Intertidal zonation of animals and plants on rocky shores in the Bristol Channel and Severn Estuary–the northern shores

The vertical distribution of common species of macroalgae and fauna on rocky shores extending through the length of the estuary is described. In the west, the shores are fully marine and exposed to Atlantic waves. In an eastward direction, greater shelter and an increasing tidal range occur along a gradient of salinity and turbidity. The flora and fauna change along this gradient. No single biological feature signals a transition from the Bristol Channel to the Severn Estuary but four arbitrary regions are recognized: a 'marine' section eastwards to Swansea, a 'transitional' section between Swansea and Cardiff, an 'estuarine' section up to Newnham, and the tidal river Severn.     

Ecology of marine algae on rocky shores and subtidal reefs in temperate Australia

Experiments in intertidal and subtidal rocky marine habitats in temperate Australia have identified the effects of various biological and physical factors on algal assemblages. In intertidal habitats, these involve micro- and macro-algae and grazing by gastropods. In subtidal habitats, interactions among micro- and macro-algae, echinoids, gastropods, micro-invertebrates and sessile invertebrates have been studied. Experimental studies on physical disturbances of algal assemblages have focussed on the effects of desiccation and storms. Most studies have not considered more than one spatial or temporal scale. Few have been concerned with seasonal influences and fewer have been concerned with variation from year to year. Most of the work lacks applicability to biogeographic comparisons. More experimental work across a variety of spatial and temporal scales is required to determine significant biological and physical processes affecting structure of algal assemblages across broad areas of temperate Australia.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.     

Predicting impacts of climate-induced range expansion: an experimental framework and a test involving key grazers on temperate rocky shores

Climate change has strong potential to modify the structure and functioning of ecosystems, but experimental field studies into its effects are rare. On rocky shores, grazing limpets strongly affect ecosystem structure and their distribution in NW Europe is changing in response to climate change. Three limpet species co-occur in SW Britain ( Patella vulgata, Patella ulyssiponensis and Patella depressa ) on open rock and in pools. Shores in Ireland are similar, but currently lack P. depressa . It is anticipated that P. depressa will expand its range into Ireland as the climate warms, but we currently lack an empirical basis to predict the consequences of this change. Recent studies show that increasing abundance of P. depressa on British shores has been accompanied by a decline of P. vulgata suggesting interspecific competition. In this study, a new experimental framework was used to examine the potential for P. depressa to affect P. vulgata on Irish shores. P. vulgata was experimentally transplanted into enclosures on open rock and in pools in both Ireland and Britain. In pools, treatments also included transplanted P. ulyssiponensis to mimic natural assemblages. Growth and mortality of P. vulgata were measured over 6 months with no differences between Ireland and Britain. In Britain, P. vulgata caged in pools with transplanted P. depressa and P. ulyssiponensis showed reduced growth, compared with when caged in pools with P. ulyssiponensis alone. There was no effect of P. depressa on the growth rate of P. vulgata on open rock. Results indicate that if the range of P. depressa extends into Ireland, it would reduce the growth of P. vulgata where it co-occurs with P. ulyssiponensis in pools. The framework used here provides a field-based approach that could be used to examine the impacts of climate-induced range expansions on the structure and functioning of other ecosystems.     

Seasonal distribution and species composition of daytime biting mosquitoes

Adults and immatures of Aedes mosquito populations were collected at temperatures between 40 and 44°C (summer), while larvae were collected at 0°C (winter). Major mosquito activities were observed from February to mid-December at various collection sites that yielded high populations of Aedes spp. from May to September, and high populations of Culex spp. and Anopheles spp. from March to September. In June to July, mosquito activity was suspended because the relative humidity was high (70%); a result of the monsoon rains. In August, with temperature ranging from 38 to 42°C, the populations of Culex , Anopheles and Aedes began to increase (36.8, 32.1 and 26.3%, respectively). Population estimates (through standard prototype Centers for Disease Control (CDC) and Biogents (BG)-sentinel) and species composition of Aedes in forest habitats indicated a rapid increase in the populations of Ae. albopictus (52.3%), Ae. aegypti (19.1%) and Ae. vittatus (28.5%) following the rainy season in July. Areas positive for Ae. albopictus had identical population levels and distribution ranges of Ae. vittatus , however, there were no Ae. aegypti in Ae. albopictus areas from August to September. The population level, seasonal distribution, habitat and areas of adult activity marked by global positioning system (GPS) coordinates are being used for reference and for species composition data of Anopheles spp. (2), Culex spp. (10) and Aedes spp. (5) in addition to associated temperature, relative humidity and physico-chemical factors of larval habitat. Global meteorological changes have caused an expansion of the active period, leading to the mosquito's possibility of being a vector of disease increasing, resulting in the spread of dengue fever.     

Do distributional shifts of northern and southern species of algae match the warming pattern?

Well-documented changes in species abundances and distributions coinciding with global warming have been increasing during recent years. A trend of raising sea-surface temperature has also been observed along the Portuguese coast which could affect intertidal species' ranges. The present study aimed at evaluating the direction and intensity of distribution changes of macroalgae in the area. The last 50-year trend of coastal air and sea temperature was reassessed, providing an accurate estimate of the warming process. Information on species' range shifts was obtained by comparing data from recent resurveys with historical records of algal distributions collected during the 1950s and 1960s. Although a prevalence of northward migrations was anticipated, this work showed a marked difference in the average direction of changes between cold- and warm-water species. Cold-water species, when considered together, showed no particular shifting trend, because the number of species that shifted north or south was the same. Contrarily, all shifting warm-water species expanded their range northwards. Therefore, generalizations about poleward range shifts due to increasing temperature should be made with caution.     

中国西南地区石漠化敏感性评价及其空间分析

石漠化是我国西南地区最为严重的生态环境问题之一,识别发生石漠化敏感区域,为岩溶地区石漠化防治提供科学依据显得十分必要。总体分析了目前中国石漠化和有关生态环境研究的资料,将石漠化敏感性影响因子归结为岩性、降水、坡度和植被等4项,并确定了各因素对石漠化敏感性影响等级,综合评价了我国西南五省(市)(包括黔、滇、贵、川、渝)石漠化敏感性及其空间分布格局。结果表明,敏感性评价结果基本反映石漠化现状,石漠化敏感区集中分布在贵州西部、南部,广西西部、东部以及云南东部等地。四川、重庆等地石漠化危害相对较小。     

北京松山国家级自然保护区野生种子植物分布及物种组成分析

采取踏查、样方和样线相结合的方法,调查了北京松山国家级自然保护区内野生种子植物的分布状况,并对其种类组成和分布区类型进行了分析。调查结果显示：该保护区内共有野生种子植物92科382属721种,其中,裸子植物3科4属5种、被子植物89科378属716种;被子植物中包含双子叶植物78科298属569种和单子叶植物11科80属147种。含20种或20种以上的科有7个,包含的属、种数量均占该保护区野生种子植物属、种总数的40%以上,优势科现象明显;含1种和含2-4种的属分别有235和128个,具有绝对优势。该保护区野生种子植物科的分布区类型可分为8个,除世界广布科外,以泛热带分布型科和北温带分布型科为主;属的分布区类型可分为15个,以北温带分布型属为主,热带性质属与温带性质属的数量比为0.20。该保护区内有国家重点保护野生植物2种、北京市重点保护野生植物52种,其中包含兰科（Orchidaceae）植物14属18种以及数量极少的丁香叶忍冬（LoniceraoblataK.S.HaoexP.S.HsuetH.J.Wang）和北京市特有植物北京水毛茛（BatrachiumpekinenseL.Liou）;该保护区内还有7种具有入侵倾向的外来植物。此外,还有北京新记录植物3种,分别为柳叶野豌豆也Viciavenosa（Willd.exLink）Maxim.页、北方红门兰（OrchisroborowskiiMaxim.）和廻旋扁蕾也Gentianopsiscontorta（Royle）Ma页。研究结果表明：该保护区的野生种子植物区系具有典型的温带性质并有一定的过渡性。     

长白山多孔菌物种多样性、区系组成及分布特征

多孔菌是木材腐朽真菌的一个重要类群,通过将木材中的纤维素、半纤维素和木质素分解成为可被自身和其他生物利用的营养物质,从而促进森林生态系统中的物质循环.经过十几年的考察和采集,发现长白山地区多孔菌物种多样性非常丰富,Shannon多样性指数达到5.06,共有246种,占中国多孔菌总数的40.7％,分别隶属于担子菌门6个目11个科80个属,其中优势科为多孔菌科.物种区系地理成分以北温带成分和世界广布成分为主,其他几种区系成分也有分布,具有明显的北温带成分区系特征.松属是长白山地区多孔菌最重要的寄主树木,该地区41.5％的多孔菌生长在松属上.该地区多孔菌主要营腐生生活,其数量与生长基质腐烂程度的相关系数达到了0.89,呈显著相关,对长白山森林生态系统的物质循环起着重要作用.长白山多孔菌物种保护程度比较高,其中稀有种和濒危种的数量均相对较多,濒危种18种,占到全国濒危种数量的37.5％.多孔菌除了在森林生态系统中发挥重要生态功能外,很多种类本身具有较高的经济价值.在保护好该生物类群的前提下,可以合理开发和利用这些宝贵的生物资源.     

The effects of grazing on the distribution and composition of low-shore algal communities on the central coast of Portugal and on the southern coast of Britain

A red algal turf is often found just below the barnacle/limpet zone of many European shores, especially on steep shores of moderate exposure. The hypothesis that grazing by limpets determines the upper limit of distribution of this red algal turf was tested on moderately exposed shores in Portugal and Britain. We also aimed to assess whether the grazing effect is modified at various spatial scales. Grazers were excluded by fences, with half-fenced and unfenced controls. Exclusion plots were rapidly colonised by green ephemeral algae in the months immediately after the beginning of the experiment (summer); these algae were later replaced by perennial algae. The percentage cover of turf-forming macroalgae showed a significant increase at both locations. The upper limit of distribution extended more than 50 cm on most of the shores studied. In contrast, control and half-fenced plots remained devoid of algae. After 2 years, ungrazed plots were mainly colonised by a red algal turf (e.g. Caulacanthus ustulatus, Gelidium spp., Laurencia pinnatifida) in Portugal, while canopy cover (Fucus serratus and Himanthalia elongata) dominated in Britain in marked contrast to the grazed plots. Physical factors acting at both local and geographical scales may explain these differences. However, although physical factors probably have an important influence on the identity, size and abundance of sublittoral fringe macroalgae, grazers play a major role in directly setting their upper limits. The effect of grazing by limpets was not consistent for all of the morphological algal groups and spatial scales considered in the present study. The effect of grazing on the cover of turf algae varied between Portugal and Britain (location scale), while effects on ephemeral and canopy algal cover varied at the shore scale within location.     

The shifts in species composition and ecological modelling in hydrobiology

Ecosystems have an enormous flexibility to meet changes in external factors and still maintain their functions. If present species are not able to cope with the conditions, given by the external factors, new species are waiting in the wings ready to take over. It is a serious shortcoming of our present ecological models, that they are not able to describe these changes in species composition. However, it seems that the thermodynamic function exergy may be used as goal function in ecological models to incorporate the flexibility of real ecosystems and the selection of species into our models of ecosystems. The application of exergy in modelling may be considered a translation of Darwin's selection into thermodynamics. The theoretical basis for the application of exergy as goal function is presented, and applications of exergy in ecological models are illustrated by several case studies.     

应用指示种预测森林管理对物种多样性及群落组成的影响

采用指示种分析方法,研究了会同亚热带森林物种多样性和群落组成对森林管理的响应.从357个林下种中鉴定出显著性指示种94个,并构造新的指示种数据集,检验指示种数据集和源群落数据集之间的关联,评估指示种对林下植被管理效应的预测潜能.结果表明:指示种数据集和源群落数据集之间存在极显著的关联(Mantel r=0.898),指示种数据集很好地预测了生物多样性的变化(回归分析,R2>0.74);指示种很好地预测了群落组成对森林管理的响应(ANOVA,F>16.79);非度量多尺度排序(NMDS)以及K-means聚类分析表明,对于不同森林管理的样地类型,指示种数据集的识别能力和源群落数据集是一致的.从物种多样性、群落组成以及在森林类型的识别上,指示种数据集和源群落数据集有一致性规律,作用几乎相同,因此森林评估可以利用指示种代替源群落预测森林管理效应,以减少森林全面调查的成本.     

Importance of intermediate disturbances for the species composition and diversity of phytoplankton in two very different Berlin lakes

Species composition and diversity of phytoplankton were studied for several years in two lakes which differ with respect to mixing conditions and nutrient limitation: Schlachtensee regularly stratifies very stably. In contrast, size and wind-exposure predispose Lake Tegel to deeper mixing; additionally, stratification is artificially destabilized by aeration. As the duration of aeration was varied, the study period includes interannual changes in mixing conditions. For both lakes, it also covers trophic change due to restoration; this was especially pronounced in Schlachtensee.Results show that mixing conditions affect species composition on two levels: on a superordinate level, lake morphology or hydrology govern stability of stratification and susceptibility to perturbation, and hence the extent to which motile species can develop. In Schlachtensee, species with some means of actively seeking preferred depths usually dominated during summer stratification: Planktothrix agardhii during the hypertrophic phase, and flagellates since restoration. In contrast, in Lake Tegel deeper mixing as a generally prevailing condition favored non-motile species. Their seasonal pattern was remarkably constant from year to year. Although changes in the extent of mixing were pronounced during the four years studied (1987–1990), these were within a range that affected species composition only slightly: in summer, cyanobacteria and diatoms represented climax species whose dominance was not offset by additional, weather-induced increases of turbulence.On a subordinate level, and within the constraints set by nutrient limitation as well as by grazing pressure, small-scale changes in mixing conditions caused by meteorological cycles were shown to strongly affect species composition and in consequence diversity: Results for the fouryear post-restoration study period at Schlachtensee show that considerable interannual variations of species composition and diversity can be attributed to variations in the frequency of meteorological changes. In accordance with the intermediate disturbance hypothesis (IDH), diversity was lowest during 1989, the year with the longest and most pronounced cycles of fair weather (14 to 27 fair days on end). However, the mechanism for this was rarely a decline of diversity caused by competitive exclusion within single long phases of stable conditions, as conceived by the intermediate disturbance hypothesis. Instead, diversity responded to changes in mixing conditions with a variety of patterns — often with low values during phases of increased mixing and with high values under quiescent conditions, especially during the first calm days just after increased mixing. Thus, not disturbance as such, but rather the rate of change between phases of disturbance and quiescence appears to determine the frequency of high diversity indices.In Lake Tegel, high diversity indices were somewhat more frequent in 1989, the year during which thermal stratification was most stable. For species adapted to frequent or continuous mixing, interjected calm phases with unusually high stability of thermal stratification may represent a disturbance of accustomed conditions. Thus, in turbulent Lake Tegel, meteorological cycles appear to act in reversal to the IDH, in a sense which may be termed intermediate quiescence hypothesis.Phosphorus limitation due to successful restoration was found to decrease winter and vernal diversity in Schlachtensee. Presumably, without nutrient constraints, new populations could grow more rapidly in response to the rapid changes of physical parameters during this season. In contrast, restoration has increased summer diversity, as phosphorus concentrations no longer allow the virtual monocultures of Planktothrix agardhii which prevailed previously. In Lake Tegel, the reduction of phosphorus concentration down to 60 µg/l P in 1989 limited biomass, but this level was still too high to significantly alter species composition or diversity.     

Genetic differentiation and species cohesion in two widespread Central American Begonia species

Begonia is one of the ten largest plant genera, with over 1500 species. This high species richness may in part be explained by weak species cohesion, which has allowed speciation by divergence in allopatry. In this study, we investigate species cohesion in the widespread Central American Begonia heracleifolia and Begonia nelumbiifolia, by genotyping populations at microsatellite loci. We then test for post-zygotic reproductive barriers using experimental crosses, and assess whether sterility barriers are related to intraspecific changes in genome size, indicating major genome restructuring between isolated populations. Strong population substructure was found for B. heracleifolia (F_ST=0.364, F′_ST=0.506) and B. nelumbiifolia (F_ST=0.277, F′_ST=0.439), and Bayesian admixture analysis supports the division of most populations into discrete genetic clusters. Moderate levels of inferred selfing (B. heracleifolia s=0.40, B. nelumbiifolia s=0.62) and dispersal limitation are likely to have contributed to significant genetic differentiation (B. heracleifolia Jost''s D=0.274; B. nelumbiifolia D=0.294). Interpopulation crosses involving a divergent B. heracleifolia population with a genome size ∼10% larger than the species mean had a ∼20% reduction in pollen viability compared with other outcrosses, supporting reproductive isolation being polymorphic within the species. The population genetic data suggest that Begonia populations are only weakly connected by gene flow, allowing reproductive barriers to accumulate between the most isolated populations. This supports allopatric divergence in situ being the precursor of speciation in Begonia, and may also be a common speciation mechanism in other tropical herbaceous plant groups.     

Predation by gulls on crabs in rocky intertidal and shallow subtidal zones of the Gulf of Maine

Most organisms in intertidal areas are marine in origin; many have distributions that extend into the subtidal zone. Terrestrial predators such as mammals and birds may exploit these animals during low tide and can have considerable effects on intertidal food webs. Several studies have shown that avian predators are capable of reducing densities of sessile and slow-moving intertidal invertebrates but very few studies have considered avian predation on mobile invertebrate predators such as crabs. In this study, we investigated predation by Great Black-backed Gulls (Larus marinus Linnaeus) on three species of crabs (Cancer borealis Stimpson, Cancer irroratus Say, and Carcinus maenas Linnaeus). The study was at Appledore Island, ME (a gull breeding island) and 8 other sites throughout the Gulf of Maine, including breeding islands and mainland sites. On Appledore Island, intertidal and subtidal zones provided over one-third of prey remains found at gull nests, and crabs were a substantial proportion (∼ 30% to 40%) of the total remains. Similarly, collections of prey remains from intertidal areas indicated that crabs were by far the most common marine prey. C. borealis was eaten far more often and C. irroratus and C. maenas less often than expected at each site. Comparing numbers of carapaces to densities of crabs in low intertidal and shallow subtidal zones at each site, we estimated that gulls remove between 15% and 64% of C. borealis during diurnal low tides. The proportion of C. borealis eaten by gulls was independent of proximity to a gull colony. Approximately 97% of the outer coast of Maine is within 20 km of a breeding island. Thus, a lot of gull predation on crabs may occur throughout the Gulf of Maine during summer months. Crabs are important predators of other invertebrates; if predation by gulls reduces the number of crabs in intertidal and shallow subtidal areas, gulls may have important indirect effects on intertidal food webs.     

Polychaetes and oligochaetes associated with intertidal rocky shores in a semi-enclosed industrial and urban embayment,with the description of two new species

The species composition and relative abundance of the annelid benthic macrofauna (Polychaeta and Oligochaeta) inhabiting the rocky intertidal zone of the ria of Ferrol (Galicia, NW Spain) were studied during field collections, from 2000 to 2002. A total of 14,619 specimens (11,585 polychaetes belonging to 76 species and 24 families and 3,034 oligochaetes belonging to 18 species and two families) were collected from 98 quantitative samples taken from 13 sampling sites. The general spatial distribution of the annelid fauna reflects an increase of the diversity from the inner to the outer part of the ria. The general patterns found in the annelid composition suggest that the assemblages were dominated by oligochaetes in the inner sheltered sampling sites and polychaetes in the outer more exposed sites. Several faunistical and taxonomical remarks on selected species are presented. Two new species of oligochaetes are described: Coralliodrilus artabrensis sp. n. and Pirodrilus fungithecatus sp. n. (Naididae, Phallodrilinae). A new biological index, based on the oligochaete/polychaete ratio (O/P), is proposed as tool to evaluate environmental quality and to monitor future changes in the environment.     

The submerged macrophytes in Lake Maarsseveen I: Changes in species composition and biomass over a six year period

The submerged macrophytes of Lake Maarsseveen I were surveyed in 1983 using SCUBA diving techniques. Only 40% of the characeans and 75% of the angiosperms detected in 1977 remained. The area colonized by submerged macrophytes was 0.45% in 1983, compared with 25.10% in 1977. The observed decreases were largely attributable to a shift of the plantcolonized areas to shallower depths. By 1983, most of the earlier predominant vegetation types had disappeared and the biomass had decreased. The decline in submerged vegetation may be attributed to increasing eutrophication, fish populations and recreational activities.