First record of <Emphasis Type="Italic">Spartina alterniflora</Emphasis> in southern Africa indicates adaptive potential of this saline grass

Spartina alterniflora was recorded in 2004 in the Great Brak Estuary, a system along the southern coast of South Africa that closes to the sea. This is alarming as this is a species with a known history as an aggressive invasive plant which has now been found 8000 km from its nearest known location and furthermore it is spreading under atypical conditions of submergence. This first recorded population in Africa indicates the adaptive potential of this invasive grass which survives inundation and non-tidal conditions for months at a time. Spartina alterniflora spread from 2566 m² in 2006 to a maximum area covered of 10,221 m² in 2011. There was an increase in silt, sediment organic matter and a significant reduction in sediment redox potential at sites invaded by S. alterniflora. When the estuary closes to the sea the water level rises and S. alterniflora is flooded, limiting opportunities for mechanical and chemical control. Application of a glyphosate-based herbicide in 2012 showed that chemical control was more effective in reducing the stands than mechanical removal. The additional use of imazapyr in 2014 significantly reduced stem density and the proportion of live stems. Spread of this invasive plant to the intertidal marshes in adjacent estuaries is a potential biodiversity threat although, fortunately, this population does not seem to produce viable seed. There is also the concern that hybridization with the resident S. maritima may occur. Important research and management questions remain i.e. how quickly will the natural marsh re-establish following eradication and how can we prevent movement of the grass to other estuaries?     

Fish assemblage structure in an estuary of the Atlantic Forest biodiversity hotspot (southern Brazil)

We described the fish assemblage in the estuary of the Guaraguaçu River (one of the largest tributaries of the Paranaguá Bay Estuary, located within Brazil’s Atlantic Forest Biosphere Reserve) from June 2005 to May 2006, and assessed the seasonal and spatial effects of abiotic environmental attributes on the fish assemblage structure. Despite some oscillations in salinity, the upper and lower estuaries had year-round persistent oligohaline and polyhaline conditions, respectively. Despite high species richness (55 species), the Guaraguaçu River Estuary fish community contains a few dominant taxa; 11% of the richness accounts for >60% of its density and biomass. The most abundant species (in terms of both biomass and density) was Atherinella brasiliensis. Species whose densities were most strongly associated with the upper estuary were Centropomus parallelus, Ctenogobius schufeldti, Eucinostomus melanopterus, Platanichthys platana, Trinectes paulistanus, and Eugerres brasilianus. Those whose densities were most strongly associated with the lower estuary were A. brasiliensis, Sphoeroides greeleyi, Eucinostomus argenteus, Sphoeroides testudineus, Diapterus rhombeus, and Harengula clupeola. Throughout the year, canonical correspondence analysis identified: (1) the pattern of horizontal stratification of salinity along the river as being the most important variable for explaining most of the fish fauna structure; and (2) a strong relationship between the fish fauna and the salinity gradient along the estuary. Analysis of similarity further confirmed that each estuarine zone supports a year-round persistent and relatively homogeneous fish species assemblage. Total mean density and biomass remained constant over time in each estuarine habitat, but density shifted in the most abundant species, which appears related to recruitment patterns. Such species and abundance persistence likely occurs because seasonal rainfall-induced changes in river discharge are not sufficient to significantly shift runoff and salinity and thus fish assemblage structure (species composition, density and biomass) along the estuary. Such a lack of seasonal fish fauna movement as a response to changes in river flow contrasts with other estuarine systems around the world.     

Incidence of <Emphasis Type="Italic">Fusarium</Emphasis> spp. on the invasive <Emphasis Type="Italic">Spartina alterniflora</Emphasis> on Chongming Island,Shanghai, China

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.     

Variability of <Emphasis Type="Italic">Mya arenaria</Emphasis> growth along an environmental gradient in the Plum Island Sound estuary,Massachusetts, USA

An understanding of the environmental factors that determine how clam growth varies in space and time improves effective mariculture and shellfish management. We examined the importance of temperature, salinity and chlorophyll-a in controlling the spatial pattern of Mya arenaria growth, the commercially important soft-shell clam, in the Plum Island Sound estuary in northeastern Massachusetts, USA. We collected clams (>5.08 cm) monthly during the April to November growing season from which we determined growth rate, maximum size (L-infinity), and time to reach a harvestable size. We also surveyed selected sites along the estuary to estimate the relationship between clam size and weight. We collected environmental data along the estuary, and our data were complemented with data collected and maintained by the Plum Island ecosystems long-term ecological research project. Clams reached harvestable size fastest and had the greatest L-infinity at the most oceanic site (Yacht Club) in the estuary. Clams had the smallest L-infinity and were slowest to reach the harvestable size at the least oceanic site (Railroad Meander). The spatial patterns of clam growth were best explained by a positive distribution of salinity. Salinity significantly accounted for 95 % of the spatial variation of clam growth in the estuary. Snow melt in spring increases freshwater input to the estuary and results in the lowest spring salinity during a year, and this explained the upper estuary limit of clam distribution. IPCC-projected climate change will cause sea-level rise and increasing precipitation in the northeastern USA, which will modify the spatial pattern of salinity in the region’s estuaries. Our research therefore suggests that future management of M. arenaria, an important economic resource for the local economy, should be concerned with the changes of salinity distribution under climate and land-use change.     

The Impacts of Above- and Belowground Plant Input on Soil Microbiota: Invasive <Emphasis Type="Italic">Spartina alterniflora</Emphasis> Versus Native <Emphasis Type="Italic">Phragmites australis</Emphasis>

Invasive plants affect soil food webs through various resource inputs including shoot litter, root litter and living root input. The net impact of invasive plants on soil biota has been recognized; however, the relative contributions of different resource input pathways have not been quantified. Through a 2 × 2 × 2 factorial field experiment, a pair of invasive and native plant species (Spartina alterniflora vs. Phragmites australis) was compared to determine the relative impacts of their living roots or shoots and root litter on soil microbial and nematode communities. Living root identity affected bacteria-to-fungi PLFA ratios, abundance of total nematodes, plant-feeding nematodes and omnivorous nematodes. Specifically, the plant-feeding nematodes were 627% less abundant when living roots of invasive S. alterniflora were present than those of native P. australis. Likewise, shoot and root biomass (within soil at 0–10 cm depth) of S. alterniflora was, respectively, 300 and 100% greater than those of P. australis. These findings support the enemy release hypothesis of plant invasion. Root litter identity affected other components of soil microbiota (that is, bacterial-feeding nematodes), which were 34% more abundant in the presence of root litter of P. australis than S. alterniflora. Overall, more variation associated with nematode community structure and function was explained by differences in living roots than root or shoot litter for this pair of plant species sharing a common habitat but contrasting invasion degrees. We conclude that belowground resource input is an important mechanism used by invasive plants to affect ecosystem structure and function.     

Co-feeding as a route for transmission of <Emphasis Type="Italic">Rickettsia conorii israelensis</Emphasis> between <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> ticks

The essential oil from Amyris balsamifera (Rutaceae) and elemol, a principal constituent of the essential oil of Osage orange, Maclura pomifera (Moraceae) were evaluated in in vitro and in vivo laboratory bioassays for repellent activity against host-seeking nymphs of the blacklegged tick, Ixodes scapularis, and the lone star tick, Amblyomma americanum. Both bioassays took advantage of the tendency of these host-seeking ticks to climb slender vertical surfaces. In one bioassay, the central portion of a vertical strip of filter paper was treated with test solution and ticks placed or allowed to crawl onto the untreated lower portion. In the other bioassay, a strip of organdy cloth treated with test solution was doubly wrapped (treatment on outer layer) around the middle phalanx of a forefinger and ticks released on the fingertip. Both amyris oil and elemol were repellent to both species of ticks. Elemol did not differ significantly in effectiveness against A. americanum from the widely used repellent deet. At 2 and 4 h after application to filter paper, 827 μg amyris oil/cm² paper repelled 80 and 55%, respectively, of A. americanum nymphs. Ixodes scapularis was repelled by lower concentrations of amyris oil and elemol than A. americanum.     

Fish larval supply to and within a lagoonal estuary: multiple sources for Barnegat Bay,New Jersey

We evaluated spatial variation in fish larval supply to a temperate, lagoon type estuary (Barnegat Bay, New Jersey) by determining species composition, size, and stage into inlets (n = 2), thoroughfares between adjacent estuaries (n = 3), and within the estuary (n = 4) in seasonal, synoptic sampling on night time flood tides during 2010–2014. Larval supply, as sampled with identical plankton nets (1 m diameter, 1 mm mesh) was dominated by post-flexion stage individuals (most 5–10 but reaching 70+ mm) from species spawned in the Atlantic Ocean from a variety of sources (e.g., Sargasso Sea, outer and inner continental shelf) and in the bay. While abundance for individual species varied among locations and years, in general, the larval composition was similar across inlets, thoroughfares, and within the bay within the same seasons. Homogenization across locations was likely the result of the tidal exchanges between the ocean, the estuary, and the adjacent locations. These exchanges provide numerous, redundant sources of larvae to this estuarine nursery. The similarity in larval supply among inlets, thoroughfares, and within the estuary indicates that the longer term study location behind Little Egg Inlet is representative for this, and probably other, estuaries along the New Jersey shore.     

Temporal and spatial impact of <Emphasis Type="Italic">Spartina alterniflora</Emphasis> invasion on methanogens community in Chongming Island,China

Methane production by methanogens in wetland is recognized as a significant contributor to global warming. Spartina alterniflora (S. alterniflora), which is an invasion plant in China’s wetland, was reported to have enormous effects on methane production. But studies on shifts in the methanogen community in response to S. alterniflora invasion at temporal and spatial scales in the initial invasion years are rare. Sediments derived from the invasive species S. alterniflora and the native species Phragmites australis (P. australis) in pairwise sites and an invasion chronosequence patch (4 years) were analyzed to investigate the abundance and community structure of methanogens using quantitative real-time PCR (qPCR) and Denaturing gradient gel electrophoresis (DGGE) cloning of the methyl-coenzyme M reductase A (mcrA) gene. For the pairwise sites, the abundance of methanogens in S. alterniflora soils was lower than that of P. australis soils. For the chronosequence patch, the abundance and diversity of methanogens was highest in the soil subjected to two years invasion, in which we detected some rare groups including Methanocellales and Methanococcales. These results indicated a priming effect at the initial invasion stages of S. alterniflora for microorganisms in the soil, which was also supported by the diverse root exudates. The shifts of methanogen communities after S. alterniflora invasion were due to changes in pH, salinity and sulfate. The results indicate that root exudates from S. alterniflora have a priming effect on methanogens in the initial years after invasion, and the predominate methylotrophic groups (Methanosarcinales) may adapt to the availability of diverse substrates and reflects the potential for high methane production after invasion by S. alterniflora.     

Interactions between the grass shrimp <Emphasis Type="Italic">Palaemonetes pugio</Emphasis> and the salt marsh grasses <Emphasis Type="Italic">Phragmites australis</Emphasis> and <Emphasis Type="Italic">Spartina alterniflora</Emphasis>

The grass shrimp Palaemonetes pugio, a species common to Spartina alterniflora-dominated marshes, may be sensitive to the invasion of the common reed Phragmites australis in northeastern US salt marshes. We examined two questions: (1) Do grass shrimp have a preference for the native plant over the non-native plant? (2) Are grass shrimp more effective foragers on P. australis? We tested the first hypothesis by comparing the amount of time shrimp spend in physical contact with the plant types over a 1-h period. Shrimp were observed under different arrangements of vegetation to control for differences in conspicuous structural features. Additionally, the amount of time shrimp spent foraging on S. alterniflora and P. australis shoots was compared to determine if shrimp graze more often on S. alterniflora. Shrimp spent significantly more time in contact with S. alterniflora only when plant types were grouped at opposite ends of aquaria, but did not exhibit a foraging preference for this plant type. To address our second question, we investigated the effects of shrimp foraging on stem epifauna, an assemblage of semi-aquatic invertebrates associated with macrophyte shoots. Previous research showed that P. australis supports a lower density of stem-dwelling epifauna relative to S. alterniflora. We hypothesized that the primary grazer of this community, P. pugio, can forage on P. australis stems more effectively due to structural differences between the two plants, causing the lower abundance of epifauna through top-down effects. We exposed individual shoots inhabited by epifauna to shrimp and compared faunal densities on exposed shoots to densities on control shoots after 18 h. The reduction of epifauna by predation was proportional on the two plant types. Therefore, top-down effects can be ruled out as an explanation for the patchy distribution of epifauna observed in P. australis–S. alterniflora marshes.     

Fish production in estuaries of Primorye

Production of fish communities in 15 different-types estuaries was assessed based on the data collected as a result of 90 surveys (860 seine stations) conducted in Primorye in 2002–2015. The main contribution to production was made by semi-anadromous species (the so-iuy mullet Liza haematocheilus, Far Eastern redfins Tribolodon spp., and Japanese smelt Hypomesus nipponensis, etc.). In both external (EP _ext) and internal (EP _int) polyhaline estuaries (EP) a substantial portion of the production was provided by resident marine species (mainly by the saffron cod Eleginus gracilis, Far Eastern smooth flounder Liopsetta pinnifasciata, and tidepool gunnel Pholis nebulosa) and southern immigrants (flathead grey mullet Mugil cephalus, dotted gizzard shad Konosirus punctatus, Japanese halfbeak Hyporhamphus sajori, and Pacific needlefish Strongylura anastomella). In mesohaline (EM) and oligohaline (EO) estuaries, the proportion of marine residents and southern immigrants was reduced to a minimum, while that of freshwater species (bighead gudgeon Gobio macrocephalus, Prussian carp Carassius gibelio, minnow Phoxinus spp., Amur bitterling Rhodeus sericeus, spiny bitterlings Acanthorhodeus spp., etc.) substantially added to the production of semi-anadromous fish. The mean fish biomass for the vegetation season varied in the 143–1463 mgC/m² range; the mean annual production was 174–4267 mgC/m² and the mean P/B ratio was 0.2–3.2. In 2007, the high annual production in the Artemovka River estuary, 9356 mgC/m², was formed by the juvenile so-iuy mullet of the strong yearclass that hatched in 2006. The lowest mean production and P/B values were typical mainly for the water bodies with a salinity more often close to that of the barrier zones (5–8‰ for α-horohalinicum and 22–26‰ for β-horohalinicum), i.e., for EM and EP _ext. This relationship is explained by the features of the osmotic regulation in fish of various origins and its ontogenetic variations. In particularly, the salinity in EM is more frequently close to the critical salinity (5–8‰, α-horohalinicum); thus, the proportion of juveniles of most of the species in the catches decreases (as their resistance to salinity variations is lower). This results in higher mean values of the specific and absolute production of fish communities in EP _int and EO as compared to those in EM. The conclusion was made that the estimates of fish production in the estuaries of Primorye are similar to those in the well-studied estuaries of the temperate, subtropical, and tropical zones. Moreover, they are comparable to the fish production estimates for mesotrophic and eutrophic lakes in northwestern Russia, substantially lower than those for large lowland rivers, and higher than those for small rivers. The fish production in seas, including the Japan/East Sea (0.20 gC/m²) and, particularly, Peter the Great Bay (0.28 gC/m²), is mostly lower than that in Primorye estuaries.     

Abiotic and biotic factors influence the habitat use of four species of <Emphasis Type="Italic">Gymnogobius</Emphasis> (Gobiidae) in riverine estuaries in the Seto Inland Sea

Gobies that are phylogenetically related or coexist in the same marine and estuarine systems often exhibit abiotic and/or biotic habitat segregation. Thus, it is possible that species of Gymnogobius inhabiting the same riverine estuaries also exhibit abiotic and/or biotic habitat segregation. The goal of this study was to determine the differences in abiotic and biotic habitat use between these species by sampling goby and host shrimps, and by examining the physical environments of the rivers where these species are found. The surveys of goby and host shrimps were conducted in the estuaries of the Saba and Ibo rivers, which drain into the Seto Inland Sea, a body of water that separates three of the four main islands of Japan. We used hand nets and shovels to collect goby and host shrimps, and measured median sediment particle size, elevation, and salinity at each site. Generalized linear models (GLMs) were used to assess the preferences in abiotic and biotic habitat use by the goby species. Median particle size, salinity, and elevation were used as the abiotic environmental predictors, whereas the presence/absence of host shrimps were re-organized into four categories consisting of “Upogebia major” only, “Nihonotrypaea japonica” only, “Upogebia major & Nihonotrypaea japonica,” and “Upogebia yokoyai,” which were used as the biotic environmental predictors. The GLMs demonstrated that median particle size had the largest influence of the abiotic variables, with goby species segregating according to differences in sediments; moreover, there was some evidence suggesting that the host and symbiont do not always correlate at the species level. Our results indicated that although there is some overlap in abiotic and biotic habitat use among the four species of Gymnogobius, the differences were broad enough to provide an explanatory mechanism as to how these species can coexist in the same river systems.     

Crustacean metamorphosis: an omics perspective

We quantified the independent impacts of flooding salinity, flooding depth, and flooding frequency on the native species, Phragmites australis and Scirpus mariqueter, and on the invasive species Spartina alterniflora in the Yangtze River Estuary, China. Total biomass of all three species decreased significantly with increasing salinity, but S. alterniflora was less severely affected than P. australis and S. mariqueter. Elevated flooding depth significantly decreased their live aboveground biomass of P. australis and S. mariqueter, while S. alterniflora still had high live aboveground biomass and total biomass even at the highest flooding depth. These findings indicated that S. alterniflora was more tolerant to experimental conditions than the two native species, and an unavoidable suggestion is the expansion of this non-native species in relation to the native counterparts in future scenarios of increased sea-level and saltwater intrusion. Even so, environmental stresses might lead to significant decreases in total biomass and live aboveground biomass of all three species, which would potentially weaken their ability to trap sediments and accumulate organic matter. However, the relatively high belowground-to-aboveground biomass ratio indicated phenotypic plasticity in response to stressful environmental conditions, which suggest that marsh species can adapt to sea-level rise and maintain marsh elevation.     

The interactive effects of created salt marsh substrate type,hydrology, and nutrient regime on <Emphasis Type="Italic">Spartina alterniflora</Emphasis> and <Emphasis Type="Italic">Avicennia germinans</Emphasis> productivity and soil development

Recent salt marsh and barrier island restoration efforts in the northern Gulf of Mexico have focused on optimizing self-sustaining attributes of restored marshes to provide maximum habitat value and storm protection to vulnerable coastal communities. Salt marshes in this region are dominated by Spartina alterniflora and Avicennia germinans, two species that are valued for their ability to stabilize soils in intertidal salt marshes. We conducted a controlled greenhouse study to investigate the influences of substrate type, nutrient level, and marsh elevation on the growth and biomass allocation of S. alterniflora and A. germinans, and the consequent effects on soil development and stability. S. alterniflora exhibited optimal growth and survival at the lowest elevation (? 15 cm below the water surface) and was sensitive to high soil salinities at higher elevations (+ 15 cm above the water surface). A. germinans performed best at intermediate elevations but was negatively affected by prolonged inundation at lower elevations. We found that although there was not a strong effect of substrate type on plant growth, the development of stressful conditions due to the use of suboptimal materials would likely be exacerbated by placing the soil at extreme elevations. Soil shear strength was significantly higher in experimental units containing either S. alterniflora or A. germinans compared to unvegetated soils, suggesting that plants effectively contribute to soil strength in newly placed soils of restored marshes. As marsh vegetation plays a critical role in stabilizing shorelines, salt marsh restoration efforts in the northern Gulf of Mexico and other storm impacted coasts should be designed at optimal elevations to facilitate the establishment and growth of key marsh species.     

Ectopic Expression of Plant RNA Chaperone Offering Multiple Stress Tolerance in <Emphasis Type="Italic">E. coli</Emphasis>

Members of the plant glycine-rich RNA-binding proteins (GR-RBPs) family have been reported in flowering, development, circadian rhythms, biotic and abiotic stresses. Particularly, GR-RBPs are reported to function as RNA chaperones, promoting growth and acclimation during cold shock. It is indispensable to further question the efficacy and mechanism of GR-RBPs under various environmental strains. Monitoring the expression of stress-regulated proteins under stress conditions has been a beneficial strategy to study their functional roles. In an effort to elucidate the NtGR-RBP1 function, stress markers such as salinity, drought, low temperature and heat stresses were studied. The NtGR-RBP1 gene was expressed in E. coli followed by the exposure to stress conditions. Recombinant E. coli expressing NtGR-RBP1 were more tolerant to stresses, e.g., salinity, drought, cold and heat shock. Recombinants exhibited higher growth rates compared to control in spot assays. The tolerance was further confirmed by monitoring the growth in liquid culture assays. Cells expressing NtGR-RBP1 under salt (500 mM NaCl), drought (20% PEG), cold (4 and 20 °C) and heat stresses (50 °C) had enhanced growing ability and better endurance. Our study supports the notion that the protective role of NtGR-RBP1 may contribute to growth and survival during diverse environmental stresses.     

The effect of gradual increase in salinity on the biomass productivity and biochemical composition of several marine,halotolerant<Emphasis Type="Bold">,</Emphasis> and halophilic microalgae

Open ponds are the preferred cultivation system for large-scale microalgal biomass production. To be more sustainable, commercial scale biomass production should rely on seawater, as freshwater is a limiting resource, especially in places with high irradiance. If seawater is used for both pond fill and evaporative volume makeup, salinity of the growth media will rise over time. It is not possible for any species to achieve optimum growth over the whole saline spectrum (from seawater salinity level up to salt saturation state). In this study, we investigated the effects of gradual salinity increase (between 35 and 233 ppt) on biomass productivity and biochemical composition (lipid and carbohydrate) of six marine, two halotolerant, and a halophilic microalgae. A gradual and slow stepped salinity increase was found to expand the salinity tolerance range of tested species. A gradual reduction in biomass productivity and maximum photochemical efficiency was observed as a consequence of increased salinity in all tested species. Among the marine microalgae, Tetraselmis showed highest biomass productivity (32 mg L^?1 day^?1) with widest salinity tolerance range (35 to 109 ppt). Halotolerant Amphora and Navicula were able to grow from 35 ppt to 129 ppt salinity. Halophilic Dunaliella was the only species capable of growing between 35 and 233 ppt and showed highest lipid content (56.2%) among all tested species. This study showed that it should be possible to maintain high biomass in open outdoor cultivation utilizing seawater by growing Tetraselmis, Amphora, and Dunaliella one after another as salinity increases in the cultivation system.     

Persistence,dispersal and genetic evolution of recently formed <Emphasis Type="Italic">Spartina</Emphasis> homoploid hybrids and allopolyploids in Southern England

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.