Genetic evidence for hybridization between the native Spartina maritima and the introduced Spartina alterniflora (Poaceae) in South-West France: Spartina × neyrautii re-examined

 Spartina alterniflora, a perennial grass native to the North American Atlantic coast, was introduced during the 19th century in western Europe (Southern England and western France) where it hybridized with the native Spartina maritima. In England, the sterile hybrid S. × townsendii gave rise by chromosome doubling to the highly fertile allopolyploid Spartina anglica, which has now invaded many salt marshes and estuaries in western Europe, and has been introduced in several continents. In South-West France, another sterile hybrid was discovered in 1892 in the Bidassoa Estuary, and named Spartina × neyrautii. According to their morphology, some authors suggested that S. × neyrautii and S. × townsendii result from reciprocal crosses. During the 20th century, the hybridization site was severely disturbed, and surviving of S. × neyrautii was questioned. In this paper, various Spartina populations are investigated in the Basque region (France and Spain), and compared to the hybrid taxa formed in England (S. × townsendii and S. anglica). The samples were analyzed using molecular fingerprinting (RAPD and ISSR) and Chloroplast DNA sequence (trnL-trnT spacer, trnL intron and trnL-trnF spacer). In the Bidassoa estuary, a hybrid isolated clone has been found, that displays additive species-specific nuclear markers of S. maritima and S. alterniflora, and that is subsequently considered as a surviving clone of S. × neyrautii. The molecular analyses indicate that S. × neyrautii and S. × townsendii share the same maternal (S. alterniflora), and paternal (S. maritima) parental species, but also that the two independent hybridization events have involved different parental (nuclear) genotypes in England and in South-West France. Received July 12, 2002; accepted October 4, 2002 Published online: March 20, 2003     

A comparison of the seed dormancy characteristics of Spartina patens and Spartina alterniflora (Poaceae)

Seed dormancy characteristics of Spartina alterniflora were delineated previously by Plyler and Carrick (American Journal of Botany, vol. 80, pp. 752–756, 1993). This study was undertaken in order to determine whether or not the dormancy characteristics of S. patens are similar. As in the previous study, the site of a dormancy mechanism was determined by assessing the germinability of surgically altered dormant seeds. Likewise, the effects of three growth-regulating substances (abscisic acid, fusicoccin, and gibberellic acid), prechilling, and light were studied by assessing the germinability of appropriately treated dormant seeds. Surgical injury to the endosperm, and to a lesser extent the scutellum, produced significant germination in S. patens, whereas only injury to the scutellum produced germination in S. alterniflora. Exogenously applied abscisic acid was highly effective in maintaining dormancy in injured seeds of both species. Gibberellic acid and fusicoccin were ineffective in promoting germination in S. patens, but fusicoccin was highly effective in breaking dormancy in 5. alterniflora. Prechilling was effective in breaking dormancy in S. patens but not in S. alterniflora. In S. patens, treatments that broke dormancy were only successful when seeds were exposed to light during the germination period. It is concluded that the dissimilarities in the dormancy mechanisms may be manifestations of the different environmental adaptations these closely related species display.     

Greater male fitness of a rare invader (Spartina alterniflora, Poaceae) threatens a common native (Spartina foliosa) with hybridization

Hybridization with abundant invaders is a well-known threat to rare native species. Our study addresses mechanisms of hybridization between a rare invader, smooth cordgrass (Spartina alterniflora) and the common native California cordgrass (S. foliosa) in the salt marshes of San Francisco Bay. These species are wind-pollinated and flower in summer. The invader produced 21-fold the viable pollen of the native, and 28% of invader pollen germinated on native stigmas (1.5-fold the rate of the native's own pollen). Invader pollen increased the seed set of native plants almost eightfold over that produced with native pollen, while native pollen failed to increase seed set of the invader. This pollen swamping and superior siring ability by the invader could lead to serial genetic assimilation of a very large native population. Unlike California cordgrass, smooth cordgrass can grow into low intertidal habitats and cover open mud necessary to foraging shorebirds, marine life, navigation, and flood control in channels. To the extent that intertidal range of the hybrids is more similar to the invader than to the native parent, introgression will lead to habitat loss for shore birds and marine life as well to genetic pollution of native California cordgrass.     

盐胁迫对大米草幼苗某些生理指标的影响

研究了大米草幼苗在不同培养盐度(0、20、30、50、100mmol/LNaCl)下,MDA、游离脯氨酸、可溶性糖、可溶性蛋白质含量以及保护酶(SOD、POD、CAT)活性等生理指标的变化情况。结果表明:保护酶(SOD、POD、CAT)活性在盐胁迫40d前逐渐上升且达显著差异。随着胁迫时间延长,MDA含量与CK相比逐渐降低。随着盐分胁迫浓度的增加及盐胁迫时间延长,大米草叶片中游离脯氨酸、可溶性糖、可溶性蛋白质含量呈上升趋势。在盐胁迫下,渗透调节物质的积累作用是大米草对盐胁迫的主要响应过程,其体内的抗氧化保护酶在此过程中也发挥了重要的作用。     

The enigmatic invasive Spartina densiflora: a history of hybridizations in a polyploidy context

The aim of this study was to explore the origin of the invasive Spartina densiflora by analysing samples from the native region (South America) and from a recently colonized area (California). A combination of various molecular data (chloroplast and nuclear sequences, molecular fingerprint) and ploidy level estimations was used to answer the question whether the reticulate phylogenetic pattern previously detected in S. densiflora was restricted to California, or alternatively, whether a more ancient hybrid origin preceded formation of this species in its native area. We found that this species is heptaploid in both its native and introduced range. Identification of nuclear homeologous sequences indicate that this species has a reticulate origin in its native range, involving a lineage related to the hexaploid clade formed by S. alterniflora, S.foliosa, and S. maritima, and another lineage related to the sub-Antarctic endemic S. arundinacea that provided the chloroplast genome. The samples from California displayed similar multilocus patterns to the samples from Chile, supporting the hypothesis that this species originated on the southeast American coast (Argentina), from where it eventually spread to the west coast of South America (Chile) first and to the Northern Hemisphere (California) later.     

三种类型互花米草抗盐生态型的分化

从美国引种成功的三种类型互花米草在不同NaCl浓度的盐渍生境中,叶细胞膜透性、渗透调节物(主要是K+、Na+)和氨基酸的变化以及光合作用、呼吸作用的变化都存在明显的差异,这是由于长期不同生境的选择和互花米草的基因型适应所造成的生态型分化的结果。按抗盐性分：G型抗性最强、F型最弱、N型居中。     

沼泽湿地互花米草植物体传输与排放甲烷特征

于各测定月的小潮日,使用悬管装置采集气样并结合气相色谱测定,对闽江河口互花米草（Spartina alterniflora）沼泽湿地互花米草植株的甲烷传输量及其主要释放部位进行了研究,另又采用静态箱法-气相色谱法测定了互花米草沼泽湿地甲烷的排放通量,以此分析互花米草植物体甲烷传输对互花米草沼泽湿地甲烷排放通量的贡献率,最后测定了互花米草植株髓腔内的甲烷浓度。结果表明,不同生长阶段的互花米草植株甲烷传输量明显不同,快速生长阶段的互花米草植株甲烷传输量最高;互花米草植株甲烷传输对互花米草沼泽湿地甲烷排放通量的贡献率介于9%-94%之间;互花米草植物体传输甲烷的主要释放部位是距地面0-20cm处,该部位对植物甲烷传输量的贡献率为50%（平均值）;髓腔内的甲烷浓度远高于大气中的甲烷浓度,且自下而上呈递减趋势。     

大米草对有机汞的耐性、吸收及转化

大米草对营养液中氯化甲基汞(MeHgCl)毒性的临界浓度为15 uml/L,是烟草的3倍.氯化甲基汞处理后,植株体内有机汞总量在增加,而营养液中有机汞总量在减少,无机汞总量则明显增加.这些结果表明,大米草可以吸收有机汞,将有机汞部分地转化为无机汞,并且无机汞较多地积累在植株的地下部,同时有一部分通过扩散或分泌进入营养液中.大米草对汞的积累作用和把有机汞转化为无机汞的转化作用在环境污染的植物修复方面有重要的利用价值.     

Characterization of microsatellite loci in Spartina species (Poaceae)

The cordgrasses in the genus Spartina have become model organisms for studying biological invasions from both ecological and genetic perspectives. Here we characterize 11 disomic loci in Spartina alterniflora that show promise for population studies and for studying hybridization events between S. alterniflora and S. foliosa. Comparisons among invasive and native S. alterniflora populations showed that levels of allelic variation are lower in invasive populations. In addition, nearly all loci that amplified in S. foliosa populations and in a swarm of S. alterniflora×foliosa hybrids were polymorphic. We also found that several loci amplified successfully in other Spartina species.     

芦苇与入侵植物互花米草的光合特性比较

以上海崇明东滩湿地外来入侵植物互花米草与本地种芦苇为研究对象,对它们的光合特性进行了比较研究,结果表明:(1)与芦苇相比,互花米草具有更高的表观量子效率(AQY)、CO2羟化效率(CE)和最大净光合速率(pmax);(2)生长季节初期,互花米草午间时段的光合、气孔导度和蒸腾速率均高于芦苇,各指标与光、温的变化基本一致;(3)互花米草的净光合速率曲线呈“单峰”型,测定指标在强光合辐射、高温条件下迅速上升,芦苇则表现出明显的“午休”现象;(4)在生长季节初期(5月份)和活跃期(9月份),互花米草的净光合速率显著高于芦苇,而在生长季节后期(11月份)则低于芦苇。该项研究有利于解释互花米草生长迅速,生产力高,竞争性强的生理生态学特性。     

Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea

Ancient DNA has revolutionized the way in which evolutionary biologists research both extinct and extant taxa, from the inference of evolutionary history to the resolution of taxonomy. Here, we present, to our knowledge, the first study to report the rediscovery of an ‘extinct’ avian taxon, the Tasman booby (Sula tasmani), using classical palaeontological data combined with ancient and modern DNA data. Contrary to earlier work, we show an overlap in size between fossil and modern birds in the North Tasman Sea (classified currently as S. tasmani and Sula dactylatra fullagari, respectively). In addition, we show that Holocene fossil birds have mitochondrial control region sequences that are identical to those found in modern birds. These results indicate that the Tasman booby is not an extinct taxon: S. dactylatra fullagari O''Brien & Davies, 1990 is therefore a junior synonym of Sula tasmani van Tets, Meredith, Fullagar & Davidson, 1988 and all North Tasman Sea boobies should be known as S. d. tasmani. In addition to reporting the rediscovery of an extinct avian taxon, our study highlights the need for researchers to be cognizant of multidisciplinary approaches to understanding taxonomy and past biodiversity.     

米草属植物入侵的生态后果及管理对策

生物入侵是全球变化的重要组成部分,可能对入侵地造成严重的经济和生态后果,所以评价外来种入侵的生态后果是入侵生态学研究的核心问题之一。本文以米草属(Spartina)植物为例,综述了其对入侵地区自然环境、生物种群、群落和生态系统的影响;结合国际上对米草属入侵种的管理策略,讨论了我国米草属植物管理中的一些重要问题。     

互花米草入侵对黄河口潮沟形态特征和植物群落分布的影响

互花米草大规模入侵滨海湿地,对潮沟形态特征和植物群落的演变产生重大影响.本研究基于2008-2020年遥感影像,利用3S技术,结合回归分析与统计分析法,分析黄河口湿地互花米草入侵的演变特征,探究其对潮沟形态特征和植物群落分布的影响.结果 表明:2008年以来,黄河口互花米草面积增长迅速,增长速度为4.47 km2·a-...     

Reciprocal hybrid formation of Spartina in San Francisco Bay

Diversity in the tRNALEU1 intron of the chloroplast genome of Spartina was used to study hybridization of native California cordgrass, Spartina foliosa, with S. alterniflora, introduced to San Francisco Bay approximately 25 years ago. We sequenced 544 bases of the tRNALEU1 intron and found three polymorphic sites, a pyrimidine transition at site 126 and transversions at sites 382 and 430. Spartina from outside of San Francisco Bay, where hybridization between these species is impossible, gave cpDNA genotypes of the parental species. S. foliosa had a single chloroplast haplotype, CCT, and this was unique to California cordgrass. S. alterniflora from the native range along the Atlantic coast of North America had three chloroplast haplotypes, CAT, TAA, and TAT. Hybrids were discriminated by random amplified polymorphic DNA (RAPD) phenotypes developed in a previous study. We found one hybrid that contained a cpDNA haplotype unknown in either parental species (TCT). The most significant finding was that hybridization proceeds in both directions, assuming maternal inheritance of cpDNA; 26 of the 36 hybrid Spartina plants from San Francisco Bay contained the S. foliosa haplotype, nine contained haplotypes of the invading S. alterniflora, and one had the cpDNA of unknown origin. Furthermore, cpDNA of both parental species was distributed throughout the broad range of RAPD phenotypes, suggesting ongoing contributions to the hybrid swarm from both. The preponderance of S. foliosa cpDNA has entered the hybrid swarm indirectly, we propose, from F1s that backcross to S. foliosa. Flowering of the native precedes by several weeks that of the invading species, with little overlap between the two. Thus, F1 hybrids would be rare and sired by the last S. foliosa pollen upon the first S. alterniflora stigmas. The native species produces little pollen and this has low viability. An intermediate flowering time of hybrids as well as pollen that is more vigourous and abundant than that of the native species would predispose F1s to high fitness in a vast sea of native ovules. Thus, spread of hybrids to other S. foliosa marshes could be an even greater threat to the native species than introductions of alien S. alterniflora.     

米草生态工程加环效益能值分析

根据生态工程加环原理,在互花米草生态工程(Spartina alterniflora Ecological Engineering,SAEE)基础上设计一个深度开发的增益环,选取天然植物纤维与互花米草提取物——生物矿质液(Biological Mineral Liquid,BML)共同制成降脂胶囊,并应用能值分析的方法对SAEE+胶囊的加环设计(SAE Eand Capsule SAEEC)进行了经济、生态、社会复合效益评估,与SAEE相比,加环设计(SAEEC)的经济投入增加,能值投资比率(Emergy investment ratio,EIR)是SAEE的1．37倍;经济收益是SAEE的2．13倍,经济收益产投比是SAEE的1．46倍;净能值效益(Netemergy yield,NEY)是SAEE的3．18倍,净能值产出率(Evaergy yield ratio,EYR)是SAEE的2．20倍,经济效益和生态效益均得到提高,体现了生态工程加环增益的基本设计原则。     

不同海滨港湾环境条件下互花米草总黄酮积累动态研究

对两个不同海滨地区的互花米草体内的总黄酮（ Ｔｏｔａｌ Ｆｌａｖｏｎｏｉｄｓ ｏｆ Ｓｐａｒｔｉｎａ ａｌｔｅｒｎｉｆｌｏｒａ, Ｔ Ｆ Ｓ）的含量及其随时间和相关环境因子变化进行研究。初步研究结果显示,互花米草 Ｔ Ｆ Ｓ的积累与土壤含盐量呈强正相关关系,与土壤含氮量、土壤有机质呈正相关关系。 Ｔ Ｆ Ｓ的积累是互花米草在高盐度条件下的一种抗逆反应。     

The effect of nutrients on adenine nucleotide levels and the adenylate energy charge ratio in Spartina alterniflora and Spartina patens

Abstract. The response of the adenylate energy charge (AEC) ratio and the adenine nucleotide pools to nutrients was studied in two perennial marsh plant species. Adenine nucleotide levels and the AEC ratio were measured in Spartina patens (Alton) Muhl. plants which were grown in the greenhouse at various nutrient levels as well as in Spartina alterniflora Loisel. transplants removed from the field but maintained in marsh soil amended with different nutrient supplements. In addition, adenine nucleotide concentrations were measured in both species in their natural environment and compared with that of the same species grown in the greenhouse with a complement of nutrients.
The addition of nutrients stimulated an increase in the individual and total adenylate pools and the AEC ratio. Low nutrient levels resulted in extremely reduced adenylate pools. The AEC ratio was significantly affected in some instances, but did not decrease proportionately with the adenine nucleotide level and was typically maintained at values above 0.60. The adenine nucleotide concentrations measured in the leaves of both species were significantly higher in greenhouse-grown plants compared to field plants, but the AEC ratios were not significantly different.
Because the AEC ratio in plants can be significantly affected by nutrient level. AEC response in field investigations should be planned with attention to the potential effect of dissimilar nutrient levels among study sites.