Role of host identity in effects of phytogenic mounds on plant assemblages and species richness on coastal arid dunes

Question: Phytogenic mounds (nebkhas) ‐ the natural accumulation of wind‐blown sediments within or around the canopies of plants ‐ have been proposed as important structures for locally maintaining high species richness in coastal and arid ecosystems. Nebkhas are assumed to increase habitat heterogeneity, but what is the importance of the nebkha host species relative to other nebkha characteristics in determining the associated plant assemblages? Are some host species more effective in creating diversity hotspots, or does a single species‐area relationship apply to all nebkhas, regardless of host species? Can the influence of the host be ascribed to its indirect effects on abiotic attributes of the nebkha complex? Methods and location: We investigated plant species richness and composition on nebkhas around six psammophytic species on Mediterranean coastal dunes of the Sinai Peninsula. Results: Plant species richness was significantly related to nebkha size by the single power function according to the general prediction of island biogeography theory, but this relationship was modified ‐ though to a limited degree ‐ by nebkha host species identity. Canonical Correspondence Analysis revealed that nebkha host species identity and nebkha environmental and non‐environmental factors significantly explained species composition on the nebkhas, but host species identity did so to a greater extent. The latter might reflect differences in seed trapping ability or free space for colonization between host species. Conclusion: Differences in community composition and richness among nebkhas formed by different host species represent a key factor in the maintenance of plant diversity on arid coastal dunes.     

Stress responses and metal tolerance of <Emphasis Type="Italic">Chlamydomonas acidophila</Emphasis> in metal-enriched lake water and artificial medium

Chlamydomonas acidophila faces high heavy-metal concentrations in acidic mining lakes, where it is a dominant phytoplankton species. To investigate the importance of metals to C. acidophila in these lakes, we examined the response of growth, photosynthesis, cell structure, heat-shock protein (Hsp) accumulation, and metal adsorption after incubation in metal-rich lake water and artificial growth medium enriched with metals (Fe, Zn). Incubation in both metal-rich lake water and medium caused large decreases in photosystem II function (though no differences among lakes), but no decrease in growth rate (except for medium + Fe). Concentrations of small Hsps were higher in algae incubated in metal-rich lake-water than in metal-enriched medium, whereas Hsp60 and Hsp70A were either less or equally expressed. Cellular Zn and Fe contents were lower, and metals adsorbed to the cell surface were higher, in lake-water-incubated algae than in medium-grown cells. The results indicate that high Zn or Fe levels are likely not the main or only contributor to the low primary production in mining lakes, and multiple adaptations of C. acidophila (e.g., high Hsp levels, decreased metal accumulation) increase its tolerance to metals and permit survival under such adverse environmental conditions. Supposedly, the main stress factor present in the lake water is an interaction between low P and high Fe concentrations.     

Geochemistry of Lake Biwa sediments revisited

Extensive chemical data for the Lake Biwa sediments were examined with statistical factor analysis to find any correlation patterns among elements and among samples. Based on those patterns, a series of x-y correlation plots of the concentrations of selected elements was constructed to see in detail how the concentrations of elements vary among different sample groups and explain the observed variation patterns.     

Linking major nutrients (C,H, N,and P) to trace metals (Fe,Mn, and Cu) in lake seston in southern Brazil

We investigated the relationships between major nutrients (C, H, N, and P) and trace metals (Cu, Fe, and Mn) in seston samples from ten lake/lagoon systems in southern Brazil. The systems were characterized by a diverse set of limnological features, including surface areas from 10⁻¹ to 10² km², water color, a _CDOM(440), from 1.4 to 12.9 m⁻¹, and electrical conductivity from 50 to 100 000 μS cm⁻¹. Seston concentrations also varied a great deal, 32-fold. The elemental (C: N, C: P, and N: P) and C: Chl-a ratios in the seston samples indicated, however, common features; i.e., most of the lakes were N-and/or P-limited, and the seston organic fraction was composed of nonvascular plants (e.g., phytoplankton). Our intersystem comparison revealed that the relative content of organic matter in seston and seston concentrations in lake water tended to correlate positively and negatively, respectively, with trace metal concentrations across the seston samples. Possible influences of elemental and C: Chl-a ratios on the association of metals with seston matrices, although theoretically important, were only partially evidenced here; positive correlations were found between C: N and also Org-H: N ratios with trace metal concentrations. We speculate that such results could be circumstantial, as the nature of the seston matrices appeared to be very similar among them. This hypothesis should thus be the theme of further research. In short, our findings suggest that C: N and Org-H: N ratios as well as the relative content of major nutrients in seston and seston concentrations can be importantly related to trace metal concentrations in seston samples. In discussing the results, however, we consider that metal-seston relationships depend on a variety of physical, chemical, and biological factors and/or variables other than those measured in this study, which could also contribute for defining and explaining variations in metal-seston concentrations in lake ecosystems.     

A new species of Jesogammarus from the Iki Island,Japan (Crustacea,Amphipoda, Anisogammaridae)

A new species of anisogammarid amphipod, Jesogammarus (Jesogammarus) ikiensis sp. n., is described from freshwaters in the Iki Island, Nagasaki Prefecture, Japan, based on results of morphological and molecular analyses. The new species is distinguished from all members of the genus by the combination of small number of setae on dorsal margins of pleonites 1–3, short and small number of setae on posterior margins of peduncular articles of antennae, mandibular article 1 without setae, well developed posterior lobes of accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5, and pectinate setae on palmar margin of female gnathopod 2. A key to all the species of Jesogammarus is provided.     

Trophic mismatch and its effects on the growth of young in an Arctic herbivore

In highly seasonal environments, timing of breeding of organisms is typically set to coincide with the period of highest resource availability. However, breeding phenology may not change at a rate sufficient to keep up with rapid changes in the environment in the wake of climate change. The lack of synchrony between the phenology of consumers and that of their resources can lead to a phenomenon called trophic mismatch, which may have important consequences on the reproductive success of herbivores. We analyzed long‐term data (1991–2010) on climate, plant phenology and the reproduction of a long‐distance Arctic migrant, the greater snow goose (Chen caerulescens atlantica), in order to examine the effects of mismatched reproduction on the growth of young. We found that geese are only partially able to adjust their breeding phenology to compensate for annual changes in the timing of high‐quality food plants, leading to mismatches of up to 20 days between the two. The peak of nitrogen concentration in plants, an index of their nutritive quality for goslings, occurred earlier in warm springs with an early snow melt. Likewise, mismatch between hatch dates of young and date of peak nitrogen was more important in years with early snow melt. Gosling body mass and structural size at fledging was reduced when trophic mismatch was high, particularly when the difference between date of peak nitrogen concentration and hatching was >9 days. Our results support the hypothesis that trophic mismatch can negatively affect the fitness of Arctic herbivores and that this is likely to be exacerbated by rising global temperatures.     

FATTY ACIDS,AMINO ACIDS,MINERAL CONTENTS,AND PROXIMATE COMPOSITION OF SOME BROWN SEAWEEDS1

This study was conducted to create a nutritional database on brown seaweeds and to popularize their consumption and utilization in Iran. The fatty acid contents, amino acids profiles, and certain mineral elements composition of some brown seaweeds, Padina pavonica (L.) Thivy, Dictyota dichotoma (Huds.) J. V. Lamour., and Colpomenia sinuosa (Mert. ex Roth) Derbés et Solier were determined. Total lipid content ranged from 1.46 ± 0.38 to 2.94 ± 0.94 g · 100 g^?1dry weight (dwt), and the most abundant fatty acids were C16:0, C18:1, C20:4 ω6, and C20:5 ω3. The unsaturated fatty acids predominated in all species and had balanced sources of ω3 and ω6 acids. Highest total polyunsaturated fatty acid (PUFA) levels occurred in C. sinuosa. The protein content of D. dichotoma was 17.73 ± 0.29 g · 100 g^?1dwt, significantly higher than the other seaweeds examined. Among amino acids essential to human nutrition, methionine (Met; in D. dichotoma and P. pavonica) and lysine (Lys; in C. sinuosa) were present in high concentrations. The crude fiber content varied by 9.5 ± 11.6 g · 100 g^?1dwt in all species. Chemical analysis indicated that ash content was between 27.02 ± 0.6 and 39.28 ± 0.7 g · 100 g^?1dwt, and that these seaweeds contained higher amounts of both macrominerals (7,308–9,160 mg · 100 g^?1dwt; Na, K, Ca) and trace elements (263–1,594 mg · 100 g^?1dwt; Fe, Ni, Mn, Cu, Co) than have been reported for edible land plants. C. sinuosa had the highest amount of Ca, Fe, and a considerable content of Na was measured in P. pavonica.     

Influence of habitat features and hunter behavior on white-tailed deer harvest

Sport hunting may help in controlling cervid populations over large areas. As with natural predators, several environmental factors can influence sport harvest. A better understanding of the environmental variables that limit the efficiency of sport hunting could provide guidelines for more efficient wildlife management using hunting. We studied white-tailed deer (Odocoileus virginianus) hunting on a high deer density island where hunting was the sole form of predation. Our objective was to study the behavior of sport hunters and determine the habitat characteristics (e.g., abundance of deer forage, visibility of the deer from the hunter's point of view, and accessibility of the territory to hunters) that are associated with a successful harvest. We collected movements and harvest site location data from 477 hunters equipped with handheld Global Positioning System (GPS) units. Harvest sites were visited and characterized, along with a paired random site, to determine the environmental conditions associated with a successful hunt. We also developed a model to predict the daily number of deer seen by hunters considering weather conditions, hunter characteristics (e.g., age, experience), and date of hunting. We used the mean number of deer seen per hunter per day as a relative index of local density in each hunted territory. At both the site and landscape scales, the combination of visibility and access had a positive effect on the distribution of harvested deer. Habitat types with less visual obstruction from vegetation enabled hunters to see more deer in a given day. At the site scale, harvested deer were located in areas with a lower density of access routes compared to areas where hunters travelled throughout the day. Using an innovative approach of studying hunter behavior with GPS technology, digital maps, and questionnaires, we highlighted the factors associated with hunter success. Our study suggests that habitat characteristics could be modified to increase harvest by improving accessibility and visibility near roads. Creating openings in mature and regenerating forest near access roads could make sport hunting a more efficient management tool, but the potential impact of increased forage availability in forest openings should not be overlooked. © 2012 The Wildlife Society.     

滇池北部湖区浮游植物时空格局及相关环境因子

为研究滇池北部湖区浮游植物的时空格局,探讨影响格局形成的关键影响因子,2008年12月至2009年6月,在滇池北部湖区选择6个点位,共开展了24次采样,调查并分析了浮游植物群落及其相关理化参数。通过比对滇池全湖周年监测数据,研究发现,北部湖区叶绿素a浓度从12月中旬开始下降,2月中旬降至最低值26.5μg/L,5月中旬达到最大值530.5μg/L。调查期间共鉴定出浮游植物74属97种,其中绿藻53种,蓝藻20种,硅藻17种,隐藻2种,金藻2种,甲藻1种,裸藻2种。蓝藻生物量在12月、3月至6月期间占优势,12月份优势种为绿色微囊藻(Microcystis viridis),3月至5月为水华束丝藻(Aphanizomenonflos-aquae),6月为惠氏微囊藻(Microcystis wesenbergii)。硅藻在1月占优势,优势种为颗粒直链藻最窄变种(Melosira granulata var.angustissima)。研究结果表明,水温高于14℃以上,微囊藻生物量迅速增加;束丝藻生物量随温度增加而增加,高于22℃时迅速减少。北部湖区6个点位浮游植物的空间差异显著,D1、D4号点微囊藻、束丝藻生物量显著高于其他四个点(P<0.01),D2、D5号点广缘小环藻生物量显著高于其他四个点(P<0.01)。研究结果显示,在富营养化严重的滇池北部湖区,水温可能为影响浮游植物种类组成及生物量的关键因子,浮游植物水平分布的差异主要由气象因素和水体营养盐共同决定。     

水盾草—南四湖外来水生植物新记录及其生境特点

外来生物入侵与生境改变被认为是导致全球生物多样性下降的两大主因[1]。其中入侵植物通过营养竞争、植被结构改变、化感作用等,影响土著植物种群和群落,进而影响生态系统结构和功能。水生植物的入侵已成为影响我国淡水水体景观和生物多样性的重要因素[2—4]。水盾草