新疆野苹果的生存现状、问题及保护策略

新疆野苹果是天山野果林的优势种,遗传多样性极其丰富,是世界苹果基因库的重要组成部分。自20世纪60年代以来,新疆野苹果种群分布面积急剧下降。然而,导致新疆野苹果种群衰退的原因尚不明确,尚无行之有效的保护措施。该文在总结前人研究的基础上,结合实地考察,进一步分析和探讨野苹果的分布现状及面对虫害、干扰和种群更新困难等问题。发现新疆野苹果在保护和研究过程中仍然存在以下问题:第一,新疆野苹果的起源和演化,仍然存在分歧。第二,新疆野苹果种群的分布面积锐减,其中3个县的分布面积减少到60年前的三分之一。第三,虽然新疆野苹果的虫害问题得到了有效控制,但是虫害预防监测体系未能全面建设。第四,新疆野苹果过度干扰的问题仍然存在,即使农田开垦和人类砍伐得到一定控制。第五,新疆野苹果更新困难的问题仍然突出,现有研究仍处于初级阶段,缺乏深入研究。针对其存在的问题,建议采取以下措施:第一,利用分子生物学等技术进一步研究新疆野苹果的起源和演化。第二,建立新疆野苹果资源监测体系,运用先进的监测技术及时有效监测新疆野苹果的资源现状。第三,建立虫害预防监测系统,及时有效监测和防治病虫害的爆发。第四,建立新疆野苹果保护区,加强原位保护和法律宣传,强化当地居民对濒危植物的保护。第五,开展新疆野苹果更新机理方面的研究,同时加强迁地保护等措施。该文提出了一些解决现存问题的方法和建议,可为新疆野苹果的科学保护与有效管理提供参考。     

微生境对黄梅秤锤树野生种群叶片功能性状的影响

植物功能性状可以反映植物应对环境变化的适应策略。本文以黄梅秤锤树(Sinojackia huangmeiensis)当前唯一野生种群为对象, 比较了3种微生境(湖边、种群中心、耕地边)中该物种的叶片功能性状均值、种内变异和叶片生态化学计量特征的差异, 分析了黄梅秤锤树对湖岸带微生境变化的响应及其适应策略。结果表明: (1) 3种微生境中土壤C、N、P含量没有显著性差异(P > 0.05), 但土壤C∶N和C∶P具有显著性差异(P < 0.05), 土壤类型和养分条件有所不同。(2)黄梅秤锤树叶片功能性状的比较用单因素方差分析和贝叶斯方差分析得出的结果一致, 均为叶长、叶面积和比叶面积在中心区域显著高于湖边(P < 0.05), 而耕地边与湖边和中心区域均没有显著差异(P > 0.05); 叶N含量在湖边显著高于中心区域和耕地边(P < 0.05), 而中心区域和耕地边间没有显著差异(P > 0.05); 叶宽、叶长/叶宽、叶干物质含量、叶C和叶P含量在3种微生境间都没有显著性差异(P > 0.05)。(3)黄梅秤锤树叶片的N∶P在湖边显著高于中心区域和耕地边(P < 0.05), C∶N在湖边显著小于中心区域和耕地边(P < 0.05), N∶P和C∶N在中心区域和耕地边没有显著性差异(P > 0.05), C∶P在3种微生境间都没有显著性差异(P > 0.05)。(4)黄梅秤锤树叶片功能性状的总体变异程度在0.02-0.28之间, 其中叶片C和N含量在湖边和中心区域的种内变异程度显著较低, 表明3种生境中湖边和中心区域黄梅秤锤树种群的稳定性相对较差。(5)湖边黄梅秤锤树主要通过增加叶N含量促进生长; 中心区域黄梅秤锤树主要通过增加叶面积和比叶面积以及提高叶N的利用效率来提高光捕获能力促进生长; 耕地边黄梅秤锤树的叶N含量和叶面积、比叶面积都处于中等水平, 通过性状之间的共同作用使植株生长达到最佳水平。以上结果表明, 由于微地形、水位波动和土壤环境条件的差异, 黄梅秤锤树对3种生境中的适应策略有所不同, 并且不是通过单一性状调整来适应环境的变化, 而是通过多种性状之间的权衡达到更好的适应效果。     

Soil pH influences patterns of plant community composition after restoration with native‐based seed mixes

Reclamation of highly disturbed lands typically includes establishing fast‐growing, non‐native plants to achieve rapid ground cover for erosion control. Establishing native plant communities could achieve ecosystem functions beyond soil erosion, such as providing wildlife habitat. Pipelines, or other disturbed corridors through a landscape, present unique challenges for establishing native plant communities given the heterogeneity of soil environments and invasive plant propagule pressure. We created two structural equation models to address multiple related hypotheses about the influence of soil pH on plant community composition (current diversity and vegetative cover of the original restoration seed mix and background flora, and invasive plant density during mix establishment and current density) of a highly disturbed landscape corridor restored with native species. To test our hypotheses we conducted a plant survey on a gas pipeline crossing two state forests in the north‐central Appalachians that had been seeded with a native‐based mixture 8 years prior. Low soil pH was a strong predictor of density of the invasive annual plant, Microstegium vimineum, and had resulted in lower species diversity and cover of the seeded mix. Overall, our data provide evidence that native‐based grass and forb mixtures can establish and persist on a wide range of soil environments and thrive in competition with invasive plants in moderately acidic to neutral soils. Advancing knowledge on restoration methods using native species is essential to improving restoration practice norms to incorporate multifunctional ecological goals.     

Expression of floral MADS-box genes in basal angiosperms: implications for the evolution of floral regulators

The ABC model of floral organ identity is based on studies of Arabidopsis and Antirrhinum, both of which are highly derived eudicots. Most of the genes required for the ABC functions in Arabidopsis and Antirrhinum are members of the MADS-box gene family, and their orthologs are present in all major angiosperm lineages. Although the eudicots comprise 75% of all angiosperms, most of the diversity in arrangement and number of floral parts is actually found among basal angiosperm lineages, for which little is known about the genes that control floral development. To investigate the conservation and divergence of expression patterns of floral MADS-box genes in basal angiosperms relative to eudicot model systems, we isolated several floral MADS-box genes and examined their expression patterns in representative species, including Amborella (Amborellaceae), Nuphar (Nymphaeaceae) and Illicium (Austrobaileyales), the successive sister groups to all other extant angiosperms, plus Magnolia and Asimina, members of the large magnoliid clade. Our results from multiple methods (relative-quantitative RT-PCR, real-time PCR and RNA in situ hybridization) revealed that expression patterns of floral MADS-box genes in basal angiosperms are broader than those of their counterparts in eudicots and monocots. In particular, (i) AP1 homologs are generally expressed in all floral organs and leaves, (ii) AP3/PI homologs are generally expressed in all floral organs and (iii) AG homologs are expressed in stamens and carpels of most basal angiosperms, in agreement with the expectations of the ABC model; however, an AG homolog is also expressed in the tepals of Illicium. The broader range of strong expression of AP3/PI homologs is inferred to be the ancestral pattern for all angiosperms and is also consistent with the gradual morphological intergradations often observed between adjacent floral organs in basal angiosperms.     

Seed reproductive biology of the rare aquatic carnivorous plant Aldrovanda vesiculosa (Droseraceae)

Despite the unprecedented global decline in extant populations of Aldrovanda vesiculosa in the last century, little is known about the reproductive biology of this iconic aquatic carnivorous plant. This study aimed to investigate the role of seed‐based reproduction in the ecology of A. vesiculosa, with particular focus on the interplay between the regulation of seed dormancy by temperature cues and the efficacy of exogenous ethylene gas to act as a germination stimulant, the desiccation capacity and long‐term storage potential of seeds for conservation purposes. Sexual reproduction appears to be extremely limited in both natural and naturalized populations across three continents, with high variability in the success of flowering and seed set between sites and between seasons. Overall, flowering yielded few fertile fruit (6–19% of flowers producing fertile fruit) and seed viability was variable but generally low (29–88%). Fecundity appears to be influenced by seasonal climatic conditions and microhabitat characteristics. Aldrovanda vesiculosa possesses physiologically dormant seeds, with germination stimulated by exposure to ethylene gas (>90% germination) at 25 °C. Seeds appear sensitive to desiccation and sub‐zero temperature storage, with no germination and markedly reduced embryo growth after storage of seeds for >1 month at 15 °C and 15% relative humidity or after short‐term (24 h) storage at ?18 °C. In the absence of significant conservation and restoration initiatives, the continuing decline of dystrophic freshwater wetland habitats globally leaves A. vesiculosa facing extinction. As the successful long‐term storage of seeds appears unfeasible based on the approaches described in this study, other alternatives for germplasm conservation such as cryostorage of vegetative tissues or zygotic embryos must be considered for establishing long‐term ex situ collections of critical germplasm.     

内蒙古大针茅草原常见植物在不同土地利用方式下的固碳相关属性

为了探究植物与固碳相关属性在不同功能群、器官和物种间的差异, 以及这些属性对不同土地利用方式的响应, 2012年8月对内蒙古大针茅草原的4个样地(长期无干扰样地、长期自由放牧样地、4年围封样地和4年围封割草样地)进行了群落调查, 并采集样地中的常见植物, 测定了与植物固碳相关的属性, 包括全碳含量、全氮含量、碳氮比、纤维素含量、木质素含量和酸性洗涤纤维含量等。以常见植物为对象, 在功能群水平研究了各土地利用方式下全碳含量、全氮含量和碳氮比的差异; 针对各样地的共有种——糙隐子草(Cleistogenes squarrosa)、大针茅(Stipa grandis)、冷蒿(Artemisia frigida)、羊草(Leymus chinensis)和猪毛菜(Salsola collina), 从物种和器官水平分析了不同土地利用方式下植物的固碳相关属性。结果表明: 大针茅草原植物不同功能群、物种和器官间的固碳相关属性存在极显著差异, 不同土地利用方式下大针茅草原不同功能型、物种和器官的固碳相关属性有显著差异。与其他利用方式相比, 4年围封割草对植物与固碳相关属性的影响最为明显, 功能群、器官和物种水平的植物氮含量均有下降。糙隐子草和猪毛菜的这些属性对长期自由放牧的响应敏感, 且方向相反。     

Feeny revisited: condensed tannins as anti-herbivore defences in leaf-chewing herbivore communities of Quercus

Abstract. 1. Community level oak–tannin–insect patterns have been largely unexplored since Paul Feeny's ground‐breaking research. Two hypotheses were tested for Quercus velutina and Q. alba in the Missouri Ozarks: abundance and richness of leaf‐chewing herbivores are negatively correlated with foliar condensed tannin concentrations and variation in condensed tannin concentrations explains variation in herbivore community structure. 2. In 2001, foliar condensed tannins in the understorey and canopy of these two oak species were quantified simultaneously with censuses of herbivores in May, during leaf expansion, and in June and August, when leaves were fully expanded. Thirty‐eight of the 134 species encountered had densities sufficient to be analysed individually (n = 10). Of those, Acronicta increta (Noctuidae) and Attelabus sp. (Curculionidae), both oak specialists, were negatively correlated with condensed tannins in the canopy of Q. alba. One additional specialist, Chionodes pereyra (Gelechiidae), was marginally negatively correlated with condensed tannins in the understorey of Q. velutina. Understorey species richness of May Q. velutina herbivores was negatively correlated with condensed tannins, as were total canopy insect density and species richness of August herbivores on Q. alba. 3. Principal component analysis (PCA) of insect abundances indicated that understorey and canopy Q. velutina and Q. alba had different communities of leaf‐chewing insects. Furthermore, condensed tannin levels contributed significantly to variation in PCA scores for Q. velutina, explaining 25% of the total variation. 4. Overall, these results indicate that specialists were more likely than generalists both to correlate negatively with condensed tannins and to occur in lower tannin habitats; abundance and richness of both early and late season fauna correlated negatively with tannins; and species were more likely to correlate negatively with condensed tannins when feeding on Q. alba than on Q. velutina and when feeding in the canopy than in the understorey. Future studies of tannin–insect interactions should manipulate leaf quality in combination with manipulations of other factors that likely influence community structure.