Vertical distribution of the relic species <Emphasis Type="Italic">Eurytemora lacustris</Emphasis> (Copepoda,Calanoida) in stratified mesotrophic lakes

The aim of this study was to determine factors affecting the vertical distribution of Eurytemora lacustris in mesotrophic lakes (Wigry, Hańcza, Szurpi?y; north-eastern Poland) during the summer stagnation. Eurytemora lacustris was found in all of the studied lakes, with the highest abundance (8 ind. L^?1) in Lake Wigry. In Lake Szurpi?y, E. lacustris has never been recorded before. The results of this study revealed that E. lacustris was most numerous in thermocline zones, suggesting that this species could temporarily tolerate warmer water and lower oxygen concentrations due to better food resources. During the study, it was found that a large part of the E. lacustris population had epibiont ciliates, in contrast to other species of zooplankton that did not have any epibionts. The improvement in the water quality of many deep lakes could lead to an increase in the abundance of E. lacustris. However, epibiont ciliates may be a threat for this species and may play a substantial role in determining the production, distribution, and community dynamics of E. lacustris.     

Long-term changes in the littoral benthos of a Norwegian subalpine lake following the introduction of the European minnow (<Emphasis Type="Italic">Phoxinus phoxinus</Emphasis>)

The littoral benthos of the subalpine lake, Øvre Heimdalsvatn, has been documented in a series of investigations carried out in 1972, 1976, 1985 and 2000. During this 28-year period there have been major changes in the benthos of the lake following the introduction of European minnow (Phoxinus phoxinus) into the lake where brown trout (Salmo trutta) was formerly the sole species. In 1972 Ephemeroptera, Trichoptera, Plecoptera and Gammarus lacustris dominated the macrobenthos, constituting 85% of faunal numbers, while Chironomidae and Oligochaeta made up only c. 6%. However, by 1976, chironomids and oligochaetes had increased in relative abundance, while G. lacustris declined. This trend towards a dominance of chironomids and oligochaetes was confirmed in 1985 and 2000, although absolute numbers of Ephemeroptera, Plecoptera and Trichoptera increased in 2000 relative to 1972 values. Gammarus lacustris had a 2-year life cycle in Øvre Heimdalsvatn. In 1972 there were significantly more females than males, but by 1976 and through to 2000 there were greater numbers of males. Despite this reduction in females, numbers of juveniles increased, although mortality, probably due to increased predation from minnows, was higher than earlier. The introduction of the alien species, the European minnow, into Øvre Heimdalsvatn has clearly changed the composition and structure of the littoral macroinvertebrate benthos.     

Genetic polymorphism,haplotype distribution,and phylogeny of <Emphasis Type="Italic">Daphnia</Emphasis> (Cladocera: Anomopoda) species from the water bodies of russia as inferred from the 16S mtDNA gene sequencing

The data on the genetic polymorphism of the most widespread Daphnia species occupying different water bodies of Russia are presented. The phylogenetic relationships between the examined species were established, and the haplotype networks were constructed. A fragment of the 16S mitochondrial DNA gene was used as a genetic marker. The results of molecular phylogenetic analysis generally coincided with modern concepts in the systematics of the genus Daphnia. The representatives of the divergent mitochondrial lineages within the D. longispina, D. pulex, and D. magna complex remain poorly investigated morphologically. For D. dentifera, a new habitat on the territory of Russia, namely, the water bodies of the Lake Baikal basin, was identified. A conclusion was made that the 16S mtDNA gene could be successfully used in phylogeographic analysis of the genus Daphnia.     

Host range extension of <Emphasis Type="Italic">Cydia pomonella</Emphasis> granulovirus: adaptation to Oriental Fruit Moth, <Emphasis Type="Italic">Grapholita molesta</Emphasis>

Among various Cydia pomonella granulovirus (CpGV) isolates, the Mexican isolate (CpGV-M) has demonstrated a significant ability to reduce damage induced by the oriental fruit moth, Grapholita molesta (Busck) (=Cydia molesta) in peach crops. To obtain a more efficient virus for G. molesta control, an experimental virus population was constructed by mixing various CpGV isolates. This mixture was then selected for replication in a G. molesta laboratory colony. After 12 successive passages on this alternative host, the insecticidal efficacy of the virus population had improved. The concentration of virus occlusion bodies required to kill 90 % of neonate larvae was 450-fold lower than that of the original isolate mixture, and 120-fold lower than that of the CpGV-M isolate alone. Following adaptation to this alternative host, the efficacy against its natural host, the codling moth, C. pomonella, was conserved. This mixed isolate population can be produced on C. pomonella without loss of efficacy, which is useful from a commercial production perspective. This adapted virus isolate mixture is likely to prove more effective than individual component isolates at controlling G. molesta.     

Dynamic variation of toxic and non-toxic <Emphasis Type="Italic">Microcystis</Emphasis> proportion in the eutrophic Daechung Reservoir in Korea

This study was conducted to determine the environmental factors affecting the level of potentially toxic Microcystis. The long-term tendencies of temperature, precipitation, and water quality factors were analyzed to determine the environmental characteristics of the Daechung Reservoir in Korea, and water samples were directly collected to analyze the dynamics of toxic and non-toxic Microcystis at weekly intervals from May to October 2012. Microcystis was the dominant genus during the study period, and it was composed of potentially toxic and non-toxic Microcystis. The fraction of potentially toxic Microcystis ranged from 6.0% to 61.1%. The amount of toxic Microcystis was highly related to the intracellular microcystin concentration (r = 0.760, P < 0.01). Therefore, the fraction of potentially toxic Microcystis is an important concern in Microcystis blooming because the intracellular microcystin concentration may reflect microcystin levels in the water. The prevalence of potentially toxic Microcystis was highly related to water temperature in Daechung Reservoir (r = 0.585, P < 0.01). Thus, temperature increase during Microcystis blooming may lead to more frequent toxic Microcystis blooms in eutrophic water bodies.     

Taxonomic composition of bacteria associated with cultivated mollusks <Emphasis Type="Italic">Crassostrea lugubris</Emphasis> and <Emphasis Type="Italic">Perna viridis</Emphasis> and with the water of the Gulf of Nha Trang lagoon,Vietnam

One hundred and four strains of heterotrophic bacteria have been isolated and characterized from two species of bivalve mollusks cultivated in the Gulf of Nha Trang (Vietnam) and from the water of a mariculture farm. The isolates have been identified on the basis of morphological, physiological, biochemical, and chemotaxonomic properties, as well as by the content of G+C bases in DNA. In the microflora of mollusks, Vibrio alginolyticus was predominant; the pathogenic species V. harveyi and V. splendidus were found as well. Staphylococci and bacilli occupied the second place in abundance after vibrios. In addition, coryneforms and enterobacteria, as well as Pseudomonas spp. and Pseudoalteromonas spp., were revealed. The composition of the water microflora was more diverse as compared with the microflora of mollusks. In the water, Bacillus spp., Vibrio spp., and Pseudomonas spp. were predominant. Brevibacterium spp. and other coryneform bacteria, as well as enterobacteria, occurred in significant amounts. In addition, Pseudoalteromonas spp., Marinococcus sp., Halobacillus sp., Shewanella sp., Sulfitobacter sp., and bacteria of the CFB cluster were noticed. The presence of pathogenic and conditionally pathogenic bacterial species in the water and mollusks is probably the reason for the high death rate of cultivated animals at the mariculture farm.     

Photosynthetic responses to soil water stress in summer in two Japanese urban landscape tree species (<Emphasis Type="Italic">Ginkgo biloba</Emphasis> and <Emphasis Type="Italic">Prunus yedoensis</Emphasis>): effects of pruning mulch and irrigation management

Key message

Stomatal regulation involves beneficial effects of pruning mulch and irrigation on leaf photosynthesis in Prunus yedoensis and Ginkgo biloba under moderate drought. G. biloba showed conservative water use under drought.

Abstract

Leaf photosynthesis is highly sensitive to soil water stress via stomatal and/or biochemical responses, which markedly suppress the growth of landscape trees. Effective irrigation management to maintain leaf photosynthesis and information on species-specific photosynthetic responses to soil water stress are essential for the sustainable management of landscape trees in Japan, in which summer drought often occurs. In order to investigate effective irrigation management, we used plants with moderate soil water stress as controls, and examined the effects of daily irrigation and pruning mulch on leaf photosynthesis in container-grown Ginkgo biloba and Prunus yedoensis, which are the first and second main tall roadside trees in Japan. Stomatal conductance was significantly increased by pruning mulch and daily irrigation, with similar increases in leaf photosynthesis being observed in P. yedoensis and G. biloba. In order to obtain information on species-specific photosynthetic responses to soil water stress, we compared the responses of leaf photosynthesis and leaf water status to reductions in soil water content (SWC) between the two species. G. biloba maintained a constant leaf water potential, leaf water content, maximum carboxylation rate, and electron transport rate with reductions in SWC, whereas reductions were observed in P. yedoensis. We concluded that pruning mulch and irrigation effectively offset the negative impact of moderate water stress on leaf photosynthesis in summer in P. yedoensis and G. biloba via stomatal regulation, and also that G. biloba maintained its photosynthetic biochemistry and leaf water status better than P. yedoensis under severe water stress.

     

mtDNA-based identification of two widespread roach species (<Emphasis Type="Italic">Rutilus</Emphasis>, Cyprinidae) characterized by sympatric zone

Test systems using multiplex PCR and restriction analysis have been designed for the simple and rapid identification of two widespread species of roach, Rutilus rutilus and R. lacustris, characterized by the sympatric zone. This method is based on the variation of nucleotide sequences of the mitochondrial markers (cytochrome oxidase I subunit and cytochrome b); it allows identifying the species omitting the DNA sequencing.     

Heat resistance of the skeletal muscle in Western Palearctic green frogs (<Emphasis Type="Italic">Rana esculenta</Emphasis> complex)

Heat resistance of the gastrocnemius muscle was studied in five species of the Rana esculenta complex. It was similar in R. bedriagae, R. lessonae, and in the European form of R. ridibunda; while North African R. saharica demonstrated a lower heat resistance. No heterosis was expressed in R. esculenta, a clonal hybrid of R. lessonae and R. ridibunda, for the heat resistance of the muscle. Moreover, this species demonstrated low heat resistance at the highest test temperature (42°C). Comparison of diploid and triploid R. esculenta syntopically occurring in the same water bodies demonstrated no differences between them, thus, suggesting that polyploidy has no effect on this parameter at least in this case.     

Heat and hypoxia give a global invader, <Emphasis Type="Italic">Gambusia holbrooki,</Emphasis> the edge over a threatened endemic fish on Australian floodplains

Deciphering the mechanisms by which climate change interacts with invasive species to affect biodiversity is a major challenge of global change biology. We conducted experiments to determine whether the global invader, Gambusia holbrooki, was more resistant to high water temperature (heat) and low dissolved oxygen (hypoxia) than a threatened native fish, Nannoperca australis. Metabolic experiments conducted at 25 and 29 °C showed that G. holbrooki had at least four times the capacity for metabolic depression during hypoxia than N. australis. An increase in environmental temperature from 25 to 29 °C had no significant impact on the critical oxygen tension, P _crit, of G. holbrooki, but significantly and strongly increased P _crit of N. australis. Gambusia holbrooki also had a lower Q ₁₀ of standard metabolic rate than N. australis. Our results indicate that G. holbrooki have physiological traits conferring greater resistance to hypoxia than N. australis, and as temperature increases, the resistance of N. australis to hypoxia was more eroded than that of G. holbrooki. Intensive monitoring of the temperature and dissolved oxygen dynamics of wetlands showed that contemporary heat waves are already causing conditions that might give G. holbrooki the edge over N. australis on Australian floodplains. Our study adds weight to recent anecdotal reports of drought and heat waves causing localised extinction of N. australis, but the proliferation of G. holbrooki.     

Morphological and molecular investigations of <Emphasis Type="Italic">Gagea</Emphasis> (Liliaceae) in southeastern Kazakhstan with special reference to putative altitudinal hybrid zones

The most important center of speciation in the genus Gagea is thought to be in Central Asia. Here, we focus on species diversity in southeastern Kazakhstan (around Almaty, Ili-Alatau range of the Western Tian-Shan mountains). We studied an elevational transect, reaching from lowland steppes to the alpine zone (500–2750 m a. s. l.), and carried out detailed morphological and molecular investigations for populations of Gagea spp. Nine species were identified in different altitudinal zones; one of these (Gagea almaatensis) is described as new to science. We could detect two altitudinal contact zones between closely related species: G. filiformis and G. granulosa (sect. Minimae), and G. almaatensis and G. kuraminica (sect. Gagea). Morphological and molecular investigations (ITS data and cpDNA networks) indicate ongoing hybridization of co-occurring G. filiformis into G. granulosa and putative bidirectional hybridization events between G. almaatensis and G. kuraminica.     

Parasitism may alter functional response comparisons: a case study on the killer shrimp <Emphasis Type="Italic">Dikerogammarus villosus</Emphasis> and two non-invasive gammarids

The Ponto-Caspian freshwater amphipod Dikerogammarus villosus has colonized most of the water bodies of continental Europe where it causes strong structural alterations in recipient communities that can lead to changes in ecosystem-level processes, mainly because of a strong predatory behaviour. Most of the D. villosus populations from the invaded range have been found infected with the co-introduced microsporidian parasite Cucumispora dikerogammari, known to decrease the predation rate of its host. Infection might thus mitigate the ecological impact of D. villosus and we wanted to test this assumption using the comparative functional response approach. We compared the relationship between resource use and resource availability (i.e. the functional response, FR) of D. villosus, either with infected individuals or not, to that of two non-invasive gammarids: Gammarus pulex and Echinogammarus berilloni. With infected individuals included, D. villosus displayed a higher FR than the two non-invasive gammarids. Although this effect was not significant, C. dikerogammari infection tended to alter the FR of D. villosus with a slight decrease in attack rate and handling time, resulting in a less steep initial slope and a higher asymptote, respectively. Removing infected D. villosus from the dataset did not affect the FR comparison with G. pulex but suppressed the difference in FR with E. berilloni. Although we cannot exclude the role of sample size reduction in this effect, this suggests that C. dikerogammari infection might increase the predation pressure on local prey populations in case of species replacement between D. villosus and E. berilloni. From a more general perspective, our study illustrates how parasites may alter our capacity to predict invasive species impacts from FR comparisons.     

Effect of selenium-containing biocomposites based on <Emphasis Type="Italic">Ganoderma</Emphasis> mushroom isolates grown in the presence of oxopropyl-4-hydroxycoumarins,on bacterial phytopathogens

Effect of selenium-containing biocomposites obtained from submerged cultures of macrobasidiomycetes Ganoderma applantum, G. cattienensis, G. colossus G. lucidum, G. neojaponicum, and G. valesiacum, on plant pathogenic bacteria Clavibacter michiganensis ssp. sepedonicus (Cms), Micrococcus luteus, Pectobacterium atrosepticum, Pectobacterium carotovorum subsp. carotovorum, Pseudomonas fluorescens, Pseudomonas viridiflava, and Xanthomonas campestris was studied. Oxopropyl-4-hydroxychromenones were used as components of the fungal nutrient media. The bacteriostatic and bactericidal activity of the Se-containing and Se-free substances of fungal origin against plant pathogenic bacteria was determined using colony-forming units count, the agar well diffusion method, and by turbidity measurements of bacterial suspensions. The composites produced from the extracellular metabolites of G. cattienensis SIE1302 with 4-hydroxy-3-(3-oxo-1,3-diphenyl propyl)-chromen-2-one (S(45)), and of G. lucidum SIE1303 with 4-hydroxy-3-(3-oxo-1-(3-nitrophenyl)-3-phenylpropyl)-chromen-2-one (S(NO₂)) possessed the most pronounced antibacterial action against Cms. The composites produced from the isolates of G. valesiacum 120702 with S(NO₂) showed the maximal antibacterial activity against Xanthomonas campestris B-610. High antimicrobial effect of G. lucidum 1315 with S(NO₂) against Xanthomonas campestris B-610 and of G. colossus SIE1301 against Pseudomonas fluorescens EL-2.1 was revealed. The pioneering information on the biological activity of coumarin series compounds in their application for producing the substances of fungal origin was obtained.     

Life history differences and latitudinal variation in recruitment in two species of arctic-boreal perciform fishes,the fish doctor <Emphasis Type="Italic">Gymnelus viridis</Emphasis> and the Arctic shanny <Emphasis Type="Italic">Stichaeus punctatus</Emphasis>

Growth and recruitment were examined in two arctic-boreal, shallow water marine perciform species: the fish doctor Gymnelus viridis (Zoarcidae) and the Arctic shanny Stichaeus punctatus (Stichaeidae). G. viridis ranges in the Canadian Arctic from northern Hudson Bay to northern Ellesmere Island, whereas S. punctatus has a more southerly range from Nova Scotia coastal waters to northern Hudson Bay. At Nuvuk Islands in northeastern Hudson Bay, where the two species are sympatric in shallow water, they had comparable juvenile growth rates but temporal variation in 0+ recruitment was substantially greater in S. punctatus. This difference may stem from their contrasting early life histories. S. punctatus spawns large numbers of small demersal eggs that hatch into pelagic larvae, whereas G. viridis spawns small numbers of large demersal eggs that hatch directly into demersal juveniles with no pelagic stage, suggesting that recruitment in G. viridis should be less sensitive to yearly variation in the onset of the ice-free period in Hudson Bay and the subsequent pulse of pelagic invertebrate production. Relative to Nuvuk, recruitment variation in G. viridis was found to be greater at Resolute, Cornwallis Island, close to its northern range limit, whereas recruitment variation in S. punctatus was not evident in Newfoundland, closer to its southern range limit.     

BrFLC5: a weak regulator of flowering time in <Emphasis Type="Italic">Brassica rapa</Emphasis>

Key message

A splicing site mutation in BrFLC5, a non-syntenic paralogue of FLOWERING LOCUS C, was demonstrated to be related to flowering time variation in Brassica rapa.

Abstract

Flowering time regulation in Brassica rapa is more complex than in Arabidopsis, as there are multiple paralogues of flowering time genes in B. rapa. Brassica rapa contains four FLOWERING LOCUS C (FLC) genes, three of which are syntenic orthologues of AtFLC, while BrFLC5 is not. BrFLC1, BrFLC2, and BrFLC3 have been reported to be involved in flowering time regulation. However, BrFLC5 has thus far been deemed a pseudogene. We detected two alternative splicing patterns of BrFLC5 resulting from a nucleotide mutation (G/A) at the first nucleotide of intron 3 (named as Pi3+1(G/A)). Genotyping of BrFLC5Pi3?+?1(G/A) for 301 B. rapa accessions showed that this single nucleotide polymorphism was significantly related to flowering time variation (p?<?0.001). In the collection, the frequency of the functional G allele (35.2%) was much lower than that of the nonfunctional A allele (59.1%); however, the frequency of the G allele was very high among the turnips (83.6%). An F2 population segregating at this locus was developed to analyze the genetic effect of BrFLC5. The result showed that the G allele individuals began to bolt two days later than the A allele individuals, indicating that BrFLC5 is a weak regulator of flowering time. BrFLC5 was expressed at the lowest level among the three analyzed BrFLCs. The late allele (G allele) was dominant to the early allele (A allele) at the BrFLC5 locus, which was in contrast to that of BrFLC1 and BrFLC2. This characteristic suggests that BrFLC5 would be more efficient for breeding premature bolting resistance in B. rapa.