Evaluation and comparison of the genetic structure of <Emphasis Type="Italic">Bunias orientalis</Emphasis> populations in their native range and two non-native ranges

We studied the invasive warty cabbage Bunias orientalis (Brassicaceae) in three geographically distinct areas. Using inter-simple sequence repeat fingerprinting, we analyzed warty cabbages, including non-native populations, from the eastern Baltic and western Siberian regions and native populations from southwestern Russia. The eastern Baltic region and western Siberia represent the two opposite directions of B. orientalis spread in climatically different zones. The genetic structures of the native and non-native B. orientalis populations were assessed through analysis of molecular variance (AMOVA) and the Bayesian clustering method and by determining the main measures of genetic diversity. AMOVA revealed considerable population differentiation in both the native and invasive ranges. Our results did not indicate a decrease in genetic diversity in the non-native populations of B. orientalis. Similar measures of genetic diversity and genetic structure were determined in the invasive populations in two geographically and ecologically distinct, non-native regions located in Europe and Asia. In both of these regions, higher genetic diversity was detected in the non-native populations than in the native region populations, which may be due to multiple introductions. However, Bayesian clustering analysis revealed slightly different sources of invasive populations in the two non-native regions. Genetic diversity patterns revealed the lack of isolation by distance between populations and confirmed the influence of anthropogenic factors on the spread of B. orientalis. The significance of native populations as germplasm resources for breeding is discussed.     

Trophic consequences of non-native pumpkinseed <Emphasis Type="Italic">Lepomis gibbosus</Emphasis> for native pond fishes

Introduced non-native fishes can cause considerable adverse impacts on freshwater ecosystems. The pumpkinseed Lepomis gibbosus, a North American centrarchid, is one of the most widely distributed non-native fishes in Europe, having established self-sustaining populations in at least 28 countries, including the U.K. where it is predicted to become invasive under warmer climate conditions. To predict the consequences of increased invasiveness, a field experiment was completed over a summer period using a Control comprising of an assemblage of native fishes of known starting abundance and a Treatment using the same assemblage but with elevated L. gibbosus densities. The trophic consequences of L. gibbosus invasion were assessed with stable isotope analysis and associated metrics including the isotopic niche, measured as standard ellipse area. The isotopic niches of native gudgeon Gobio gobio and roach Rutilus rutilus overlapped substantially with that of non-native L. gibbosus, and were also substantially reduced in size compared to ponds where L. gibbosus were absent. This suggests these native fishes shifted to a more specialized diet in L. gibbosus presence. Both of these native fishes also demonstrated a concomitant and significant reduction in their trophic position in L. gibbosus presence, with a significant decrease also evident in the somatic growth rate and body condition of G. gobio. Thus, there were marked changes detected in the isotopic ecology and growth rates of the native fish in the presence of non-native L. gibbosus. The implications of these results for present and future invaded pond communities are discussed.     

Reconciling the biogeography of an invader through recent and historic genetic patterns: the case of topmouth gudgeon <Emphasis Type="Italic">Pseudorasbora parva</Emphasis>

The genetic variability and population structure of introduced species in their native range are potentially important determinants of their invasion success, yet data on native populations are often poorly represented in relevant studies. Consequently, to determine the contribution of genetic structuring in the native range of topmouth gudgeon Pseudorasbora parva to their high invasion success in Europe, we used a dataset comprising of 19 native and 11 non-native populations. A total of 666 samples were analysed at 9 polymorphic microsatellite loci and sequenced for 597 bp of mitochondrial DNA. The analysis revealed three distinct lineages in the native range, of which two haplogroups were prevalent in China (100%), with a general split around the Qinling Mountains. Dating of both haplogroups closely matched past geological events. More recently, its distribution has been influenced by fish movements in aquaculture, resulting in gene flow between previously separated populations in Northern and Southern China. Their phylogeography in Europe indicate as few as two introductions events and two dispersal routes. Microsatellite data revealed native populations had higher genetic diversity than those in the invasive range, a contrast to previous studies on P. parva. This study confirms the importance of extensive sampling in both the native and non-native range of invasive species in evaluating the influence of genetic variability on invasion success.     

Drivers of Central European urban land snail faunas: the role of climate and local species pool in the representation of native and non-native species

The importance of macroclimate and dispersal limitation in the broad-scale variation of European urban land snail assemblages is likely to differ between native and non-native species because of the southern origin of many non-native snails, often spread by humans. We sampled land snails in each of 32 European cities and compiled from the literature a list of land snail species reported from the surroundings of each city. To quantify the predictive power of climate and local species pools, beta-sim dissimilarity matrices of both native and non-native species were explored using MDS and RDA ordination methods, Mantel tests with bootstrapping of each dataset, and multivariate homogeneity analysis of group variances. We observed no significant relation between the numbers of non-native species found in the cities and their surroundings (p > 0.133), while the percentage of native species in the cities derived from their local species pools decreased significantly with the increasing species richness of local faunas (r_S = ?0.75, p < 0.001). Assemblage variation of urban native species was explained mostly by the difference between mean January and July temperatures (21.3 %), with the major role of July temperature (18.0 %). In contrast, variation of non-native species assemblages was mainly explained by January temperature (19.9 %). The congruence in faunal similarities between the cities and the surrounding areas was higher in native (r = 0.46, p < 0.001) than in non-native species (r = 0.36, p < 0.001). Overall native faunas were significantly more homogeneous than the non-native faunas. Our results suggest that recent climate warming may foster geographical expansions of many non-native land snail species as their distributions are controlled mainly by January temperature.     

Genetic diversity and structure of the globally invasive tree, <Emphasis Type="Italic">Paraserianthes lophantha</Emphasis> subspecies <Emphasis Type="Italic">lophantha</Emphasis>, suggest an introduction history characterised by varying propagule pressure

An emerging insight in invasion biology is that intra-specific genetic variation, human usage, and introduction histories interact to shape genetic diversity and its distribution in populations of invasive species. We explore these aspects for the tree species Paraserianthes lophantha subsp. lophantha, a close relative of Australian wattles (genus Acacia). This species is native to Western Australia and is invasive in a number of regions globally. Using microsatellite genotype and DNA sequencing data, we show that native Western Australian populations of P. lophantha subsp. lophantha are geographically structured and are more diverse than introduced populations in Australia (New South Wales, South Australia, and Victoria), the Hawaiian Islands, Portugal, and South Africa. Introduced populations varied greatly in the amount of genetic diversity contained within them, from being low (e.g. Portugal) to high (e.g. Maui, Hawaiian Islands). Irrespective of provenance (native or introduced), all populations appeared to be highly inbred (F _IS ranging from 0.55 to 0.8), probably due to selfing. Although introduced populations generally had lower genetic diversity than native populations, Bayesian clustering of microsatellites and phylogenetic diversity indicated that introduced populations comprise a diverse array of genotypes, most of which were also identified in Western Australia. The dissimilarity in the distribution and number of genotypes in introduced regions suggests that non-native populations originated from different native sources and that introduction events differed in propagule pressure.     

PhragNet: crowdsourcing to investigate ecology and management of invasive <Emphasis Type="Italic">Phragmites australis</Emphasis> (common reed) in North America

Invasion biology research, often performed by scientists at relatively small spatial scales, provides experimental precision but may be limited in generalizability. Conversely, large-scale invasive species management represents a largely untapped wealth of information on invasion ecology and management, but such data are difficult to capture and synthesize. We developed a network (“PhragNet”) of individuals managing wetlands occupied by native and non-native lineages of the invasive wetland grass Phragmites australis (common reed). This network collected environmental and genetic samples, habitat data, and management information to identify environmental and plant community associations of Phragmites invasion and patterns of management responses. Fifty managers overseeing 209 Phragmites stands in 16 US states and ON, Canada participated. Participants represented federal agencies (26%), municipalities (20%), NGOs (20%), academia (14%), state agencies (12%), and private landowners (8%). Relative to the native lineage, non-native Phragmites occurred in areas with higher nitrate/nitrite and ammonium than non-native Phragmites. Stand interiors had higher soil electrical conductivity than nearby uninvaded areas, consistent with use of road salt promoting spread of Phragmites. Non-native Phragmites co-occurred with fewer plant species than native Phragmites and was actively targeted for management. Herbicide was applied to 51% of non-native stands; surprisingly, 11% of native stands were also treated with herbicide. This project demonstrates the utility of crowdsourcing standardized data from resource managers. We conclude by describing how this approach could be expanded into an adaptive management framework, strengthening connections between wetland management and research.     

Morphometry of non-native black bullhead <Emphasis Type="Italic">Ameiurus melas</Emphasis> from Slovakia

The study on the external morphology of the non-native black bullhead (Ameiurus melas) was carried out on a population from Slovakia, based on triple regression and geometrical analysis. The breakpoints distribution in distance-based morphometric characters indicated that black bullhead reached its definitive phenotype early in ontogeny. Ontogenetic changes in external morphology occurred continuously throughout the whole size-range of the sample examined, and inter-individual morphological variation was very low. Such uniformity may reflect the possible founder effect and/or little phenotypic plasticity of this non-native population. No sexual dimorphism was observed. This is the first detailed study on external morphology of the species, and as such it contributes to the assessment of phenotypic plasticity and/or overall morphological variability of black bullhead’s invasive populations.     

Non-native aquatic animals introductions have driven disease emergence in Europe

In this paper it is argued, using examples of disease emergence in aquatic animals in Europe, that the introduction of non-native species drives disease emergence by both extending the geographic range of parasites and pathogens and facilitating host-switching. Enteric red mouth disease and infectious haematopoietic necrosis of salmonids have extended their geographic range from North America to Europe with the import of live fish (Pimephales promelas) and rainbow trout eggs, respectively. Host-switching results in disease emergence when previously unidentified commensal organisms or known pathogen switch to new naïve hosts. The most serious endemic diseases of wild aquatic animals in Europe in recent years can be traced to the introduction of non-native species. Across Europe dramatic populations declines have occurred in native crayfish (e.g. Astacus astacus), oysters (Ostrea edulis) and eels (Anguilla anguilla), all which can be attributed, in varying degrees, to diseases (crayfish plague, Bonamia ostreae and Anguillicoloides crassus, respectively) introduced with non-native species. The severe adverse effects at a population level can be attributed to the lack of immunity in the new hosts. The impact of parasites more recently introduced to Europe, Sphaerothecum destruens (the rosette agent), and Batrachochytrium dendrobatidis, have yet to be fully determined. Both are generalists, with wide host ranges, and may present serious threats to native species. Aquaculture is the key driver for the introduction of non-native species. Most farming systems allow pathogen exchange between farmed and wild populations which underpins host-switching. Subsequently movements of animals between farms may result in the spread of newly emerged diseases. The introduction of non-native aquatic animals drives disease emergence, thus the ex-ante assessment of these hazards is severely limited. Generic risk mitigation measures (e.g. movement of disinfected eggs in place of live animals) and improved methods for rapid detection of new diseases are vital.     

Establishment of <Emphasis Type="Italic">Anolis sagrei</Emphasis> on Bermuda represents a novel ecological threat to Critically Endangered Bermuda skinks (<Emphasis Type="Italic">Plestiodon longirostris</Emphasis>)

Bermuda is an isolated, oceanic island with only one endemic terrestrial vertebrate, the Critically Endangered Bermuda skink (Plestiodon longirostris; Squamata, Scincidae). Major declines in P. longirostris populations have been caused primarily by habitat loss and mortality via invasive species (e.g., predation from birds and cats) and human waste products (e.g., trapped in discarded bottles). However, biotic interactions and interspecific competition with invasive lizards have also been identified as potentially detrimental to P. longisrostris populations. Here, we provide the first occurrence records of a highly invasive lizard, the Cuban brown anole (Anolis sagrei), on Bermuda. We assess the brown anole’s diet, habitat use, morphology, and island-wide distribution for comparison to the native skink, P. longirostris. Results of this study indicate that A. sagrei in Bermuda are highly terrestrial (>60% of all lizards observed on the ground vs. in trees) and forage primarily on terrestrial invertebrates. These data indicate substantial ecological overlap with the exclusively-terrestrial P. longirostris. This is in contrast to the other established non-native lizards on Bermuda, which are principally arboreal and have successfully coexisted with P. longirostris for >60 years. At present, the geographic distributions of A. sagrei and P. longirostris do not overlap. However, all extant skink populations are within several kilometers of brown anole populations (with the nearest being <0.5 km). The extensive overlap in ecological niche between the Bermuda skink and the invasive brown anole will likely present a serious conservation threat if contact is made. This study is exceptional in providing clear in situ ecological data which predict a conservation threat of an established invasive species to a Critically Endangered island endemic prior to coexistence. Continued monitoring of this situation as P. longirostris and A. sagrei inevitably come into contact will allow these a priori hypotheses of conservation risk via ecological overlap to be tested.     

The widespread and overlooked replacement of <Emphasis Type="Italic">Spartina maritima</Emphasis> by non-indigenous <Emphasis Type="Italic">S. anglica</Emphasis> and <Emphasis Type="Italic">S. townsendii</Emphasis> in north-western Adriatic saltmarshes

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.     

Anthropogenic signature in the incidence and distribution of an emerging pathogen of poplars

The introduction and establishment of non-native plant pathogens into new areas can result in severe outbreaks. Septoria leaf spot and canker caused by Sphaerulina musiva is one of the most damaging poplar diseases in northeastern and north-central North America. Stem and branch cankers can be devastating on susceptible trees, leading to tree death and reduced biomass in commercial plantations. In the Pacific Northwest region of North America, the first report of the disease was made in 2006 in the Fraser Valley of British Columbia (BC), Canada. To investigate the incidence and distribution of S. musiva from its point of introduction into BC, five plantations of Populus trichocarpa (black cottonwood), 500 P. trichocarpa trees from natural populations, and 23 plantations of hybrid poplars were surveyed by using real-time PCR assays targeting S. musiva and its native sister species, S. populicola. Our survey suggests a strong anthropogenic signature to the emergence of the non-native S. musiva. Detection frequency of S. musiva was high in hybrid poplar plantations (116 trees infected, 54.2 % of the sampled trees), while detection of the native S. populicola was limited to 13.1 % (22 trees infected). By contrast, in natural stands of P. trichocarpa, less than 2 % of the trees were positive for S. musiva (7 trees) while ~75 % were positive for S. populicola (433 trees). All the S. musiva detections in natural stands of the native P. trichocarpa were from trees located in the vicinity (<2.5 km) of hybrid poplar plantations. Identification of the genotypes found in the hybrid poplar plantations revealed that they are in majority F1 progeny from P. trichocarpa × P. deltoides (T × D) (82 %) and P. nigra × P. maximowiczii (N × M) (7.8 %) crosses, which are generally susceptible (intermediate level of susceptibility between the two parental species) to the canker disease. Our results suggest that the emergence of S. musiva in BC is related to the planting of susceptible hybrid poplars. Even if the disease has not yet established itself in natural poplar populations outside of the Fraser Valley, infected plantations could act as a reservoir that could promote its spread into nearby native P. trichocarpa populations.     

Mycorrhizal detection of native and non-native truffles in a historic arboretum and the discovery of a new North American species, <Emphasis Type="Italic">Tuber arnoldianum</Emphasis> sp. nov.

During a study comparing the ectomycorrhizal root communities in a native forest with those at the Arnold Arboretum in Massachusetts (USA), the European species Tuber borchii was detected on the roots of a native red oak in the arboretum over two successive years. Since T. borchii is an economically important edible truffle native to Europe, we conducted a search of other roots in the arboretum to determine the extent of colonization. We also wanted to determine whether other non-native Tuber species had been inadvertently introduced into this 140-year-old Arboretum because many trees were imported into the site with intact soil and roots prior to the 1921 USDA ban on these horticultural practices in the USA. While T. borchii was not found on other trees, seven other native and exotic Tuber species were detected. Among the North American Tuber species detected from ectomycorrhizae, we also collected ascomata of a previously unknown species described here as Tuber arnoldianum. This new species was found colonizing both native and non-native tree roots. Other ectomycorrhizal taxa that were detected included basidiomycetes in the genera Amanita, Russula, Tomentella, and ascomycetes belonging to Pachyphlodes, Helvella, Genea, and Trichophaea. We clarify the phylogenetic relationships of each of the Tuber species detected in this study, and we discuss their distribution on both native and non-native host trees.     

Biogeographic differences between native and non-native populations of crayfish alter species coexistence and trophic interactions in mesocosms

Biogeographical comparisons of native and non-native populations allow researchers to understand the degree to which traits contributing to invasion success are intrinsic or change during the invasion process. Here, we investigate whether traits underlying interspecific competition change following invasion and whether these alter the impacts of two crayfish congeners that have invaded into each other’s native ranges. Specifically, we compared native and non-native populations of rusty (Faxonius rusticus) and virile crayfish (F. virilis). We compared native and non-native populations of each species using laboratory assays to examine aggression and large mesocosms with the congeners in sympatry to examine growth and survival as well as impacts on lower trophic levels. We found that non-native virile crayfish were more aggressive in response to a threat than native virile crayfish and exhibited greater growth and survival in sympatry with rusty crayfish. These intraspecific differences were large enough to alter coexistence between species in the mesocosm experiment, which is consistent with patterns of coexistence between these species in the field. We did not observe differences in traits between native and non-native rusty crayfish, but rusty crayfish were consistently competitively dominant over virile crayfish in paired laboratory assays. Non-native populations of both species had greater impacts on lower trophic levels than native populations. Taken together, these findings provide new evidence that trait changes during invasions may enhance ecological impacts of invasive animals and their ability to compete with closely related native species.     

Competition between native Antarctic vascular plants and invasive <Emphasis Type="Italic">Poa annua</Emphasis> changes with temperature and soil nitrogen availability

Over the last decades human have introduced non-native organisms to Antarctica, including the grass species Poa annua. This non-native grass under constant growth temperatures has been shown negatively affect the growth of the only two native Antarctic vascular plants, Deschampsia antarctica and Colobanthus quitensis, under constant growth temperatures. However, whether there are changes in the interaction between these species under warmer conditions is an important question. In cold ecosystems, soil nutrient status directly affects plant responses to increases in temperature and Antarctic soils are highly variable in nutrient supply. Thus, in this study we experimentally assessed the interaction between the non-native Poa with the two native Antarctic vascular plant species at two different temperatures and levels of nutrient availability. Individual mats of the study species were collected in King George Island, and then transported to Concepcion where we conducted competition experiments. In the first experiment we used soil similar to that of Antarctica and plants in competition were grown at two temperatures: 5°/2° and 11°/5 °C (day/night temperature). In a second experiment plants were grown in these two temperature regimes, but we varied nitrogen (N) availability by irrigating plants with Hoagland solutions that contained 8000 or 300 µM of N. Overall, Poa exerted a competitive effect on Deschampsia but only at the higher temperature and higher N availability. At 5°/11 °C the competitive response of Deschampsia to Poa was of similar magnitude to the competitive effect of P. Deschampsia, and the competitive effect was greater with at low N. The competitive effect of Poa was similar to the competitive response of Colobanthus to Poa at both temperatures and N levels. Thus, at low temperatures and N soil content the native Antarctic species might withstand Poa invasion, but this might change with climate warming.     

Effects of the density of the invasive macrophyte <Emphasis Type="Italic">Hydrilla verticillata</Emphasis> and root competition on growth of one native macrophyte in different sediment fertilities

The occurrence of non-native species at high densities may generate competition for resources and possibly exclude native species in various environments. We evaluated the effects of increased densities of the non-native invasive macrophyte Hydrilla verticillata on the growth of the native species Egeria najas in different sediment types and with only root interactions or root?+?shoot interactions. We tested the hypothesis that the effect of the invasive on the native species is density dependent and that it is greater when competition for light and nutrients occurs (root?+?shoot interactions). The results of these experiments demonstrated that increased density of the invasive species H. verticillata significantly decreased the growth of the native species independent of sediment type (sand or mud sediments). When plants competed for water and sediment resources (root?+?shoot interactions), the native species was more impacted by the invasive than when they competed only for water resources (only shoots interacting). Our results show that E. najas is probably unable to colonize sites highly colonized by hydrilla, and this applies to both sand and mud sediments. This outcome suggests that H. verticillata is a threat for E. najas and likely other native submerged species in South America.     

Effects of Probiotics on Survival,Growth and Digestive Enzymes Activities in Freshwater Prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> (De Man 1879)

A study was conducted to examine the effects of three probiotics, Lactobacillus sporogenes, Bacillus subtilis and Saccharomyces cerevisiae on the survival, growth and digestive enzymes activities of the freshwater prawn Macrobrachium rosenbergii post larvae (PL). The probiotics, L. sporogenes (4 %), B. subtilis (3 %) and S. cerevisiae (4 %) were taken and mixed with basal diet. Diet without probiotics served as control. These probiotics diets were fed to M. rosenbergii PL for a period of 60 days. After the feeding trail, the growth parameters such as survival, weight gain, specific growth rate and protein efficiency rate were found to be significantly (P < 0.05) higher in 4 % S. cerevisiae incorporated diet fed PL when compared with control. In the case of feed conversion rate just the reverse was seen (P < 0.05) at this concentration. This indicates its superior quality among different concentrations of probiotics tested. Activities of digestive enzymes, such as protease, amylase and lipase were significantly (P < 0.05) higher at this concentration (4 % S. cerevisiae). Some of essential and non-essential amino acids also significantly elevated in probiotics supplemented diet fed prawns. This study indicated that probiotics, S. cerevisiae incorporated diets were beneficial for M. rosenbergii in terms of increasing growth, enzyme and amino acid production.     

Competition among river planktivores: are native planktivores still fewer and skinnier in response to the Silver Carp invasion?

Planktivorous Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis have successfully invaded much of the Upper Mississippi River System and its tributaries during the last 30 years. During the initial years of the invasion, concurrent declines in the body condition and the catch per unit effort (CPUE) of planktivorous Gizzard Shad Dorosoma cepedianum and Bigmouth Buffalo Ictiobus cyprinellus were attributed to competition with Asian carp. Using an additional seven years of data (2007–2013), we assessed whether Silver Carp have continued to exert adverse pressure on the condition, CPUE, and biomass of native planktivores or whether there is evidence of a potential rebound in the populations of native planktivores. The extended data set reaffirms the body condition and the CPUE of Bigmouth Buffalo remain significantly reduced. However, unlike previous analyses, we also observed significant reductions in the CPUE of Gizzard Shad. Additionally, new results show that the CPUE and biomass of Bigmouth Buffalo were more inversely related to Silver Carp CPUE and biomass relative to the CPUE and biomass of Gizzard Shad. These results reinforce that Silver Carp likely suppress native planktivores and also suggest that diet and other life-history traits may explain some of the subtle differences in species-specific responses. Our results also emphasize that long-term data can be critical to understanding how non-native species can influence native fish population dynamics and how this influence may change over time.     

Effects of macrophyte leachate on <Emphasis Type="Italic">Anabaena</Emphasis> sp. and <Emphasis Type="Italic">Chlamydomonas moewusii</Emphasis> growth in freshwater tropical ecosystems

This study reports on the effects of dissolved organic matter (DOM) derived from the aquatic macrophyte Pistia stratiotes (collected from a tropical reservoir) on the mixotrophic growth of two phytoplankton species (Chlamydomonas moewusii and Anabaena sp.). The DOM from P. stratiotes had a mainly aliphatic structure, low molecular weight, low cellulose and lignin content and high carbon content. The addition of DOM (5% v/v) significantly decreased the growth rate of Anabaena sp. but increased the chlorophyll a concentration of C. moewusii. Higher light intensity (100 versus 30 µmol m^?2 s^?1) was important for Anabaena sp., increasing its growth rate and chlorophyll content. The use of DOM from P. stratiotes to mitigate cyanobacterial blooms should be further explored in future studies.     

Estimates of Heritability for Growth and Shell Color Traits and Their Genetic Correlations in the Black Shell Strain of Pacific Oyster <Emphasis Type="Italic">Crassostrea gigas</Emphasis>

The Pacific oyster Crassostrea gigas has been introduced widely and massively and became an economically important aquaculture species on a global scale. We estimated heritabilities of growth and shell color traits and their genetic correlations in black shell strain of C. gigas. Analyses were performed on 22 full-sib families in a nested mating design including 410 individuals at harvest (24 months of age). The parentage assignment was inferred based on four panels of multiplex PCR markers including 10 microsatellite loci and 94.9% of the offspring were unambiguously assigned to single parent pairs. The Spearman correlation test (r = ? 0.992, P < 0.001) demonstrated the high consistency of the shell pigmentation (SP) and L* and their same efficacy in shell color measurements. The narrow-sense heritability estimated under the animal model analysis was 0.18 ± 0.12 for shell height, 0.25 ± 0.16 for shell length, 0.10 ± 0.09 for shell width, 0.42 ± 0.20 for total weight, 0.32 ± 0.18 for shell weight, and 0.68 ± 0.16 for L*, 0.69 ± 0.16 for shell pigmentation, respectively. The considerable additive genetic variation in growth and shell color traits will make it feasible to produce genetic improvements for these traits in selective breeding program. High genetic and phenotypic correlations were found among growth traits and among shell color traits. To optimize a selection strategy for both fast growth and pure dark shell strain of C. gigas, it is proposed to take both total weight and black shell as joint objective traits in selective breeding program. Our study offers an important reference in the process of selective breeding in black shell color stain of C. gigas and will facilitate to develop favorable breeding strategies of genetic improvements for this economically important strain.     

Heteroplasmy due to chloroplast paternal leakage: another insight into <Emphasis Type="Italic">Phragmites</Emphasis> haplotypic diversity in North America

Chloroplasts contain several copies of their DNA, and intra-individual haplotypic variation (heteroplasmy) is common in plants, but unexplored in the cosmopolitan genus Phragmites. The aims of this study were to assess if heteroplasmy due to paternal leakage of the chloroplast occurs in Phragmites and which new insights into the evolutionary history of Phragmites australis in North America can be identified from the heteroplasmic variation. Eight non-native P. australis haplotypes occur in North America and can interbreed with P. australis ssp. americanus and P. australis var. berlandieri, creating opportunities for biparental inheritance of distinctive haplotypes. The polymorphism in the trnT-trnL sequence length revealed seventeen cases of heteroplasmy worldwide, in contact zones of distantly related haplotypes and in known hybrid populations, nine of which occurred in North America. In America, the cloned sequences, combined with nuclear markers, identified recombined haplotypes between native P. australis ssp. americanus and invasive P. australis haplotype M, and between the species P. mauritianus and P. australis, due to chloroplast paternal leakage. The occurrence of heteroplasmy and recombined haplotypes suggest a local origin for some of the rare non-native haplotypes occurring in North America, and plastid leakage events in the evolutionary histories of P. australis ssp. americanus and P. australis var. berlandieri.