Genetic structure of endangered lake chubsucker Erimyzon sucetta in Canada reveals a differentiated population in a precarious habitat

We used mitochondrial DNA to assess the genetic structure of endangered lake chubsucker Erimyzon sucetta across its Canadian range. We found unique mitochondrial haplotypes in Lyons Creek, a tributary of the Niagara River that faces a strong potential for habitat deterioration. Lyons Creek may therefore serve as a reservoir of unique genetic diversity. The sensitivity of Lyons Creek, combined with the genetic uniqueness of its E. sucetta population, call for further investigation into whether this population should be considered a separate designatable unit for conservation purposes.     

Mass-transfer-limited nitrate uptake on a coral reef flat,Warraber Island,Torres Strait,Australia

Previous research has identified a relationship between the rate of dissipation of turbulent kinetic energy, , and the mass-transfer-limited rate of uptake by a surface, herein called the ^1/4 law, and suggests this law may be applicable to nutrient uptake on coral reefs. To test this suggestion, nitrate uptake rate and gravitational potential energy loss have been measured for a section of Warraber Island reef flat, Torres Strait, northern Australia. The reef flat section is 3 km long, with a 3 m tidal range, and on the days measured, subject to 6 m s^–1 tradewinds. The measured nitrate uptake coefficient, S , on two consecutive days during the rising tide was 1.23±0.28 and 1.42±0.52×10^–4 m s^–1. The measured loss of gravitational potential energy across the reef flat, GPE , on the same rising tides over a 178 m section was 208±24 and 161±20 kg m^–1 s^–2. Assuming the GPE is dissipated as turbulent kinetic energy in the water column, and using the ^1/4 law, the mass-transfer-limited nitrate uptake coefficient, S_MTL , on the two days was 1.57±0.03 and 1.45±0.04×10^–4 m s^–1. Nitrate uptake on Warraber Island reef flat is close to the mass-transfer limit, and is determined by oceanographic nitrate concentrations and energy climate.Communicated by B.C. Hatcher     

Coralline algae indicate Pleistocene evolution from deep,open platform to outer barrier reef environments in the northern Great Barrier Reef margin

Coralline algae from a drill core in Ribbon Reef 5 have been used to interpret changes in the depositional palaeoenvironments in the northern Australian Great Barrier Reef over the last 790 ka. Three main coralline algal assemblages, each dominated by members of a particular subfamily, have been distinguished by quantitative analysis: (1) mastophoroid assemblages, usually occurring as crusts on corals, are typical of the shallowest reef settings; (2) lithophylloid assemblages within algal nodules may represent shallow-water, cooler environments or deeper reef subenvironments; and (3) melobesioid assemblages are characteristic of deeper-water platform areas. The algal assemblages between 96 and 210 m b.s.f. (metre below sea floor) record a fluctuating but progressive shallowing-upwards from deep, outer-platform to shallower, non-reefal depositional environments. Two intervening episodes dominated by mastophoroids represent two phases of reef growth. The section above 96 m b.s.f. comprises several stacked reefs in which mastophoroid crusts similar to the present-day shallow-water assemblages predominate.Electronic Supplementary Material Supplementary material is available for this article at .Communicated by: Geological Editor P.K. Swart     

Cytogenetics of the Anopheles gambiae complex in Sudan, with special reference to An. arabiensis: relationships with East and West African populations

The species composition of malaria vector mosquitoes belonging to the Anopheles gambiae complex (Diptera: Culicidae) from >40 localities in Sudan, representing most ecological situations, was determined by analysis of ovarian polytene chromosomes. Of 2162 females, 93% were identified as An. arabiensis Patton and 7% were An. gambiae Giles sensu stricto. No hybrids were found between the two species. Anopheles arabiensis occurred in all but two sites, whereas An. gambiae s.s. was effectively limited to the southernmost, more humid localities. For chromosomal paracentric inversions, the degree of polymorphism was low in An. gambiae s.s. (inversions 2La, 2Rb and 2Rd), higher in An. arabiensis (inversions Xe, 2Ra, b, bc, d1, s; 3Ra, d). Anopheles gambiae samples from Sudan were all apparently panmictic, i.e. they did not show restricted gene flow such as observed among West African populations (interpreted as incipient speciation). Chromosomal inversion patterns of An. gambiae in southern Sudan showed characteristics of intergrading Savanna/Forest populations similar to those observed in comparable eco-climatic situations of West Africa. Anopheles arabiensis was polymorphic for inversion systems recorded in West Africa (2Ra, 2Rb, 2Rdl, 3Ra) and for a novel 2Rs polymorphism, overlapping with inversion systems 2Rb and 2Rd1. Samples carrying the 2Rs inversion were mostly from Khashm-el-Girba area in central-eastern Sudan. In the great majority of the samples all polymorphic inversions were found to be in Hardy-Weinberg equilibrium. Sudan populations of An. arabiensis should therefore be considered as generally panmictic. Anopheles arabiensis shows more inversion polymorphism in west than in east African populations. Sudan populations have more evident similarities with those from westwards than those from eastwards of the Great Rift Valley. The possible influence of the Rift on evolution of An. arabiensis is discussed.     

Long-term response of the biotic community to fluctuating water levels and changes in water quality in Cootes Paradise Marsh,a degraded coastal wetland of Lake Ontario

During the early 1900s, more than 90% of the surface area of Cootes Paradise Marsh was covered with emergent vegetation; currently, less than 15% of the surface is covered with aquatic vegetation and the remainder is wind-swept, turbid, open water. The loss of emergent cover is significantly correlated with mean annual water levels that increased more than 1.5 m over the past 60 years. Species diversity and the percent cover of the submerged macrophtye community also declined dramatically after the 1940s, coincident with decreased water clarity and increased nutrients from pollution by sewage and stormwater effluent. Phosphorus levels in the marsh dropped ten-fold after the sewage plant was upgraded to a tertiary-treatment facility in 1978; however, there was no measurable improvement in water clarity, in spite of a decrease in chlorophyll concentrations. Long-term changes in the composition of the planktonic, benthic and fish communities accompanied changes in water clarity, nutrient status and macrophyte cover. Phytoplankton changed from a community dominated by diverse taxa of green algae and diatoms during the 1940s, to a less diverse community dominated by a few taxa of green and blue-green algae in the 1970s, then to a much more diverse community recently, including many taxa of green algae, diatoms and chrysophytes; however, because water turbidity continues to be high, and algae tolerant of low light levels are now very abundant. Daphnia, which were prominent during the 1940s (especially in the vegetated sites) were replaced in the 1970s by smaller zooplankton such as the cladoceran, Bosmina, and several rotifer species including Brachionus, Asplanchna and Keratella. In the recent survey conducted in 1993 and 1994, small-bodied forms still dominate the turbid open-water areas, while medium-sized cladocerans such as Moina were common near macrophyte beds. Generally, total herbivorous zooplankton biomass tended to be highest next to Typha beds and declined with increasing distance from the plants. Conversely, biomass of edible algae at these sites increased with distance from the macrophytes. Species diversity of aquatic insects declined dramatically over the past 40 years, from 57 genera (23 families and 6 orders) in 1948, to 9 genera (6 families and 3 orders) in 1978, to only 5 genera (3 families and 2 orders) in 1995. The diverse benthic community present 5 decades ago has now been replaced by a community consisting primarily of chironomid larvae, oligochaetes and other worms associated with low-oxygen environments. These successional changes illustrate the impact of natural (fluctuating water levels) and anthropogenic (deterioration in water quality) stressors on the character of the biotic communities, and reveal the complex interactions among the various trophic levels and the abiotic environment as degradation and remediation proceeded.     

Population genetic structure, phylogeography and spawning philopatry in walleye (Stizostedion vitreum) from mitochondrial DNA control region sequences

Mitochondrial (mt) DNA control region sequences were used to test the genetic and phylogeographic structure of walleye Stizostedion vitreum populations at different geographical scales: among spawning sites, lake basins, lakes, and putative glacial refugia in the Great Lakes region. Sequencing 199 walleye revealed nucleotide substitutions and tandemly repeated sequences that varied in copy number, as well as in sequence composition, in 1200 bp of the mtDNA control region. Variable numbers of copies of an 11-bp tandem repeat showed no geographical patterning and were not used in further analyses. Substitutions in the other areas of the control region yielded 19 haplotypes, revealing phylogeographic structure and significant differences among glacial refugia, lakes, basins and some spawning sites. Differences among spawning populations were consistent with reduced gene flow, philopatry and possible natal homing. Analysis of spawning populations showed consistency of genotypic frequencies among years and between males and females, supporting philopatry in both sexes. The unglaciated plateau in southern Ohio, USA housed a very different haplotype that diverged prior to the Missouri, Mississippi and Atlantic glacial refugia types. Haplotypes from the three refugia colonized the Great Lakes after retreat of the Wisconsin glaciers, and their present distribution reflects the geography of their prior isolation and differential colonization. Populations that became associated with spawning localities appear to have diverged further due to philopatry, resulting in fine-scale phylogeographic structuring.     

Spatial and temporal patterns in maternal energetic traits of yellow perch (Perca flavescens) in Lake Erie

1. For many fish species, survival during early life stages is linked to the size and energetic condition of females prior to reproduction. For example, females in good energetic condition are often more fecund and produce larger eggs and offspring than those in poor condition. 2. We measured the characteristics of female yellow perch (Perca flavescens) that may influence annual population fluctuations. From 2005 to 2007, we measured spatial variation in female reproductive traits, such as age, length, mass and energy density (J g^?1) of somatic tissues and ovaries among four spawning aggregations of yellow perch in western and central Lake Erie. 3. Maternal traits, such as somatic energy density and spawner age distribution, differed between the western and central basin, whereas reproductive traits, such as fecundity and ovarian energy density, differed across years. 4. To understand the implications of observed differences in demographic rates (growth and mortality rates) between basins, we developed a deterministic model to simulate the total egg production in the western and central basins under different scenarios of fishing mortality. 5. High growth rates and low mortality rates combined to produce higher modelled estimates of total egg production in the central than in the western basin, and a larger proportion of eggs were produced by old age classes in the central basin than in the western basin. 6. Our results demonstrate that changing harvest levels for populations with different demographic rates can influence total reproductive output through complex interactions between age‐specific mortality, growth and size‐specific fecundity, which has implications for the population dynamics of yellow perch and related species across a broad geographic range.     

AN ASSESSMENT OF ECOLOGICAL CHANGES DURING THE RECENT HISTORY OF LAKE ONTARIO BASED ON SILICEOUS ALGAL MICROFOSSILS PRESERVED IN THE SEDIMENTS1,2

Quantitative analysis of siliceous algal microfossils (diatoms and chrysophytes) in a radiometrically dated core of Lake Ontario sediments shows striking modifications of the flora produced and preserved, apparently as a result of anthropogenic modification of nutrient loadings to the lake, Qualitatively similar microfossil assemblages were deposited during the period ca. 1700–1815. A single major event is recorded in assemblages deposited ca. 1769. Between this event horizon and ca. 1815 there was an apparent increase in algal production, but minimal change in species composition. A major disturbance occurred at the level of the Ambrosia horizon, ca. 1831–1847. Assemblages deposited between ca. 1855 and 1900 indicate increasing eutrophication. We infer that silica limitation became important by about 1860 and that the system reached its greatest effective production ca. 1900. Major modification of the flora occurred in the period ca. 1900–1945, with most local extinctions of major indigenous populations occurring ca. 1920–1945. Assemblages deposited in the period ca. 1945–1975 are composed of some stenothermal populations also present in pre-disturbance assemblages, a large component of benthic and nearshore planktonic species, and a number of apparently planktonic populations rarely recorded from large temperate lakes, particularly species of the genus Nitzschia. Our results indicate that the major factor driving species succession in Lake Ontario was phosphorus enrichment and consequent depletion of available silica supplies. Our results also show the importance of a species' physical niche in determining its survival under these conditions.     

选择性冠状静脉动脉化搭桥术中不同移植物的应用疗效比较

目的:对比选择性冠状静脉动脉化(SCVBG)搭桥治疗弥漫性右冠状动脉狭窄病变中选择乳内动脉和大隐静脉作为桥血管的治疗效果。方法:选择2008年10月到2014年10月在我院行SCVBG搭桥的84例患者资料,其中选择大隐静脉作为桥血管进行冠状静脉动脉化搭桥患者46例(大隐静脉桥组),选择乳内动脉作为桥血管进行冠状静脉动脉化搭桥患者38例(乳内动脉桥组)。随访记录两组患者的生存情况、近期复查超声心动图、冠状动脉CTA及心绞痛复发率。结果:乳内动脉桥组患者总生存率(100%)明显高于大隐静脉桥组(82.6%)(P0.05)。乳内动脉桥组患者桥血管和心中静脉通畅率(100%)明显大于大隐静脉桥组(54.35%)(P0.05)。两组患者左心室射血分数(LVEF)较治疗前明显增加,左心室舒张期末内径(LVEDD)较治疗前明显减小(P0.05)。治疗后,乳内动脉桥组患者心绞痛复发率明显小于大隐静脉桥组(P0.05)。结论:SCVBG搭桥治疗弥漫性右冠状动脉狭窄病变中,选择乳内动脉桥效果优于大隐静脉桥,能明显提高桥血管和心中静脉通畅率,降低心绞痛复发率。