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Maritime Spartina spp. are powerful ecosystem engineers that accrete sediment, define shorelines, create habitat, and generate prodigious primary productivity both where they are native and where they have been introduced. Invasive Spartina spp. can compete vigorously with native species, diminish biota, change hydrology, and confound human uses of estuaries. Herbicides have been effective in controlling several Spartina spp. invasions. One of the most recent successes is a 15-year campaign that has virtually eliminated S. alterniflora from the large, century-old invasion in Willapa Bay, WA, USA. Hybridization between native and introduced Spartina spp. has created new species and hybrid swarms. In San Francisco Bay, CA, USA (SF Bay) a complicated situation continues to play out from the purposeful introduction of S. alterniflora, which hybridized with native California cordgrass, S. foliosa. The hybrids spread rapidly and led to a long list of environmental problems, which led to an herbicide program that was successful in greatly diminishing the hybrid and saving the open mud habitat of migratory shorebirds. However, it was belatedly realized that the non-migratory, endangered Ridgeway’s rail uses the tall, dense hybrid Spartina as a surrogate for habitat that was lost during the twentieth century to urbanization and agricultural transformation of marshes around SF Bay. This realization has made difficult the simultaneous management of hybrid Spartina, wildlife conservation, and marsh restoration in San Francisco Bay. Restoration of native vegetation could satisfy the multiple goals of preserving open mud and conserving Ridgeway’s rail.  相似文献   

3.
In Southampton Water, UK, the recent (c. 150 years ago) interspecific hybridisation between Spartina alterniflora (2n = 6x = 62; A-genome) and S. maritima (2n = 6x = 60; M-genome) gave rise to the homoploid hybrid (S. × townsendii, 2n = 6x = 62), and subsequently to the invasive allododecaploid species S. anglica (2n = 12x = 120–124) that has since spread worldwide. To address the question of dynamics of mixed ploidy populations involving these plants, we analysed several Spartina populations (fifty one individuals) in Southern England, UK, one of which was the presumed place of origin of the homoploid hybrid (Hythe). Using a combination of flow cytometry and ribosomal DNA (rDNA) genotyping we were able to identify the genomic composition and ploidy level of each individual analysed. The data show that the homoploid hybrid still dominates the population at Hythe (82 % of individuals collected in that locality) since its origin in the nineteenth century. We also identified S. × townsendii for the first time on Hayling Island (66 % individuals), indicating dispersal beyond its likely origin. The fertile allododecaploid S. anglica was mainly found in populations outside the initial hybridisation site, on Hayling Island and at Eling Marchwood. Quantification of the rDNA contributions from each parental genome showed that the ratios were mostly balanced in S. × townsendii. However, two (3 %) S. anglica individuals analysed have lost nearly all M-genome homeologs, indicating extensive repeat loss. Such variation indicates that despite the presumed single allopolyploid origin of S. anglica and genetic uniformity at other loci, it has undergone substantial changes at the rDNA loci following genome duplication.  相似文献   

4.
Intercontinental introductions are widespread in the genus Spartina, with important ecological and evolutionary consequences. The native or introduced status of Spartina species is then critical with regard to biodiversity assessment, especially for vulnerable Mediterranean coastline ecosystems. Spartina versicolor was first recorded in southern France in 1849, then successively in various places on the European and North-African Mediterranean and Atlantic coasts. This species is considered to be either a European native or an invasive species introduced from North America which has a high morphological similarity to the Atlantic American species Spartina patens. We performed extensive sampling of S. versicolor in Europe and North Africa (from natural populations and herbarium collections) and compared these samples to other European and American Spartina species (including S. patens). Chromosome counts were reported for the first time and revealed that S. versicolor is tetraploid (2n = 4x = 40). Phylogenetic analyses based on chloroplast and nuclear ribosomal DNA sequences did not reveal any molecular variation within S. versicolor. In this species, a single haplotype, that is identical to one haplotype of S. patens, was found in the four chloroplast and the nuclear ribosomal ITS regions investigated. In addition, simple sequence repeat markers were used and revealed a low level of genetic diversity within S. versicolor, suggesting that the introduction of S. versicolor occurred from a narrow genetic pool of S. patens from North America.  相似文献   

5.
Non-native Spartina spp. have invaded many coastal saltmarshes worldwide. Introduced Spartina may cause problems like displacement of native vegetation and hybridisation with native species, leading to changes to relevant ecosystem services and saltmarsh geomorphology. Here we report the extensive and so far overlooked replacement of the native Spartina maritima by non-native S. anglica and S. townsendii along 400 km of the coast of the north-western Adriatic Sea (Mediterranean Sea). We analysed the distribution of both native and non-native Spartina spp. along the six main saltmarsh areas in the region, and produced maps of their presence by using a combination of genetic tools, morphological analysis and geotagged photographs, complemented with field observations. We also reviewed historical herbaria from the region to explore when the first non-native introductions could have occured. We found that S. anglica and S. townsendii are unexpectedly widespread, having established along the whole study region, in one lagoon totally replacing the local native species. Its introduction happened virtually unnoticed, and misidentified herbarium specimens date back as early as 1987. We discuss the ecological implications of this overlooked extensive replacement, and the need for a comprehensive assessment of the status of the saltmarshes in this region, both to protect the few remaining patches of the native S. maritima and control the spread of the non-native species across the Mediterranean Sea.  相似文献   

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Hybridization between alien and native species is biologically very important and could lead to genetic erosion of native taxa. Solidago × niederederi was discovered over a century ago in Austria and described by Khek as a natural hybrid between the alien (nowadays regarded also as invasive) S. canadensis and native S. virgaurea. Although interspecific hybridization in the genus Solidago is considered to be relatively common, hybrid nature of S. × niederederi has not been independently proven using molecular tools, to date. Because proper identification of the parentage for the hybrid Solidago individuals solely based on morphological features can be misleading, in this paper we report an additive polymorphism pattern expressed in the ITS sequences obtained from individuals representing S. × niederederi, and confirm the previous hypothesis that the parental species of this hybrid are S. canadensis and S. virgaurea. Additionally, based on variability at the cpDNA rpl32-trnL locus, we showed that in natural populations hybridization occurs in both directions.  相似文献   

8.
Plant invasions can alter the trophic interactions of invaded ecosystems because of phenological differences between native and invasive plants that may affect the population dynamics and diets of indigenous arthropod herbivores. This issue, however, has seldom been studied. We here report on how abundance and diet of a local tussock moth (Laelia coenosa) are affected by the invasive plant Spartina alterniflora in a Chinese salt marsh previously dominated by the moth’s native host plant, Phragmites australis. We monitored the population dynamics of L. coenosa from four types of hosts: (1) Phragmites in its monoculture, (2) Spartina in its monoculture, and either (3) Phragmites, or (4) Spartina in PhragmitesSpartina mixtures. Additionally, we tested the diet of L. coenosa from the mixtures with isotope analysis. We found that the larval densities of L. coenosa were similar on Spartina and Phragmites in their respective monocultures and mixtures in summer but were greater on Spartina than on Phragmites in autumn. Stable isotope analysis showed that Spartina was a food resource for L. coenosa. The change in the insect’s population dynamics associated with Spartina invasion might be caused by phenological differences between Spartina and Phragmites in that Spartina has a longer growing season than Phragmites. Our study indicates that the extended phenology of Spartina invasion has altered the abundance and diet of the indigenous herbivorous insect (L. coenosa) previously feeding on native Phragmites. We predict such alternation may increase the consuming pressure to native plants via apparent competition, and thereby may facilitate the further invasion of the exotic plants in the salt marsh.  相似文献   

9.
Saline wetlands may be well suited for purifying contaminated water from saline agriculture and aquaculture or from freshwater-based agriculture in areas subject to increased salinity. However, case studies on the nutrient removal efficiency of halophyte species are scarce, especially for temperate regions. Here we tested the nutrient removal efficiency and ability to store nutrients in aboveground and belowground biomass of three halophyte species, Aster tripolium, Bolboschoenus maritimus subsp. compactus, and Spartina anglica, in a greenhouse microcosm experiment at two salinity levels. Nutrient removal from water differed among the species: Spartina had the highest nitrogen removal, Bolboschoenus and Spartina had the highest phosphorus removal. The species also differed in the allocation of the nutrient uptake. Bolboschoenus had the highest absolute uptake of nitrogen and phosphorus in shoots, whereas Spartina had the highest uptake of nitrogen and phosphorus in roots. The applicability of these three species in constructed saline wetlands depends on the local salinity and water regime.  相似文献   

10.
Numerous termite species have been introduced outside their native ranges by human transport, and some have become invasive. The dampwood termite Zootermopsis nevadensis (Hagen), which is native to western North America, has been introduced to and become established in Kawanishi City, Hyogo Prefecture, Japan. Zootermopsis nevadensis is subdivided into two subspecies based on cuticular hydrocarbon (CHC) phenotypes: Znevadensis nevadensis and Znevadensis nuttingi (Haverty and Thorne). Here, we identified Znevadensis in Japan as hybrids between the two subspecies. Chemical analysis showed the presence of 7,15-dimethylhenicosane and 5,17-dimethylhenicosane in the CHCs of Znevadensis in Japan, corresponding to the CHC phenotype of Znnevadensis. Conversely, all mitochondrial cytochrome c oxidase subunit I sequences of Znevadensis in Japan were identical to sequences from Znnuttingi and hybrids between the two subspecies from a native hybrid zone in California, USA. In addition, phylogenetic analysis showed that Znevadensis in Japan formed a clade with Znnuttingi and hybrids between the two subspecies. Our results show discordance between the chemical and genetic features of Znevadensis in Japan, indicating that individuals of Znevadensis in Japan are hybrids between the two subspecies.  相似文献   

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Plectosphaerella cucumerina (Lindf.) W. Gams was evaluated as a bioherbicide for Cirsium arvense L. (Scop.) using a Canadian and a New Zealand isolate. Both isolates defoliated C. arvense when applied at 1013 conidia ha?1 in water volumes ranging from 250 to 6400 l ha?1 with a rapid decline in effect with declining conidial dose. Repeat application and the addition of the adjuvant Pulse® penetrant to the conidial suspension increased the disease severity in C. arvense. Maximum disease occurred at 20 °C with a 48 h post-application dew period. The experiments demonstrate that P. cucumerina can defoliate C. arvense under the environmental conditions of temperate pastures where the weed is problematic. The results also show that modifications to formulation and strategic application may reduce the 48 h dew period requirement and risk to non-target species respectively, supporting the conclusion that the fungus has potential as a bioherbicide for C. arvense.  相似文献   

13.
Two new species of bothriocephalidean tapeworms, Bothriocephalus australis n. sp. from the flatheads Platycephalus bassensis Cuvier (type host) and P. aurimaculatus Knapp off southern Australia and B. celineae n. sp. from a hybrid serranid Cephalopholis aurantia (Val.) × C. spiloparaea (Val.) from off New Caledonia, are described. B. australis is unique in the possession of the combination of the three characters: an elongate, obliquely situated cirrus-sac; a wide genital atrium surrounded by chromophilic cells; and a well-developed apical disc. Bcelineae is typified by the presence of a low number of testes per segment (14–26), forming one or two incomplete longitudinal bands on each side of segment, and the small size of the strobila (total length 24 mm) which consists of less than 100 segments.  相似文献   

14.
When non-native, genetically diverse species are introduced, hybridization with native congeners may erode the genetic composition of local species, perhaps even resulting in extinction. While such events may lead to adverse consequences at the community and ecosystem level, few studies exist on ecologically important tree species. In the genus Platanus, introgressive hybridization is widespread, and one common ornamental species, introduced to California during the late 19th century, is itself a hybrid. Our microsatellite analysis of more than 400 Platanus trees from north-central California reveals a complex pattern of invasion and hybridization in an age-structured population. By using size as a proxy for age, we have demonstrated that the Platanus population of north-central California has recently gained genetic diversity and effective population size. Principal coordinate analysis (PCoA) and genetic admixture analysis (STRUCTURE) both reveal a strong differentiation of genotypes into two main genetic clusters, with a large number of admixed genotypes. One of the genetic clusters identified is heavily biased towards younger trees, including samples from locations with relatively recently planted ornamental trees likely to be P. × hispanica (formerly known as P. × acerifolia). We conclude that the two genetic clusters correspond to the native P. racemosa and the introduced invasive hybrid species P. × hispanica. Additional hybridization between the invasive ornamental and the native species has occurred in California, and recent hybrid trees are more likely to be younger than trees without admixture. Our findings suggest that the observed increase in genetic diversity among California Platanus is due to rampant ongoing introgression, which may be threatening the continued genetic distinctiveness of the native species. This is cause for concern from a conservation standpoint, due to a direct loss of genetic distinctiveness, and a potential reduction in habitat value of associated species.  相似文献   

15.
Galerucella placida Baly (Coleoptera: Chrysomelidae) is a promising biocontrol agent of the rice-field weed Polygonum orientale L. (Polygonaceae) in India and Bangladesh. The longevity of G. placida adults was related with nutrients and antinutrients of young, mature and senescent leaves of P. orientale. Mature leaves of P. orientale had higher level of nutrients (carbohydrates, proteins, lipids, nitrogen and amino acids) and lower level of antinutrients (phenols and flavonols) compared to young and senescent leaves. Higher level of carbohydrates, proteins, lipids, nitrogen, amino acids including water content, and lower phenol and flavonol content of mature leaves had influenced higher survival of G. placida. Total larval developmental and pupal periods were 26.27 ± 0.45 SE and 7.06 ± 0.17 SE days on mature weed leaves, respectively; whilst adult males and females lived for 52.15 ± 0.33 SE and 58.0 ± 0.38 SE days on mature leaves, respectively. Fecundity of individual G. placida was 133.3 ± 3.2 SE eggs during life time. The net reproductive rate, generation time, intrinsic rate of increase, finite rate of increase and doubling time were 66.675, 27.5376, 0.1525, 1.2502 and 4.5452 days, respectively, under laboratory conditions (27 ± 0.5 °C, 12L:12D photoperiod, 65 ± 5% RH).  相似文献   

16.
Spread of smooth cordgrass (Spartina alterniflora) in China is an exceptional example of unanticipated outcomes arising from intentional introductions. It has been proposed that in China, management strategies used to establish S. alterniflora inadvertently promoted evolutionary outcomes that have contributed to other Spartina invasions. In this study, we assessed whether S. alterniflora in China exhibits genetic signatures of mechanisms known to promote invasion success, including large founding populations, evolved self-fertility, ‘superior source ecotypes’, and post-introduction admixture. This involved comparing microsatellite genotype and chloroplast haplotype variation among Chinese populations to other invasive S. alterniflora populations as well as native range populations, inclusive of samples from all reported source areas. We found distinct signatures of source population contributions to Chinese populations, as well as evidence of post-introduction admixture, and no evidence of limitations from a genetic bottleneck. Measures of inbreeding were well below what has been found in other non-native populations that have evolved self-fertility. Differences in genetic diversity among sites were similar to latitudinal patterns in the native range, but could be attributable to introduction history. Comparisons to other invasive populations indicate that a combination of common and idiosyncratic processes have contributed to the success of S. alterniflora in China and elsewhere, with intentional introductions promoting mechanisms that accelerate rates of spread and widespread invasion.  相似文献   

17.
Fusarium palustre is an endophyte/pathogen of Spartina alterniflora, a saltmarsh grass native to North America that has been associated in the USA with a saltmarsh decline known as Sudden Vegetation Dieback (SVD). Since the intentional introduction of S. alterniflora to stabilize mud flats on Chongming Island, Shanghai, China, S. alterniflora has become invasive, but shows no symptoms of dieback even though F. palustre can be isolated from the plant. When declining S. alterniflora from SVD sites in the northeastern USA were assayed for Fusarium species, an average of 8 % of tissues sampled gave rise to a species of Fusarium of these, 64 % were F. palustre and 16 % were F. incarnatum, a nonpathogenic species. To determine if low densities of F. palustre could explain the lack of dieback symptoms on S. alterniflora from Chongming Island, we assessed the incidence and distribution of Fusarium spp. on S. alterniflora from 12 sites on Chongming Island. On average, 26 % of the stem and root tissues sampled were colonized by a Fusarium species. Of 196 isolates recovered from S. alterniflora, 44 % were F. incarnatum and 41 % were F. palustre. Species determinations were confirmed for a subset of these isolates using a phylogenetic analysis of partial sequences of the translation elongation factor (tef) gene. The observation that Fusarium incidence on S. alterniflora was much greater on Chongming Island than in the USA survey raises the question as to why S. alterniflora on Chongming Island is showing no dieback. Other factors, such as predator release, enhanced nutritional, edaphic and/or other unidentified environmental constraints on Chongming Island may afford S. alterniflora protection from dieback.  相似文献   

18.
The effects of plant growth regulators (PGRs) and organic elicitors (OEs) on in vitro propagation of Eucomis autumnalis was established. Three-year-old ex vitro grown plants from organogenesis of E. autumnalis and somatic embryogenesis (previously reported protocol) of Drimia robusta were investigated for antibacterial activity. In vitro propagation from leaf explants of E. autumnalis was established using different PGRs and OE treatments for mass propagation, biomass production and bioactivity analysis to supplement the use of wild plant material. Prolific shoots (16.0?±?0.94 shoots per explant) were obtained with MS (Murashige and Skoog in Physiol Plant 15:473–497, 1962) medium containing 100 mg l?1 haemoglobin (HB), 10 µM benzyladenine (BA) and 2 µM naphthaleneacetic acid (NAA). The shoots were rooted effectively with a combination of 2.5 µM indole-3-acetic acid and 5.0 µM indole-3-butyric acid. The plantlets were successfully acclimatized in a vermiculite-soil mixture (1:1 v/v) in the greenhouse. Three-year-old ex vitro-grown E. autumnalis and D. robusta plants derived via organogenesis and somatic embryogenesis respectively exhibited antibacterial activity and varied with PGR and OE treatments, plant parts and bacteria. The leaves of E. autumnalis ex vitro-derived from a combination of HB, BA and NAA followed by the individual treatments of BA and HB gave the best antibacterial activities (<?1 mg ml?1: minimum inhibitory concentration from 0.098 to 0.78 mg ml?1) against all tested pathogenic bacteria (Bacillus subtilis, Enterococcus faecalis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa). The bulbs of D. robusta ex vitro-derived from solid culture with 10 µM picloram, 1 µM thidiazuron and 20 µM glutamine exhibited good antibacterial activity against E. faecalis, M. luteus and S. aureus when compared with other treatments and mother plants. The ex vitro-grown E. autumnalis and D. robusta biomass produced with PGRs along with OE treatments confirmed a good potent bioresource and can be used as antibacterial agents. The in vitro plant regeneration of E. autumnalis and D. robusta protocols and ex vitro plants could be used for conservation strategies, bioactivity and traditional medicinal use.  相似文献   

19.
Life history strategies of batoid fishes have evolved within dynamic marine ecosystems. Adaptations in reproductive and developmental biology are paramount to the survival of species, and therefore knowledge of growth rates to maturity is fundamental for identifying constraints on the conservation of populations. The butterfly rays (Myliobatiformes: Gymnuridae) are highly derived batoids with generally low reproductive potentials for which age and growth information remains unknown. In this study we applied high-resolution X-ray computed tomography (HRXCT) to vertebral centra from a stingray for the first time to estimate age, and used a multimodel approach to investigate growth of spiny butterfly ray, Gymnura altavela. Estimated ages of the oldest male and female were 11 and 18 yrs. at disk widths (WD) 1355 mm and 2150 mm, respectively. Disk width-at-age data were analyzed using three growth models (von Bertalanffy, logistic, Gompertz), and the most parsimonious and empirically supported model was the logistic function with sex treated as a fixed effect on asymptotic disk width (WD ) and k parameters. Model parameter estimates were (males) WD  = 1285.46 ± 67.27 mm, k = 0.60 ± 0.10, and (females) WD  = 2173.51 ± 129.78 mm, k = 0.27 ± 0.04. Results indicated sexually dimorphic growth patterns, with males growing faster and reaching asymptotic size at earlier ages than females. These age and growth results are the first reported for the genus, and suggest that G. altavela grows at a similar rate as some teleosts and batoids, and relatively fast among chondrichthyans.  相似文献   

20.
Combined genetic and morphological data indicate frequent hybridisation between the wood ants Formica polyctena Förster 1850 and F. rufa Linnaeus 1761 in Central Europe. The genetic and morphological traits give a concordant picture of hybridisation with a strong correlation between the genotypic admixture proportions at 19 microsatellite loci and the first vectors of a principal component analysis (P < 0.001) and of a 3-class discriminant analysis (P < 0.001) of 15 quantitative morphological characters. This integrative approach enabled a grouping into F. polyctena, the hybrid and rufa. Genetic differentiation between the hybrid and F. rufa is significantly larger than between the hybrid and polyctena, indicating gene flow mainly between the latter entities. A suggested gene flow bias towards F. polyctena agrees with differential queen acceptance and mating behaviour. Both genetic and phenotypic colony parameters indicate predominance of monogyny in F. rufa but of polygyny in polyctena and the hybrid. Hybrids are intermediate between the parental species in body size, diagnostic morphological characters, monogyny frequency, size of nest population, nest diameter and infestation rate with epizootic fungi. The three entities respond differently to woodland fragmentation. Hybrids are significantly more abundant in forests with a coherent area <300 ha than in woodland above this size. Regions with high hybrid frequency in Germany—the Eastern Oberlausitz (23%) and the Baltic Sea islands Darss, Hiddensee and Rügen (28%)—are characterised by a fragmented woodland structure whereas regions with low hybrid frequency—Brandenburg and the lower Erzgebirge (3.4%)—have clearly larger and more coherent forest systems. Data from other European countries indicate habitat fragmentation to be a facilitating factor but no essential precondition for interspecific hybridisation in these ants. Hybrids are hypothesised to have selective advantage in fragmented systems because of combining the main reproductive and dispersal strategies of the parental species.  相似文献   

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