Mitochondrial DNA polymorphism among alpine populations of Gammarus lacustris (Crustacea, Amphipoda)

1. Mitochondrial DNA sequence analysis was used to investigate the phylogeographic structure among populations of the amphipod Gammarus lacustris isolated in high altitude lakes from the Northern to the Southern Alps, and to investigate the historical and demographic events that may have accompanied this differentiation.
2. The comparison of a 376‐base segment of the mitochondrial cytochrome c oxidase I gene in fifty‐four specimens from nine different populations reveals no variation within populations. However, northern populations appear divergent from those from the Southern Alps. A particular population, located at the limit between the Northern and Southern Alps shows an intermediate haplotype related to the southern lineage.
3. Consideration of the different mitochondrial lineages, together with geographical differences among populations, suggests a scenario for the post‐glacial colonization of G. lacustris in the alpine lakes.     

Clonal diversity of populations of Calamagrostis epigejos in relation to environmental stress and habitat heterogeneity

The clonal diversity of four populations of the vegetatively propagating grass Calamagrostis epigejos was studied with isozyme markers From each population, 100 individuals were sampled within a 10 × 10 m gnd In two populations of unpolluted sites 5 and 10 clones were distinguished, respectively Higher levels of clonal diversity were found m the populations at an abandoned sewage farm (59 clones) and around a copper smelter (92 clones) The level of clonal diversity observed suggests that sexual recruitment is important for the genetic structure in this species On the unpolluted, presumably more suitable habitats, the clonal diversity was lower than on the habitats polluted with heavy metals The results are discussed in relation to environmental stress and habitat heterogeneity, with the conclusion that in the unpolluted habitats intraspecific competition results in low clonal diversity On the other hand, stressful conditions decrease the importance of competition and facilitate the coexistence of a great number of clones     

Molecular nature of the cryotolerant lake amphipod Gammarus lacustris

Gammarus lacustris were studied in an attempt to identify the mechanism of subzero temperature adaptation, which enables this species to survive in winter under natural conditions. G. lacustris hemolymph contained a high concentration of glucose (42.4 mg/ml of hemolymph). In addition, galactose, mannose, xylose, zellobiose, and unidentifiable disaccharides and oligosaccharides were found, though at much lower concentrations (0.94-3.26 mg/ml). The glycerol concentration in the gammarus hemolymph was about 5-20 times as low as in many other animals surviving at subzero temperatures (16.2 mg/ml). Other sugars and polyhydric alcohols were discovered only in traces amounts in the hemolymph. Antifreeze proteins were not found in the gammarus.     

Breeding bird diversity in relation to environmental gradients in China

Geographic variation in species richness has been explained by different theories such as energy, productivity, energy–water balance, habitat heterogeneity, and freezing tolerance. This study determines which of these theories best account for gradients of breeding bird richness in China. In addition, we develop a best-fit model to account for the relationship between breeding bird richness and environment in China. Breeding bird species richness in 207 localities (3271 km² per locality on average) from across China was related to thirteen environmental variables after accounting for sampling area. The Akaike's information criterion (AIC) was used to evaluate model performance. We used Moran's I to determine the magnitude of spatial autocorrelation in model residuals, and used simultaneous autoregressive model to determine coefficients of determination and AIC of explanatory variables after accounting for residual spatial autocorrelation. Of all environmental variables examined, normalized difference vegetation index, a measure of plant productivity, is the best variable to explain the variance in breeding bird richness. We found that species richness of breeding birds at the scale examined is best predicted by a combination of plant productivity, elevation range, seasonal variation in potential evapotranspiration, and mean annual temperature. These variables explained 47.3% of the variance in breeding bird richness after accounting for sampling area; most of the explained variance in richness is attributable to the first two of the four variables.     

Molecular diversity of small balsam populations in relation to site characteristics

Climatic shifts within recent decades created favorable conditions for invasive species flourishing in more Northern parts of Europe. Our study was aimed at evaluation of genetic variability and habitat features of Impatiens parviflora populations growing in Lithuania. Twenty one populations were selected and analysed using simple sequence repeat (SSR) and randomly amplified polymorphic DNA (RAPD) assays. Evaluated by SSRs, 315 individuals were all monomorphic and homozygous at 4 loci and heterozygous at 1 locus. RAPD analyses revealed that the percentage of polymorphic DNA loci (% P) per population ranged from 7 to 39% and genetic differentiation between populations was Φ_PT=0.790 (P<0.01). Genetic distances among populations (0.135–0.426) correlated significantly with geographical distances (r=0.183; P<0.008). Populations in overmoistured soil contained higher % P (28.3) when compared to drier soil (18.7; P<0.05). All recorded populations were close to roads; their % P did not depend on proximity to buildings, light intensity or population size. Our RAPD analyses indicate multiple introductions of this species in Lithuania. Analyses of I. parviflora at SSR and RAPD loci show that the invasion process is reflected in genetic structure.     

Demography of alpine red squirrel populations in relation to fluctuations in seed crop size

Vertebrate population dynamics, social organisation and space use often are closely associated with the distribution of critical resources, such as food. Tree squirrels are ideal models to study these relationships, since both key demographic parameters (reproduction, survival and dispersal) and spatio-temporal variation in food supplies (measured as seed-crop size) can be reliably estimated. In this paper we test the following two predictions underlying the association between annual food abundance and demography in six alpine red squirrel populations, both with and without time-lag effects: 1) between-season and between-year fluctuations in survival rate, population density and increase parallel those in food availability; and 2) individuals follow a resource tracking strategy and increase in density mainly the year after a rich seed-crop. Red squirrels occurred at higher densities in Scots pine forest, characterised by stable seed-crops, than in Norway spruce with more abundant but more variable seed crops. Fluctuations in numbers were positively correlated with food availability, measured as annual conifer seed-crop sizes. Overall, adult survival rates were higher than those of subadults, and survival substantially fluctuated between seasons and years. Autumn densities and rates of population increase (summer-autumn) were strongly correlated with the same year's autumn seed-crop, while correlations with the previous year's seed-crop (time-lag models) were either weak (population density) or absent (population increase). Results of this paper show that fluctuations in red squirrel densities in habitats with strong temporal variation in seed production are more closely linked with food availability than in more stable habitats. In addition, in the Alpine conifer forests squirrel population sizes, in autumn, increase in synchrony with food resources, eliminating the population lag normally present when resources are produced in pulses.     

The peritrophic membrane and faecal pellets of Gammarus lacustris limnaeus Smith

SUMMARY. Gammarus lacustris limnaeus Smith was fed decomposed autumnshed leaves of maple ( Acer saccharum Marsh.) and poplar ( Populus tremuloides Michx.). Faecal pellets were collected at various time intervals after egestion and examined under a light and a scanning electron microscope. Nearly all the faecal pellets collected up to a period of about 7 h after egestion possessed a thin, tightly-fitting peritrophic membrane while those that had been outside the gut of the animal for a longer time lacked a peritrophic membrane. Presumably, after egestion faecal pellets swell because of absorption of water leading to eventual rupture and loss of the membrane. The surface of newly extruded pellets is devoid of microbes and microbes seem to play a very insignificant role in the loss of peritrophic membrane from the pellets.     

The influence of experimental scale on estimating the predation rate of Gammarus lacustris (Crustacea: Amphipoda) on Daphnia in an alpine lake

We examined the effect of experimental scale on the predationrate of Gammarus lacustris preying on Daphnia middendorffianain 20 l cubitainers, 2800 l mesocosms and diurnal whole-lakesurveys. The predation rate differed significantly among experimentalscales. It was highest in the 20 l cubitainers, intermediatein the 2800 l mesocosms and lowest in the lake. At all experimentalscales, the predation of G.lacustris on D.middendorffiana increasedas a linear function of prey density (Type I functional response).Very different predation rates were calculated for the wholelake depending on whether D.middendorffiana densities were estimatedfrom whole-water column hauls or stratified depth hauls. Thishighlights the importance of accurately determining the spatialdistribution of prey for estimating reliable in situ predationrates. We also determined prey selection by G.lacustris. Daphniamiddendorffiana was strongly selected over the calanoid copepodHesperodiaptomus arcticus. When presented with different sizedDaphnia, G.lacustris preyed size selectively on individuals2 mm. Our results show that the predation rate of small invertebratepredators is sensitive to a wide range of experimental conditionsand needs to be corroborated at a variety of scales. We concludethat the impact of G.lacustris on zooplankton communities wouldbe strongest in small fishless lakes or ponds.     

四种松毛虫表型性状多样性与环境因子的关系

对马尾松毛虫、落叶松毛虫、云南松毛虫、思茅松毛虫4种松毛虫的8个表型性状(蛹重、蛹长、雌雄虫体重、雌雄虫翅展和雌雄虫体长)进行了遗传多样性分析.结果表明:8项性状指标在4种松毛虫之间差异极显著;在所有性状中变异系数最大的是蛹重(CV=51.99％);对各种群变异系数比较分析发现,变异系数最大的是落叶松毛虫,最小的是云南松毛虫.主成分分析表明,蛹长、雌虫体重和雌虫翅展3个主分量构成的信息量基本能代表这8个性状的变异.系统聚类的结果为马尾松毛虫与落叶松毛虫聚为第一分支,思茅松毛虫和云南松毛虫聚为第二分支.松毛虫属昆虫表型性状的变异与生态环境因子的相关性较密切.     

Ingestion and Adsorption of Bacillus thuringiensis subsp. israelensis by Gammarus lacustris in the Laboratory

Several groups of Gammarus lacustris adults were exposed to solutions containing 0.5 and 5.0 mg of Bacillus thuringiensis subsp. israelensis per liter for 1- or 24-h periods by using traditional static bioassay exposure procedures. During a postexposure holding period, fecal pellets were removed and plated on tryptic soy agar to determine B. thuringiensis subsp. israelensis spore content. The experiments verified that traditional exposure procedures assure ingestion of B. thuringiensis subsp. israelensis spores and provided a mean dose estimate of 1,948 spores ingested per test animal with a 95% confidence interval ranging from 891 to 4,296 (1-h exposure, 5.0 mg/liter). It was also found that dose level is highly dependent upon both exposure duration and concentration and that relatively short exposures can result in a relatively long-term retention of spores postexposure (≥30 days). Body burden experiments established that large numbers of spores adsorb to the bodies of test animals during exposure and may in part explain the long-term retention of spores in the test system postexposure. These results imply that in field applications of microbial control agents, toxicologically unaffected but exposed organisms might transport the agent to untreated sites, expanding the effective treatment area and the number of organisms exposed.     

Refugial races and postglacial colonization history of the freshwater amphipod Gammarus lacustris in Northern Europe

The systematic structure and postglacial population history of the freshwater amphipod Gammarus lacustris were explored in an allozyme survey of 65 populations across Northern Europe. A strong multilocus pattern of differentiation discriminated populations of the north‐east (north‐eastern Norway, northern Finland) from those in the west and the south (southern and central Scandinavia, Denmark, Poland). This principal division is attributed to postglacial colonization of the area by two main refugial races or lineages, one from the east (Russia), the other from the south (north‐western European continent). The strongly diverged Eastern and Western races (Nei's D= 0.3, from 22 loci) now meet in a secondary contact zone across a narrow sector of northernmost Norway. Genetic population compositions in this zone vary in a mosaic pattern, and show no evidence of reproductive incompatibility. Similar contacts of eastern and western lineages, far older than the latest glaciation, are now known from a number of taxa and they constitute a general pattern in Fennoscandian phylogeography. Within the Western Gammarus race, the populations through coastal north‐western Norway are further distinguished from those in southern Scandinavia and Denmark by a set of unique alleles at high frequencies (D = 0.12). This suggests an independent early colonization of the coastal region by another distinct stock, either along an early deglaciated coastal corridor from the south‐west, or directly from the ice‐free continental shelf off the Norwegian coast – a hypothesis that has also previously been presented for G. lacustris, and parallels controversial suggestions of local refugia for other taxa in Scandinavia. The coastal population type only later could come into contact with Gammarus invading over the mountains from the south; these two population types now smoothly intergrade. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 523–542.     

Plant species diversity and composition of wet grasslands in relation to environmental factors

Relationships between environmental factors and plant species-richness as well as the composition of plant species in wet grasslands from the order Molinietalia caeruleae were studied with a view to quantifying the relative contribution of different abiotic factors, such as soil chemical parameters, climatic conditions and human impact to diversity of vascular plants and floristic composition. Data and soil samples were collected from 88 plots across Slovenia from regions at the eastern edge of the Po plain, karstic and pre-Alpine mountain regions and the western part of the Pannonian plain, which are classified to sub-Mediterranean, Dinnaric, pre-Alpine and sub-Pannonian phytogeographic areas. Plant diversity was positively correlated with the content of exchangeable Ca²⁺ in soil and the amount of annual precipitation, while significant negative correlation was calculated in case of the plant-available phosphorous content and altitude. Moreover, plant species richness was also negatively correlated with altitude. Among the groups of environmental factors the group of soil factors revealed the strongest correlation with species richness, followed by climatic and topographic group. The order of these groups was the same in the explanation of species composition. Variance of plant species composition was best explained with altitude, soil pH, geographical gradient, frequency of flooding, mean annual temperature, date of mowing, humidity, annual amount of precipitation as well as with the content of plant-available phosphorous, total nitrogen, exchangeable Mg²⁺ and Ca²⁺ in the soil.     

Niche segregation of terrestrial alpine beetles (Coleoptera) in relation to environmental gradients and phenology

At Finse, south Norway (60°36'N, 7°30'E), 247 pitfall traps were set in forty-seven alpine habitats. More than 21,000 individuals were caught, including thirteen species of Carabidae, forty-six Staphylinidae and twenty-eight species from other families. The locations were selected to maximize variation in soil water contents between the habitats, but minimize variation in time of snowmelt and aspect. Soil water content of the sites was highly correlated with soil organic content, and showed little variation between dry and rainy periods. A reciprocal averaging (RA) ordination of the sites and coleoptera species gave results similar to a direct gradient analysis based on soil water content of the sample sites, clearly showing the importance of habitat humidity. Riverside and mire habitats had the most distinct species composition. Niche segregation among the species was studied based on guild, soil humidity preference, seasonal activity pattern and altitudinal range. Most species were well separated along one or more of these niche dimensions. No species from the wettest habitats were autumn active, otherwise all permutations of the described niche dimensions were used. Carabids and herbivores from various families were all spring active, while 38% of the staphylinids, mainly in the subfamily Omaliinae, were autumn active. In cases where species were not clearly separated, their behaviour, morphology, size, diet, etc. were considered.     

Ecophysiological adaptations of two Mediterranean red algae in relation to distribution

Effects of irradiance and temperature on the Mediterranean red algae Eupogodon spinellus and Eupogodon planus were tested. Growth of both species was saturated at an irradiance of 10–20?μmol?m^?2?s^?1, which is in accordance with their sublittoral habitat. Eupogodon spinellus and E. planus survived permanently at temperatures between 8 and 30?°C. The temperature optimum for growth was 25?°C with suboptimal growth occurring at (10?)15 and 30?°C in both species. At their collection locality (Corsica), potential monthly growth yields would be highest in summer and in winter would be only about 20% of the maximum. Reproductive requirements could be determined only in E. planus. Gametophytes reproduced both in long and in short days but only at 20?°C. Tetrasporophytes reproduced at 15–20?°C but only in short days. Geographic distribution boundaries are not set by growth or survival limits. However, the reproductive requirements of E. planus did account for its restricted distribution in the Mediterranean and on the Canary Islands.     

Pairing success of male Gammarus lacustris infected by two acanthocephalans: a comparative study

The costs of parasitism to host reproduction can be best assessedusing field studies to determine overall mating success andexperimental studies to examine how parasites may affect matingbehavior. We compared the influence of two parasites, Polymorphusparadoxus and P. marilis (Acanthocephala), on the pairing successof their intermediate host (Gammarus lacustris, Crustacea) inboth the field and laboratory. Parasitism significantly loweredthe pairing success of male gammarids. In the field, P. paradoxus-infectedmales paired significantly less often than P. marilis-infectedor uninfected males. Those infected by P. marilis were alsofound in precopula significandy less often than uninfected ones.In the laboratory, the pairing success of males infected byeither parasite was significantly reduced in both competitiveand noncompetitive situations. As in the field studies, thepairing success of P. paradoxus-infected males was significantlylower than that of P. marilis-infected and uninfected males.Polymorphus marilis-infected males were also outcompeted byuninfected individuals, however, their pairing success improvedwhen alone with a female (noncompetitive experiments). We relatethe differential influence of the two parasites on the pairingsuccess of male gammarids to their effects on the physiologyand behavior of G. lacustris.     

青藏高原高寒草地植物物种丰富度及其与环境因子和生物量的关系

在青藏高原进行了大范围的群落调查 ,研究高原的两种主要草地群落类型———高寒草甸和高寒草原的植物物种丰富度及其变化。结果表明 :(1)在 5 0个样地 2 5 0个 1m× 1m的样方中 ,共出现 2 6 7种植物 ,其中高寒草甸179种 ,高寒草原 135种。在高寒草甸 ,1m2 样方内物种数最多为 32种 ,最少的仅为 3种 ;在高寒草原 ,物种数最多为 18种 /m2 ,最少的仅为 2种 /m2 。 (2 )物种丰富度随经度和纬度的增加呈增加趋势 ;随海拔的上升呈减少趋势。对物种丰富度与环境因子之间进行逐步回归 ,发现物种丰富度与生长季降水和温暖指数呈显著正相关。 (3)物种丰富度与地上生物量呈显著正相关。