Myriophyllum quitense (Haloragaceae) in the United States

A systematic study of more than 15,000Myriophyllum specimens from 189 North American herbaria yielded 63M. quitense specimens. Late 19th century collections were made from Henry's Fork of the Snake River in Jefferson County, Idaho, in 1872, from Santa Cruz Creek, Tucson, Pima County, Arizona, in 1881, from Yellowstone Lake in 1885, and from Crook County, Oregon, in 1894. Twentieth century collections have been made from Yellowstone National Park, at several sites along the Snake River in Idaho, in Summit County, Utah, in Lassen and Shasta counties of northern California, at numerous sites along the Deschutes River, and in Benton County, Oregon, and at three sites in Washington. We contend that the species was introduced into North America by migratory waterfowl more than 100 years ago. Only in the Yellowstone Lake and numerous Deschutes River habitats in which populations now exist are environmental conditions conducive to full morphological development of the species in North America.     

A Conspectus of Myriophyllum (Haloragaceae) in North America

Thirteen species of the genus Myriophyllum are found in North America; ten are native, three have been introduced. A key to the species is provided and previous conflicting taxonomic treatments are assessed. The possibility of a polyploid series involving four species is considered and dismissed. Eight of the common species are found to exhibit sufficient phenotypic plasticity to account for most if not all the taxonomic problems encountered.     

Myriophyllum quitense and myriophyllum ussuriense (Haloragaceae) in British Columbia,Canada

Myriophyllum quitense andM. ussuriense are added to the flora of British Columbia, Canada.Myriophyllum quitense has not been previously reported in Canada, and this is the first report ofM. ussuriense for the North American continent. Problems with the identification of these species, and their distributions and habitats are discussed. The somatic chromosome numbers of 2n=42 forM. quitense and 2n=21 forM. ussuriense were found. A key for the identification ofMyriophyllum taxa growing in British Columbia is given.     

两种狐尾藻属（小二仙草科）植物在中国的新记录

互花狐尾藻 Myriophyllum alterniflorum DC.和刺果狐尾藻M．tuberculatum Roxb．为中国首次记录。     

Two species of the genus Myriophyllum L. (Haloragaceae) newly recorded in China

Myriophyllum alterniflorum DC. and M. tuberculatum Roxb. of the Haloragaceae, are reported as new records in China.     

Comparison of leaf morphology among submersed species of Myriophyllum (Haloragaceae) from different habitats and geographical distributions

An image analysis system was used to calculate the surface area and volume of the submerged leaves of seven species of Myriophyllum. We separated the species into two categories based on their distribution and habitat differences and compared their surface area, volume, dry mass, specific leaf area, and surface to volume ratios. The geographic location and habitat of the species explained the greatest percentage of total variance for these variables when compared by analysis of variance. A leaf shape analysis was performed by regressing surface area with volume for each species. Interspecific comparisons of leaf shape were made using analysis of covariance. Fundamental interspecific differences in submerged leaf shape, associated with differences in their geographic distributions and habitats, are explained as adaptations for different nutrient uptake regimes.     

Decline of the invasive submersed macrophyte Myriophyllum spicatum (Haloragaceae) associated with herbivory by larvae of Acentria ephemerella (Lepidoptera)

Myriophyllum spicatum, an exotic submersed macrophyte causing serious lake management problems throughout much of North America, decreased markedly in biomass in Cayuga Lake, NY, USA, since the beginning of the 1990s. Over the same period, however, the total biomass of all species of submersed macrophytes did not decline, and native macrophytes gained in abundance. The aquatic moth larva, Acentria ephemerella, was first observed on milfoil plants in Cayuga Lake in 1991. However, due to its cryptic habit the larva may have been present prior to that year. When the density of these grazers is high, herbivory by Acentria causes severe damage to the apical meristem of M. spicatum. This moth larva and another milfoil herbivore, Euhrychiopsis lecontei are widespread in 26 lakes surveyed in New York State; they are present in 25 and 24 lakes, respectively. Estimates of Acentria larval densities in summer in Cayuga Lake are 27 to 100 m^-2, and a quantitative survey of larvae hibernating in milfoil stems revealed mean densities of 500 m^-2 in late fall in Seneca Lake. In laboratory experiments, Acentria larvae feed on a wide variety of macrophytes commonly found in New York State. Although Acentria is not a specialist feeder, its life cycle is closely tied to M. spicatum through the moth's use of apical tips and stems for summer and winter refuges; thus deleterious damage to other macrophytes is low. This revised version was published online in July 2006 with corrections to the Cover Date.     

Micropropagation of Myriophyllum Alterniflorum (Haloragaceae) for Stream Rehabilitation: First In Vitro Culture and Reintroduction Assays of a Heavy-Metal Hyperaccumulator Immersed Macrophyte

Nowadays, submersed aquatic macrophytes play a key role in stream ecology and they are often used as biomonitors of freshwater quality. So, these plants appear as natural candidates to stream rehabilitation experiments. Among them, the stream macrophyte Myriophyllum alterniflorum is used recently as biomonitor and is potentially useful for the restoration of heavy-metal contaminated localities. The best way to obtain a mass production of watermilfoil plants is micropropagation. We developed in vitro culture of M. alterniflorum and the effects of five media on the plant development were assessed. Five morphological and four physiological endpoints were examined leading to the recommendation of the Murashige and Skoog medium for ecotoxicological studies on chlorophyllous parts, and of the Gaudet medium for root cytotoxicity and phytoremediation studies. Micropropagated clones were acclimatized in a synthetic medium and in situ reintroduction was performed efficiently. This is the first report of micropropagated plants transplantation in streams. The successful establishment of watermilfoil beds even in polluted areas strongly suggested that ecological restoration using micropropagated watermilfoil is a promising biotechnology for phytoremediation and rehabilitation of degraded areas. Moreover, high bioconcentration factors evidenced that watermilfoil hyperaccumulates Cd and Cu, and could be potentially used in phytoremediation studies.     

Influence of geography and environment on patterns of genetic differentiation in a widespread submerged macrophyte,Eurasian watermilfoil (Myriophyllum spicatum L., Haloragaceae)

The effects of geographic and environmental variables on the pattern of genetic differentiation have been thoroughly studied, whereas empirical studies on aquatic plants are rare. We examined the spatial genetic differentiation of 58 Myriophyllum spicatum populations distributed throughout China with 12 microsatellite loci, and we analyzed its association with geographic distance, geographic barriers, and environmental dissimilarity using causal modeling and multiple matrix regression with randomization (MMRR) analysis. Two genetic clusters were identified, and their geographic distribution suggested mountain ranges as a barrier to gene flow. The causal modeling revealed that both climate and geographic barriers significantly influenced genetic divergence among M. spicatum populations and that climate had the highest regression coefficient according to the MMRR analysis. This study showed that geography and environment together played roles in shaping the genetic structure of M. spicatum and that the influence of environment was greater. Our findings emphasized the potential importance of the environment in producing population genetic differentiation in aquatic plants at a large geographic scale.     

The discovery of Myriophyllum exalbescens Fernald (Haloragaceae) in Europe and the typification of M.spicatum L. And M.verticillatum L.

Myriophyllum exalbescens Fernald, hitherto regarded as a North American endemic, has been fund to occur widely as a native plant in northern Europe, where it has occasionally been distinguished as a subspecies or variety of M.spicatum L.under the epithet squamosum Linnacus original concept of M.spicalum appears to have included M.exalbescens (and also M. Alterniflorum DC.) but selection of Burser VII(1)79 at UPS as lectotvpe ensures the continued use of the epithet spicatum for the native Eurasian weed species to which it is customarily applied. .M.verlicillalum L., the name of a morphologically similar species, is also lectotypified in a way that preserves its current usage. Distinguishing features of M.exalbescens and M.spicatum are provided along with details of the synonymy and presently known distribution in Europe of M.exalbescens .     

Glycolate Metabolism in Eurasian Watermilfoil (Myriophyllum spicatum)

The metabolism of glycolate by Eurasian watermilfoil (Myriophyllum spicatum L.), a submersed angiosperm, was studied by feeding radioactive glycolate and glyoxylate and by analysis of glycolate and glycolic acid oxidase. Evidence for operation of the glycolate pathway is given. Glycolic acid oxidase occurs at levels comparable to amounts in species showing photorespiration. This species has a high affinity for CO₂ and a possible mechanism for it is described.     

The complete chloroplast genome of Myriophyllum spicatum reveals a 4‐kb inversion and new insights regarding plastome evolution in Haloragaceae

Myriophyllum, among the most species‐rich genera of aquatic angiosperms with ca. 68 species, is an extensively distributed hydrophyte lineage in the cosmopolitan family Haloragaceae. The chloroplast (cp) genome is useful in the study of genetic evolution, phylogenetic analysis, and molecular dating of controversial taxa. Here, we sequenced and assembled the whole chloroplast genome of Myriophyllum spicatum L. and compared it to other species in the order Saxifragales. The complete chloroplast genome sequence of M. spicatum is 158,858 bp long and displays a quadripartite structure with two inverted repeats (IR) separating the large single copy (LSC) region from the small single copy (SSC) region. Based on sequence identification and the phylogenetic analysis, a 4‐kb phylogenetically informative inversion between trnE‐trnC in Myriophyllum was determined, and we have placed this inversion on a lineage specific to Myriophyllum and its close relatives. The divergence time estimation suggested that the trnE‐trnC inversion possibly occurred between the upper Cretaceous (72.54 MYA) and middle Eocene (47.28 MYA) before the divergence of Myriophyllum from its most recent common ancestor. The unique 4‐kb inversion might be caused by an occurrence of nonrandom recombination associated with climate changes around the K‐Pg boundary, making it interesting for future evolutionary investigations.     

Differential responses of <Emphasis Type="Italic">Myriophyllum alterniflorum</Emphasis> DC (Haloragaceae) organs to copper: physiological and developmental approaches

Copper is an essential element for the function of metabolic pathways in many living organisms like photosynthesis in plants. But, for the last decades, anthropogenic sources and release of Cu lead to environmental pollution particularly in aquatic ecosystems. The aquatic plant, Myriophyllum alterniflorum, known as a bioindicator of metal pollution, could be used as biomonitor. The aim of this study is to evaluate biomarkers responses of watermilfoil during Cu pollution at high environmental levels (100 μg l⁻¹ CuSO₄) in controlled conditions. Morphological and anatomical features like a new double endodermis (DE) layer were evidenced in response to Cu treatment. Moreover, physiological parameters like pigments contents, osmotic potential and proline content present a differential response to Cu stress in young and old leaves of watermilfoil. Finally, despite a rapid and strong phytoaccumulation of Cu, only young leaves are slightly affected in their cell membrane integrity as indicated by MDA content. In comparison with the Cu effect on other aquatic macrophytes, M. alterniflorum develops particular protection mechanisms like the ROS scavenging using proline rather than carotenoids, the reduction of water loss with the DE and the heavy metal elimination through senescence to protect preferentially the photosynthetic components of the young leaves and the main-stem elongation. Due to its Cu sensitivity, M. alterniflorum appears as important in the field of environmental studies using plant biomarkers.     

Effects of eutrophication and snails on Eurasian watermilfoil (Myriophyllum spicatum) invasion

Exotic species can invade and establish new habitats both as a result of their own traits, and as a result of the characteristics of the environment they invade. Here, we show that the abundance of the invasive submerged aquatic plant, Myriophyllum spicatum (Eurasian watermilfoil) is highly dependent on the conditions of the environment in a mesocosm experiment. M. spicatum is allelopathic towards epiphytic algae, and in the absence of algivorous snails, we found that the abundance of both algae and M. spicatum significantly increased with experimentally increased nutrient loading, while the abundance of native submerged macrophytes declined. However, when snails were present, snail biomass increased with increasing nutrient loading, and M. spicatum biomass was consistently low while native submerged macrophyte biomass was consistently high. Our results stress the importance of the interaction between species traits and environmental conditions when considering the invasiveness of certain exotic species and the invasibility of certain environments.     

Extensive clonality in the endangered shrub Haloragodendron lucasii (Haloragaceae) revealed by allozymes and RAPDs

The occurrence of clonality in threatened plants can have important implications for their conservation. In this study, allozymes and RAPDs were used to determine the extent of clonality in the endangered shrub Haloragodendron lucasii (Haloragaceae), which is known from only four sites within an 8 km range. Allozyme markers identified only six multilocus genotypes among the 53 ramets sampled across the four sites, although a total of 54 different genotypes were possible with the three polymorphic allozyme loci detected. The polymorphic bands detected in the RAPD analysis were capable of producing 2⁴⁶ genotypes, but again only six multilocus genotypes were delineated. The allozyme and RAPD data were congruent at three of the four sites. At the fourth site two genotypes were detected by each marker; however, once combined, three multilocus genotypes were observed. The probabilities that the observed number of replicates of each combined allozyme and RAPD genotype could be generated by sexual reproduction were less than 10^–18, leaving little doubt that clonality is the explanation for the observed patterns of genotypes. The genetic conclusions are supported by root excavations which show potential for vegetative reproduction and the observation of no sexual reproduction in the species. The recognition of extensive clonality in H. lucasii has had immediate implications for the conservation management of the species and resulted in changes to the management priorities for the species. Thus it is clear that appropriate genetic studies can play an important role in the management of threatened species.     

Notes on Bletia (Orchidaceae)

New species ofBletia from Mexico are described and illustrated:B. concolor, B. similis, andB. urbana. The identity ofB. campanulata Llave & Lex. is discussed, andB. reflexa Lindl. is considered to be a distinct species. Several South American epithets are treated as synonyms ofB. campanulata. A key to the recognized species ofBletia is given.