invader dominance. Differences in plasticity among populations appears to play an important role in predictions of the spread and potentially the impacts of invasive species.
... Here, propagule pressure was positively associated with both the likelihood of establishment and population growth rates (thus abundances) after three years (Grevstad 1999) as well as population persistence to year ten postintroduction (Grevstad 2006); unfortunately, abundance in year ten was not reported. Thus, for these two examples propagule pressure appears to have been similarly related to establishment and post-establishment abundances (see also Fauvergue et al. 2007, Burgess and Marshall 2011, Britton and Gozlan 2013, Estrada et al. 2016, Lange and Marshall 2016. Whether this pattern is general remains to be seen, but increased demographic stochasticity in small populations should yield a positive association between abundance and the likelihood of population persistence over time and thus a similar relationship between propagule pressure and both metrics (although see Memmott et al. 2005 for a contrary example). ...
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Colonization is a critical filter, setting the stage for short‐term and long‐term population success. Increased propagule pressure (e.g., more founding individuals) usually enhances colonization; however, this pattern may be driven by purely numeric effects, population genetic diversity effects, or both. To determine the independent and interactive effects of propagule pressure and genetic diversity, we conducted a seed addition experiment in the field using the ruderal annual Arabidopsis thaliana. Propagule pressure treatments spanned five levels, from 32 to 960 seeds per 0.25‐m² plot. Founder populations were composed of one, four, or eight genotypes and exposed to ambient or reduced levels of interspecific competition. Genotype monocultures were included to quantify additive vs. non‐additive effects. Populations were followed for three generations, with abundance, population persistence and genotype retention (the proportion of introduced genotypes persisting over time) as the major response variables. Increased propagule pressure enhanced abundance immediately following introduction, particularly where nutrient availability was high and competition reduced. Greater propagule pressure also increased the likelihood of population persistence and genotype retention through three generations. However, most populations experienced rapid abundance declines over time, yielding no relationship between propagule pressure and third‐generation abundance across persisting populations. Under reduced competition, increased genetic diversity led to a marginal increase in persistence through the third generation that was more pronounced, and statistically significant, in low nutrient conditions. Genetic diversity did not affect persistence through the first generation, thus indicating that genetic diversity effects strengthened over time. Nevertheless, genotypic mixture populations fell short of expectations based on performance in monocultures (negative non‐additive effects). Increased genetic diversity was also associated with abundance declines, largely due to one particularly high‐performing genotype in the lowest diversity treatments (i.e., genotypic identity effects). Overall, our results indicate that increases in both propagule pressure and genetic diversity can enhance colonization success but are highly context dependent. They also highlight novel ways in which both factors can impact the retention of introduced genetic diversity over time. Our findings pinpoint the determinants of a fundamental population process and have key implications for applications where enhanced or suppressed colonization is desired, including ecological restoration and invasive species management.
... The initial size of A. donax rhizomes was found to be related to the level of sprouting (Santín-Montanyá et al. 2014) and yield biomass (Copani et al. 2013). Estrada et al. (2016) and Peng et al. (2017) found that rhizome segments containing three or more nodes significantly enhanced the establishment of invasive species such as alligator weed [Alternanthera philoxeroides (Mart.) Griseb.] and cogongrass [Imperata cylindrica (L.) P. Beauv.]. ...
Article
Giant reed ( Arundo donax L.) has recently shown great potential as a feedstock for the bioenergy industry. However, before A. donax can be grown commercially, due to its invasive nature, management strategies must be developed to reduce the risk of unintended spread. This research was conducted in northeastern Oregon (USA) during two growing seasons. Nine control strategies were evaluated in a field that previously had A. donax as a crop. The control strategies included mechanical practices (stem cutting and rhizome digging), physical practices (covering with an opaque tarp), chemical practices (glyphosate applications at different rates and timings), and a combination of these practices. Spring samplings of A. donax regrowth in the season following treatments indicated that stem cutting in the spring without follow-up control practices provided no control. Covering plants with a tarp after cutting them (either with or without a glyphosate treatment after cutting) resulted in 96% control. Application of glyphosate alone also resulted in excellent control, although timing of application was an important factor for maximizing efficacy. The best results were found when the maximum dose (10.2 L ai ha ⁻¹ ) was split among two or three applications (>99% of control) compared with the maximum dose applied once (75% to 94%). Control was lower (73% to 89%) for two of the strategies that included mechanical practices, stem cutting + glyphosate and rhizome digging, in comparison to other strategies involving tarps and/or glyphosate applications (88% to 100%). Results indicated that it is very difficult to eradicate volunteer A. donax in 1 yr, but very good control can be achieved with several of the strategies tested.
... Propagule pressure-a function of the number of individuals released into a new region per introduction event and number of discrete introduction events-has been widely shown to influence the establishment and spread of non-native plants (Lockwood et al. 2005;Simberloff 2009). By contrast, the role of propagule quality (referred to as the physical condition of a propagule, following Estrada et al. 2016) has received less attention (Rejmánek and Richardson 1996;Smith and Walters 1999;Quinn and Holt 2009;Lange and Marshall 2016). ...
... In particular, the role of propagule quality has been little explored in clonal plants with vegetative reproduction, a trait often associated with high invasiveness in both terrestrial and marine environments (Ceccherelli and Cinelli 1999;Kolar and Lodge 2001;Renoncourt and Meinesz 2002). To date, few studies have experimentally assessed how propagule quality influences the invasion success of these plants, showing that fragment characteristics, such as their size and number of internodes, are key determinants of plant performance (Smith and Walters 1999;Quinn and Holt 2009;Estrada et al. 2016). In addition, how the performance of vegetative propagules differing in quality varies across heterogeneous landscapes is yet to be explored (but see Uyà et al. 2018). ...
... Our study shows that both fragment quality and sediment characteristics influence C. cylindracea fragment survival and, hence, are likely to influence long-term spreading dynamics of this seaweed. More generally, it supports previous evidence of propagule quality to be a determinant of invasion success (Smith and Walters 1999;Quinn and Holt 2009;Estrada et al. 2016;Lange and Marshall 2016), but also brings novel evidence by demonstrating that these effects are likely context-dependent. Organic loading, promoting fragment survival, may sustain the persistence and spread of this seaweed in sedimentary environments. ...
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Although propagule pressure is recognized as an important determinant of invasion dynamics, the role of propagule quality (i.e. the physical condition of a propagule) has received little attention. In particular, how the performance of vegetative propagules differing in quality varies across heterogeneous landscapes is yet to be explored. Caulerpa cylindracea is a clonal, invasive seaweed, widely distributed in the Mediterranean. By means of a laboratory experiment, we investigated how variation in the quality of seaweed fragments (intact vs. frond-removal vs. rhizoid-removal) influenced their survival on control versus sediments enriched with detritus from the native seagrass, Posidonia oceanica. The survival of seaweed fragments was low on non-enriched sediments, irrespective of their characteristics. On enriched sediments, survival was high in control and rhizoid-removal fragments, but low in frond-removal fragments. Our study shows that both fragment quality and sediment characteristics influence the survival of C. cylindracea propagules and, hence, long-term spreading dynamics of this seaweed. More generally, it brings novel evidence showing that the effects of propagule quality on invasion success are context-dependent.