The fertility research of "Huajin 6", a new variety of honeysuckle.

The aim of this study was to investigate the fertility of "Huajin 6" and the effect of exogenous methyl jasmonate on its fertility. In this study, "Huajin 6", "Huajin 6" treated with methyl jasmonate and "Damaohua" were used as the research objects, the stamen phenotypes and the shape of pollen grains were observed, pollen viability and stigma receptivity were measured. The results showed that the pistil structure and function were normal, and although the stamen anthers did not dehisce, they were still capable of producing pollen with a certain amount of vigor. Methyl jasmonate could promote the opening of the flowers of "Huajin 6" and improve the development of pollen grains to a certain extent, but it could not promote anthers dehiscence of "Huajin 6". This study can provide theoretical guidance for the cultivation of new honeysuckle varieties using "Huajin 6".

Reproductive biology of an endangered lithophytic shrub and implications for its conservation.

BACKGROUND: Plants in cliff habitats may evolve specific reproductive strategies to cope with harsh environments, and unraveling these reproductive characteristics can improve our understanding of survival strategies and lithophyte evolution. This understanding is especially important for efforts to protect rare and endemic plants. Here, we investigated the reproductive biology of Lonicera oblata, an endangered lithophytic shrub that is scattered in highly fragmented and isolated cliff habitats of the Taihang and Yan mountains in North China. RESULTS: Flowers of L. oblata are herkogamous and protandrous, characteristics that can prevent autogamy at the single-flower level, and insects are necessary for pollination. The outcrossing index, pollen/ovule ratio, and the results of hand pollination were measured and all revealed a mixed mating system for L. oblata, that combines cross-fertilization and partial self-fertilization. The floral traits of L. oblata of zygomorphic and brightly yellowish corolla, heavy fragrance, and rich nectar, suggest an entomophilous pollination system. Sweat bees were observed as the most effective pollinators but their visiting frequencies were not high. Pollen limitation may limit the reproductive success of L. oblata. CONCLUSIONS: We determined the reproductive characteristics of L. oblata, a critically endangered species endemic to cliffs in North China, providing insight into its endangerment and suggesting conservation strategies. L. oblata has highly pollinator-dependent self-fertilization as part of a mixed mating system. Floral features such as low-flowering synchrony, asynchronous anthers dehiscence, and high duration of stigma receptivity, improve pollination efficiency in the case of low pollinator service. Our work provides reference information to understand the survival strategies and conservation of L. oblata and other lithophytes.

Comparative transcriptomics analysis revealing flower trichome development during flower development in two Lonicera japonica Thunb. cultivars using RNA-seq.

BACKGROUND: Lonicera japonica Thunb. (L. japonica) has the functions of clearing away heat and detoxifying, broad-spectrum antibacterial and anti-virus, etc. More than 70% of anti-inflammatory and cold Chinese patent medicines contain L. japonica. Trichomes comprise specialized multicellular structures that have the capacity to synthesize and secrete secondary metabolites and protect plants from biotic and abiotic stresses. The extraction of trichome secretions has great commercial value. However, little is known about the trichome formation mechanism in L. japonica. Therefore, the study of trichome development between different varieties provides a basis for selecting suitable planting resources. RESULTS: Here, we present a genome-wide comparative transcriptome analysis between two L. japonica cultivars, toward the identification of biological processes and functional gene activities that occur during flowering stage trichome development. In this study, the density and average lengths of flower trichomes were at their highest during three-green periods (S2). Using the Illumina RNA-Seq method, we obtained 134,304 unigenes, 33,733 of which were differentially expressed. In an analysis of 40 differentially expressed unigenes (DEGs) involved in trichome development, 29 of these were transcription factors. The DEGs analysis of plant hormone signal transduction indicated that plant growth and development may be independent of gibberellin (GA) and cytokinine (CTK) signaling pathways, and plant stress may be independent of jasmonic acid (JA) and ethylene (ET) signaling pathways. We screened several genes involved in the floral biosynthesis of odors, tastes, colors, and plant hormones, and proposed biosynthetic pathways for sesquiterpenoid, triterpenoid, monoterpenoid, flavonoid, and plant hormones. Furthermore, 82 DEGs were assigned to cell cycles and 2616 were predicted as plant resistance genes (PRGs). CONCLUSIONS: This study provides a comprehensive characterization of the expression profiles of flower development during the seven developmental stages of L. japonica, thereby offering valuable insights into the molecular networks that underly flower development in L. japonica.

[Effects of different temperature stress on cell membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonicea].

The study is aimed to explore the effects of stress at different temperatures( 35,45,55 ℃) on membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonica,and provide theoretical basis for reducing deterioration and revealing browning mechanism during postharvest processing of L. japonica. The cell membrane permeability( relative conductivity,MDA content),active oxygen metabolism( SOD,POD,PPO,CAT activity) and the accumulation of effective substances( chlorogenic acid,luteolin,neochlorogenic acid,cryptochlorogenic acid,3,5-dicaffeoylquinic acid,3,4-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid) of L. japonica were all studied by constant temperature drying method,and the results were analyzed by the SPSS 17. 0 statistical software. The results showed that MDA content in L. japonica was increased by 151. 14% at 35 ℃,SOD,POD,PPO and CAT activity were 29. 73%,42. 86%,105. 02% and 10. 74% higher than at 45 ℃,respectively. The order of effective substance content in L. japonica was 35 ℃ >45 ℃ >55 ℃. The changes of membrane permeability,activity of active oxygen metabolizing enzyme and accumulation of active components were significantly affected by different temperature stress. The indexes showed that physiological and active oxygen metabolizing enzyme activity of L. japonica was the highest under 35 ℃ stress,chlorogenic acid and luteolin were effectively accumulated,which provides basic data for solving browning problem in the postharvest processing of L. japonica.

[Effect of calcium on ion contents and expression of photosynthetic related genes in honeysuckle under salt stress].

Exogenous calcium can enhance the resistance of certain plants to abiotic stress. Research have demonstrated that exogenous calcium could enhances the resistance of honeysuckle under salt stress by promoting the transmission of photosynthetic electrons.The aim of this study was to investigate the effects of exogenous calcium on the contents of Na~+,K~+,Ca~(2+),Mg~(2+)and the expression of photosynthetic related genes Cab and rbc L. In this study,we used ICP-OES to analysis ion contents and used qRT-PCR to analysis the expression patterns of Cab and rbc L. The results showed that CaCl_2 significantly enhanced the K~+-Na~+,Ca~(2+)-Na~+,Mg~(2+)-Na+ratio of honeysuckle treated with 50 and 100 mmol·L~(-1) NaCl. Meanwhile,Cab and rbc L were significantly up-regulated under short-term salt stress,and CaCl_2 promoted this trend. From the two gene expression patterns,rbc L rapidly up-regulated on the first day of stress and then decreased,and was more sensitive to environmental changes. In summary,exogenous calcium could alleviate salt stress and increase plant development by increasing intracellular K~+-Na~+,Ca~(2+)-Na~+,Mg~(2+)-Na+ratio,and the transient overexpression of Cab and rbc L.

[Regulation of exogenous calcium on photosynthetic system of honeysuckle under salt stress].

Exogenous calcium can enhance the resistance of certain plants to abiotic stress. However,the role of calcium insaltstressed honeysuckle is unclear. The study is aimed to investigate the effects of exogenous calcium on the biomass,chlorophyll content,gas exchange parameters and chlorophyll fluorescence of honeysuckle under salt stress. The results showed that the calcium-treated honeysuckle had better photochemical properties than the salt-stressed honeysuckle,such as PIABS,PItotal,which represents the overall activity of photosystemⅡ(PSⅡ),and related parameters for characterizing electron transport efficiency φP0,ψE0,φE0,σR,and φR are significantly improved. At the same time,the gas exchange parameters Gs,Ci,Trare also maintained at a high level. In summary,exogenous calcium protects the activity of PSⅡ,promotes the transmission of photosynthetic electrons,and maintains a high Ci,therefore enhances the resistance of honeysuckle under salt stress.

Effects of different temperature stress on cell membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonicea / 中国中药杂志

The study is aimed to explore the effects of stress at different temperatures( 35,45,55 ℃) on membrane permeability,active oxygen metabolism and accumulation of effective substances in Lonicera japonica,and provide theoretical basis for reducing deterioration and revealing browning mechanism during postharvest processing of L. japonica. The cell membrane permeability( relative conductivity,MDA content),active oxygen metabolism( SOD,POD,PPO,CAT activity) and the accumulation of effective substances( chlorogenic acid,luteolin,neochlorogenic acid,cryptochlorogenic acid,3,5-dicaffeoylquinic acid,3,4-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid) of L. japonica were all studied by constant temperature drying method,and the results were analyzed by the SPSS 17. 0 statistical software. The results showed that MDA content in L. japonica was increased by 151. 14% at 35 ℃,SOD,POD,PPO and CAT activity were 29. 73%,42. 86%,105. 02% and 10. 74% higher than at 45 ℃,respectively. The order of effective substance content in L. japonica was 35 ℃ >45 ℃ >55 ℃. The changes of membrane permeability,activity of active oxygen metabolizing enzyme and accumulation of active components were significantly affected by different temperature stress. The indexes showed that physiological and active oxygen metabolizing enzyme activity of L. japonica was the highest under 35 ℃ stress,chlorogenic acid and luteolin were effectively accumulated,which provides basic data for solving browning problem in the postharvest processing of L. japonica.

Drought Alleviated the Negative Effects of Elevated O3 on Lonicera maackii in Urban Area.

Open top chambers were used to study the changes in photosynthesis, physiology and stomata characteristics in 1-year-old Lonicera maackii seedlings exposed to drought (DT, 30%-35% soil saturated water content) or/and elevated ozone (EO, 80 ppb). The results showed that DT or/and EO significantly decreased net photosynthetic rate (Pn), stomatal conductance (gs), maximum photochemical efficiency (Fv/Fm), but increased the activity of superoxide dismutase (SOD), and malondialdehyde content (p < 0.05). Compared with EO alone, the combination of EO and DT caused higher values in Pn, Fv/Fm, SOD activity (p < 0.05), and smaller stomata size and lower visible injury rate. DT alleviated the adverse impact of EO on the shrub by increasing enzyme activity and decreasing stomatal size, particularly stomatal width. The study provided increasing evidence that moderate drought might exert a beneficial effect on the tested plants to adapt to the future climate change, particularly in high ozone regions.

Effectiveness of Winkler Litter Extraction and Pitfall Traps in Sampling Ant Communities and Functional Groups in a Temperate Forest.

Selection of proper sampling methods for measuring a community of interest is essential whether the study goals are to conduct a species inventory, environmental monitoring, or a manipulative experiment. Insect diversity studies often employ multiple collection methods at the expense of researcher time and funding. Ants (Formicidae) are widely used in environmental monitoring owing to their sensitivity to ecosystem changes. When sampling ant communities, two passive techniques are recommended in combination: pitfall traps and Winkler litter extraction. These recommendations are often based on studies from highly diverse tropical regions or when a species inventory is the goal. Studies in temperate regions often focus on measuring consistent community response along gradients of disturbance or among management regimes; therefore, multiple sampling methods may be unnecessary. We compared the effectiveness of pitfalls and Winkler litter extraction in an eastern temperate forest for measuring ant species richness, composition, and occurrence of ant functional groups in response to experimental manipulations of two key forest ecosystem drivers, white-tailed deer and an invasive shrub (Amur honeysuckle). We found no significant effect of sampling method on the outcome of the ecological experiment; however, we found differences between the two sampling methods in the resulting ant species richness and functional group occurrence. Litter samples approximated the overall combined species richness and composition, but pitfalls were better at sampling large-bodied (Camponotus) species. We conclude that employing both methods is essential only for species inventories or monitoring ants in the Cold-climate Specialists functional group.

Rainfall variability counteracts N addition by promoting invasive Lonicera maackii and extending phenology in prairie.

Although encroaching woody plants have reduced the global extent of grasslands, continuing increases in soil nitrogen availability could slow this trend by favoring resident herbaceous species. At the same time, projected increases in rainfall variability could promote woody encroachment by aligning spatiotemporal patterns of soil moisture availability with the needs of woody species. We evaluated the responses of two deciduous woody species to these simulated environmental changes by planting seedlings of Quercus palustris and Lonicera maackii into tallgrass prairie communities grown under a factorial combination of increased rainfall variability and nitrogen addition. Lonicera maackii growth was reduced 20% by nitrogen addition, and increased rainfall variability led to 33% larger seedlings, despite greater competition for light and soil resources. In contrast, Q. palustris growth showed little response to either treatment. Increased rainfall variability allowed both species to retain their leaves for an additional 6.5 d in autumn, potentially in response to wetter end-of-season shallow soils. Our findings suggest increases in rainfall variability will counteract the inhibitory effect of nitrogen deposition on growth of L. maackii, extend autumn phenology, and promote the encroachment of some woody species into grasslands.

Saline stress enhanced accumulation of leaf phenolics in honeysuckle (Lonicera japonica Thunb.) without induction of oxidative stress.

Honeysuckle (Lonicera japonica Thunb.) is a traditional medicinal plant in Chinese, and chlorogenic acid and luteolosid are its specific bioactive phenolic compounds. This study was to investigate leaf antioxidant responses in honeysuckle to saline stress with emphasis on phenolics through hydroponic experiments and field trials. NaCl stress did not stimulate antioxidant system including superoxide dismutase, ascorbate peroxidase, catalase and ascorbate, and had no significant effect on lipid peroxidation in the leaves. Consistently, no inhibition on photochemical capacity of photosystems suggested that reactive oxygen species (ROS) was maintained at a normal level under NaCl stress. However, leaf phenolic synthesis was activated by NaCl stress, indicated by elevated genes transcription and activity of phenylalanine ammonia-lyase and increased phenolics concentration. Specifically, leaf chlorogenic acid concentration was increased by 67.43% and 48.86% after 15 days of 150 and 300 mM NaCl stress, and the increase of luteolosid concentration was 54.26% and 39.74%. The accumulated phenolics hardly helped detoxify ROS in vivo in absence of oxidative stress, but the elevated phenolic synthesis might restrict ROS generation by consuming reduction equivalents. As with NaCl stress, soil salinity also increased concentrations of leaf phenolics including chlorogenic acid and luteolosid without exacerbated lipid peroxidation. In conclusion, leaf phenolics accumulation is a mechanism for the acclimation to saline stress probably by preventing oxidative stress in honeysuckle; leaf medicinal quality of honeysuckle can be improved by saline stress due to the accumulation of bioactive phenolic compounds.

Co-occurring nonnative woody shrubs have additive and non-additive soil legacies.

To maximize limited conservation funds and prioritize management projects that are likely to succeed, accurate assessment of invasive nonnative species impacts is essential. A common challenge to prioritization is a limited knowledge of the difference between the impacts of a single nonnative species compared to the impacts of nonnative species when they co-occur, and in particular predicting when impacts of co-occurring nonnative species will be non-additive. Understanding non-additivity is important for management decisions because the management of only one co-occurring invader will not necessarily lead to a predictable reduction in the impact or growth of the other nonnative plant. Nonnative plants are frequently associated with changes in soil biotic and abiotic characteristics, which lead to plant-soil interactions that influence the performance of other species grown in those soils. Whether co-occurring nonnative plants alter soil properties additively or non-additively relative to their effects on soils when they grow in monoculture is rarely addressed. We use a greenhouse plant-soil feedback experiment to test for non-additive soil impacts of two common invasive nonnative woody shrubs, Lonicera maackii and Ligustrum sinense, in deciduous forests of the southeastern United States. We measured the performance of each nonnative shrub, a native herbaceous community, and a nonnative woody vine in soils conditioned by each shrub singly or together in polyculture. Soils conditioned by both nonnative shrubs had non-additive impacts on native and nonnative performance. Root mass of the native herbaceous community was 1.5 times lower and the root mass of the nonnative L. sinense was 1.8 times higher in soils conditioned by both L. maackii and L. sinense than expected based upon growth in soils conditioned by either shrub singly. This result indicates that when these two nonnative shrubs co-occur, their influence on soils disproportionally favors persistence of the nonnative L. sinense relative to this native herbaceous community, and could provide an explanation of why native species abundance is frequently depressed in these communities. Additionally, the difference between native and nonnative performance demonstrates that invasive impact studies focusing on the impact only of single species can be insufficient for determining the impact of co-occurring invasive plant species.

Flower-visitor selection on floral integration in three contrasting populations of Lonicera implexa.

PREMISE OF THE STUDY: Geographic differences in flower visitor assemblages might lead to among-population differences in the magnitude and pattern of floral integration. However, the role of current pollinator visitation in shaping the magnitude and pattern of floral trait correlations is still controversial. METHODS: We used individual-level data on floral morphology, flower visitation, and fitness to assess if floral integration (at flower and floral-module level) and the covariance structure of floral traits varied among three populations of Lonicera implexa differing in the importance of long-tongue (hawk moths) and short-tongue (bees and small beetles) pollinators; and to assess whether this variation was related to the selection pressures exerted by flower visitors. KEY RESULTS: Short-tongue pollinators preferentially visited plants with floral traits that enhanced flower accessibility; consequently, there was directional selection for accessibility (integration at floral-module level) in the populations where they dominated or codominated. In the population with both short- and long-tongue pollinators, disruptive selection on corolla width and directional selection against whole-flower integration was also found. Dominance by long-tongue pollinators (hawk moths) resulted in disruptive selection on whole-flower integration. Overall, the conflicting selection pressures that were found matched among-population differences in covariance structure: populations with short-tongue pollinators showed correlations between corolla-tube width and other floral traits that were absent in the population pollinated primarily by hawk moths. CONCLUSIONS: Conflicting selection on floral integration mediated by floral visitors can occur even in nearby populations of a species with restricted floral morphology.

Effects of nectar robbing on male and female reproductive success of a pollinator-dependent plant.

BACKGROUND AND AIMS: Nectar robbers affect host fitness in different ways and by different magnitudes, both directly and indirectly, and potentially constitute an important part of pollination interactions. The aim of this study was to assess the effect of nectar robbing on several variables that characterize the reproductive success of Lonicera etrusca, a pollinator-dependent plant with long, tubular flowers that produce abundant nectar. METHODS: Using fluorescent powder dye as a proxy for pollen, the distance of pollen dispersal was compared for robbed and non-robbed flowers. Artificial nectar robbing treatments were applied to test its effects on four additional measures of reproductive success, namely the quantity of pollen exported, fruit set, seed/ovule ratio and seed weight. KEY RESULTS: Nectar robbing was not found to have any significant negative consequences on female and male components of reproductive success as determined through the five variables that were measured. CONCLUSIONS: Although L. etrusca exhibits high levels of nectar robbing and nectar robbers are common floral visitors, no evidence was found of detrimental changes in the components of reproductive success. A combination of morphological and ecological mechanisms is proposed to explain how plants may compensate for the energetic loss caused by the nectar robbers.

Evolution of marginal populations of an invasive vine increases the likelihood of future spread.

The prediction of invasion patterns may require an understanding of intraspecific differentiation in invasive species and its interaction with climate change. We compare Japanese honeysuckle (Lonicera japonica) plants from the core (100-150 yr old) and northern margin (< 65 yr old) of their North American invaded range to determine whether evolution during invasion increases the probability of future expansion. Plants from populations in the core and margin were compared in two sites beyond the northern range edge to assess their potential to invade novel areas. Data were compared with previous work to assess the effect of latitudinal climate on L. japonica spread. Winter survival in current climates was modeled and projected for future climates to predict future spread. Margin plants were larger and had 60% greater survival than core plants at sites beyond the northern range edge. Overall, winter survival decreased with increasing latitude and decreasing temperature, and was greater in margin plants than core plants. Models suggested that greater winter tolerance in margin populations has increased L. japonica's northward spread by 76 km, and that this survival advantage will persist under future climates. These results demonstrate that evolution during invasion may increase spread beyond predictions using increasing global temperatures alone.

Comparative Herbivory Rates and Secondary Metabolite Profiles in the Leaves of Native and Non-Native Lonicera Species.

Non-native plants introduced to new habitats can have significant ecological impact. In many cases, even though they interact with the same community of potential herbivores as their new native competitors, they regularly receive less damage. Plants produce secondary metabolites in their leaves that serve a range of defensive functions, including resistance to herbivores and pathogens. Abiotic factors such as nutrient availability can influence the expression of defensive traits, with some species exhibiting increased chemical defense in low-nutrient conditions. Plants in the genus Lonicera are known to produce a diverse array of these secondary metabolites, yet non-native Lonicera species sustain lower amounts of herbivore damage than co-occurring native Lonicera species in North America. In this study, we searched for evidence of biochemical novelty in non-native species, and quantified its association with resistance to herbivores. In order to achieve this, we evaluated the phenolic and iridoid glycoside profiles in leaves of native and non-native Lonicera species grown under high and low fertilization treatments in a common garden. We then related these profiles to naturally occurring herbivore damage on whole plants in the garden. Herbivore damage was greater on native Lonicera, and chemical profiles and concentrations of selected putative defense compounds varied by species. Geographic origin was an inconsistent predictor of chemical variation in detected phenolics and iridoid glycosides (IGs). Overall, fertilization did not affect herbivore damage or measures of phenolics or IGs, but there were some fertilization effects within species. While we cannot conclude that non-natives were more chemically novel than native Lonicera species, chemical defense profiles and concentrations of specific compounds varied by species. Reduced attraction or deterrence of oviposition, specific direct resistance traits, or a combination of both may contribute to reduced herbivory and competitive advantages for non-native Lonicera in North America.

Plant-soil interactions promote co-occurrence of three nonnative woody shrubs.

Ecosystems containing multiple nonnative plant species are common, but mechanisms promoting their co-occurrence are understudied. Plant-soil interactions contribute to the dominance of singleton species in nonnative ranges because many nonnatives experience stronger positive feedbacks relative to co-occurring natives. Plant-soil interactions could impede other nonnatives if an individual nonnative benefits from its soil community to a greater extent than its neighboring nonnatives, as is seen with natives. However, plant-soil interactions could promote nonnative co-occurrence if a nonnative accumulates beneficial soil mutualists that also assist other nonnatives. Here, we use greenhouse and field experiments to ask whether plant-soil interactions (1) promote the codominance of two common nonnative shrubs (Ligustrum sinense and Lonicera maackii) and (2) facilitate the invasion of a less-common nonnative shrub (Rhamnus davurica) in deciduous forests of the southeastern United States. In the greenhouse, we found that two of the nonnatives, L. maackii and R. davurica, performed better in soils conditioned by nonnative shrubs compared to uninvaded forest soils, which. suggests that positive feedbacks among co-occurring nonnative shrubs can promote continued invasion of a site. In both greenhouse and field experiments, we found consistent signals that the codominance of the nonnatives L. sinense and L. maackii may be at least partially explained by the increased growth of L. sinense in L. maackii soils. Overall, significant effects of plant-soil interactions on shrub performance indicate that plant-soil interactions can potentially structure the co-occurrence patterns of these nonnatives.

The role of silicon in physiology of the medicinal plant (Lonicera japonica L.) under salt stress.

Silicon(Si) is the only element which can enhance the resistance to multiple stresses. However, the role of silicon in medicinal plants under salt stress is not yet understood. This experiment was conducted to study the effects of silicon addition on the growth, osmotic adjustments, photosynthetic characteristics, chloroplast ultrastructure and Chlorogenic acid (CGA) production of Honeysuckle plant (Lonicera japonica L.) under salt-stressed conditions. Salinity exerted an adverse effect on the plant fresh weight and dry weight, whilst 0.5 g L(-1) K2SiO3 · nH2O addition obviously improved the plant growth. Although Na(+) concentration in plant organs was drastically increased with increasing salinity, higher levels of K(+)/Na(+) ratio was obtained after K2SiO3 · nH2O addition. Salinity stress induced the destruction of the chloroplast envelope; however, K2SiO3 · nH2O addition counteracted the adverse effect by salinity on the structure of the photosynthetic apparatus. K2SiO3 · nH2O addition also enhanced the activities of superoxide dismutase and catalase. To sum up, exogenous Si plays a key role in enhancing its resistance to salt stresses in physiological base, thereby improving the growth and CGA production of Honeysuckle plant.

'Bigger data' on scale-dependent effects of invasive species on biodiversity cannot overcome confounded analyses: a comment on Stohlgren & Rejmánek (2014).

A recent study by Stohlgren & Rejmánek (SR: Stohlgren TJ, Rejmánek M. 2014 Biol. Lett. 10. (doi:10.1098/rsbl.2013.0939)) purported to test the generality of a recent finding of scale-dependent effects of invasive plants on native diversity; dominant invasive plants decreased the intercept and increased the slope of the species-area relationship. SR (2014) find little correlation between invasive species cover and the slopes and intercepts of SARs across a diversity of sites. We show that the analyses of SR (2014) are inappropriate because of confounding causality.