Evidence for evolution of increased competitive ability for invasive Centaurea solstitialis, but not for naturalized C. calcitrapa

Plant G × Microbial E: Plant Genotype Interaction with Soil Bacterial Community Shapes Rhizosphere Composition During Invasion

It is increasingly recognized that different genetic variants of hosts can uniquely shape their microbiomes. Invasive species often evolve in their introduced ranges, but little is known about the potential for their microbial associations to change during invasion as a result. We asked whether host genotype (G), microbial environment (E), or their interaction (G × E) affected the composition and diversity of host-associated microbiomes in Centaurea solstitialis (yellow starthistle), a Eurasian plant that is known to have evolved novel genotypes and phenotypes and to have altered microbial interactions, in its severe invasion of CA, USA. We conducted an experiment in which native and invading plant genotypes were inoculated with native and invaded range soil microbial communities. We used amplicon sequencing to characterize rhizosphere bacteria in both the experiment and the field soils from which they were derived. We found that native and invading plant genotypes accumulated different microbial associations at the family level in each soil community, often counter to differences in family abundance between soil communities. Root associations with potentially beneficial Streptomycetaceae were particularly interesting, as these were more abundant in the invaded range field soil and accumulated on invading genotypes. We also found that bacterial diversity is higher in invaded soils, but that invading genotypes accumulated a lower diversity of bacteria and unique microbial composition in experimental inoculations, relative to native genotypes. Thus variation in microbial associations of invaders was driven by the interaction of plant G and microbial E, and rhizosphere microbial communities appear to change in composition in response to host evolution during invasion.

A review of plants strategies to resist biotic and abiotic environmental stressors

Plants exposed to a variety of abiotic and biotic stressors including environmental pollution and global warming pose significant threats to biodiversity and ecosystem services. Despite substantial literature documenting how plants adapt to distinct stressors, there still is a lack of knowledge regarding responses to multiple stressors and how these affects growth and development. Exposure of plants to concurrent biotic and abiotic stressors such as cadmium and drought, leads to pronounced inhibition in above ground biomass, imbalance in oxidative homeostasis, nutrient assimilation and stunted root growth, elucidating the synergistic interactions of multiple stressors culminating in adverse physiological outcomes. Impact of elevated heavy metal and water deficit exposure extends beyond growth and development, influencing the biodiversity of the microenvironment including the rhizosphere nutrient profile and microbiome. These findings have significant implications for plant-stress interactions and ecosystem functioning that prompt immediate action in order to eliminate effect of pollution and address global environmental issues to promote sustainable tolerance for multiple stress combinations in plants. Here, we review plant tolerance against stress combinations, highlighting the need for interdisciplinary approaches and advanced technologies, such as omics and molecular tools, to achieve a comprehensive understanding of underlying stress tolerance mechanisms. To accelerate progress towards developing stress-tolerance in plants against multiple environmental stressors, future research in plant stress tolerance should adopt a collaborative approach, involving researchers from multiple disciplines with diverse expertise and resources.

Estimation of climate-induced increased risk of Centaurea solstitialis L. invasion in China: An integrated study based on biomod2

Introduction

Invasive alien plants (IAPs) are major hazards to biodiversity, human health, and the agricultural economy. As one of the most aggressive species of IAPs, the distribution area of Centaurea solstitialis L. has increased exponentially in the past two years since its invasion into Xinjiang, China, in July 2014. Predicting the potential geographic distributions (PGDs) of C. solstitialis in China can provide theoretical support for preventing the continued spread of this weed.

Methods

In this study, based on 5,969 valid occurrence records of C. solstitialis and 33 environmental variables, we constructed an ensemble model to predict suitable habitats for C. solstitialis under climate change scenarios.

Results

Our results showed that the mean true skill statistic (TSS) values, area under the receiver operating characteristic (ROC) curve (AUC), and Cohen’s Kappa (KAPPA) for the ensemble model were 0.954, 0.996, and 0.943, respectively. The ensemble model yielded more precise predictions than those of the single model. Temperature seasonality (Bio4), minimum temperature of the coldest month (Bio6), precipitation of the driest month (Bio14), and human influence index (HII) have significantly disrupted the PGDs of C. solstitialis in China. The total (high) suitability habitat area of C. solstitialis in China was 275.91 × 104 (67.78 × 104) km2, accounting for 71.26 (7.06)% of China. The PGDs of C. solstitialis in China under the current climate were mainly in East China (Shandong, Jiangsu, Shanghai, Zhejiang, and Anhui), Central China (Henan, southwestern Shanxi, southern Shaanxi, southern Gansu, Hubei, Hunan, Jiangxi, Chongqing, and Guizhou), and South China (southern Tibet, eastern Sichuan, Yunnan, Guangxi, Guangdong, Fujian, and Taiwan). Under future climate scenarios, the total suitability habitat area for C. solstitialis will expand, whereas the high suitability habitat area will decrease.

Discussion

The main manifestation is that the shift of southeast China into a moderate suitability habitat, and the total suitability habitats will be extended to northwest China. More focus needs to be placed on preventing further spread of C. solstitialis in northwest China.

Genetically Based Trait Differentiation but Lack of Trade-offs between Stress Tolerance and Performance in Introduced Canada Thistle

Trade-offs between performance and tolerance of abiotic and biotic stress have been proposed to explain both the success of invasive species and frequently observed size differences between native and introduced populations. Canada thistle seeds collected from across the introduced North American and the native European range were grown in benign and stressful conditions (nutrient stress, shading, simulated herbivory, drought, and mowing), to evaluate whether native and introduced individuals differ in performance or stress tolerance. An additional experiment assessed the strength of maternal effects by comparing plants derived from field-collected seeds with those derived from clones grown in the glasshouse. Introduced populations tended to be larger in size, but no trade-off of stress tolerance with performance was detected; introduced populations had either superior performance or equivalent trait values and survivorship in the treatment common gardens. We also detected evidence of parallel latitudinal clines of some traits in both the native and introduced ranges and associations with climate variables in some treatments, consistent with recent climate adaptation within the introduced range. Our results are consistent with rapid adaptation of introduced populations, but, contrary to predictions, the evolution of invasive traits did not come at the cost of reduced stress tolerance.

Soil origin corresponds with variation in growth of an invasive Centaurea, but not of non-invasive congeners

Why only a small proportion of exotic species become invasive is an unresolved question. Escape from the negative effects of soil biota in the native range can be important for the success of many invasives, but comparative effects of soil biota on less successful exotic species are poorly understood. Studies of other mechanisms suggest that such comparisons might be fruitful. Seeds of three closely related Centaurea species with overlapping distributions in both their native range of Spain and their nonnative range of California were grown to maturity in pots to obtain an F1 generation of full sibling seeds with reduced maternal effects. Full sibling F1 seeds from both ranges were subsequently grown in pots with inoculations of soil from either the native or nonnative ranges in a fully orthogonal factorial design. We then compared plant biomass among species, regions, and soil sources. Our results indicate that escape from soil pathogens may unleash the highly invasive Centaurea solstitialis, which was suppressed by native Spanish soils but not by soils from California. In contrast, the two non-invasive Centaurea species grew the same on all soils. These results add unprecedented phylogenetically controlled insight into why some species invade and others do not.

Allelopathy and its coevolutionary implications between native and non-native neighbors of invasive Cynara cardunculus L

Invasive plants apply new selection pressures on neighbor plant species by different means including allelopathy. Recent evidence shows allelopathy functions as remarkably influential mediator for invaders to be successful in their invaded range. However, few studies have determined whether native and non-native species co-occurring with invaders have evolved tolerance to allelopathy. In this study, we conducted germination and growth experiments to evaluate whether co-occurring native Juncus pallidus and non-native Lolium rigidum species may evolve tolerance to the allelochemicals induced by Cyanara cardunculus in Australian agricultural fields. The test species were germinated and grown in pots filled with collected invaded and uninvaded rhizosphere soil of C. cardunculus with and without activated carbon (AC). Additionally, a separate experiment was done to differentiate the direct effects of AC on the test species. The soil properties showed invaded rhizosphere soils had higher total phenolic and lower pH compared with uninvaded soils. We found significant reduction of germination percentage and seedling growth in terms of above- and belowground biomass, and maximum plant height and root length of native in the invaded rhizosphere soil of C. cardunculus, but little effect on non-native grass species. Even soil manipulated with AC showed no significant differences in the measured parameters of non-native except aboveground biomass. Taken together, the results indicate allelochemicals induced by C. cardunculus exert more suppressive effects on native than non-native linking the coevolved tolerance of those.