Application of PAT Probes in Aluminum Phosphate Adjuvant Manufacturing.

PURPOSE: This study is focused on monitoring process parameters and quality attributes of aluminum phosphate (AlPO4) using multiple in-line probes incorporated into an industrial-scale adjuvant suspension manufacturing unit. METHODS: The manufacturing of aluminum adjuvant suspension was monitored at manufacturing scale using conductivity, turbidity, infrared, and particle sizing and count probes to follow the continuous evolution of particle formation and size distribution, and the reaction kinetics during the synthesis of AlPO4. RESULTS: The data showed that AlPO4 forms large particles at the early stages of mixing, followed by a decrease in size and then stabilization towards the later stages of mixing and pH adjustment. The results provided a complementary view of process events and assisted in optimizing several parameters, e.g., flow rate of reactants AlCl3 and Na3PO4 solutions, mixing rate, pH, and conductivity of AlPO4, as well as adjuvant quality attribute such as particle size, thus streamlining and shortening the process development stage. CONCLUSION: The results of this study showed the usefulness of the in-line probes to automate continuous assessment of AlPO4 batch-to-batch consistency during in-house adjuvant production at the industrial scale.

Predator-induced prey dispersal can cause hump-shaped density-area relationships in prey populations.

Predation can both reduce prey abundance directly (through density-dependent effects) and indirectly through prey trait-mediated effects. Over the years, many studies have focused on describing the density-area relationship (DAR). However, the mechanisms responsible for the DAR are not well understood. Loss and fragmentation of habitats, owing to human activities, creates landscape-level spatial heterogeneity wherein patches of varying size, isolation and quality are separated by a human-modified "matrix" of varying degrees of hostility and has been a primary driver of species extinctions and declining biodiversity. How matrix hostility in combination with trait-mediated effects influence DAR, minimum patch size, and species coexistence remains an open question. In this paper, we employ a theoretical spatially explicit predator-prey population model built upon the reaction-diffusion framework to explore effects of predator-induced emigration (trait-mediated emigration) and matrix hostility on DAR, minimum patch size, and species coexistence. Our results show that when trait-mediated response strength is sufficiently strong, ranges of patch size emerge where a nonlinear hump-shaped prey DAR is predicted and other ranges where coexistence is not possible. In a conservation perspective, DAR is crucial not only in deciding whether we should have one large habitat patch or several-small (SLOSS), but for understanding the minimum patch size that can support a viable population. Our study lends more credence to the possibility that predators can alter prey DAR through predator-induced prey dispersal.

Ecological release and patch geometry can cause nonlinear density-area relationships.

A primary driver of species extinctions and declining biodiversity is loss and fragmentation of habitats owing to human activities. Many studies spanning a wide diversity of taxa have described the relationship between population density and habitat patch area, i.e., the density-area relationship (DAR), as positive, neutral, negative or some combination of the three. However, the mechanisms responsible for these relationships remain elusive. We employ a theoretical spatially explicit population model built upon the reaction-diffusion framework with absorbing boundary conditions to model a habitat specialist dwelling in islands of habitat surrounded by a hostile matrix. We consider patches with a convex or non-convex geometry. Our results show that a single species following logistic-type population growth exhibits a strictly positive and continuous DAR. However, when multiple asymptotically stable steady states are preset in the system, a discontinuous DAR arises. In the case of two species governed by diffusive Lotka-Volterra growth and competitive interactions, we observe that overall DAR structure can be either (1) positive, (2) positive for small areas and neutral for large, or (3) hump-shaped, i.e., positive for area below a threshold and negative for area above. Patch complexity such as non-convex geometry can cause discontinuities in DAR slope for a single species and create qualitatively different patterns in a competitive system as compared to a convex patch. We also compared our theoretical results with two empirical studies (Anolis lizards on islands and crossbills and pine squirrels in forest fragments) where the pragmatic view of DAR fails to give a mechanistic understanding of what was observed. Close qualitative agreement between theoretical and observed DAR indicates that our model gives a reasonable explanation of the mechanisms underpinning DAR found in those studies. From a conservation perspective, the DAR is crucial to the identification of valuable habitat fragments that favor high abundance and the design of a reserve for a target species. When it comes to protecting a single species, these results suggest that there is unlikely to be a simple solution and that conservation decisions should always be made on a case-by-case basis.

Metabolomic Evenness Underlies Intraspecific Differences Among Lineages of a Wetland Grass.

The metabolome represents an important functional trait likely important to plant invasion success, but we have a limited understanding of whether the entire metabolome or targeted groups of compounds confer an advantage to invasive as compared to native taxa. We conducted a lipidomic and metabolomic analysis of the cosmopolitan wetland grass Phragmites australis. We classified features into metabolic pathways, subclasses, and classes. Subsequently, we used Random Forests to identify informative features to differentiate five phylogeographic and ecologically distinct lineages: European native, North American invasive, North American native, Gulf, and Delta. We found that lineages had unique phytochemical fingerprints, although there was overlap between the North American invasive and North American native lineages. Furthermore, we found that divergence in phytochemical diversity was driven by compound evenness rather than metabolite richness. Interestingly, the North American invasive lineage had greater chemical evenness than the Delta and Gulf lineages but lower evenness than the North American native lineage. Our results suggest that metabolomic evenness may represent a critical functional trait within a plant species. Its role in invasion success, resistance to herbivory, and large-scale die-off events common to this and other plant species remain to be investigated.

Frequency of Occurrence and Population-Dynamic Consequences of Different Forms of Density-Dependent Emigration.

Emigration is a fundamental process affecting species' local, regional, and large-scale dynamics. The paradigmatic view in ecology is that emigration is density independent (DIE) or positive density dependent (+DDE). However, alternative forms are biologically plausible, including negative (-DDE), U-shaped (uDDE), and hump-shaped (hDDE) forms. We reviewed the empirical literature to assess the frequency of different forms of density-dependent emigration and whether the form depended on methodology. We also developed a reaction-diffusion model to illustrate how different forms of DDE can affect patch-level population persistence. We found 145 studies, the majority representing DIE (30%) and +DDE (36%). However, we also regularly found -DDE (25%) and evidence for nonlinear DDE (9%), including one case of uDDE and two cases of hDDE. Nonlinear DDE detection is likely hindered by the use of few density levels and small density ranges. Based on our models, DIE and +DDE promoted stable and persistent populations. uDDE and -DDE generated an Allee effect that decreases minimum patch size. Last, -DDE and hDDE models yielded bistability that allows the establishment of populations at lower densities. We conclude that the emigration process can be a diverse function of density in nature and that alternative DDE forms can have important consequences for population dynamics.

Effects of Patch-Matrix Composition and Individual Movement Response on Population Persistence at the Patch Level.

Fragmentation creates landscape-level spatial heterogeneity which in turn influences population dynamics of the resident species. This often leads to declines in abundance of the species due to increased susceptibility to edge effects between the remnant habitat patches and the lower quality "matrix" surrounding these focal patches. In this paper, we formalize a framework to facilitate the connection between small-scale movement and patch-level predictions of persistence through a mechanistic model based on reaction-diffusion equations. The model is capable of incorporating essential information about edge-mediated effects such as patch preference, movement behavior, and matrix-induced mortality. We mathematically analyze the model's predictions of persistence with a general logistic-type growth term and explore their sensitivity to demographic attributes in both the patch and matrix, as well as patch size and geometry. Also, we provide bounds on demographic attributes and patch size in order for the model to predict persistence of a species in a given patch based on assumptions on the patch/matrix interface. Finally, we illustrate the utility of this framework with a well-studied planthopper species (Prokelisia crocea) living in a highly fragmented landscape. Using experimentally derived data from various sources to parameterize the model, we show that, qualitatively, the model results are in accord with experimental predictions regarding minimum patch size of P. crocea. Through application of a sensitivity analysis to the model, we also suggest a ranking of the most important model parameters based on which parameter will cause the largest output variance.

Intraspecific variation in indirect plant-soil feedbacks influences a wetland plant invasion.

Plant-soil feedbacks (PSFs) influence plant competition via direct interactions with pathogens and mutualists or indirectly via apparent competition/mutualisms (i.e., spillover to co-occurring plants) and soil legacy effects. It is currently unknown how intraspecific variation in PSFs interacts with the environment (e.g., nutrient availability) to influence competition between native and invasive plants. We conducted a fully crossed multi-factor greenhouse experiment to determine the effects of Phragmites australis rhizosphere soil biota, interspecific competition, and nutrient availability on biomass of replicate populations from one native and two invasive lineages of common reed (P. australis) and a single lineage of native smooth cordgrass (Spartina alterniflora). Harmful soil biota consistently dominated PSFs involving all three P. australis lineages, reducing biomass by 10%. Indirect PSFs (i.e., soil biota spillover) from the two invasive P. australis lineages reduced S. alterniflora biomass by 7%, whereas PSFs from the native P. australis lineage increased S. alterniflora biomass by 6%. Interestingly, interspecific competition and PSFs interacted to weaken their respective impacts on S. alterniflora, whereas they exerted synergistic negative effects on P. australis. Phragmites australis soil biota decreased S. alterniflora biomass when grown alone (i.e., a soil legacy), but increased S. alterniflora biomass when grown with P. australis, suggesting that P. australis recruits harmful generalist soil biota or facilitates S. alterniflora via spillover (i.e., apparent mutualism). Soil biota also reduced interspecific competition impacts on S. alterniflora, although it remained competitively inferior to P. australis across all treatments. Competitive interactions and responses to nutrients did not differ among P. australis lineages, indicating that interspecific competition and nutrient deposition may not be key drivers of P. australis invasion in North America. Although soil biota, interspecific competition, and nutrient availability appear to have no direct impact on the success of invasive P. australis lineages in North America, intraspecific lineage variation in indirect spillover and soil legacies from P. australis occur and may have important implications for co-occurring native species and restoration of invaded habitats. Our study integrates multiple factors linked to plant invasions, highlighting that indirect interactions are likely commonplace in influencing plant community dynamics and invasion success and impacts.

Geographic variation in apparent competition between native and invasive Phragmites australis.

Apparent competition, the negative interaction between species mediated by shared natural enemies, is thought to play an important role in shaping the structure and dynamics of natural communities. However, its importance in driving species invasions, and whether the strength of this indirect interaction varies across the latitudinal range of the invasion, has not been fully explored. We performed replicated field experiments at four sites spanning 900 km along the Atlantic Coast of the United States to assess the presence and strength of apparent competition between sympatric native and invasive lineages of Phragmites australis. Four herbivore guilds were considered: stem-feeders, leaf-miners, leaf-chewers and aphids. We also tested the hypothesis that the strength of this interaction declines with increasing latitude. Within each site, native and invasive plants of P. australis were cross-transplanted between co-occurring native and invasive patches in the same marsh habitat and herbivore damage was evaluated at the end of the growing season. Apparent competition was evident for both lineages and involved all but the leaf-chewer guild. For native plants, total aphids per plant was 296% higher and the incidence of stem-feeding and leaf-mining herbivores was 34% and 221% higher, respectively, when transplanted into invasive than native patches. These data suggest that invasive P. australis has a negative effect on native P. australis via apparent competition. Averaged among herbivore types, the indirect effects of the invasive lineage on the native lineage was 57% higher than the reverse situation, suggesting that apparent competition was asymmetric. We also found that the strength of apparent competition acting against the native lineage was comparable to the benefits to the invasive lineage from enemy release (i.e., proportionately lower mean herbivory of the invasive relative to the native taxa). Finally, we found the first evidence that the strength of apparent competition acting against the native lineage (from stem-feeders only) decreased with increasing latitude. These results suggest that not only could apparent competition be of tantamount importance to enemy release in enhancing the establishment and spread of invasive taxa, but also that these indirect and direct herbivore effects could vary over the invasion range.

Variable prey development time suppresses predator-prey cycles and enhances stability.

Although theoretical models have demonstrated that predator-prey population dynamics can depend critically on age (stage) structure and the duration and variability in development times of different life stages, experimental support for this theory is non-existent. We conducted an experiment with a host-parasitoid system to test the prediction that increased variability in the development time of the vulnerable host stage can promote interaction stability. Host-parasitoid microcosms were subjected to two treatments: Normal and High variance in the duration of the vulnerable host stage. In control and Normal-variance microcosms, hosts and parasitoids exhibited distinct population cycles. In contrast, insect abundances were 18-24% less variable in High- than Normal-variance microcosms. More significantly, periodicity in host-parasitoid population dynamics disappeared in the High-variance microcosms. Simulation models confirmed that stability in High-variance microcosms was sufficient to prevent extinction. We conclude that developmental variability is critical to predator-prey population dynamics and could be exploited in pest-management programs.

Biogeography of a plant invasion: plant-herbivore interactions.

Theory predicts that native plant species should exhibit latitudinal gradients in the strength of their interactions with herbivores. We hypothesize that if an invasive plant species exhibits a different latitudinal gradient in response to herbivores (e.g., a nonparallel gradient), it can create large-scale heterogeneities in community resistance/susceptibility to the invasive species. We conducted a study of latitudinal variation in the strength of herbivory and defenses of native genotypes of Phragmites australis in North America (NA) and Europe (EU) and European invasive genotypes in NA. Within NA, we tested whether (1) invasive genotypes are better defended and suffer less herbivory than co-occurring native genotypes, (2) herbivory and defenses of native P. australis decreases with increasing latitude; and (3) invasive genotypes exhibit either no latitudinal gradient, or a nonparallel latitudinal gradient in herbivory and defenses compared to native genotypes. For the European genotypes, we tested two additional hypotheses: (4) defenses, nutritional condition, and herbivory would differ between the native (EU) and invasive ranges (NA) and (5) latitudinal gradients in defenses and herbivory would be similar between ranges. Within NA, chewing damage, internal stem-feeding incidence, and aphid abundance were 650%, 300%, and 70% lower, respectively, on invasive than native P. australis genotypes. Genotypes in NA also differed in nutritional condition (percent N, C:N ratio), but there was little support for invasive genotypes being better defended than native genotypes. For the European genotypes, herbivory was significantly lower in the invaded than native range, supporting the enemy-release hypothesis. Defense levels (leaf toughness and total phenolics) and tissue percent C and percent N were higher in the invaded than native range for European genotypes. Overall, latitudinal gradients in P. australis nutritional condition, defenses, and herbivory were common. Interestingly, chewing damage and stem-feeder incidence decreased with latitude for native P. australis genotypes in NA and EU, but no latitudinal gradients in response to herbivores were evident for invasive genotypes in NA. Nonparallel latitudinal gradients in herbivory between invasive and native P. australis suggest that the community may be more susceptible to invasion at lower than at higher latitudes. Our study points to the need for invasion biology to include a biogeographic perspective.

Response of native insect communities to invasive plants.

Invasive plants can disrupt a range of trophic interactions in native communities. As a novel resource they can affect the performance of native insect herbivores and their natural enemies such as parasitoids and predators, and this can lead to host shifts of these herbivores and natural enemies. Through the release of volatile compounds, and by changing the chemical complexity of the habitat, invasive plants can also affect the behavior of native insects such as herbivores, parasitoids, and pollinators. Studies that compare insects on related native and invasive plants in invaded habitats show that the abundance of insect herbivores is often lower on invasive plants, but that damage levels are similar. The impact of invasive plants on the population dynamics of resident insect species has been rarely examined, but invasive plants can influence the spatial and temporal dynamics of native insect (meta)populations and communities, ultimately leading to changes at the landscape level.

Dieback and dredge soils of Phragmites australis in the Mississippi River Delta negatively impact plant biomass.

Phragmites australis is exhibiting extensive dieback in the Lower Mississippi River Delta (MRD). We explored the potential for restoration of these marshes by (1) characterizing the chemical profiles of soils collected from healthy and dieback stands of P. australis and from sites recently created from dredge-disposal soils that were expected to be colonized by P. australis and (2) experimentally testing the effects of these soil types on the growth of three common P. australis lineages, Delta, Gulf and European. Soil chemical properties included Al, Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Zn, % organic matter, % carbon, % nitrogen, and pH. Dieback soils were characterized by higher % organic matter, % carbon, % nitrogen, and higher S and Fe concentrations, whereas healthy soils had higher Cu, Al, P and Zn. In comparison, dredge sites were low in nutrients and organic matter compared to healthy soils. Rhizomes of each P. australis lineage were planted in each soil type in a common garden and greenhouse and allowed to grow for five months. Aboveground biomass was 16% lower in dieback and 44% lower in dredge soils than in healthy soils. However, we could detect no significant differences in response to soil types among lineages. Although dredge and dieback sites are not optimal for P. australis growth, plants can thrive on these soils, and we recommend restorative measures be initiated as soon as possible to minimize soil erosion.

Vegetation dieback in the Mississippi River Delta triggered by acute drought and chronic relative sea-level rise.

Vegetation dieback and recovery may be dependent on the interplay between infrequent acute disturbances and underlying chronic stresses. Coastal wetlands are vulnerable to the chronic stress of sea-level rise, which may affect their susceptibility to acute disturbance events. Here, we show that a large-scale vegetation dieback in the Mississippi River Delta was precipitated by salt-water incursion during an extreme drought in the summer of 2012 and was most severe in areas exposed to greater flooding. Using 16 years of data (2007-2022) from a coastwide network of monitoring stations, we show that the impacts of the dieback lasted five years and that recovery was only partial in areas exposed to greater inundation. Dieback marshes experienced an increase in percent time flooded from 43% in 2007 to 75% in 2022 and a decline in vegetation cover and species richness over the same period. Thus, while drought-induced high salinities and soil saturation triggered a significant dieback event, the chronic increase in inundation is causing a longer-term decline in cover, more widespread losses, and reduced capacity to recover from acute stressors. Overall, our findings point to the importance of mitigating the underlying stresses to foster resilience to both acute and persistent causes of vegetation loss.

Mechanisms driving the density-area relationship in a saproxylic beetle.

Mechanisms underlying density-area relationships (correlations between population density and patch size) have rarely been tested experimentally. It is often assumed that higher density on large patches is evidence that large patches are high quality (i.e. have greater survival and reproduction), but the same pattern could result from disproportionate movement from small to large patches. Movement-based and within-patch processes must be experimentally separated to show that large patches are indeed of higher quality, but few studies have done so. We experimentally tested movement-based and within-patch hypotheses to explain the positive density-area relationship observed for a saproxylic (decayed wood-dependent) beetle, Odontotaenius disjunctus Illiger (Coleoptera: Passalidae). In separate experiments we quantified (1) immigration into and (2) finite growth rate within logs (=patches) that varied in size and density of conspecific beetles. A log was 11.7-fold [95 % confidence interval (CI) 3.4-40.8) and 10.5-fold (95 % CI 2.7-40.9) more likely to contain a new immigrant if it was large or contained a conspecific pair of beetles, respectively. Neither log size nor conspecific density was associated with changes in finite growth rate that would lead to higher density: decreased log size and increased conspecific density reduced finite growth rate in direct proportion to the loss in available resources per mating pair. We conclude that movement behavior rather than habitat quality is responsible for the positive density-area relationship for O. disjunctus. An important implication of our results is that population density is an imperfect indicator of habitat quality.

Estimation of the diffusion rate and crossing probability for biased edge movement between two different types of habitat.

One of the fundamental goals of ecology is to examine how dispersal affects the distribution and dynamics of insects across natural landscapes. These landscapes are frequently divided into patches of habitat embedded in a matrix of several non-habitat regions, and dispersal behavior could vary within each landscape element as well as the edges between elements. Reaction-diffusion models are a common way of modeling dispersal and species interactions in such landscapes, but to apply these models we also need methods of estimating the diffusion rate and any edge behavior parameters. In this paper, we present a method of estimating the diffusion rate using the mean occupancy time for a circular region. We also use mean occupancy time to estimate a parameter (the crossing probability) that governs one type of edge behavior often used in these models, a biased random walk. These new methods have some advantages over other methods of estimating these parameters, including reduced computational cost and ease of use in the field. They also provide a method of estimating the diffusion rate for a particular location in space, compared to existing methods that represent averages over large areas. We further examine the statistical properties of the new method through simulation, and discuss how mean occupancy time could be estimated in field experiments.

Density-dependent within-patch movement behavior of two competing species.

Movement behavior is central to understanding species distributions, population dynamics and coexistence with other species. Although the relationship between conspecific density and emigration has been well studied, little attention has been paid to how interspecific competitor density affects another species' movement behavior. We conducted releases of two species of competing Tribolium flour beetles at different densities, alone and together in homogeneous microcosms, and tested whether their recaptures-with-distance were well described by a random-diffusion model. We also determined whether mean displacement distances varied with the release density of conspecific and heterospecific beetles. A diffusion model provided a good fit to the redistribution of T. castaneum and T. confusum at all release densities, explaining an average of >60% of the variation in recaptures. For both species, mean displacement (directly proportional to the diffusion rate) exhibited a humped-shaped relationship with conspecific density. Finally, we found that both species of beetle impacted the within-patch movement rates of the other species, but the effect depended on density. For T. castaneum in the highest density treatment, the addition of equal numbers of T. castaneum or T. confusum had the same effect, with mean displacements reduced by approximately one half. The same result occurred for T. confusum released at an intermediate density. In both cases, it was total beetle abundance, not species identity that mattered to mean displacement. We suggest that displacement or diffusion rates that exhibit a nonlinear relationship with density or depend on the presence or abundance of interacting species should be considered when attempting to predict the spatial spread of populations or scaling up to heterogeneous landscapes.

DNA assays for genetic discrimination of three Phragmites australis subspecies in the United States.

Premise: To genetically discriminate subspecies of the common reed (Phragmites australis), we developed real-time quantitative (qPCR) assays for identifying P. australis subsp. americanus, P. australis subsp. australis, and P. australis subsp. berlandieri. Methods and Results: Utilizing study-generated chloroplast DNA sequences, we developed three novel qPCR assays. Assays were verified on individuals of each subspecies and against two non-target species, Arundo donax and Phalaris arundinacea. One assay amplifies only P. australis subsp. americanus, one amplifies P. australis subsp. australis and/or P. australis subsp. berlandieri, and one amplifies P. australis subsp. americanus and/or P. australis subsp. australis. This protocol enhances currently available rapid identification methods by providing genetic discrimination of all three subspecies. Conclusions: The newly developed assays were validated using P. australis samples from across the United States. Application of these assays outside of this geographic range should be preceded by additional testing.

Successional changes in plant resistance and tolerance to herbivory.

Despite considerable research on plant defenses, we know very little about how temporal changes in the environment may influence resistance and tolerance levels, or the costs and benefits of these defense strategies for long-lived plant species. We hypothesized that, in successional habitats, predictable environmental changes should favor strong plasticity in defense phenotypes and that the costs, benefits, and levels of tolerance and resistance will change with environmental context. Using a widely distributed, old-field perennial, late goldenrod (Solidago altissima), we conducted a field experiment to test these predictions. We planted goldenrod genets exhibiting varying levels of resistance and tolerance into three early-successional and three late-successional fields (approximately three and 15 years in age, respectively) and experimentally measured resistance and tolerance levels and their associated costs and selection coefficients. We found a significant effect of successional stage but no effect of genotype or stage-genotype interaction on defense levels. Genets planted in early-successional fields appeared to be more resistant and less tolerant to herbivory than those same genets planted in late-successional fields. There were significant trade-offs between resistance and tolerance in early-successional fields but not in late-successional fields. Each late-successional field exhibited a significant cost or selection gradient for resistance, but there was no general pattern of resistance costs or selection gradients specific to a successional stage class. In contrast, there was evidence of stage-specific costs of tolerance; late-successional fields exhibited significant costs of tolerance whereas early-successional fields did not. There was no evidence of direct selection for or against tolerance in either stage. Our results suggest that defense phenotypes might change in qualitative ways during succession. High resistance in early stages may be attributed to associational effects of the early-successional community, reducing the probability of damage, and despite a cost of tolerance in late stages, tolerance may be beneficial in mitigating the effects of both herbivory and environmental stresses (i.e., low light availability) that limit fitness in these fields. This study provides experimental evidence that succession can strongly influence defense phenotypes and promote temporal variability in relative resistance and tolerance levels.

Resistance and tolerance to herbivory in Solidago altissima (Asteraceae): genetic variability, costs, and selection for multiple traits.

PREMISE OF THE STUDY: Quantifying the genetic variability, fitness costs, and selection gradients associated with plant defense traits is necessary to understand their evolution and continued persistence in populations. Few studies have simultaneously examined the costs, benefits, and genetic variability in multiple traits related to plant resistance and tolerance to herbivory. • METHODS: Using 103 Solidago altissima (Asteraceae) genets from two populations previously studied in situ, we conducted a common garden experiment to assess genetic variability, costs, selection gradients, and correlations among resistance, tolerance, and various resistance and tolerance traits (i.e., lateral branching, relative growth rate, leaf addition and senescence rate, specific leaf area, and leaf toughness). • KEY RESULTS: We report evidence for significant genetic variability in resistance and various tolerance-related traits but low broad-sense heritability (H(2) < 0.14) for all traits. For all traits examined, no correlation existed between trait levels of parent ramets (measured in their field of origin) and daughter ramets (measured in the common garden), suggesting plasticity in goldenrod traits. We found a strong cost of resistance and selection gradient against high resistance. Conversely, we found no evidence of costs but did find significant selection gradients favoring increased tolerance and many tolerance trait levels. • CONCLUSIONS: Our study suggests that herbivores impose selection favoring increased tolerance and reduced resistance in goldenrods. In this environment, we expect that over time, resistant genets will decrease in frequency. Despite strong selection pressures, the evolution of tolerance in this environment may be constrained by the low broad-sense heritability in tolerance traits.

Increased ploidy of Butomus umbellatus in introduced populations is not associated with higher phenotypic plasticity to N and P.

Separate introductions or post-introduction evolution may lead to multiple invader genotypes or cytotypes that differ in growth rates, biomass or chemical profile responses (phenotype) to a range of environments. If the invader has high trait plasticity to a range of resource levels, then sediment N or P enrichment may enhance invasiveness. However, the ways in which ploidy, plasticity, and available N or P interact are unknown for most species despite the potential to explain spread and impacts by invaders with multiple introduced lineages. We conducted a common garden experiment with four triploid and six diploid populations of Butomus umbellatus, collected from across its invasive range in the USA. Plants were grown under different N or P nutrient levels (4, 40, 200, 400 mg L-1 N; 0.4, 4, 40 mg L-1 P) and we measured reaction norms for biomass, clonal reproduction and tissue chemistry. Contrary to our expectation, triploid B. umbellatus plants were less plastic to variation in N or P than diploid B. umbellatus in most measured traits. Diploid plants produced 172 % more reproductive biomass and 57 % more total biomass across levels of N, and 158 % more reproductive biomass and 33 % more total biomass across P than triploid plants. Triploid plants had lower shoot:root ratios and produced 30 % and 150 % more root biomass than diploid plants in response to increases in N and P, respectively. Tissue chemistry differed between cytotypes but plasticity was similar; N was 8 % higher and C:N ratio was 30 % lower in triploid than diploid plants across levels of N and plant parts, and N was 22 % higher and C:N ratio 27 % lower across levels of P and plant parts. Our results highlight differences in nutrient response between cytotypes of a widespread invader, and we call for additional field studies to better understand the interaction of nutrients and ploidy during invasion.