Resilience of Zostera marina habitats and response of the macroinvertebrate community to physical disturbance caused by clam harvesting

The consequences of physical disturbances to seagrasses depend on disturbance frequency relative to the capacity for recolonization and recovery following fragmentation. In a subtidal seagrass meadow of Zostera marina L., following a season of clam harvesting, we compared the temporal change of shoot density and biomass of this seagrass together with the community structure of the associated macroinvertebrates, at two sites differing in the intensity of the physical disturbance. The impacted site showed significantly lower shoot density and total biomass than the non-impacted site initially. The increase in above-ground biomass over four months (May to September) of this species was significantly higher (46%) at the impacted site than in the area not affected by the disturbance. Four months after cessation of the extraction activity, the biomass and density values of Z. marina reached similar values to those measured in the non-impacted site. The sexual reproductive effort of the seagrass population affected by the disturbance (4%) was significantly lower than at the non-impacted site (10%), which could influence genetic diversity and the seed bank. The community structure of molluscs showed 54% similarity between sites at the beginning of the study. Four months later, mollusc communities increased to a similarity of 74%. The current closure season (four months annually) established for the recovery of the exploited stocks of bivalves allowed the recovery of Z. marina density and biomass. Nevertheless, other population properties, such as those related to reproductive patterns, remained altered by the disturbance.     

The difficult legacy of Turing’s wager

Neuron modeling may be said to have originated with the Hodgkin and Huxley action potential model in 1952 and Rall’s models of integrative activity of dendrites in 1964. Over the ensuing decades, these approaches have led to a massive development of increasingly accurate and complex data-based models of neurons and neuronal circuits. ModelDB was founded in 1996 to support this new field and enhance the scientific credibility and utility of computational neuroscience models by providing a convenient venue for sharing them. It has grown to include over 1100 published models covering more than 130 research topics. It is actively curated and developed to help researchers discover and understand models of interest. ModelDB also provides mechanisms to assist running models both locally and remotely, and has a graphical tool that enables users to explore the anatomical and biophysical properties that are represented in a model. Each of its capabilities is undergoing continued refinement and improvement in response to user experience. Large research groups (Allen Brain Institute, EU Human Brain Project, etc.) are emerging that collect data across multiple scales and integrate that data into many complex models, presenting new challenges of scale. We end by predicting a future for neuroscience increasingly fueled by new technology and high performance computation, and increasingly in need of comprehensive user-friendly databases such as ModelDB to provide the means to integrate the data for deeper insights into brain function in health and disease.     

Natural variation reveals contrasting abilities to cope with alkaline and saline soil among different <Emphasis Type="Italic">Medicago truncatula</Emphasis> genotypes

Aims

Urban soils are the basis of many ecosystem services in cities. Here, we examine formerly residential vacant lot soils in Cleveland, Ohio and Detroit, Michigan, USA for their potential to provide multiple ecosystem services. We examine two key contrasts: 1) differences between cities and 2) differences within vacant lots created during demolition, specifically pre-existing (i.e., prior to demolition) soils outside of the building footprint and fill soils added within the former building’s footprint.

Methods

Deep soil cores were collected from vacant lots in Cleveland and Detroit. Soil properties that are proxies for three ecosystem services were measured: hydraulic conductivity for stormwater retention, topsoil depth and soil nitrogen (N) level for support for plant growth, and soil carbon (C) content for C storage.

Results

Both city and soil group contrasts created distinct ecosystem service provisioning based on proxy measures. Cleveland soils had greater hydraulic conductivity and greater soil C and N levels but thinner topsoil layers than Detroit. Within vacant lots of both cities, pre-existing soils had greater soil C and N levels, but lower hydraulic conductivity values than fill soils.

Conclusions

Soil properties of vacant lots were generally suitable for providing multiple ecosystem services. City-level differences in soil properties created differences in ecosystem service potential between cities and these differences were evident in pre-existing and fill soils. When comparing between cities, though, fill soils were more similar than pre-existing soils indicating some homogenization of ecosystem service potential with greater redistribution of soil.

     

Community-based natural resource use and management of Bigodi Wetland Sanctuary,Uganda, for livelihood benefits

Conservation and sustainable management of wetlands requires participation of local stakeholders, including communities. The Bigodi Wetland is unusual because it is situated in a common property landscape but the local community has been running a successful community-based natural resource management programme (CBNRM) for the wetland for over a decade. Whilst external visitors to the wetland provide ecotourism revenues we sought to quantify community benefits through the use of wetland goods such as firewood, plant fibres, and the like, and costs associated with wild animals damaging farming activities. We interviewed 68 households living close to the wetland and valued their cash and non-cash incomes from farming and collection of non-timber forest products (NTFPs) and water. The majority of households collected a wide variety of plant and fish resources and water from the wetland for household use and livestock. Overall, 53% of total household cash and non-cash income was from collected products, mostly the wetland, 28% from arable agriculture, 12% from livestock and 7% from employment and cash transfers. Female-headed households had lower incomes than male-headed ones, and with a greater reliance on NTFPs. Annual losses due to wildlife damage were estimated at 4.2% of total gross income. Most respondents felt that the wetland was important for their livelihoods, with more than 80% identifying health, education, craft materials and firewood as key benefits. Ninety-five percent felt that the wetland was in a good condition and that most residents observed the agreed CBNRM rules regarding use of the wetland. This study confirms the success of the locally run CBNRM processes underlying the significant role that the wetland plays in local livelihoods.     

Impairment of <Emphasis Type="Italic">ntc</Emphasis>A gene revealed its role in regulating iron homeostasis,ROS production and cellular phenotype under iron deficiency in cyanobacterium <Emphasis Type="Italic">Anabaena</Emphasis> sp. PCC 7120

Iron deficiency ends up into several unavoidable consequences including damaging oxidative stress in cyanobacteria. NtcA is a global nitrogen regulator controls wide range of metabolisms in addition to regulation of nitrogen metabolism. In present communication, NtcA based regulation of iron homeostasis, ROS production and cellular phenotype under iron deficiency in Anabaena 7120 has been investigated. NtcA regulates the concentration dependent iron uptake by controlling the expression of furA gene. NtcA also regulated pigment synthesis and phenotypic alterations in Anabaena 7120. A significant increase in ROS production and corresponding reduction in the activities of antioxidative enzymes (SOD, CAT, APX and GR) in CSE2 mutant strain in contrast to wild type Anabaena 7120 also suggested the possible involvement of NtcA in protection against oxidative stress in iron deficiency. NtcA has no impact on the expression of furB and furC in spite of presence of consensus NtcA binding site (NBS) and ?10 boxes in their promoter. NtcA also regulates the thylakoid arrangement as well as related photosynthetic and respiration rates under iron deficiency in Anabaena 7120. Overall results suggested that NtcA regulates iron acquisition and in turn protect Anabaena cells from the damaging effects of oxidative stress induced under iron deficiency.     

Molecular evolution of glutathione peroxidase (<Emphasis Type="Italic">Gpx</Emphasis>) family genes in desert poplar (<Emphasis Type="Italic">Populus euphratica</Emphasis> Oliv.)

Populus euphratica Oliv. is a poplar species that is distributed mainly in deserts, making it an interesting model in which to investigate molecular mechanisms underlying different stress responses. Here, we used molecular population genetic methods to detect potential selection in candidate genes belonging to the P. euphratica glutathione (GSH) peroxidase (Gpx) family, which are associated with an enzymatic mechanism that combats oxidative damage caused by reactive oxygen species (ROS) in plant cells; earlier studies have shown that Gpx proteins play important roles in coping with increased ROS levels during biotic and abiotic stresses in plants. We analyzed the nucleotide diversity and divergence patterns of five loci encoding Gpx genes, and 16 reference loci used as controls, in order to detect departures from the neutral expectation. Gpx1 has an excess of mid-frequency alleles; high intraspecific nucleotide diversity, distributed in the upper tail of the simulated neutral model; and extensive LD, showing strong evidence of balancing selection/local adaptation. The Gpx3.2 gene exhibits very low nucleotide diversity and divergence, suggesting that it has evolved under strong purifying selection. We failed to detect any evidence for natural selection at the other loci (Gpx2, Gpx4, and Gpx5) compared with the reference loci. The results show that nucleotide diversity and/or divergence differ greatly between members of the Gpx gene family, resulting from differential selective pressure acting on genes, and that adaptive evolution influenced the distribution of P. euphratica in desert regions.     

Genetic differentiation between clone collections and natural populations of European black poplar (<Emphasis Type="Italic">Populus nigra</Emphasis> L.) in turkey

The European black poplar (Populus nigra L.) is an ecologically and economically important tree species for Turkey. The important and major genetic resources of species for future breeding and ex situ conservation purposes have been archived in a clone bank in Ankara by selecting clones from natural populations and old plantations throughout Turkey. There is no study to date assessing genetic composition these materials. Two-hundred-thirty-three P. nigra clones from six geographic region of Turkey (clone collection populations), and 32 trees from two natural populations (Tunceli and Melet) were genotyped by using 12 nuclear microsatellite DNA markers. There were nine clones which duplicated in various frequencies. The analysis carried out with removal of the duplicated clones revealed a moderately high genetic diversity in studied populations. The observed heterozygosities ranged from 0.59 in Tunceli natural to 0.69 in Central Anatolia clone collection populations. In general, there was excess of heterozygosity in the studied populations. Populations composed of clone collections were significantly differentiated from natural populations (F _ST = 0.17), while there was little differentiation among those populations in the clone collection (F _ST = 0.03). Two distantly located natural populations with small sizes also differed from each other (F _ST = 0.17). Genetic structure analysis revealed two distinct groups (clone collection vs natural populations) with very high membership values (>92%). Clone collection populations had high level of admixture while natural populations had homogenous genetic structure. The presence of large number of clonal duplication, reduced genetic differentiation, and high level of admixture in clone collection populations indicate that genetic resources of European black poplar were highly degraded through genetic erosion and pollution caused by intensive cultural practices and extensive dispersal of clonal materials. To understand genetic diversity and its structural pattern thoroughly in the six clone collection populations, a further study with extensive and systematic sampling of European black poplar populations in major river ecosystems in Turkey will be useful.     

Extreme Selection Unifies Evolutionary Game Dynamics in Finite and Infinite Populations

We show that when selection is extreme—the fittest strategy always reproduces or is imitated—the unequivalence between the possible evolutionary game scenarios in finite and infinite populations resolves, in the sense that the three generic outcomes—dominance, coexistence, and mutual exclusion—emerge in well-mixed populations of any size. We consider the simplest setting of a 2-player-2-strategy symmetric game and the two most common microscopic definitions of strategy spreading—the frequency-dependent Moran process and the imitation process by pairwise comparison—both in the case allowing any intensity of selection. We show that of the seven different invasion and fixation scenarios that are generically possible in finite populations—fixation being more or less likely to occur and rapid compared to the neutral game—the three that are possible in large populations are the same three that occur for sufficiently strong selection: (1) invasion and fast fixation of one strategy; (2) mutual invasion and slow fixation of one strategy; (3) no invasion and no fixation. Moreover (and interestingly), in the limit of extreme selection 2 becomes mutual invasion and no fixation, a case not possible for finite intensity of selection that better corresponds to the deterministic case of coexistence. In the extreme selection limit, we also derive the large population deterministic limit of the two considered stochastic processes.