A model for range expansion of an introduced species: the common waxbill Estrilda astrild in Portugal

Abstract. The common waxbill Estrilda astrild was first introduced to Portugal from Africa in 1964, and has spread across much of the country and into Spain. We modelled the expansion of the common waxbill on a 20 × 20 km UTM grid in 4‐year periods from 1964 to 1999. The time variation of the square root of the occupied area shows that this expansion process is stabilizing in Portugal, and reasons for this are discussed. Several methods used to model biological expansions are not appropriate for the present case, because little quantitative data are available on the species ecology and because this expansion has been spatially heterogeneous. Instead, colonization on a grid was modelled as a function of several biophysical and spatio‐temporal variables through the fitting of a multivariate autologistic equation. This approach allows examination of the underlying factors affecting the colonization process. In the case of the common waxbill it was associated positively with its occurrence in adjacent cells, and affected negatively by altitude and higher levels of solar radiation.     

Predicting patterns of vascular plant species richness with composite variables: a meso-scale study in Finnish Lapland

This paper is an attempt, using statistical modelling techniques, to understand the patterns of vascular plant species richness at the poorly studied meso-scale within a relatively unexplored subarctic zone. Species richness is related to floristic-environmental composite variables, using occurrence data of vascular plants and environmental and spatial predictor variables in 362 1 km² grid squares in the Kevo Nature Reserve. Species richness is modelled in two different way. First, by detecting the major floristic-environmental gradients with the ordination procedure of canonical correspondence analysis, and subsequently relating these ordination axes to species richness by generalized linear modelling. Second, species richness is directly related to the composite environmental factors of explanatory variables, using partial least squares regression. The most important explanatory variables, as suggested by both approaches, are relatively similar, and largely reflect the influence of altitude or altitudinally related variables in the models. The most prominent floristic gradient in the data runs from alpine habitats to river valleys, and this gradient is the main source of variation in species richness. Some local environmental variables are also relatively important predictors; the grid squares rich in vascular plant taxa are mainly located in the lowlands of the reserve and are characterised by rivers and brooks, as well as by abundant cliff walls. The two statistical models account for approximately the same amount of variation in the species richness, with more than half of the variation unexplained. Potential reasons for the relatively modest fit are discussed, and the results are compared to the characteristics of the diversity-environment relationships at both broader- and finer-scales.     

Modelling the species richness distribution of French dung beetles (Coleoptera, Scarabaeidae) and delimiting the predictive capacity of different groups of explanatory variables

Aim To predict French Scarabaeidae dung beetle species richness distribution, and to determine the possible underlying causal factors. Location The entire French territory has been studied by dividing it into 301 grid cells of 0.72 × 0.36 degrees. Method Species richness distribution was predicted using generalized linear models to relate the number of species with spatial, topographic and climate variables in grid squares previously identified as well sampled (n = 66). The predictive function includes the curvilinear relationship between variables, interaction terms and the significant third‐degree polynomial terms of latitude and longitude. The final model was validated by a jack‐knife procedure. The underlying causal factors were investigated by partial regression analysis, decomposing the variation in species richness among spatial, topographic and climate type variables. Results The final model accounts for 86.2% of total deviance, with a mean jack‐knife predictive error of 17.7%. The species richness map obtained highlights the Mediterranean as the region richest in species, and the less well‐explored south‐western region as also being species‐rich. The largest fraction of variability (38%) in the number of species is accounted for by the combined effect of the three groups of explanatory variables. The spatially structured climate component explains 21% of variation, while the pure climate and pure spatial components explain 14% and 11%, respectively. The effect of topography was negligible. Conclusions Delimiting the adequately inventoried areas and elaborating forecasting models using simple environmental variables can rapidly produce an estimate of the species richness distribution. Scarabaeidae species richness distribution seems to be mainly influenced by temperature. Minimum mean temperature is the most influential variable on a local scale, while maximum and mean temperature are the most important spatially structured variables. We suggest that species richness variation is mainly conditioned by the failure of many species to go beyond determined temperature range limits.     

流溪河大型底栖动物群落的时空分布及其影响因子

流溪河位于我国热带与亚热带过渡区,其底栖动物种类丰富,群落的物种组成结构具有明显的区域性,掌握该地区的物种组成特征及与环境要素的关系是建立生态监测与评估方法的基础。于2018年的枯水期（3月、12月）和丰水期（6月、9月）,自流溪河上游至下游共计20个段面对底栖动物进行了定量采样,同时测定了相应的环境因子,采用多元统计方法对流溪河水环境与群落结构及其相关关系进行了分析。共检出底栖动物76个分类单元,隶属于7纲20目50科,其中水生昆虫相对丰度最高,占69.39%。在4个优势分类单元中,摇蚊族（Chironomini）相对丰度为20.19%,河蚬（Corbicula fluminea）、短沟蜷属的一种（Semisulcospira sp.1）、双突细蜉（Caenis bicornis）,相对丰度在7%-9%之间。底栖动物丰度和种类多样性均与浊度呈显著负相关;枯水期底栖动物丰度与总磷呈显著负相关,丰水期则呈显著正相关。在丰水期,不同河流级别上底栖动物群落具有明显的差异,表现较强的分布格局,而在枯水期这种分布格局不明显。典范对应分析（CCA）表明,在丰水期,影响或解释流溪河底栖动物群落变化的主要因子为pH、溶解氧、水温、电导率和硅酸盐,而在枯水期则为pH和硝态氮。受电站与采沙的影响,部分河段发生非自然断流和底质的显著改变,导致底质与水深等数据的异常变化,反映了人类活动对该河流生境与环境的重要影响。     

Phenotypic plasticity in Philonotis fontana (Bryopsida: Bartramiaceae)

Abstract

Gametophytes from six populations of the moss Philonotis fontana (Hedw.) Brid. were grown under two light and two water regimes in order to assess the effects of these environmental factors on gametophytic architecture and leaf and leaf-cell dimensions. Both light and water affectedgrowth, but the light treatments had a greater effect, and on more characters, than did the water treatments. Significant population effects under common garden conditions point to genetic variation for several traits, and population × environmental treatment interactions demonstratedgenetic variation for patterns of phenotypic plasticity, i.e. plants differed in their 'norms of reaction'. Variation among populations in leaf dimensions tended to have a strong genetic component (20–30% of the total variation), whereas cell dimensions showed relatively little geneticvariation (<10% of the total).     

Stream macroinvertebrate response to catchment urbanisation (Georgia, U.S.A.)

SUMMARY 1. The effects of catchment urbanisation on water quality were examined for 30 streams (stratified into 15, 50 and 100 km² ± 25% catchments) in the Etowah River basin, Georgia, U.S.A. We examined relationships between land cover (implying cover and use) in these catchments (e.g. urban, forest and agriculture) and macroinvertebrate assemblage attributes using several previously published indices to summarise macroinvertebrate response. Based on a priori predictions as to mechanisms of biotic impairment under changing land cover, additional measurements were made to assess geomorphology, hydrology and chemistry in each stream. 2. We found strong relationships between catchment land cover and stream biota. Taxon richness and other biotic indices that reflected good water quality were negatively related to urban land cover and positively related to forest land cover. Urban land cover alone explained 29–38% of the variation in some macroinvertebrate indices. Reduced water quality was detectable at c. >15% urban land cover. 3. Urban land cover correlated with a number of geomorphic variables such as stream bed sediment size (–) and total suspended solids (+) as well as a number of water chemistry variables including nitrogen and phosphorus concentrations (+), specific conductance (+) and turbidity (+). Biotic indices were better predicted by these reach scale variables than single, catchment scale land cover variables. Multiple regression models explained 69% of variation in total taxon richness and 78% of the variation in the Invertebrate Community Index (ICI) using phi variability, specific conductance and depth, and riffle phi, specific conductance and phi variability, respectively. 4. Indirect ordination analysis was used to describe assemblage and functional group changes among sites and corroborate which environmental variables were most important in driving differences in macroinvertebrate assemblages. The first axis in a non‐metric multidimensional scaling ordination was highly related to environmental variables (slope, specific conductance, phi variability; adj. R²=0.83) that were also important in our multiple regression models. 5. Catchment urbanisation resulted in less diverse and more tolerant stream macroinvertebrate assemblages via increased sediment transport, reduced stream bed sediment size and increased solutes. The biotic indices that were most sensitive to environmental variation were taxon richness, EPT richness and the ICI. Our results were largely consistent over the range in basin size we tested.     

Seasonal changes in fish catch and environmental variables in a large Tropical Lake,Volta, Ghana

Fish species assemblage and selected environmental variables were monitored in Lake Volta from September 2014 to August 2016 to determine seasonal variability in species composition, catch and environmental variables that determine the structure of the fish community. A total of 1,557 individual fish belonging to 41 species, 25 genera and 13 families were recorded. The important fish species with respect to frequency of occurrence, abundance and weight, respectively, were as follows: Chrysichthys (100%; 43.03%; 17.93%), tilapias (100%; 28.97%; 17.86%), Alestes (100%; 14.13%; 32.10%) and Bagrus (91.67%; 5.65%; 12.80%) in that order. The composition of fish species and their temporal variation in experimental catches were similar to that of commercial catches. There were no significant differences (p > 0.05) in species abundance, weight and diversity indices between the dry and wet seasons. The modal class of length frequency distribution of the dominant species in the catch, Chrysichthys, reduced from 125 mm in 2006 to 95 mm in the current study indicating overfishing. Environmental variables considered showed little variation and within optimal ranges for fish survival and did not differ significantly between seasons. Canonical Correspondence Analysis showed that environmental variables explained 43.30% of the variation in species abundance with Lake water level, nitrite‐nitrogen and total dissolved solids being the main environmental factors influencing the structure of the fish community.     

长白山次生杨桦林优势更新幼苗空间分布及环境解释

为了解长白山次生杨桦林中优势更新幼苗的空间分布及其与环境因子之间的关系,以5.2 hm²（200 m×260 m）固定样地更新幼苗的全面定位调查和环境因子调查本底数据为基础,对样地内个体数量排序前5的优势更新幼苗进行分析。结果表明：在中小距离尺度上,水曲柳（Fraxinus mandshurica）（0-90 m）、色木槭（Acer mono）（0-60 m）、紫椴（Tilia amurensis）（0-60 m、90-150 m）和假色槭（Acer pseudo-sieboldianums）（0-90 m）更新幼苗的空间分布关系为显著正自相关,呈聚集性分布;群落水平上,环境变量和空间变量对5种优势更新幼苗的空间分布变异解释能力为61%,其中,纯粹空间变量的解释度为56%,而纯粹环境变量的解释度不足1%;种群水平上,环境因子对更新幼苗的空间分布有一定影响,其中,水曲柳幼苗的空间分布与土壤有机质、土壤全钾和土壤水分显著相关,色木槭幼苗的空间分布与土壤有机质和土壤全磷显著相关,紫椴幼苗的空间分布与土壤全磷显著相关,假色槭幼苗的空间分布与土壤水分显著相关;簇毛槭（Acer barbinerve）幼苗的空间分布与环境因子未表现出显著的相关性。长白山次生杨桦林中优势更新幼苗多为聚集性分布,环境因子对其分布有一定影响。     

Empirical realised niche models for British higher and lower plants – development and preliminary testing

Question: Can useful realised niche models be constructed for British plant species using climate, canopy height and mean Ellenberg indices as explanatory variables? Location: Great Britain. Methods: Generalised linear models were constructed using occurrence data covering all major natural and semi‐natural vegetation types (n=40 683 quadrat samples). Paired species and soil records were only available for 4% of the training data (n=1033) so modelling was carried out in two stages. First, multiple regression was used to express mean Ellenberg values for moisture, pH and fertility, in terms of direct soil measurements. Next, species presence/absence was modelled using mean indicator scores, cover‐weighted canopy height, three climate variables and interactions between these factors, but correcting for the presence of each target species in training plots to avoid circularity. Results: Eight hundred and three higher plants and 327 bryophytes were modelled. Thirteen per cent of the niche models for higher plants were tested against an independent survey dataset not used to build the models. Models performed better when predictions were based only on indices derived from the species composition of each plot rather than measured soil variables. This reflects the high variation in vegetation indices that was not explained by the measured soil variables. Conclusions: The models should be used to estimate expected habitat suitability rather than to predict species presence. Least uncertainty also attaches to their use as risk assessment and monitoring tools on nature reserves because they can be solved using mean environmental indicators calculated from the existing species composition, with or without climate data.     

Ecological preference between generalist and specialist rodents: spatial and environmental correlates of phenotypic variation

Different ecological preferences among species may result in differences in response to similar environmental variation. To test this hypothesis, we assessed the patterns of skull and mandible size and shape variation in three Sigmodontinae mice from agroecosystems of central Argentina with increasing degree of specialization: Calomys musculinus, Akodon azarae and Oxymycterus rufus. Spatial patterns in size and shape were analysed after controlling for allometry and sexual dimorphism using a total of 697 specimens. We then evaluated the covariation between shape, climatic and environmental variables and assessed the contribution of distinct climatic and environmental variables to phenotypic variability. Oxymycterus rufus displayed a marked spatial structure, and there was a high correlation between shape, climatic and environmental variables in this species. Climatic and environmental variables had a moderate effect on the phenotype of A. azarae, and were not correlated with morphological variation in C. musculinus. Our study highlights the difference in phenotypic responses to spatial and environmental gradients across coexisting species, specialist species displaying a more marked spatial structure in morphology than generalist species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 180–203.     

MICROGEOGRAPHIC GENETIC STRUCTURE OF MORPHOLOGICAL AND LIFE HISTORY TRAITS IN A NATURAL POPULATION OF IMPATIENS CAPENSIS

To investigate the microgeographic spatial structure of genetic variation for quantitative traits in a natural population of Impatiens capensis, we performed a common-garden greenhouse experiment. Seedlings were collected at 10-m intervals from a 40 times 40-m permanent grid in a natural population and grown to maturity in a greenhouse. From these parents, 3 self-fertilized seed families per grid point were then grown in a randomized design in the greenhouse and scored for a variety of morphological and life-history traits. Virtually all of the traits displayed significant variation among families, and many were significantly heterogeneous among grid points, indicating microgeographic genetic differentiation on a fine spatial scale. Overall morphological divergence, measured as Mahalanobis distances between grid points, increased with geographical distance. In general, spatial autocorrelation coefficients of grid point character means were positive at 11–20 m and negative beyond 40 m, although power for significance testing was low. The first factor in a principal component analysis of grid point means was positively loaded on height-related traits and negatively loaded on total reproduction at 50 days, accounting for 31% of the variation. This factor displayed significant positive spatial autocorrelation at 11–20 m and negative autocorrelation at >40 m. The remaining factors showed no detectable spatial structuring among grid points. These differences in spatial pattern among characters suggest that forces other than drift may have influenced the genetic structure of the population. There was no evidence for density-dependent selection; seedling density was not significantly correlated with the grid point mean of any trait.     

Multivariate analysis of a fine-scale breeding bird atlas using a geographical information system and partial canonical correspondence analysis: environmental and spatial effects

Aim To assess the relative roles of environment and space in driving bird species distribution and to identify relevant drivers of bird assemblage composition, in the case of a fine‐scale bird atlas data set. Location The study was carried out in southern Belgium using grid cells of 1 × 1 km, based on the distribution maps of the Oiseaux nicheurs de Famenne: Atlas de Lesse et Lomme which contains abundance for 103 bird species. Methods Species found in < 10% or > 90% of the atlas cells were omitted from the bird data set for the analysis. Each cell was characterized by 59 landscape metrics, quantifying its composition and spatial patterns, using a Geographical Information System. Partial canonical correspondence analysis was used to partition the variance of bird species matrix into independent components: (a) ‘pure’ environmental variation, (b) spatially‐structured environmental variation, (c) ‘pure’ spatial variation and (d) unexplained, non‐spatial variation. Results The variance partitioning method shows that the selected landscape metrics explain 27.5% of the variation, whilst ‘pure’ spatial and spatially‐structured environmental variables explain only a weak percentage of the variation in the bird species matrix (2.5% and 4%, respectively). Avian community composition is primarily related to the degree of urbanization and the amount and composition of forested and open areas. These variables explain more than half of the variation for three species and over one‐third of the variation for 12 species. Main conclusions The results seem to indicate that the majority of explained variation in species assemblages is attributable to local environmental factors. At such a fine spatial resolution, however, the method does not seem to be appropriated for detecting and extracting the spatial variation of assemblages. Consequently, the large amount of unexplained variation is probably because of missing spatial structures and ‘noise’ in species abundance data. Furthermore, it is possible that other relevant environmental factors, that were not taken into account in this study and which may operate at different spatial scales, can drive bird assemblage structure. As a large proportion of ecological variation can be shared by environment and space, the applied partitioning method was found to be useful when analysing multispecific atlas data, but it needs improvement to factor out all‐scale spatial components of this variation (the source of ‘false correlation’) and to bring out the ‘pure’ environmental variation for ecological interpretation.     

Abundance of Three Bacterial Populations in Selected Streams

The population sizes of three bacterial species, Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida, were examined in water and sediment from nine streams in different parts of the United States using fluorescent in situ hybridization (FISH). Population sizes were determined from three sites (upstream, midstream, and downstream) in each stream to compare differences in the occurrence and distribution of the species within each stream and among streams. Physical and chemical variables measured reflected differences in environmental conditions among the streams. In the water, B. cepacia numbers were highest in the agricultural, Iowa stream. P. putida numbers were highest in the southern coastal plain streams, Black Creek (GA) and Meyers Branch (SC). Compared to the other two species, the abundance of A. calcoaceticus was similar in all the streams. In sediment, the greatest abundance of all three species was found in the Iowa stream, while the lowest was in Hugh White Creek (NC). Detrended correspondence analysis (DCA) explained 95.8% and 83.9% of the total variation in bacterial numbers in water and sediment of the streams, respectively. In sediments and water, B. cepacia numbers were related to nitrate concentrations. A. calcoaceticus in water clustered with several environmental variables (i.e., SRP, pH, and conductivity) but benthic populations were less well correlated with these variables. This study reveals the potential influence of various environmental conditions on different bacterial populations in stream communities.     

Modelling the limits on the response of net carbon exchange to fertilization in a south-eastern pine forest

Using a combination of model simulations and detailed measurements at a hierarchy of scales conducted at a sandhills forest site, the effect of fertilization on net ecosystem exchange (NEE) and its components in 6‐year‐old Pinus taeda stands was quantified. The detailed measurements, collected over a 20‐d period in September and October, included gas exchange and eddy covariance fluxes, sampled for a 10‐d period each at the fertilized stand and at the control stand. Respiration from the forest floor and above‐ground biomass was measured using chambers during the experiment. Fertilization doubled leaf area index (LAI) and increased leaf carboxylation capacity by 20%. However, this increase in total LAI translated into an increase of only 25% in modelled sunlit LAI and in canopy photosynthesis. It is shown that the same climatic and environmental conditions that enhance photosynthesis in the September and October periods also cause an increase in respiration The increases in respiration counterbalanced photosynthesis and resulted in negligible NEE differences between fertilized and control stands. The fact that total biomass of the fertilized stand exceeded 2·5 times that of the control, suggests that the counteracting effects cannot persist throughout the year. In fact, modelled annual carbon balance showed that gross primary productivity (GPP) increased by about 50% and that the largest enhancement in NEE occurred in the spring and autumn, during which cooler temperatures reduced respiration more than photosynthesis. The modelled difference in annual NEE between fertilized and control stands (approximately 200 1;g 2;C 3;m^?2 y^?1) suggest that the effect of fertilization was sufficiently large to transform the stand from a net terrestrial carbon source to a net sink.     

The relative influences of exotic species and environmental factors

Spatial variation in the native fish community of the lower Guadiana basin (southern Iberia) was related to both biotic (abundance of exotic species) and environmental factors using canonical correspondence analysis, CCA. After choosing the best predictors among the environmental and biotic variables, we partitioned the total variation in native species abundances (18 species-size combinations by 44 sampling locations matrix) into that accounted for (1) solely by selected environmental variables, (2) solely by selected biotic variables, (3) by both environmental and biotic variables together, and (4) that unexplained. Of the 22 variables initially considered in the environmental CCA, only RIVER (dummy variable codifying sampling locations belonging to the main river), SALT (dummy variable codifying sampling locations belonging to tributaries that discharge to the brackish Guadiana), substrate heterogeneity, and macrobenthos abundance were selected as best predictors. In the biotic CCA, three species-size combinations were selected from the eight considered: Micropterus salmoides > 150 mm in total length (TL), Lepomis gibbosus > 100 mm in TL and Gambusia holbrooki. The total variation in the native fish community was partitioned into the following components: pure environmental (24.4%), pure biotic (12.4%), shared (9.2%) and unexplained (54.0%). There was a significant influence of exotic fish on native community variation after accounting for the effect of environmental factors. This revised version was published online in July 2006 with corrections to the Cover Date.     

Species richness–environment relationships within coastal sclerophyll and mesophyll vegetation in Ku‐ring‐gai Chase National Park,New South Wales,Australia

Abstract Patterns in species richness from a wide range of plant communities in Ku‐ring‐gai Chase National Park, New South Wales, Australia, were examined in relation to a number of environmental variables, including soil physical and chemical characteristics. Total species richness and richness of three growth‐form types (trees, shrubs and ground cover) were determined in duplicate 500‐m² quadrats from 50 sites on two geological substrata: Hawkesbury Sandstone and Narrabeen shales and sandstones. Generalized linear models (GLM) were used to determine the amount of variation in species richness that could be significantly explained by the measured environmental variables. Seventy‐three per cent of the variation in total species richness was explained by a combination of soil physical and chemical variables and site attributes. The environmental variables explained 24% of the variation in tree species richness, 67% of the variation in shrub species richness and 62% of the variation in ground cover species richness. These results generally support the hypothesis of an environmental influence on patterns in total species richness and richness of shrubs and ground cover species. However, tree species richness was not adequately predicted by any of the measured environmental variables; the present environment exerts little influence on the richness of this growth‐form type. Historical factors, such as fire or climatic/environmental conditions at time of germination or seedling establishment, may be important in determining patterns in tree species richness at the local scale.     

Local and regional factors determining aquatic and semi-aquatic bug (Heteroptera) assemblages in rivers and streams of Greece

Heteroptera species were collected from 48 sites distributed throughout the mainland and island complexes of Greece during 1999–2004. The aims of this study were to investigate Heteroptera distribution and abundance in Greek streams, identify the environmental factors that are linked to variation in their assemblages and to partition the influence of environmental and spatial components, alone and in combination, on Heteroptera community composition. Canonical ordination techniques (CCA) were used to determine the relationship between environmental variables and species abundance, while variation partitioning was performed using partial CCA to understand the importance of different explanatory variables in Heteroptera variation. Heteroptera variation was decomposed into independent and joint effects of local (physicochemical variables, microhabitat composition, stream width and depth), regional (land use/cover) and geographic variables (longitude, latitude, altitude and distance to source). Land use/cover, aquatic and riparian vegetation, stream size and water chemistry were the most important factors structuring Heteroptera assemblages. At regional scale, bug assemblages were mainly divided into those found in forested and agricultural landscapes, following water quality and microhabitat composition at local scale. Local variables accounted for 48% of the total explained variation, regional variables for 20% whereas geographical position appeared to be the least influencing factor (8.5%). The results of partial constraint analyses suggested that local variables play a major role in Heteroptera variation followed by regional variables. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

The Definition of British Water Beetle Species Pools (Coleoptera) and their Relationship to Altitude, Temperature, Precipitation and Land Cover Variables

Pooled water beetle species lists from 1826 British national grid 10-km squares were analysed using multivariate ordination and classification methods. The relationships of pool groups to the climate, altitude and land cover variables were assessed using constrained and partial ordinations. Ordination of the species pool data indicated a major trend between squares in the north-west of Scotland and those in southern England, illustrating differences in acid and basic water standing water. Secondary variation was from acid standing water to fast-flowing streams and rivers. Classification generated nine species pool groups. These showed a distinct north-west to south-east trend but there was no obvious coastal or brackish water effect on distribution. The climatic and land cover variables were all significantly related to each other, and to north-south variation in grid square location, but the constrained ordination results indicated that that the most important influence on water beetle species pool distribution was mean summer temperature. Although the amount of variation explained by the environmental variables was low, spatial variation in the environmental predictors was almost as important as the environmental variables themselves in determining species pool composition. Mean annual temperature was also strongly correlated with species pool distribution with two land cover variables slightly less important. Altitude and precipitation had the least influence. The water beetle national recording scheme database appears to be of sufficiently high quality for environmental investigations at the British scale. There is considerable potential for the synthesis of invertebrate species distribution, land cover and climate change predictions in the assessment of environmental change. The results, together with previous work on other invertebrate species, indicate that changing summer temperatures may have a considerable influence on the distribution British invertebrate species.     

Incorporation of spatial structure into the analysis of relationships between environment and marine microbiological parameters

During the RV A. Veimer cruise on 16 August 1990, the bacterialproduction, the bacterial total number and the plate count were estimated atnine sampling stations at four depths along a transect from the Estonianinshore area to the middle of the Gulf of Finland. To analyze thevariability of microbiological parameters, the spatial structure wasintroduced into the statistical model and combined with the environmentalvariables. The total explained variation of the bacterial production was74%, of which 62% was represented by the covariation betweenthe environmental variables and the spatial structure. The variation in thebacterial production data that was explained by the environmental variables,independently of the spatial structure, was 9%, and variation due tospatial structure without environmental variables equaled 12%. Thepatterns of distribution of the bacterial total number and the plate countwere related only to the spatial structure (explained variation 30%and 27%, respectively). This revised version was published online in July 2006 with corrections to the Cover Date.