Adaptive and non‐adaptive evolution of trait means and genetic trait correlations for herbivory resistance and performance in an invasive plant

The EICA‐hypothesis predicts that invading plants adapt to their novel environment by evolving increased performance and reduced resistance in response to the release from natural enemies, and assumes a resource allocation tradeoff among both trait groups as mechanistic basis of this evolutionary change. Using the plant Silene latifolia as a study system, we tested these predictions by investigating whether 1) invasive populations evolved lower resistance and higher performance, 2) this evolutionary change is indeed adaptive, and 3) there is a negative genetic correlation between performance and resistance (i.e. a tradeoff) in native and introduced individuals. Moreover, we sampled eight native and eight invasive populations and determined their population co‐ancestry based on neutral SSR‐markers. We performed controlled crossings to produce five sib‐groups per population and exposed them to increased and reduced levels of enemy attack in a full‐factorial experiment to estimate performance and resistance. With these data, we performed trait‐by‐trait comparisons between ranges with ‘animal models’ that account for population co‐ancestry to quantify the amount of variance in traits explained by non‐adaptive versus adaptive evolution. Moreover, we tested for genetic correlations among performance and resistance traits within sib‐groups. We found significant reductions in resistance and increases in performance in invasive versus native populations, which could largely be attributed to adaptive evolution. While we detected a non‐significant trend towards negative genetic performance × resistance correlations in native populations, invasive populations exhibited both significant and non‐significant positive correlations. In summary, these results do not support a shift of performance and resistance trait values along a tradeoff line in response to enemy release, as predicted by EICA. They rather suggest that the independent evolution of both traits is not constrained by a tradeoff, and that various selective agents (including resource availability) interact in shaping both traits and in weakening negative genetic correlations in the invaded habitat.     

Release from natural enemies mitigates inbreeding depression in native and invasive Silene latifolia populations

Inbreeding and enemy infestation are common in plants and can synergistically reduce their performance. This inbreeding ×environment (I × E) interaction may be of particular importance for the success of plant invasions if introduced populations experience a release from attack by natural enemies relative to their native conspecifics. Here, we investigate whether inbreeding affects plant infestation damage, whether inbreeding depression in growth and reproduction is mitigated by enemy release, and whether this effect is more pronounced in invasive than native plant populations. We used the invader Silene latifolia and its natural enemies as a study system. We performed two generations of experimental out‐ and inbreeding within eight native (European) and eight invasive (North American) populations under controlled conditions using field‐collected seeds. Subsequently, we exposed the offspring to an enemy exclusion and inclusion treatment in a common garden in the species’ native range to assess the interactive effects of population origin (range), breeding treatment, and enemy treatment on infestation damage, growth, and reproduction. Inbreeding increased flower and leaf infestation damage in plants from both ranges, but had opposing effects on fruit damage in native versus invasive plants. Inbreeding significantly reduced plant fitness; whereby, inbreeding depression in fruit number was higher in enemy inclusions than exclusions. This effect was equally pronounced in populations from both distribution ranges. Moreover, the magnitude of inbreeding depression in fruit number was lower in invasive than native populations. These results support that inbreeding has the potential to reduce plant defenses in S. latifolia, which magnifies inbreeding depression in the presence of enemies. However, future studies are necessary to further explore whether enemy release in the invaded habitat has actually decreased inbreeding depression and thus facilitated the persistence of inbred founder populations and invasion success.     

Decreased indirect defense in the invasive tree, Triadica sebifera

In the absence of coevolved natural enemies, plants are expected to experience selection away from costly herbivore defenses toward growth and reproduction [evolution of increased competitive ability hypothesis (EICA)], yet no one has demonstrated EICA for an indirect defense trait. Likewise, we have little understanding of how constitutive and induced levels of defense vary among native and invasive plant populations. We conducted a greenhouse experiment in the introduced range to test whether invasive populations have reduced constitutive and induced investment in an indirect defense trait, extrafloral nectar (EFN) production, compared to native populations of Chinese tallow tree, Triadica sebifera, through an experimental leaf damage treatment. Overall, native populations invested more in indirect defense: Native populations had a greater number (+16?%) and percentage of leaves producing EFN (35 vs. 28?%), produced more EFN (63?% greater volume), and produced more sugar (+33?%) compared to invasive populations, independent of damage treatment. Of these traits, number of leaves producing EFN and volume of EFN exhibited a trade-off between constitutive and induced investment but these did not depend on plant origin. Our results are the first to support the EICA hypothesis for an indirect defense trait. This suggests that tri-trophic interactions such as indirect defense are under similar selection as direct defense traits within introduced populations. Despite reduced investment in EFN production, invasive populations still retain the ability to produce EFN, which may enable invasive plants to defend against herbivores in the introduced range.     

For or against: the importance of variation in growth rate for testing the EICA hypothesis

The evolution of increased competitive ability (EICA) hypothesis proposes that invasive species evolve decreased defense and increased competitive ability following natural enemy release. Previous studies have found evidence both for and against EICA. The resource-enemy release hypothesis (R-ERH) suggests that fast-growing species may experience stronger enemy release than slow-growing species. On the basis of R-ERH, the prediction of EICA will be held true for slow-growing genotypes, i.e., the slow-growing genotypes from the introduced range will be less resistant to herbivory and grow faster than those from the home range; while the EICA will not be held for fast-growing genotypes, i.e., there will be no significant differences in growth and defense traits between the introduced and native fast-growing genotypes. We tested these predictions preliminarily using five populations of the invasive plant Alternanthera philoxeroides. This species has two varieties in its home range, which showed a distinct growth-defense strategy: the northern A. p. var. acutifolia (Apa) had higher growth rate but lower resistance, while the southern A. p. var. obtusifolia (Apo) had lower growth rate but higher resistance level. Our results suggest that the EICA hypothesis is consistent with the slow-growing Apo, but not with the fast-growing Apa. We suggest that evolutionary changes in growth or resistance following enemy release are influenced by variation in growth rate within an invasive alien plant. These findings have important implications for the EICA hypothesis, and may partially explain why previous studies have found evidence both for and against EICA.     

Response to enemies in the invasive plant Lythrum salicaria is genetically determined

Background and Aims

The enemy release hypothesis assumes that invasive plants lose their co-evolved natural enemies during introduction into the new range. This study tested, as proposed by the evolution of increased competitive ability (EICA) hypothesis, whether escape from enemies results in a decrease in defence ability in plants from the invaded range. Two straightforward aspects of the EICA are examined: (1) if invasives have lost their enemies and their defence, they should be more negatively affected by their full natural pre-invasion herbivore spectrum than their native conspecifics; and (2) the genetic basis of evolutionary change in response to enemy release in the invasive range has not been taken sufficiently into account.

Methods

Lythrum salicaria (purple loosestrife) from several populations in its native (Europe) and invasive range (North America) was exposed to all above-ground herbivores in replicated natural populations in the native range. The experiment was performed both with plants raised from field-collected seeds as well as with offspring of these where maternal effects were removed.

Key Results

Absolute and relative leaf damage was higher for introduced than for native plants. Despite having smaller height growth rate, invasive plants attained a much larger final size than natives irrespective of damage, indicating large tolerance rather than effective defence. Origin effects on response to herbivory and growth were stronger in second-generation plants, suggesting that invasive potential through enemy release has a genetic basis.

Conclusions

The findings support two predictions of the EICA hypothesis – a genetically determined difference between native and invasive plants in plant vigour and response to enemies – and point to the importance of experiments that control for maternal effects and include the entire spectrum of native range enemies.     

Interactive effects of habitat productivity and herbivore pressure on the evolution of anti-herbivore defense in invasive plant populations

The evolution of increased competitive ability (EICA) hypothesis predicts that plants released from natural enemies should evolve to become more invasive through a shift in resource allocation from defense to growth. Resource availability in the environment is widely regarded as a major determinant of defense investment and invasiveness, and thus should be incorporated into the conceptual framework of EICA. Analysis of a simple model from the optimal defense literature demonstrates that, in contrast to the EICA hypothesis, enemy release is neither sufficient nor necessary for evolution of reduced resistance among introduced plants when habitat productivity co-varies. In particular, if the invasive range is more nutrient-poor than the native range, there could be selection for more plant defenses even with enemy release.     

A comparison of native and invasive populations of three clonal plant species in Germany and New Zealand

Aim Our aim was to test for changes in growth patterns of three clonally growing plant species (Achillea millefolium, Hieracium pilosella and Hypericum perforatum) between native and invaded regions. We addressed the hypotheses that with differing important life‐history traits, invasive populations perform better than native populations, and that this expected better performance is linked to weakened trade‐offs between individual growth and sexual and clonal reproduction. Location Germany and New Zealand. Methods We conducted field surveys for the three above‐mentioned species in both native German and invasive New Zealand populations, and collected data at both population and individual levels. Results At the population level, the proportion of flowering plants, population size and population density were all higher in invasive populations. Similarly, at the individual level, the number of stolons per plant, stolon–biomass ratio and population crowdedness (local plant density in a specified area around a target plant) were significantly higher in New Zealand. Plant height did not differ between countries, and plant biomass was lower in New Zealand than in Germany for Achillea millefolium and Hypericum perforatum. These two species showed significant trade‐offs between individual growth and sexual and clonal reproduction. Achillea millefolium exhibited a weakened trade‐off in its invaded range, where the same proportion of flowering plants was sustained at much higher levels of population crowdedness than in its native range. Main conclusions The apparent invasion success of the three study species is generally due to better overall performance in their respective invaded ranges. In respect of both Achillea millefolium and Hypericum perforatum, this is driven primarily by increased vegetative reproduction. In contrast, Hieracium pilosella seems to benefit more from increased sexual reproduction in its invaded range. Shifts in trade‐offs as a general trend seem to be of minor importance.     

Changes in Defense of an Alien Plant Ambrosia artemisiifolia before and after the Invasion of a Native Specialist Enemy Ophraella communa

The evolution of increased competitive ability hypothesis (EICA) predicts that when alien plants are free from their natural enemies they evolve lower allocation to defense in order to achieve a higher growth rate. If this hypothesis is true, the converse implication would be that the defense against herbivory could be restored if a natural enemy also becomes present in the introduced range. We tested this scenario in the case of Ambrosia artemisiifolia (common ragweed) – a species that invaded Japan from North America. We collected seeds from five North American populations, three populations in enemy free areas of Japan and four populations in Japan where the specialist herbivore Ophraella communa naturalized recently. Using plants grown in a common garden in Japan, we compared performance of O. communa with a bioassay experiment. Consistent with the EICA hypothesis, invasive Japanese populations of A. artemisiifolia exhibited a weakened defense against the specialist herbivores and higher growth rate than native populations. Conversely, in locations where the herbivore O. communa appeared during the past decade, populations of A. artemisiifolia exhibited stronger defensive capabilities. These results strengthen the case for EICA and suggest that defense levels of alien populations can be recuperated rapidly after the native specialist becomes present in the introduced range. Our study implies that the plant defense is evolutionary labile depending on plant-herbivore interactions.     

Living with the enemy: parasites and pathogens of the ladybird <Emphasis Type="Italic">Harmonia axyridis</Emphasis>

Harmonia axyridis is an invasive alien predator in many countries across the world. The rapid establishment and spread of this species is of concern because of the threat it poses to biodiversity as a generalist predator. Understanding the mechanisms that contribute to the success of this species as an invader is not only intriguing but also critical to our understanding of the processes governing such invasions. The enemy release hypothesis (ERH) could explain the rapid population growth of many invasive alien species. However, empirical evidence in support of the ERH is lacking. An alternative hypothesis that could explain rapid population growth is evolution of increased competitive ability (EICA). Here we provide an overview of the parasites and pathogens of coccinellids with a particular focus on H. axyridis as a host. We examine the differential susceptibility of host species and highlight the resilience of H. axyridis in comparison to other coccinellids. We recognise the paucity and limitations of available information and suggest that studies, within a life-table framework, comparing life history traits of H. axyridis in both the native and introduced ranges are necessary. We predict that H. axyridis could benefit from both enemy release and EICA within the introduced range but require further empirical evidence.     

Increased performance of Cirsium arvense from the invasive range

The Evolution of Increased Competitive Ability (EICA) hypothesis suggests that plants from the invasive range should perform better than plants of the same species from the native range. To properly test this, we need to compare growth of plants from the two ranges in a common environment. Ideally, all the natural enemies should be excluded, to make sure that the differences are not due to different response of plants from the two ranges to the natural enemies. We used the above design to examine the difference in growth and reproduction in Cirsium arvense plants from the invasive (North America) and native range (Europe). To account for possible differences within the ranges, we used plants from two regions, separated by at least 1000 km, in each range. Because the higher performance of species from the invasive range can be caused by their higher ability to acquire resources we compared growth of the plants in two different nutrient levels. The results indicate that plants from the invasive range are larger in most size parameters as well as parameters more closely related to fitness. For aboveground biomass, the response of plants from the invasive range to nutrient addition was weaker than that of plants from the native range and the difference between the ranges was stronger in the nutrient poor substrate. The results are in agreement with the EICA hypothesis and suggest that plants from the invasive range have higher ability to use resources and are thus able to perform well also in nutrient poor conditions.     

Release from belowground enemies and shifts in root traits as interrelated drivers of alien plant invasion success: a hypothesis

Our understanding of the interrelated mechanisms driving plant invasions, such as the interplay between enemy release and resource‐acquisition traits, is biased by an aboveground perspective. To address this bias, I hypothesize that plant release from belowground enemies (especially fungal pathogens) will give invasive plant species a fitness advantage in the alien range, via shifts in root traits (e.g., increased specific root length and branching intensity) that increase resource uptake and competitive ability compared to native species in the alien range, and compared to plants of the invader in its native range. Such root‐trait changes could be ecological or evolutionary in nature. I explain how shifts in root traits could occur as a consequence of enemy release and contribute to invasion success of alien plants, and how they could be interrelated with other potential belowground drivers of invasion success (allelopathy, mutualist enhancement). Finally, I outline the approaches that could be taken to test whether belowground enemy release results in increased competitive ability and nutrient uptake by invasive alien plants, via changes in root traits in the alien range.     

Contemporary variations of immune responsiveness during range expansion of two invasive rodents in Senegal

Biological invasions provide unique opportunities for studying life history trait changes over contemporary time scales. As spatial spread may be related to changes in parasite communities, several hypotheses (such as the evolution of increased competitive ability (EICA) or EICA‐refined hypotheses) suggest immune changes in invasive species along invasion gradients. Although native hosts may be subject to similar changes in parasite selection pressures, their immune responses have been rarely investigated in invasion contexts. In this study, we evaluated immune variations for invasive house mice Mus musculus domesticus, invasive black rats Rattus rattus and native rodents Mastomys erythroleucus and Mastomys natalensis along well‐characterised invasion gradients in Senegal. We focused on antibody‐mediated (natural antibodies and complement) and inflammatory (haptoglobin) responses. One invasion route was considered for each invasive species, and environmental conditions were recorded. Natural‐antibody mediated responses increased between sites of long‐established invasion and recently invaded sites only in house mice. Both invasive species exhibited higher inflammatory responses at the invasion front than in sites of long‐established invasion. The immune responses of native species did not change with the presence of invasive species. These patterns of immune variations do not support the EICA and EICA refined hypotheses, and they rather suggest a higher risk of exposure to parasites on the invasion front. Altogether, these results provide a first basis to further assess the role of immune changes in invasion success.     

Phenotypes of Two Generations of Sporobolus airoides Seedlings Derived from Acroptilon repens‐invaded and Non‐invaded Grass Populations

Although the ecological impacts of invasive species are well known, the evolutionary impacts on recipient native grass communities are not. We suggest that remnant native plants may provide desirable seed sources for restoration and native plant production. Native populations exposed to the selective pressures associated with exotic invasion may retain traits that increase their ability to coexist with invasive species. Two generations of Sporobolus airoides Torr. (Alkali sacaton) plants derived from lineages collected from within long‐term invaded areas of Acroptilon repens (L.) DC (Russian knapweed) and from adjacent non‐invaded areas were propagated in a greenhouse to evaluate generational changes in phenotypic traits from the production environment. Given the difference in invasion history of the two populations, we hypothesized that invaded and non‐invaded subpopulations would differ phenotypically. Phenotypic measurements revealed that invaded subpopulations had greater vegetative growth, whereas non‐invaded subpopulations had increased sexual reproduction. Phenotypic expression changed from the first to the second generation, predominantly in the invaded subpopulation. Generational phenotypic shifts are disadvantageous for native seed production which requires a standard product to sell commercially. However, phenotypic variation may improve field seed survival. This research demonstrates the potential value of targeting post‐invasion remnant grass populations for restoration.     

Temperate trees and shrubs as global invaders: the relationship between invasiveness and native distribution depends on biological traits

Many woody plants have been recently recognized as major invasive species with serious impacts on species diversity and functioning of invaded ecosystems. We evaluated the global invasion success of temperate trees and shrubs with native ranges in central Europe and explored the role of their native distribution and that of biological traits in determining whether they have become invasive in other parts of the world. Of the 94 species forming the source-area species pool, 27 % are known to be invasive in at least one region of the world. Generalized linear models on phylogenetically non-informed analyses revealed that tall woody plants flowering early in the season, and occupying many grid cells in the native range are significantly more likely to become successful invaders than species not possessing these traits. However, other traits can partly reduce the disadvantages resulting from low regional frequencies in the native range and consequent lower probability of them being introduced elsewhere. Species that do not depend for reproduction on another individual, those pollinated by wind and dispersed by animals are likely to become invasive even if they do not have extensive native distributions. However, of these traits only the regional frequency in the native range remained significant when phylogenetic relationships were taken into account. This indicates that the effect of the regional frequency is generic, valid across all woody species, and fine-tuned by advantageous biological traits inherited from common ancestors, shared by groups of phylogenetically-related species. Traits that only appeared significant in the phylogenetically non-informed analyses should be considered as specific for shrubs and trees of central Europe. Mode of reproduction was only significant in the phylogenetically-informed analysis, indicating that reproduction exclusively by seed favours invasiveness of woody species. From the management perspective, however, the predictive value of some traits is not diminished by them being phylogenetically constrained since we are not interested whether the behaviour of particular species is a result of evolutionary history but how we can treat specific cases of invasion.     

飞机草入侵种群与原产地种群生长性状的差异

飞机草(Chromolaena odorata)是我国热带地区危害严重的外来入侵植物,为揭示适应进化对其成功入侵的贡献,在同质种植园中,比较研究了飞机草10个入侵地种群与12个原产地种群生长性状的差异,为排除奠基者效应的可能影响,进一步比较了飞机草10个入侵地种群与其原产地可能的祖先种群间的差异。结果表明,飞机草10个入侵地种群的基茎、株高、分枝数、生物量和比叶面积均显著高于12个原产地种群;与可能的祖先种群相比,飞机草10个入侵种群的生物量、分枝数和比叶面积仍更高。这些结果表明,在长期的入侵过程中飞机草通过进化提高了资源向生长的分配,支持增强竞争能力的进化假说。     

Increased reproductive capacity and physical defense but decreased tannin content in an invasive plant

Abstract Plant invasions create novel plant–insect interactions. The EICA (evolution of increased competitive ability) hypothesis proposes that invasive plants will reallocate resources from defense to growth and/or reproduction because they have escaped from their co‐evolved insect natural enemies. Testing multiple herbivory by monophagous and oligophagous herbivores and simultaneous measurement of various plant traits will provide new insights into the evolutionary change of invasive plants. In this context, we conducted a common garden experiment to compare plant growth and reproduction, chemical and physical defense, and plant responses to herbivory by different types of herbivores between invasive North American populations and native East Asian populations of mile‐a‐minute weed, Persicaria perfoliata. We found that invasive mile‐a‐minute exhibited lower biomass, flowered earlier and had greater reproductive output than plants from the native range. Compared with native populations, plants from invasive populations had lower tannin content, but exhibited higher prickle density on nodes and leaves. Thus our results partially support the EICA hypothesis. When exposed to the monophagous insect, Rhinoncomimus latipes and the oligophagous insects, Gallerucida grisescens and Smaragdina nigrifrons, more damage by herbivory was found on invasive plants than on natives. R. latipes, G. grisescens and S. nigrifrons had strong, moderate and weak impacts on the growth and reproduction of mile‐a‐minute, respectively. The results indicate that mile‐a‐minute may have evolved a higher reproductive capacity in the introduced range, and this along with a lack of oligophagous and monophagous herbivores in the new range may have contributed to its invasiveness in North America.     

Leaf trait relationships of native and invasive plants: community- and global-scale comparisons

Leaf carbon capture strategies of native and exotic invasive plants were compared by examining leaf traits and their scaling relationships at community and global scales. Community-level leaf trait data were obtained for 55 vascular plant species from nutrient-enriched and undisturbed bushland in Sydney, Australia. Global-scale leaf trait data were compiled from the literature for 75 native and 90 exotic invasive coexisting species. At the community level, specific leaf area (SLA), foliar nitrogen and phosphorus (N(mass) and P(mass)) and N:P ratio were significantly higher for exotics at disturbed sites compared with natives at undisturbed sites, with natives at disturbed sites being intermediate. SLA, N(mass) and P(mass) were positively correlated, with significant shifts in group means along a common standardized major axis (SMA) slope. At the global scale, invasives had significantly higher N(mass), P(mass), assimilation rate (A(mass) and A(area)) and leaf area ratio (LAR) than natives. All traits showed positive correlations, with significant shifts in group means along a common slope. For a given SLA, invasives had higher A(mass) (7.7%) and N(mass) (28%). Thus, exotic invasives do not have fundamentally different carbon capture strategies from natives but are positioned further along the leaf economics spectrum towards faster growth strategies. Species with leaf traits enabling rapid growth will be successful invaders when introduced to novel environments where resources are not limited.     

Phenotypic trait differences between Iris pseudacorus in native and introduced ranges support greater capacity of invasive populations to withstand sea level rise

Aim

Tidal wetlands are greatly impacted by climate change, and by the invasion of alien plant species that are being exposed to salinity changes and longer inundation periods resulting from sea level rise. To explore the capacity for the invasion of Iris pseudacorus to persist with sea level rise, we initiated an intercontinental study along estuarine gradients in the invaded North American range and the native European range.

Location

San Francisco Bay-Delta Estuary; California, USA and Guadalquivir River Estuary; Andalusia, Spain.

Methods

We compared 15 morphological, biochemical, and reproductive plant traits within populations in both ranges to determine if specific functional traits can predict invasion success and if environmental factors explain observed phenotypic differences.

Results

Alien I. pseudacorus plants in the introduced range had more robust growth than plants in the native range. The vigour of the alien plants was reflected by expression of higher leaf water content, fewer senescent leaves per leaf fan, and more carbohydrate storage reserves in rhizomes than plants in the native range. Moreover, alien plants tended to show higher specific leaf area and seed production than native plants. I. pseudacorus plants in the introduced range were less affected by increasing salinity and were exposed to deeper inundation water along the estuarine gradient than those in the native range.

Main Conclusions

Functional trait differences suggest mature populations of I. pseudacorus in the introduced range have greater adapted capacity to adjust to environmental stresses induced by rising sea level than those in the native range. Knowledge of these trait responses can be applied to improve risk assessments in invaded estuaries and to achieve climate-adapted conservation goals for conservation of the species in its native range.     

Functional trait similarity of native and invasive herb species in subtropical China—Environment-specific differences are the key

The attempt to identify traits associated with plant invasions has revealed ambiguous results to date. Accounting for environmental and temporal variation in multispecies trait comparisons of native and invasive species might help explain such inconsistency.The relative importance of light and nutrient availability was tested in a greenhouse experiment on trait expression and variation of 15 native and 15 invasive herb species from Southeast China. In addition, N uptake of a subset of these species and its temporal pattern were assessed by means of a ¹⁵N tracer experiment.A predominant lack of significant differences between the two status groups indicated strong overall trait similarities, thus supporting the ‘join-the-local’ hypothesis. However, at high light levels, the invasive species displayed significantly higher trait relative growth rates, whereas the native species had a higher tissue quality as displayed in a higher dry matter content of shoots and leaves. The invasion success of the invasive species could neither be explained by a general higher N uptake nor by a distinction in temporal N uptake strategy between native and invasive species.Despite comparable fundamental niches of the species, increased growth rates under beneficial light conditions may provide a head start advantage for invasive species compared to native ones. The present study confirms the assumption of an opportunistic strategy for invasive species and emphasizes the need to assess trait variation between native and invasive species in different environmental contexts.     

Cuscuta australis restrains three exotic invasive plants and benefits native species

In this study we conducted field investigations to examine the effects of native Cuscuta australis on three exotic invasive plants (i.e. Ipomoea cairica, Mikania micrantha, and Wedelia trilobata) and on the invaded native communities. The results showed that C. australis produced high infection rates on the exotic invasive hosts but low ones on the native species. Furthermore, the results showed that C. australis exhibited vigorous growth and high reproduction when it grew on M. micrantha and W. trilobata, indicating that these exotic invasive plants are more rewarding hosts than are native plants for C. australis. C. australis infection was positively related to the growth traits (e.g. biomass, cover, and total leaf area) and nutrient contents (e.g. N, P, and K) of the exotic invasive plants. The infections of C. australis significantly decreased the growth and nutrient contents of exotic invasive hosts, and the host?Cparasite interactions benefited the native species with increased species richness and biodiversity, facilitating the recovery of invaded native communities. This study provides a model for a native agent to both resist exotic invasive plants and benefit other native species. Furthermore, it indicates that certain native agents in invaded regions can be an effective and environmentally benign alternative to traditional biological control.