To the importance of genetic diversity of Phragmites australisin the development of reed stands

Reed stands in Germany and Europe were investigatedwith respect to their genetic diversity by means ofRandom Amplified Polymorphic DNA (RAPD) via thePolymerase Chain Reaction (PCR-fingerprinting).Different types of clonal distribution could bedistinguished: monoclonal reed stands and polyclonalreed stands, and among the latter, stands with low orhigh numbers of different clones as well as standswith mosaic-like coexisting or intermingling clones.Furthermore, clonal distribution and the expansion ofdifferent clones was observed within a newlydeveloping reed population. The findings appear tosupport a model of colonization postulating thatpopulations initiated by seeds are initiallygenetically diverse, but over time become dominated byone or a few clones adapted to the prevailing siteconditions. Thus, low genetic diversity seems to bethe result of a natural selection process. Clonaldiversity within a reed population and the type ofclonal distribution are discussed with regard to theirimportance for the reed stand's ability to adapt tochanging site conditions and eventually for itssurvival or die-back.     

Reed die-back in southern Europe? A case study from Central Italy

Common reed die-back is a widely investigated phenomenon in Central Europe, not frequently recorded in S-European areas and almost unknown in the Mediterranean Basin. Symptoms of reed decline recently observed in the Italian Peninsula provided the starting point for a detailed investigation on a reed population in one of the largest freshwater ecosystems in Central Italy. The analyses were conducted over two vegetative seasons in 19 plots at seven locations. A set of 13 morphologic and phenologic reed traits were screened, monitored and statistically analysed. The data indicated the presence of the reed die-back syndrome in a wet Mediterranean ecosystem and enabled us to highlight a set of usable traits to detect the condition of decline. Among them, the stem height and diameter, the number of nodes, the relative growth rate and the lateral root diameter resulted the most significant factors highlighting the declining condition. Some environmental characteristics of the reed stands were also taken into account. The period of submersion and the presence of standing litter emerged as important features of the stands, strictly related to the degree of decline in the population. The results draw attention to the risk, in southern Europe too, of the loss of an ecosystem which plays an important role in biodiversity conservation.     

Dolichopodid Biodiversity and Site Quality Assessment of Reed Marshes And Grasslands in Belgium (Diptera: Dolichopodidae)

The conservation value of grassland and reed marsh habitats in Belgium was determined on the basis of dolichopodid communities (Diptera: Dolichopodidae). Four grassland and one reed marsh sites within the 'Bourgoyen-Ossemeersen' Nature Reserve (B.O.) (Ghent) were sampled with white water traps from March 1993 until March 1994. Subsequently, these soil faunas were compared with those of reed marsh habitats in 'Het Meetjeslandse Krekengebied' (M.K.) sampled in 1990. Comparisons of species communities were carried out by means of multivariate analysis techniques. The DCA and CCA on the B.O. sites produced a clear separation between the grassland and the reed marsh communities. Light intensity and soil humidity were among the most important factors determining species distributions. The comparison between the B.O. and M.K. communities revealed that sampling sites were clustered according to their geographical location rather than to habitat type. Overall species richness and diversity was not significantly different between grasslands and reed marshes. However, conservation quality estimates of the sites using the Site Conservation Quality Index (SCQI) indicated that reed marshes comprise a considerably larger number of rare and Red Data Book species. Moreover, besides typical reed marsh-inhabiting species, reed marshes also house species with other ecological affinities sometimes in rather high abundance. As a result, reed marshes are considered highly valuable for the survival of several wetland dolichopodid species.     

Genetic diversity of riverine reed stands indicating the water regime of the habitat

Although genetic diversity of reed stands developing in habitats with unchanged water levels have been frequently investigated, little is known about reed propagation along rivers, where fluctuating water levels may provide various conditions for germination and seedling development.The present paper evaluates genetic diversity of reed stands grown in (i) an oxbow with significant water level fluctuations related to the flood events in the main river; (ii) a separated oxbow which has lost connection to the main channel; and (iii) artificially controlled running water with low water level fluctuation. At each site, reed stands were investigated along transects parallel to the shore and multilocus phenotypes were determined by microsatellite analysis.The results demonstrated that genetic diversity of riverine reed stands can indicate the water regime of the habitat. Reed colonizes mostly by vegetative propagation where regular inundation can impede germination and seedling development and, therefore, genetic diversity is low in the whole stand. If a former oxbow becomes practically a lake, the clonal diversity and colonization processes are similar to those observed in regular lakes; clone number decreases toward the open water. When reed forms floating mats (i.e. the effect of water level fluctuation is excluded), generative reproduction prevails in the entire stand, resulting in high genetic diversity even at the open water edge of the stand.     

Comparison between biomass and C,N, P,S contents of vigorous and die-back reed stands of Lake Fertő/Neusiedler See

The production of vigorous and die-back sites of the same reed belt and nutrient content of reed were studied to detect possible causes of reed die-back. Shoot density, total aboveground and belowground biomass and their C, N, P and S contents were also determined.     

Structure and changes of macroinvertebrate community colonizing decomposing rhizome litter of common reed at Lake Fertő/Neusiedler See (Hungary)

Hydrobiologia - Rhizome litter of Phragmites australis were enclosed in litter bags of 1 mm mesh size and submerged in a die-back reed stand of Lake Fert?/Neusiedler See (Hungary). Species...     

Assessment of aquatic and terrestrial reed (Phragmites australis) stands

A survey of recent publications shows that research on Phragmites australishas oftenapplied character because of the considerableecological and economic significance of the species.The main applications are water treatment, agriculture(food production or weed control) and natureconservation. In Europe, most research on natural reedstands has been motivated by reed die-back and effortstowards protection or restoration. Reed progressionand reed control have been the main concerns in otherparts of the world, and reed progression has alsoreceived increasing attention in Europe. While reeddie-back generally affects aquatic stands, progressioncan occur at both terrestrial and aquatic sites, andit can be desired (e.g. lake shore restoration)or unwanted (e.g. in species-rich fens ormarshes). Therefore, reed stands need to be assessedindividually to decide on management aims andappropriate methods. The varying status of Phragmites australisformed the background of the`European Reed Conference' held in Zürich/Switzerlandin October 1998. The seven contributions published inthis special issue are introduced with particularreference to differences between aquatic andterrestrial reed stands and to approaches used in theirassessment.     

An overview of the effects of phytotoxins on Phragmites australis in relation to die-back

The accumulation in sediments of the low molecular weight, volatile, monocarboxylic acids and/or sulphide, generated by the decay of (i) the underground parts of the reed and/or (ii) organic deposits produced under eutrophic conditions, may play a crucial part in Phragmites die-back. In the field high levels of some of these phytotoxins have been detected at certain die-back sites and in sediments containing the rotting underground parts of the plant.Symptoms of die-back include a clumped habit, stunting and death of roots and shoots, bud death, premature senescence of shoots, weakened stems, impeded aeration of the underground parts of the plant due to callus development, blockages within the vascular systems, lignification and suberisation of laterals and apical regions of adventitious roots and lower levels of starch in rhizomes. Poor convective aeration of the rhizome system has also been associated with higher proportions of alanine, γ-amino butyric acid and serine in culm bases, indicating hypoxic metabolism in the underground system.In laboratory experiments plants developed almost all of the growth, morphological and anatomical symptoms of die-back when treated with various single phytotoxins, e.g. acetic, propionic, n- and iso-butyric and n-caproic acids and sulphide at concentrations reported for die-back sites and/or associated with the decaying underground parts of the plant. For each acid alone, a concentration of ca. 1 mM, was highly toxic at pH 4.5, but relatively non-toxic at pH 6.0. However, when a cocktail of the five acids was applied (where each acid was 1 mM) the mixture proved to be toxic even at pH 6.     

Genetic structure in a fragmented Northern Hemisphere rainforest: large effective sizes and high connectivity among populations of the epiphytic lichen Lobaria pulmonaria

An extraordinary diversity of epiphytic lichens is found in the boreal rainforest of central Norway, the highest-latitude rainforest in the world. These rainforest relicts are located in ravine systems, and clear cutting has increased the distance between remaining patches. We hypothesized that the relatively small lichen populations in the remaining forest stands have suffered a depletion of genetic diversity through bottlenecks and founder events. To test this hypothesis, we assessed genetic diversity and structure in the populations of the tripartite lichen Lobaria pulmonaria using eight SSR loci. We sampled thalli growing on Picea abies branches and propagules deposited in snow at three localities. Contrary to expectations, we found high genetic diversity in lichen and snow samples, and high effective sizes of the studied populations. Also, limited genetic differentiation between populations, high historical migration rates, and a high proportion of first generation immigrants were estimated, implying high connectivity across distances <30km. Almost all genetic variation was attributed to variation within sites; spatial genetic structures within populations were absent or appeared on small scales (5-10m). The high genetic diversity in the remaining old boreal rainforests shows that even relict forest patches might be suitable for conservation of genetic diversity.     

Effect of eutrophication on culm architecture of lakeshore Phragmites reeds

The eutrophication of lakes in central Europe has been assumed to be at least partly responsible for a widespread die-back of fringing Phragmites australis reeds. To test the ‘eutrophication hypothesis’ on a broad data basis, lakeshore reed stands at 41 lakes of known trophic status and 10 stands in waste water and sludge treatment plants in Denmark and north Germany (North data subset, n=26), and south Germany, Switzerland and Austria (South data subset, n=25) were investigated. A total of 24 culm performance variables in three different shoot classes were analyzed by two-way ANOVA with the geographic origin and the ‘relative trophic index’ as factors. The geographic origin had a pronounced influence on culm architecture, whereas the effect of the trophic level mostly failed to be significant in the ANOVA. The culms from the North reed stands showed a weaker performance throughout than those from the South stands for a given trophic level. However, some of the morphometric traits in the North stands were significant positively correlated with the trophic level but very few significant cases were observed in the South data subset. Three hypotheses are discussed to explain the geographic effect: climatic effects, geochemistry of lake water and sediments, and trophic history of the lakes. It is concluded that lake eutrophication does not influence the culm performance negatively and that eutrophication cannot be regarded as a general cause in reed decline.     

Some Aspects of the Importance of Genetic Diversity in Phragmites australis (Cav.) Trin. ex Steudel for the Development of Reed Stands

Various sites of Phragmites australis in Germany (Uckermark and Mark Brandenburg) and sites in Hungary and Denmark were investigated by PCR fingerprinting in order to determine their genetic diversity. Genetic similarities were calculated and, based on this, a cluster analysis was performed. The genetic similarity of reed clones around one lake ranged from between 70 to 100%, that of clones from different lakes was clearly lower. The further apart the clones were situated from each other, the less similar they were. At a wetland site near the shore a sudden colonisation by several new Phragmites clones was observed. This site was located in front of a well established genetically almost homogenous stand within the eulittoral. All the results are discussed in connection with a proposed model of establishment and development of water reed stands: colonization, selection of best adapted clones by competition and the stability of stands.     

Invasion of <Emphasis Type="Italic">Nipponaclerda biwakoensis</Emphasis> (Hemiptera: Aclerdidae) and <Emphasis Type="Italic">Phragmites australis</Emphasis> die-back in southern Louisiana,USA

Common reed, Phragmites australis (Cav.) Trin. Ex Steud., is the dominant emergent vegetation in the lower Mississippi River Delta (MRD), Louisiana, USA and is comprised primarily of introduced lineages of different phylogeographic origins. Dense stands of P. australis are important for protecting marsh soils from wave action and storm surges. In the Fall of 2016, while investigating symptoms of die-back of Phragmites stands in the lower marsh, a non-native scale was found infesting affected stands in high densities. Identified as Nipponaclerda biwakoensis (Kuwana) (Hemiptera: Aclerdidae), the scale was well established across the lower MRD. This report represents the first recorded population of Nipponaclerda biwakoensis in North America. Intriguingly, there are noticeable differences in die-back symptoms and in scale densities among different lineages of Phragmites in the MRD, with stands of the well-known European invasive lineage appearing healthier and having lower scale densities than other Phragmites lineages. Given its apparent relationship with the die-back syndrome, the scale may have serious implications for the health and stability of Phragmites marsh communities across coastal Louisiana. Efforts are currently underway to investigate the role of the scale and other abiotic stressors in the die-backs and potential management solutions.     

Lakeside reed border characteristics at Lake Constance (Untersee): A comparison between 1981–1983 and 1994

Eutrophication and the associated proliferation offilamentous algae were often considered importantcauses of reed die-back that occurred in the sixtiesand seventies at Lake Constance. According to thishypothesis the reduction in lake water nutrientconcentrations during the eighties and nineties shouldhave reduced the abundance of filamentous algae andwhich should have reduced the supposed mechanicalimpact of filamentous algae on the lakeside reedstands. To examine whether this had actually occurred,the condition of the lakeside reed border at LakeConstance (Untersee) was surveyed in 1994 and resultswere compared to those of similar surveys carried outin the years 1981–83. The extent of mechanical damageto reed stalks, the amount of macrophyte wash and thedegree of shoreline erosion were assessed forshoreline segments of 25 m along a total shorelinelength of 65 km. The results showed that mechanicaldamage to reed stalks was generally higher in 1994than in 1981–83, while macrophyte wash and shorelineerosion were generally less severe. The decreasedamount of macrophyte wash was associated with a changein macrophyte species composition from a dominance offloating filamentous algae to a dominance of rootedPotamogetonaceaeand fragile Characeae,and therefore probably was due to the lower nutrientconcentrations of the lake. The opposite trends foundfor mechanical damage to reed stands and the amount ofmacrophyte wash between 1981–83 and 1994, as well asthe absence of relation between the two variables in1994, suggested that macrophyte wash had only a minoreffect on the condition of lakeside reed stands atLake Constance. Highly damaged reed stands and erodedcliffs were often located at wind exposed sites orclose to highly frequented shipping routes in 1994,suggesting that mechanical stress from waves wasresponsible for the damage. Due to the lakewardprogression of reed stands during the early nineties,reed stalks were, on average, located in deeper waterin 1994 than in 1981–83. This might have strengthenedthe mechanical stress from wave action even more andhave caused the higher frequency of mechanical damageto reed stalks. Other causes of damage such asmacrophyte wash, roosts of birds or bird swarmsprobably played a minor and only local role.     

Effects of an artificial protection structure on the sandy shore macrofaunal community: the special case of Lido di Dante (Northern Adriatic Sea)

Biomanipulation of eutropicated peaty lakes has rarely been successful; clear water with dense macrophyte stands fails to develop in most cases. It was unclear whether (1) high turbidity due to resuspension by benthivorous fish or wind is the major cause of low macrophyte density or whether (2) the establishment of submerged macrophyte stands is prevented by a lack of propagules, low cohesive strength of the lake sediment, high concentrations of phytotoxics, grazing by waterfowl and/or shading by periphyton growth. These hypotheses were tested in an experiment in a shallow peat lake in the Netherlands (Terra Nova). Removal of fish from a 0.5 ha experimental site resulted in clear water and the development of a dense (90% coverage) and species-rich (10 species) submerged vegetation. At a fish-stocked site and a control site the water remained turbid and dense macrophyte stands did not develop. The establishment of submerged macrophytes appeared not to be limited by a lack of propagules. Introduced plants grew poorly in turbid water, but very well in clear water. Exclosures showed that bird grazing reduced the plant biomass. In clear water grazing seemed to enhance the vegetation diversity. Periphyton development did not prevent plant growth in clear water. After the experiment, the fish stock was greatly reduced in the whole lake (85 ha), to test if (3) in a large lake, submerged macrophyte stands will not develop after biomanipulation. In the first season after fish reduction, transparency increased and species-rich submerged macrophyte stands developed, covering 60% of the shallow parts of the lake. Most of the species known to have occurred in the past re-established. The results indicate that high turbidity caused by benthivorous fish in combination with bird grazing were the major causes of the absence of submerged macrophyte stands in this lake. Abiotic conditions after the clearing of the lake were suitable for the growth of macrophytes. We infer that the restoration potential of submerged macrophyte stands in eutrophicated peaty lakes can be high, and results can be obtained quickly.     

Habitat-specific pigmentation in a freshwater isopod: adaptive evolution over a small spatiotemporal scale

Pigmentation in the freshwater isopod Asellus aquaticus (Crustacea) differed between habitats in two Swedish lakes. In both lakes, isopods had lighter pigmentation in stands of submerged vegetation, consisting of stoneworts (Chara spp.), than in nearby stands of reed (Phragmites australis). Experimental crossings of light and dark isopods in a common environment showed that pigmentation had a genetic basis and that genetic variance was additive. Environmental effects of diet or chromatophore adjustment to the background had minor influence on pigmentation, as shown by laboratory rearing of isopods on stonewort or reed substrates, as well as analyses of stable isotope ratios for isopods collected in the field. In both study lakes, the average phenotype became lighter with time (across generations) in recently established stonewort stands. Taken together, these results indicate that altered phenotype pigmentation result from evolutionary responses to local differences in natural selection. Based on the assumption of two generations per year, the evolutionary rate of change in pigmentation was 0.08 standard deviations per generation (haldanes) over 20 generations in one lake and 0.22 haldanes over two generations in the other lake. This genetic change occurred during an episode of population growth in a novel habitat, a situation known to promote adaptive evolution. In addition, stonewort stands constitute large and persistent patches, characteristics that tend to preserve local adaptations produced by natural selection. Results from studies on selective forces behind the adaptive divergence suggest that selective predation from visually oriented predators is a possible selective agent. We found no indications of phenotype-specific movements between habitats. Mating within stonewort stands was random with respect to pigmentation, but on a whole-lake scale it is likely that mating is assortative, as a result of local differences in phenotype distribution.     

Role of domestication in shaping <Emphasis Type="Italic">Castanea sativa</Emphasis> genetic variation in Europe

The genetic structure of sweet chestnut (Castanea sativa Mill.) across Europe was assessed using 73 inter-simple sequence repeat markers to screen 1,768 individuals from 68 stands distributed across 29 sites in five European countries (Italy, France, Spain, Greece, and UK). At each site, trees were sampled from three distinct management types (domestication levels): naturalized stands, managed coppice, and grafted fruit orchards. In more than a third of the orchards, nonlocal genetic material (grafted clones) were evident, showing (as predicted) large differences from the other two domestication levels for most of the within-population genetic diversity parameters estimated. Randomly generated linkage disequilibrium analysis revealed weak though significant differences in two-locus allelic correlations between naturalized stands and coppice, suggesting that long-term management techniques may influence the genetic makeup of the populations. Multivariate analysis revealed the existence of five distinct gene pools across the study area; three were located in Greece, one on the northwestern coast of the Iberian peninsula and a large gene pool covering the rest of the Mediterranean basin. The implications of the results are discussed in relation to developing conservation strategies for chestnut genetic resources in Europe.     

Seasonal Abundance and Species Richness of Birds in Common Reed Habitats in Lake Erie

Abstract: Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.     

Genetic variation and population structure of swimming crab (Portunus trituberculatus) inferred from mitochondrial control region

Genetic variation and population structure in Portunus trituberculatus along the coast of China were revealed according to 617 bp of mitochondrial DNA control region. 90 polymorphic sites defined 53 distinct haplotypes, showing a moderately high diversity among 72 individuals sampled from eight localities. Neighbor-joining tree, statistics analyses of gene flow and genetic differentiation index indicated two populations from Beihai and Laizhou had differentiated. The population from Yingkou, Dandong, Laizhou and Beihai had smaller genetic diversity compared to that from Ningbo, Lianyungang, Qingdao and Japan according to the genetic distance. And mantel test showed significant positive correlation between genetic distance and geographic distance for P. trituberculatus. TCS parsimony network suggested that all the animals sampled were probably the result of recent divergence from a common ancestral haplotype but for Laizhou population. Moreover, the haplotype distribution appeared to correlate with a recent colonization followed by localized genetic differentiation. Mismatch distribution results suggested that Ningbo, Yingkou, Qingdao, Lianyungang and Japan populations, particularly Dandong population had experienced a sudden demographic or spatial expansion. The Pleistocene glaciations might contribute to this process.     

Clonal diversity and genetic differentiation in Ilex leucoclada M. patches in an old-growth beech forest

We investigated clonal diversity within patches of Ilex leucoclada and genetic variation within and among patches using random amplified polymorphic DNA (RAPD) markers in a 1-ha plot within an old-growth beech forest. We found 38 patches that exhibited a clumped distribution in the middle of the plot. We identified a total of 166 RAPD phenotypes among the 215 stems sampled from 27 patches that were completely within the plot. The population showed high clonal diversity within patches (mean number of genets relative to number of stems = 0.79; mean Simpson's D = 0.89). Variation in RAPD phenotypes among patches was highly significant (PhiST in the molecular variance analysis = 0.316, P < 0.001), indicating genetic differentiation among patches. Pairwise genetic distances, PhiST, among patches did not correlate with geographical distances among patches. The cluster analysis based on the genetic distances showed few clear clusters of patches, indicating no spatial genetic structure among patches. High levels of clonal diversity both within patches and within the population may be explained by multiple founders, seedling recruitment during patch-formation, and somatic mutation. The significant genetic differentiation among patches may be caused by separate founding events and/or kin structuring within patches.     

New occurrence of reed bed decline in southern Europe: Do permanent flooding and chemical parameters play a role?

Based on the experimental design proposed in similar studies, macromorphological and ecological traits of common reed beds were analysed at Lake Chiusi (Central Italy), together with selected chemical parameters in sediments and interstitial waters and aerial images of the site, in order to investigate reed decline and search for possible correlations among data. Typical symptoms of the reed dieback syndrome were detected, thus enlarging the occurrence of this phenomenon in southern Europe. Permanently dry, permanently flooded and partially flooded stands show different levels of decline, with the permanent flooding always co-occurring with reed dieback. Only few of the considered chemical parameters seem to play a role in reed decline (nitrates, rubidium, nickel, barium, manganese), although no clear pattern was identified. Data suggest that the co-occurrence of some chemicals with stressing conditions might affect the growth even of an efficient metal accumulator, as reed is generally considered.