Target-site and non-target-site resistance mechanisms confer multiple resistance to glyphosate and 2,4-D in Carduus acanthoides.

Carduus acanthoides L. is mainly a range-land weed, but in the 2010s has begun to invade GM crop production systems in Córdoba (Argentina), where glyphosate and 2,4-D have been commonly applied. In 2020, C. acanthoides was found with multiple resistance to these two herbicides. In this study, the mechanisms that confer multiple resistance to glyphosate and 2,4-D, were characterized in one resistant (R) population of C. acanthoides in comparison to a susceptible (S) population. No differences in 14C-herbicide absorption and translocation were observed between R and S populations. In addition, 14C-glyphosate was well translocated to the shoots (∼30%) and roots (∼16%) in both R and S plants, while most of 14C-2,4-D remained restricted in the treated leaf. Glyphosate metabolism did not contribute to resistance of the R population; however, as corroborated by malathion pretreatment, the mechanism of resistance to 2,4-D was enhanced metabolism (63% of the herbicide) mediated by cytochrome P450 (Cyt-P450). No differences were found in baseline EPSPS activity, copy number, and/or gene expression between the R and S populations, but a Pro-106-Ser mutation in EPSPS was present in the R population. Multiple resistances in the R population of C. acanthoides from Argentina were governed by target site resistance (a Pro-106 mutation for glyphosate) and non-target site resistance (Cyt-P450-based metabolic resistance for 2,4-D) mechanisms. This is the first case of resistance to glyphosate and 2,4-D confirmed for this weed in the world.

Fructobacillus cardui sp. nov., isolated from a thistle (Carduus nutans) flower.

A Fructobacillus strain was isolated from the flower of a nodding thistle (Carduus nutans) collected in Bavaria, Germany. The strain is Gram-positive, rod-shaped, non-motile, non-sporulating, catalase- and oxidase-negative, and facultatively anaerobic. Growth can be detected at 10-37 °C and pH 4 to 9. The genome size is about 1.56 Mbp and the G+C content is 43.76 mol%. Assignment to the genus Fructobacillus was done by average nucleotide identity (ANI), 16S rRNA gene sequence and multilocus sequence analyses. Calculations of ANI and digital DNA-DNA hybridization values indicate a novel species with Fructobacillus tropaeoli DSM 23246T (93.58% ANI and 57.9 % dDDH) being its closest relative. Therefore, a new species named Fructobacillus cardui sp. nov. with TMW 2.2452T (=DSM 113480T=CECT 30515T) as type strain is proposed.

Pest management in future climates: Warming reduces physical weed management effectiveness.

Climate change alters many aspects of weed performance and may also alter the effectiveness of management practices to control pests. Despite this concern, entire categories of widely used management practices, such as physical control, remain understudied in this context. We conducted a field experiment growing the invasive pest musk thistle (Carduus nutans) at ambient and experimentally elevated temperatures. We tested mowing management strategies that varied in the timing of a single mowing event relative to thistles' stem elongation phenology and compared these with an unmowed control. Results from this experiment informed demographic models to project population growth rates for different warming/mowing scenarios. Compared to plants grown under ambient conditions, warmed thistles were more likely to survive the same mowing treatment, flowered earlier in the season, grew to taller heights, and produced more flowering capitula. Proportional reductions in plant height and capitulum production caused by mowing were smaller under warming. Warming did not change the relative ranking of mowing treatments; mowing late in the growing season (2 weeks after individuals first reached a height of 40 cm) was most effective at ambient temperatures and under warming. Warming caused significant increases in projected local population growth rate for all mowing treatments. For invasive musk thistle, warmed individuals outperformed individuals grown at ambient temperatures across all the mowing treatments we considered. Our results suggest that to achieve outcomes comparable to those attainable at today's temperatures, farmers will need to apply supplemental management, possibly including additional mowing effort or alternative practices such as chemical control. We recommend that scientists test management practices under experimental warming, where possible, and that managers monitor ongoing management to identify changes in effectiveness. Information about changes in managed weeds' mortality, fecundity, and phenology can then be used to make informed decisions in future climates.

Phenolic Composition of Inflorescences of Carduus nutans L.

Carduus nutans L. (Compositae) has been extensively used for medicinal purposes. As other representatives of the genus it is implemented in the treatment of liver disorders and used as diuretic and digestive agent. Previous studies have determined the predominant classes of secondary metabolites in Carduus species. Among the major representatives of their extracts flavonoids, phenolic acids, coumarins, sterols and terpenes were identified. The antiradical capacity of three extracts assessed in the DPPH test revealed the highest radical scavenging properties of methanol extract (the EC50 618±10.03 µg/mL) and based on these results it was selected for phenolic content determination. (TPC=61.49 mg/g). To understand better the induced pharmacological effects of the plant the aim of the study was to determine the composition of the methanol extract from the inflorescences of C. nutans and to study their phenolic composition. In order to determine the composition in a more efficient way, the crude extract was fractionated and subjected to hydrolyses. As a result more than twenty phenolic acids and flavonoids were identified in the extract and fractions by HPLC-DAD and/or HPLC-ESI-TOF-MS. The total extract was later subjected to fractionation by centrifugal partition chromatography using the Arizona system composed of hexane/ethyl acetate/methanol/water (0.7 : 4 : 0.8 : 4 v/v/v/v) to produce fractions enriched in flavonoids that are of high pharmacological significance.

Apigenin Isolated from Carduus crispus Protects against H2O2-Induced Oxidative Damage and Spermatogenic Expression Changes in GC-2spd Sperm Cells.

Testicular oxidative stress is one of the most common factors underlying male infertility. Welted thistle, Carduus crispus Linn., and its bioactive principles are attracting scientific interest in treating male reproductive dysfunctions. Here, the protective effects of apigenin isolated from C. crispus against oxidative damage induced by hydrogen peroxide (H2O2) and dysregulation in spermatogenesis associated parameters in testicular sperm cells was investigated. Cell viabilities, ROS scavenging effects, and spermatogenic associated molecular expressions were measured by MTT, DCF-DA, Western blotting and real-time RT-PCR, respectively. A single peak with 100% purity of apigenin was obtained in HPLC conditions. Apigenin treated alone (2.5, 5, 10 and 20 µM) did not exhibit cytotoxicity, but inhibited the H2O2-induced cellular damage and elevated ROS levels significantly (p < 0.05 at 5, 10 and 20 µM) and dose-dependently. Further, H2O2-induced down-regulation of antioxidant (glutathione S-transferases m5, glutathione peroxidase 4, and peroxiredoxin 3) and spermatogenesis-associated (nectin-2 and phosphorylated-cAMP response element-binding protein) molecular expression in GC-2spd cells were attenuated by apigenin at both protein and mRNA levels (p < 0.05). In conclusion, our study showed that apigenin isolated from C. crispus might be an effective agent that can protect ROS-induced testicular dysfunctions.

Carduus edelbergii Rech. f. Mediated Fabrication of Gold Nanoparticles; Characterization and Evaluation of Antimicrobial, Antioxidant and Antidiabetic Potency of the Synthesized AuNPs.

Background: Due to the high expense, less effectiveness and more side effects of available synthetic medicine, the researchers and communities are focusing on phyto-based natural bioactive compounds, which are considered safer for the treatment of syndromes and chronic diseases. Aim: The current project was aimed to determine the phytochemicals constituents available in the aerial parts of methanol extract of Carduus edelbergii via GC-MS, fabrication of AuNPs mediated with the mentioned extract; characterization and evaluation of antimicrobial, antioxidant and antidiabetic potency of the synthesized AuNPs. Methods: Confirmation of green synthesis of AuNPs, functional groups responsible for the reduction in Au+, size and crystallinity, morphology and quantity of gold (Au) were carried out by Ultraviolet-Visible (UV-Vis) spectroscopy, Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and dispersive X-ray (EDX), respectively, whereas in vitro antioxidant characteristics were assessed by DPPH and ABTS assays. Wistar albino rats were used to test the anti-diabetic properties of the methanol extract and AuNPs. Results: GC-MS revealed that the diluted methanol extract of Carduus edelbergii consists of about 19 chemical constituents. Among the identified compounds, the 13-Docosenoic acid, methyl ester, (Z)­has the highest concentration (38.16%), followed by 9-Octadecenoic acid, methyl ester, (E)­(15.72%) and n-Hexadecanoic acid (15.07%). Methanol extract and its fabricated nanoparticles showed significant antioxidant and antimicrobial activities. In vivo antidiabetic study revealed a noteworthy (p < 0.05) decline in body weight and HDL and elevated concentration of blood glucose, bilirubin, creatinine, urea, triglyceride, VLDL, LDL, ALP, ALT and AST in diabetic control. The said changes were recovered significantly (p < 0.05) by treatment of diabetic rats with methanol extract (150 and 300 mg/Kg BW) and AuNPs of Carduus edelbergii (5 and 10 mg/Kg BW). Conclusion: The green synthesized AuNPs exhibit significant antioxidant, antimicrobial and antidiabetic characteristics.

Determination of biological activity of Carduus lanuginosus: an endemic plant in Turkey.

The genus Carduus is traditionally used in the Anatolian folk medicine for treating various diseases. Therefore, the enzyme inhibiting potential, antioxidant-antimicrobial activity, and phytochemical profile of Carduus lanuginosus extracts were investigated. The analysis of phenolic compounds was carried out by using RP-HPLC for the chemical characterization of methanol extract. The total polyphenols, total phenolic and flavonoid contents, antioxidant activity (ABTS and DPPH assay), α-amylase, and α-glucosidase inhibition activities were determined using colorimetric methods. Moreover, the antimicrobial activity was examined using the disc diffusion and microdilution methods. The ethylacetate extract was found to have the highest flavonoid and phenolic content. The water and hexane extracts showed strong enzyme inhibitory activity against the α-amylase and α-glucosidase. The methanol extract was found to contain high concentration of chlorogenic acid. The hexane and ethylacetate extracts showed to have significant MIC values on Enterococcus faecium. In conclusion, the extracts of C. lanuginosus might have a significant potential for the use as a natural pharmaceutical agent.

Unrecognized impact of a biocontrol agent on the spread rate of an invasive thistle.

Herbivores may significantly reduce plant populations by reducing seed set; however, we know little of their impact on seed movement. We show for the first time that the receptacle-feeding weevil Rhinocyllus conicus not only reduces seed production by the invasive thistle Carduus nutans but also inhibits release and subsequent wind dispersal of seeds. These effects generate large, though different, impacts on spatial spread and local abundance in two populations with differing demography, located in the United States and New Zealand. Furthermore, the mechanism is context dependent, with the largest effects through increased terminal velocity in the United States but through reduced seed production in New Zealand. Our results show that the benefit of biocontrol programs may have been underestimated; screenings of potential biocontrol agents should examine effects on pest dispersal and spread, as well as on abundance.

Roots of the invasive species Carduus nutans L. and C. acanthoides L. produce large amounts of aplotaxene, a possible allelochemical.

The invasive thistle Carduus nutans has been reported to be allelopathic, yet no allelochemicals have been identified from the species. In a search for allelochemicals from C. nutans and the closely related invasive species C. acanthoides, bioassay-guided fractionation of roots and leaves of each species were conducted. Only dichloromethane extracts of the roots of both species contained a phytotoxin (aplotaxene, (Z,Z,Z)-heptadeca-1,8,11,14-tetraene) with sufficient total activity to potentially act as an allelochemical. Aplotaxene made up 0.44 % of the weight of greenhouse-grown C. acanthoides roots (ca. 20 mM in the plant) and was not found in leaves of either species. It inhibited growth of lettuce 50 % (I 50) in soil at a concentration of ca. 0.5 mg g(-1) of dry soil (ca. 6.5 mM in soil moisture). These values gave a total activity in soil value (molar concentration in the plant divided by the molarity required for 50 % growth inhibition in soil = 3.08) similar to those of some established allelochemicals. The aplotaxene I 50 for duckweed (Lemna paucicostata) in nutrient solution was less than 0.333 mM, and the compound caused cellular leakage of cucumber cotyledon discs in darkness and light at similar concentrations. Soil in which C. acanthoides had grown contained aplotaxene at a lower concentration than necessary for biological activity in our short-term soil bioassays, but these levels might have activity over longer periods of time and might be an underestimate of concentrations in undisturbed and/or rhizosphere soil.

Elevated temperatures shift flower head height distributions and seed dispersal patterns in two invasive thistle species.

Climate change may significantly alter how organisms disperse, with implications for population spread and species management. Wind-dispersed plants have emerged as a useful study system for investigating how climate change affects dispersal, although studies modeling wind dispersal often assume propagules are released from a single point on an individual. This simplifying assumption, while useful, may misestimate dispersal. Here, we investigate the effects of climate change on dispersal distances and spread rates, examining how these quantities shift when accounting for all points of seed release on an individual. Using the wind-dispersed invasive thistles Carduus nutans and Carduus acanthoides, we quantify temperature-driven shifts in the distribution of flower head heights using a passive warming field experiment, and estimate how these shifts affect dispersal using the Wald analytical long-distance (WALD) model; for C. nutans, we use existing demographic data to simulate how these shifts affect population spread rates. We also compare dispersal distances for both warmed and ambient temperature plants, considering the entire distribution of flower head heights versus the common assumption of point-source seed release at the maximum height. For experimentally grown individuals, an ~0.6°C higher growing temperature increased mean and maximum flower head height by 14.1 cm (15.0%) and 14.0 cm (13.2%), respectively, in C. nutans and by 21.2 cm (26.6%) and 31.8 cm (36.7%), respectively, in C. acanthoides. Seeds from warmed individuals were more likely to exceed a given dispersal distance than those from their unwarmed counterparts; warmed C. nutans and C. acanthoides seeds were on average 1.36 and 1.71 times as likely, respectively, to travel 10 m or more in dispersal simulations, with this disparity increasing at longer dispersal distances. For C. nutans, increased growing temperatures boosted simulated rates of population spread by 42.2%, while assuming dispersal from a maximum height point source rather than the true distribution of flower head heights increased simulated spread by up to 28.5%. Our results not only demonstrate faster population spread under increased temperatures, but also have substantial implications for modeling such spread, as the common simplifying assumption of dispersal from a single maximum height source may substantially overestimate spread rates.

Two new glycosides from Carduus acanthoides.

Two new glycosides, syringic acid-4-O-ß-L-arabinopyranoside and kaempferol-3-O-α-L-rhamnopyranosyl-7-O-ß-D-glucuronopyranoside, were isolated from whole plants of Carduus acanthoides (Asteraceae), and their structures were elucidated on the basis of spectroscopic analysis.

Inhibition of key enzymes linked to obesity by preparations from Mediterranean dietary plants: effects on α-amylase and pancreatic lipase activities.

One of the most important strategy in the treatment of obesity includes the development of nutrient digestion and absorption inhibitors. Inhibition of digestive enzymes is one of the most widely studied mechanisms used to determine the potential efficacy of natural products as hypolipidemic and hypoglycaemic agents. In vitro studies here reported were performed to evaluate the inhibitory activity of five species(as hydroalcoholic extracts) of edible plants from Calabria region (Italy) on amylase and lipase by monitoring the hydrolysis of p-NPC and the hydrolysis of glycoside bonds indigestible carbohydrate foods. The formulation obtained from Clematis vitalba L. exhibited the strongest inhibitory effect on pancreatic lipase (IC50=0.99 mg/ml) and on α-amylase(IC50=31.52 µg/ml). In order to explore metabolome production HPTLC analysis of the extracts was performed, revealing the predominance of (±)-catechin, caffeic acid and chlorogenic acid in C. vital ba formulation at concentration of 23.18±3.14,13.63±0.65 and 18.88±0.76 mg/g, respectively. GC/MS analysis was used to identify fatty acids and terpene composition.

[Chemical constituents from whole plants of Carduus acanthoides].

Fourteen compounds were isolated from wholeplants of Carduus acanthoides by various chromatographic techniques including column chromatography over HP-20 macroporous resin, MCI gel, silica gel, Sephadex LH-20 and ODS and reversed-phase HPLC. Their structures were identified as salidroside (1), 2-(3,4-dihydroxyphenyl)-ethyl-O-beta-D-glucopyranoside (2), 3,5-di-hydroxyphenethyl alcohol-3-O-beta-D-glucopyranoside (3), p-coumaric acid (4), 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl) propan-1-one (5), 3-hydroxy-1-(4-hydroxy-3,5-dimethoxyphenyl) propan-1-one (6), syringin (7), p-hydroxybenzaldehyde (8), salicylic acid (9), tachioside (10), vanillic acid-4-O-beta-D-glucopyranoside (11), syringic aldehyde (12), 2,6-dimethoxy-4-hydroxyphenol-1-O-beta-D-glucopyranoside (13), and 2, 6-dimethoxy-p-hydroquinone-4-0-P-D-glucopyranoside (14) on the basis of spectroscopic data analysiS. All compounds were isolated from the genus Carduus for the first time except for compounds 4 and 7.

Bottom-up effects may not reach the top: the influence of ant-aphid interactions on the spread of soil disturbances through trophic chains.

Soil disturbances that increase nutrient availability may trigger bottom-up cascading effects along trophic chains. However, the strength and sign of these effects may depend on attributes of the interacting species. Here, we studied the effects of nutrient-rich refuse dumps of the leaf-cutting ant, Acromyrmex lobicornis, on the food chain composed of thistles, aphids, tending ants and aphid natural enemies. Using stable isotopes tracers, we show that the nitrogen accumulated in refuse dumps propagates upward through the studied food chain. Thistles growing on refuse dumps had greater biomass and higher aphid density than those growing in adjacent soil. These modifications did not affect the structure of the tending ant assemblage, but were associated with increased ant activity. In contrast to the expectations under the typical bottom-up cascade effect, the increase in aphid abundance did not positively impact on aphid natural enemies. This pattern may be explained by both an increased activity of tending ants, which defend aphids against their natural enemies, and the low capacity of aphid natural enemies to show numerical or functional responses to increased aphid density. Our results illustrate how biotic interactions and the response capacity of top predators could disrupt bottom-up cascades triggered by disturbances that increase resource availability.

Abundance, reproduction, and seed predation of an alpine plant decrease from the center toward the range limit.

Biogeographic models predict that, because of increasingly unfavorable and stressful conditions, populations become less frequent, smaller, less dense, and less reproductive toward the range edges. These models have greatly influenced the thinking on geographical range limits and have broad implications for ecology, evolution, and conservation. However, empirical tests of the models have rarely investigated comprehensive sets of population properties. We studied population size and density and a broad set of fitness-related traits in 66 populations of the alpine thistle Carduus defloratus along a latitudinal (615 km) and altitudinal (342-2300 m) gradient from the European Alps in the south to the northern range limit in the low mountain ranges of central Germany. Regression analysis indicated that population size and plant density declined with decreasing altitude from the center to the range margin, but plant size increased. In spite of the larger size of plants, the number of seeds produced strongly declined toward the range margin, mainly due to an increase in seed abortion. The number of flowering plants in a population influenced all components of reproduction. Plants in large populations initiated more seeds, aborted fewer seeds, and produced more and larger seeds per plant. The probability that seeds were attacked by insect larvae and the proportion of seeds damaged decreased strongly from the center to the margin of the distribution. However, in spite of the much lower level of parasitization, plants at the range margin produced far fewer viable seeds. Fluctuating asymmetry of leaf width, an indicator of developmental instability, was similar across the range and not related to population size.

Integrating multiple disturbance aspects: management of an invasive thistle, Carduus nutans.

BACKGROUND AND AIMS: Disturbances occur in most ecological systems, and play an important role in biological invasions. We delimit five key disturbance aspects: intensity, frequency, timing, duration and extent. Few studies address more than one of these aspects, yet interactions and interdependence between aspects may lead to complex outcomes. METHODS: In a two-cohort experimental study, we examined how multiple aspects (intensity, frequency and timing) of a mowing disturbance regime affect the survival, phenology, growth and reproduction of an invasive thistle Carduus nutans (musk thistle). KEY RESULTS: Our results show that high intensity and late timing strongly delay flowering phenology and reduce plant survival, capitulum production and plant height. A significant interaction between intensity and timing further magnifies the main effects. Unexpectedly, high frequency alone did not effectively reduce reproduction. However, a study examining only frequency and intensity, and not timing, would have erroneously attributed the importance of timing to frequency. CONCLUSIONS: We used management of an invasive species as an example to demonstrate the importance of a multiple-aspect disturbance framework. Failure to consider possible interactions, and the inherent interdependence of certain aspects, could result in misinterpretation and inappropriate management efforts. This framework can be broadly applied to improve our understanding of disturbance effects on individual responses, population dynamics and community composition.

Invasional interference due to similar inter- and intraspecific competition between invaders may affect management.

As the number of biological invasions increases, the potential for invader-invader interactions also rises. The effect of multiple invaders can be superadditive (invasional meltdown), additive, or subadditive (invasional interference); which of these situations occurs has critical implications for prioritization of management efforts. Carduus nutans and C. acanthoides, two congeneric invasive weeds, have a striking, segregated distribution in central Pennsylvania, U.S.A. Possible hypotheses for this pattern include invasion history and chance, direct competition, or negative interactions mediated by other species, such as shared pollinators. To explore the role of resource competition in generating this pattern, we conducted three related experiments using a response-surface design throughout the life cycles of two cohorts. Although these species have similar niche requirements, we found no differential response to competition between conspecifics vs. congeners. The response to combined density was relatively weak for both species. While direct competitive interactions do not explain the segregated distributional patterns of these two species, we predict that invasions of either species singly, or both species together, would have similar impacts. When prioritizing which areas to target to prevent the spread of one of the species, it is better to focus on areas as yet unaffected by its congener; where the congener is already present, invasional interference makes it unlikely that the net effect will change.

Protection of apigenin against kainate-induced excitotoxicity by anti-oxidative effects.

Apigenin (5,7,4'-trihydroxyflavone) is a principal ingredient of Cirsium japonicum. These experiments were performed to determine whether apigenin has neuroprotective effects against kainic acid (KA)-induced excitotoxicity in vitro and in vivo. Intraperitoneal (i.p.) administration of apigenin (25, 50 mg/kg) decreased the seizure scores induced by KA injection (40 mg/kg, i.p.) in mice. In addition, the convulsion onset time was significantly delayed by apigenin administration. Moreover, we found that apigenin blocked KA-induced seizure-form electroencephalogram (EEG) discharge activity in the brain cortex. In hippocampal cells, apigenin inhibited KA-induced excitotoxicity in a dose-dependent manner as measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. To study the possible mechanisms underlying the in vitro neuroprotective effects of apigenin against KA-induced cytotoxicity, we also examined the effect of apigenin on intracellular reactive oxygen species (ROS) elevations in cultured hippocampal neurons and found that apigenin treatment dose-dependently inhibited intracellular ROS elevation. The remarkable reduction of glutathione (GSH) levels induced by KA in hippocampal tissues was reversed by apigenin in a dose-dependent manner. In addition, similar results were obtained after pretreatment with free radical scavengers such as trolox and dimethylthiourea (DMTU). Finally, after confirming the protective effect of apigenin in hippocampal CA3 region, we found apigenin is an active compound in KA-induced neuroprotection. These results collectively indicate that apigenin alleviates KA-induced excitotoxicity by quenching ROS as well as inhibiting GSH depletion in hippocampal neurons.

Pollinator Behavior Mediates Negative Interactions between Two Congeneric Invasive Plant Species.

Simultaneously flowering plant species may indirectly interact with each other by influencing the quantity of pollinator visitation and/or the quality of pollen that is transferred. These effects on pollination may depend on how pollinators respond to floral resources at multiple levels. In this study, we demonstrate pollinator-mediated negative interactions between two invasive plants, Carduus acanthoides and Carduus nutans. Using constructed arrays of the two species, alone and in mixture, we quantified pollinator visitation at the patch and individual plant levels and measured seed production. We found that co-occurrence of our species led to a shift in pollinator services at both levels. Greater interference occurred when arrays were small and spacings between neighboring plants were large. A spatially explicit movement model suggests that pollinator foraging behavior, which mediates the interactions between plants, was driven by floral display size rather than species identity per se. Pollinator behavior significantly reduced the proportion of seed set for both species relative to that in single-species arrays. Overall, the dependence of pollinator behavior on patch size, spacing between plants, and patch composition can lead to pollinator-mediated plant interactions that range from facilitative to competitive.

Importance of individual and environmental variation for invasive species spread: a spatial integral projection model.

Plant survival, growth, and flowering are size dependent in many plant populations but also vary among individuals of the same size. This individual variation, along with variation in dispersal caused by differences in, e.g., seed release height, seed characteristics, and wind speed, is a key determinant of the spread rate of species through homogeneous landscapes. Here we develop spatial integral projection models (SIPMs) that include both demography and dispersal with continuous state variables. The advantage of this novel approach over discrete-stage spread models is that the effect of variation in plant size and size-dependent vital rates can be studied at much higher resolution. Comparing Neubert-Caswell matrix models to SIPMs allowed us to assess the importance of including individual variation in the models. As a test case we parameterized a SIPM with previously published data on the invasive monocarpic thistle Carduus nutans in New Zealand. Spread rate (c*) estimates were 34% lower than for standard spatial matrix models and stabilized with as few as seven evenly distributed size classes. The SIPM allowed us to calculate spread rate elasticities over the range of plant sizes, showing the size range of seedlings that contributed most to c* through their survival, growth and reproduction. The annual transitions of these seedlings were also the most important ones for local population growth (lambda). However, seedlings that reproduced within a year contributed relatively more to c* than to lambda. In contrast, plants that grow over several years to reach a large size and produce many more seeds, contributed relatively more to lambda than to c*. We show that matrix models pick up some of these details, while other details disappear within wide size classes. Our results show that SIPMs integrate various sources of variation much better than discrete-stage matrix models. Simpler, heuristic models, however, remain very valuable in studies where the main goal is to investigate the general impact of a life history stage on population dynamics. We conclude with a discussion of future extensions of SIPMs, including incorporation of continuous time and environmental drivers.