Microsatellite markers for an invasive tetraploid tree,Chinese tallow (Triadica sebifera)

We present six polymorphic microsatellite loci for Chinese tallow tree (Triadica sebifera, Euphorbiaceae), which is native to East Asia and is an aggressive, invasive species in the southeastern USA, particularly along the Coastal Plain. Microsatellite loci were tested for polymorphism across a total of 79 individuals from populations across the native range of China and in introduced populations of the southeastern USA, California, Hawaii, and Australia. Across these samples, we found a high level of polymorphism, suggesting they will be useful for deducting the introduction history of this invasive species.     

入侵植物乌桕防御策略的适应性进化研究

生长于不同昆虫群落胁迫下的植物地理种群可能进化出不同的防御策略。入侵植物在原产地同时受到专食性昆虫和广食性昆虫的取食危害, 而在入侵地“逃逸”了专食性昆虫的取食危害。入侵植物对不同类型昆虫防御策略的演化可能在其成功入侵的过程中起着至关重要的作用。该文主要以原产中国入侵北美的木本植物乌桕(Triadica sebifera)为例, 并结合其他入侵植物防御策略演化的研究, 从抗性和耐受性、直接抗性和间接抗性、组成抗性和诱导抗性三个方面系统分析不同昆虫选择压力下入侵植物防御策略的演化, 同时探讨入侵植物防御策略演化对生物防治效果的影响, 指出未来的重点研究方向。     

Potential distribution of the invasive tree Triadica sebifera (Euphorbiaceae) in the United States: evaluating climex predictions with field trials

Models that project introduced species distributions based on the climates in native and potential introduced ranges can provide valuable insights on the extent of a species' future spread. Yet, the lack of direct field evaluation of these range projections remains a major limitation. We evaluated results from the climex model in conjunction with results from seed and plant field trials in assessing environmental constraints to spread of the invasive tree Triadica sebifera (Chinese tallow tree) in the southeastern USA. climex incorporates key climatic parameters to generate large‐scale projections of potential distributions based on the climate across the species' current distribution. By employing field trials within microhabitats within and beyond the tree's current range, we were able to determine seed and young plants' response to the heterogeneity of the environment at regional scales. Based on projections of the climex model, T. sebifera has the potential to spread 500 km northward beyond its current distribution in the southeastern USA; minimum temperature and limited precipitation are the key climatic constraints in the eastern and western USA, respectively. climex results correlate strongly with seed germination across sites in the southeastern USA. These results do not however correlate with plant growth rates, which were often higher in sites with low projected climatic suitability. Competition and herbivory were not constraints on the growth of T. sebifera in our field trials and were therefore not responsible for the lack of correlation between model results and plant growth rates. If the minimum and maximum temperatures were to rise by 2 °C, the range of T. sebifera could extend northward 700 km beyond its current distribution. While both climex and the field trials indicate that T. sebifera is capable of extensive northward spread in the eastern USA, results of field trials indicate that the patterns of invasion within the region are likely to vary substantially with local site conditions.     

Effects of enhanced UV-B radiation and nitrogen deposition on the growth of invasive plant Triadica sebifera

Aims Exotic plant invasions are important components of global change, threatening both the stability and function of invaded ecosystems. Shifts in competitive ability of invasive plants versus their native congeners have been documented. Enhanced UV-B radiation and nitrogen (N) deposition might interact with soil biota communities impacting the invasion process of exotic plant species. To understand the potential effects by UV-B and N with soil biota on plant growth would enhance our understanding of the mechanisms in plant invasions in the context of global change.
Methods We conducted a full-factorial pot experiment in the native range (China) of Triadica sebifera invading US to investigate how UV-B radiation, N and soil biota together determined their seedling growth.
Important findings The results showed that UV-B radiation, N and soil sterilization together impacted the growth of T. sebifera seedlings. UV-B radiation induced changes in biomass allocation with larger leaf biomass observed in response to UV-B radiation. In addition, N increased aboveground biomass and decreased root biomass simultaneously. Soil biota imposed positive effects on growth of T. sebifera, and the addition of N amplified these positive effects. The negative effects by UV-B radiation on growth of T. sebifera showed no response to N addition. Plant height, leaf biomass and total biomass of the invasive T. sebifera populations out- performed those of the native ones. In addition, invasive T. sebifera populations weakened the dependence of root/shoot ratio and root biomass on local soil microorganisms than native populations, but enhanced that of leaf area ratio.     

土壤微生物对不同种源乌桕生长的影响

【背景】土壤微生物对植物成功入侵具有重要影响,研究中国本地土壤微生物对美国入侵种乌桕的净生长效应有利于进一步理解乌桕成功入侵的机理。【方法】以本地和入侵2个种源多个种群的乌桕为试验材料,通过对土壤进行灭菌处理,研究土壤微生物对不同种源乌桕幼苗生长的影响。【结果】土壤微生物对入侵种乌桕具有正效应,与本地种相比,入侵种乌桕幼苗总生物量、相对生长速度、根冠比以及总叶面积、叶面积比、比叶面积等生物学指标在新鲜土壤中均表现出明显优势。种源和土壤处理间存在交互效应的指标显示土壤微生物去除对入侵种乌桕的抑制作用更为明显。这一结果与土壤自然天敌逃逸假说相背,入侵种乌桕在一定程度上具有较本地种更强的土壤微生物利用能力,在非根际土壤微生物的作用下入侵种乌桕具有较强的生长能力和明显的竞争优势。【结论与意义】本研究证实土壤微生物可能对乌桕成功入侵具有不可忽略的作用。由于该试验在乌桕起源地进行,结合在乌桕入侵地进行的研究有助于进一步分析土壤微生物对入侵的贡献作用;研究土壤微生物与入侵植物的互作关系有助于对入侵物种进行准确预测和有效控制,减少生物入侵对生态系统功能的破坏。     

Latitudinal and altitudinal patterns of soil nematode communities under tallow tree (Triadica sebifera) in China

Plant Ecology - Because nematodes are an important component of soil ecosystems, patterns of soil nematode community structure along geographic gradients have received considerable attention....     

Synergistic effects of the invasive Chinese tallow (Triadica sebifera) and climate change on aquatic amphibian survival

Changes in climate and the introduction of invasive species are two major stressors to amphibians, although little is known about the interaction between these two factors with regard to impacts on amphibians. We focused our study on an invasive tree species, the Chinese tallow (Triadica sebifera), that annually sheds its leaves and produces leaf litter that is known to negatively impact aquatic amphibian survival. The purpose of our research was to determine whether the timing of leaf fall from Chinese tallow and the timing of amphibian breeding (determined by weather) influence survival of amphibian larvae. We simulated a range of winter weather scenarios, ranging from cold to warm, by altering the relative timing of when leaf litter and amphibian larvae were introduced into aquatic mesocosms. Our results indicate that amphibian larvae survival was greatly affected by the length of time Chinese tallow leaf litter decomposes in water prior to the introduction of the larvae. Larvae in treatments simulating warm winters (early amphibian breeding) were introduced to the mesocosms early in the aquatic decomposition process of the leaf litter and had significantly lower survival compared with cold winters (late amphibian breeding), likely due to significantly lower dissolved oxygen levels. Shifts to earlier breeding phenology, linked to warming climate, have already been observed in many amphibian taxa, and with most climate models predicting a significant warming trend over the next century, the trend toward earlier breeding should continue if not increase. Our results strongly suggest that a warming climate can interact with the effects of invasive plant species, in ways we have not previously considered, to reduce the survival of an already declining group of organisms.     

Predicted range expansion of Chinese tallow tree (Triadica sebifera) in forestlands of the southern United States

Aim We present an integrated approach for predicting future range expansion of an invasive species (Chinese tallow tree) that incorporates statistical forecasting and analytical techniques within a spatially explicit, agent‐based, simulation framework. Location East Texas and Louisiana, USA. Methods We drew upon extensive field data from the US Forest Service and the US Geological Survey to calculate spread rate from 2003 to 2008 and to parameterize logistic regression models estimating habitat quality for Chinese tallow within individual habitat cells. We applied the regression analyses to represent population spread rate as a function of habitat quality, integrated this function into a logistic model representing local spread, and coupled this model with a dispersal model based on a lognormal kernel within the simulation framework. We simulated invasions beginning in 2003 based on several different dispersal velocities and compared the resulting spatial patterns to those observed in 2008 using cross Mantel’s tests. We then used the best dispersal velocity to predict range expansion to the year 2023. Results Chinese tallow invasion is more likely in low and flat areas adjacent to water bodies and roads, and less likely in mature forest stands and in pine plantations where artificial regeneration by planting seedlings is used. Forecasted invasions resulted in a distribution that extended from the Gulf Coast of Texas and Louisiana northward and westward as much as 300 km, representing approximately 1.58 million ha. Main conclusions Our new approach of calculating time series projections of annual range expansion should assist land managers and restoration practitioners plan proactive management strategies and treatments. Also, as field sampling continues on the national array of FIA plots, these new data can be incorporated easily into the present model, as well as being used to develop and/or improve models of other invasive plant species.     

乌桕叶片及其乳汁中酚类物质比较分析

大戟科乌桕（Triadica sebifera）是我国南方重要的经济和绿化树种。分析了乌桕叶片乳汁中单宁和类黄酮的含量,并与叶片中单宁和类黄酮的含量进行对比。研究发现,在乳汁和叶片中共同检测到的2种单宁和2种类黄酮物质,它们在叶片中的浓度远远高于乳汁中的浓度。这表明乌桕中的单宁和类黄酮这类防御物质主要存在于叶片中。乌桕各种群间单宁与类黄酮含量都有显著差异,这可能是不同种群所处的生态环境以及面临植食昆虫的不同而导致的。     

Loss of specificity: native but not invasive populations of Triadica sebifera vary in tolerance to different herbivores

During introduction, invasive plants can be released from specialist herbivores, but may retain generalist herbivores and encounter novel enemies. For fast-growing invasive plants, tolerance of herbivory via compensatory regrowth may be an important defense against generalist herbivory, but it is unclear whether tolerance responses are specifically induced by different herbivores and whether specificity differs among native and invasive plant populations. We conducted a greenhouse experiment to examine the variation among native and invasive populations of Chinese tallow tree, Triadica sebifera, in their specificity of tolerance responses to herbivores by exposing plants to herbivory from either one of two generalist caterpillars occurring in the introduced range of Triadica. Simultaneously, we measured the specificity of another defensive trait, extrafloral nectar (EFN) production, to detect potential tradeoffs between resistance and tolerance of herbivores. Invasive populations had higher aboveground biomass tolerance than native populations, and responded non-specifically to either herbivore, while native populations had significantly different and specific aboveground biomass responses to the two herbivores. Both caterpillar species similarly induced EFN in native and invasive populations. Plant tolerance and EFN were positively correlated or had no relationship and biomass in control and herbivore-damaged plants was positively correlated, suggesting little costs of tolerance. Relationships among these vegetative traits depended on herbivore type, suggesting that some defense traits may have positive associations with growth-related processes that are differently induced by herbivores. Importantly, loss of specificity in invasive populations indicates subtle evolutionary changes in defenses in invasive plants that may relate to and enhance their invasive success.     

UV-B has larger negative impacts on invasive populations of Triadica sebifera but ozone impacts do not vary

Aims Abiotic stresses may interact with each other to determine impacts on plants so that their combined impact is less than or more than additive. Increasing UV-B radiation and surface ozone (O 3) are two major components of global change that may have such interactive impacts. Moreover, invasive and native populations of plants may respond differently to stresses as they can vary in primary and secondary metabolism.Methods Here, we conducted a factorial field experiment with open-top chambers assigned to an ozone treatment (ambient, 100 ppb, or 150 ppb) and UV-B treatment (ambient or increased 20%). We grew seedlings of native and invasive populations of Triadica sebifera in these chambers for one growing season.Important findings Invasive plants grew faster than native plants in ambient UV-B but they did not differ significantly in elevated UV-B. Litter production of invasive plants was especially sensitive to UV-B in a way that increased with UV-B for native plants but decreased for invasive plants which may be important for nutrient cycling. In ambient UV-B, total mass decreased as ozone increased. Total mass was lower with elevated UV-B but there was no additional impact of increasing ozone. Leaf area did not decrease with UV-B so SLA and LAR were lowest at ambient ozone levels. These results suggest that the effects of ozone will depend on UV-B conditions perhaps due to changes in foliar traits. The traits that allow invasive populations of plants to be successful invaders may make them especially sensitive to UV-B which may reduce their success in future climatic conditions.     

Differences in seed properties and germination between native and introduced populations of Triadica sebifera

很多入侵植物的种子比原产地植物的种子萌发的更快,这可能有利于它们成功入侵。为了理解生物入侵过程,对入侵植物的入侵种群 和原产地种群的种子特性和萌发特征同时进行评估极为必要。本研究中,我们以乌桕(Triadica sebifera)为研究对象探究种子萌发和种子 特征的种内差异。 我们利用采于2017年的乌桕种子,来自中国的12个原产地种群和美国的12个引入地种群,测定种子的物理性状(体积、重量、种皮硬度和种皮厚度)和化学特性[种仁的粗脂肪、可溶性蛋白质、糖、赤霉素(GA)和脱落酸(ABA)],并在中国的温室中测定种子的发芽率和萌发时间。此外,我们在美国用采自2016年和2017年的种子开展了研究地点(中国和美国)和种子采集年份(2016年和2017年)对种子萌发影响的比较实验。 来自引入地的种子要比来自原产地的种子萌发更快。种子的物理和化学特性测定结果表明：与原产地种子相比,引入地种子更大、种仁内含有的赤霉素浓度以及GA:ABA比更高,但粗脂肪含量较低。种子重量、种皮硬度、种皮厚度、种仁脱落酸、可溶性蛋白质和糖含量在引入地和原产地之间没有显著差异。在中国和美国温室间的种子萌发率具有相关性,但种群的萌发率具有年际变化。我们的研究结果表明,体积较大和赤霉素含量较高的种子可能有助于快速萌发,这可能也有利于乌桕在引入地的入侵。     

Positive and negative biotic interactions and invasive Triadica sebifera tolerance to salinity: a cross‐continent comparative study

Exotic plant species may exhibit abiotic niche expansions that enable them to persist in a greater variety of habitat types in their introduced ranges than in their native ranges. This may reflect variation in limitation by different abiotic niche dimensions (realized niche shift) or phenotypic effects of biotic interactions that vary among ranges (realized niche expansion). Novel abiotic and biotic environments in the introduced range may also lead to genetic changes in exotic plant traits that enhance their abiotic stress tolerance (fundamental niche expansion). Here, we investigated how biotic interactions (aboveground herbivory and soil organisms) affect plant salinity tolerance using the invasive species Triadica sebifera from China (native range) and US (introduced range) populations grown in common gardens in both ranges. Simulated herbivory significantly reduced survival in saline treatments with reductions especially large at low salinity. Soil sterilization had a negative effect on survival at low salinity in China but had a positive effect on survival at low salinity in the US. Triadica survival and biomass were higher for US populations than for China populations, particularly in China but salinity tolerance did not depend on population origin. On average, arbuscular mycorrhizal (AM) colonization was higher for US populations, US soils and low salinity. These factors had a significant, positive, non‐additive interaction so that clipped seedlings from US populations in low saline US soils had high levels of AM colonization. Overall, our results show that phenotypic biotic interactions shape Triadica's salinity tolerance. Positive and negative biotic interactions together affected plant performance at intermediate stress levels. However, only aboveground damage consistently affected salinity tolerance, suggesting an important role for enemy release in expanding stress tolerance.     

Soil sterilization and fertility impacts on urease and belowground mass specific phosphatase activity vary among Chinese tallow tree (Triadica sebifera) populations

Plant Ecology - Invasive plants from introduced populations may utilize soil nutrients more efficiently and increase their performance relative to those from native populations but this may vary...     

Quarantine host range of Bikasha collaris,a potential biological control agent of Chinese tallowtree (Triadica sebifera) in North America

Chinese tallowtree, Triadica sebifera (L.) Small (Euphorbiaceae), is one of the worst invasive weeds of the southeastern USA impacting coastal wetlands, forests, and natural areas. Traditional mechanical and chemical controls have been unable to limit the spread, and this invasive species continues to expand its range. A proposed biological control candidate, the flea beetle Bikasha collaris (Baly) (Coleoptera: Chrysomelidae), shows high specificity for the target weed Chinese tallowtree. Results from a series of no‐choice and choice feeding tests of B. collaris adults and larvae indicated that this flea beetle was highly specific to Chinese tallowtree. The larvae of B. collaris feed by tunneling in the roots, whereas the adults feed on the leaves of Chinese tallowtree. A total of 77 plant taxa, primarily from members of the tallow plant family Euphorbiaceae, were tested in numerous test designs. Larval no‐choice tests indicated that larvae completed development only on two of the non‐target taxa. Of 80 B. collaris larvae fed roots of Hippomane mancinella L. and 50 larvae fed roots of Ricinus communis L., two and three larvae completed development, respectively. The emerging adults of these five larvae died within 3 days without reproducing. Larval choice tests also indicated little use of these non‐target taxa. Adult no‐choice tests indicated little leaf damage by B. collaris on the non‐targets except for Ditrysinia fruticosa (Bartram) Govaerts & Frodin and Gymnanthes lucida Sw. When given a choice, however, B. collaris adults consumed much less of the non‐targets D. fruticosa (7.4%) and G. lucida (6.1%) compared with the control leaves. Finally, no‐choice oviposition tests indicated that no eggs were produced when adults were fed all non‐target taxa, except those fed G. lucida. These B. collaris adults fed G. lucida leaves produced an average of 4.6 eggs compared with 115.0 eggs per female when fed Chinese tallowtree. The eggs produced from adults fed G. lucida were either inviable or the emerging larvae died within 1 day. These results indicate that the flea beetle B. collaris was unable to complete its life cycle on any of the non‐target taxa tested. If approved for field release, B. collaris will be the first biological control agent deployed against Chinese tallowtree in the USA. This flea beetle may play an important role in suppressing Chinese tallowtree and contribute to the integrated control of this invasive weed.     

A new species of Gadirtha Walker (Nolidae,Eligminae): a proposed biological control agent of Chinese tallow (Triadica sebifera (L.) Small) (Euphorbiaceae) in the United States

Gadirtha fusca sp. n., is described from Guangxi Province, China. Gadirtha fusca differs in forewing color and pattern, male and female genitalia, and in larval pattern from all other species of Gadirtha. Gadirtha fusca has been evaluated as a potential biological control agent for Chinese tallow (Triadica sebifera (L.) Small, Euphorbiaceae) in the southeastern United States. Adult, male and female genitalia, larva, and pupa are described, illustrated, and compared with Gadirtha impingens Walker.     

Parental investment decision rules in tree swallows: parental defense, abandonment, and the so-called Concorde Fallacy

I conducted an experiment to detect the importance of past investmentand expected benefits to reproductive "decision making" by treeswallows (Tachycineta bicolor). Three experimental groups, balancedfor measurable indicators of parental quality, were created:one had its clutch reduced in size near the beginning of incubation,the second had its brood reduced near chickfledging, and thethird had no brood or clutch reduction. All experimental groupswere tested for differences in 19 measures of parental defensebehavior at the same stage in the nesting cycle by exposingthem on successive days to two different predators, a ferretand a rat snake, at the nest box. There were no detectable effectsof experimental treatment on parental defense; however, therewere differences in abandonment frequency related to the severityof experimental clutch reduction. These results suggest thattree swallows respond to differences in expected benefits in"deciding" whether or not to abandon a nesting attempt. Becausepast investment can affect the prospective costs of abandonmentand renesting, the most natural currency for comparing costsand benefits is prospective. Adopting such a currency for parental"decisions" lessens concern over the so-called Concorde Fallacy,but it highlights our relative ignorance of how past reproductiveeffort influences the costs of future reproduction. [Behav Ecol1991,2:133–142]     

Proteomics in the fruit tree science arena: New insights into fruit defense,development, and ripening

Fruit tree crops are agricultural commodities of high economic importance, while fruits also represent one of the most vital components of the human diet. Therefore, a great effort has been made to understand the molecular mechanisms covering fundamental biological processes in fruit tree physiology and fruit biology. Thanks to the development of cutting‐edge “omics” technologies such as proteomic analysis, scientists now have powerful tools to support traditional fruit tree research. Such proteomic analyses are establishing high‐density 2DE reference maps and peptide mass fingerprint databases that can lead fruit science into a new postgenomic research era. Here, an overview of the application of proteomics in key aspects of fruit tree physiology as well as in fruit biology, including defense responses to abiotic and biotic stress factors, is presented. Α panoramic view of ripening‐related proteins is also discussed, as an example of proteomic application in fruit science.