Principal Component Analysis Axes Research Articles

Disturbance regimes in a wetland remnant: implications for trait-displacements and shifts in the assemblage structure of carabid beetles (Coleoptera: Carabidae)

Studies on disturbance regimes involving carabid beetles have mainly focused on forest habitats. We therefore decided to analyze the effects of disturbance on carabid communities in a wetland remnant (Lake Chiusi, central Italy). Results highlighted the presence of a disturbance gradient affecting the species richness and trait-displacement of carabid communities. Carabids were sampled with pitfall traps from March to October 2008 at nine randomly selected sample stations; a set of landscape attributes were also collected. Principal Component Analysis (PCA) and generalized linear mixed models (GLMMs) were used to link the distribution of carabid life-history traits and species richness with the most informative combination of landscape attributes. The first PCA axis (PC1) showed significant correlation with “distance to the lake shoreline” and “perimeter-area ratio”, highlighting the presence of a disturbance-axis. The second and third axes accounted only for a trivial portion of the total variance. GLMMs revealed a progressive decrease in the number of hygrophilous species from the core of the wetland to its outer areas. Similar trends were observed for species richness and for predator species with good dispersal ability and larval period in summer. Our results highlight the importance of taking into account community-wide functional implications in landscape ecology studies.

Incorporating evolutionary processes into conservation planning using species distribution data: a case study with the western Mediterranean herpetofauna

AbstractAim To incorporate evolutionary processes into conservation planning using species distribution patterns and environmental gradients as surrogates for genetic diversity.Location Western Mediterranean Basin.Methods Distributions of 154 herpetological species were predicted using maximum entropy models, and groups of significantly co‐occurring species (biotic elements) were identified. Environmental gradients were characterized for the complete area and for the area covered by each biotic element, by performing a principal component analysis on the data matrix composed of nine environmental variables. The first two principal component analysis axes were classified into four categories each, and those categories were combined with each other resulting in an environmental classification with 16 categories. To identify priority conservation areas, biotic elements and environmental categories were used as surrogates for the neutral and adaptive components of genetic diversity, respectively. Priority areas for conservation were identified under three scenarios: (1) setting targets for species only; (2) setting targets for species and for each environmental category of the overall area; and (3) setting targets for each species and for each environmental category within each biotic element.Results Nine biotic elements were identified – four for the amphibians and five for the reptiles. Priority areas identified in the three scenarios were similar in terms of amount of area selected, but exhibited low spatial agreement.Main conclusions Prioritization exercises that integrate surrogates for evolutionary processes can deliver spatial priorities that are fairly different to those where only species representation is considered. While new methods are emerging to incorporate molecular data in conservation prioritization, it is unlikely to be enough data for enough taxa for this to be feasible in many regions. We develop an approach using surrogates for both the neutral and adaptive components of genetic diversity that may enhance biodiversity persistence and representation when molecular data are not available or geographically comprehensive.

Volatile Constituents of Pinus pinea L. Needles

The composition of the essential oil hydro-distilled from needles of Pinus pinea L. trees, collected from six populations coming from Northern Tunisia was determined by GC and GC/MS analysis. Fifty-seven components, accounting for 94.4–99.9% of the oil were identified. As expected, the majority of the identified metabolites were found to be monoterpenes and sesquiterpenes. Monoterpenes account about 76% with 34 of 57 compounds identified. The principal component was limonene (35.9%) followed by α-pinene (6.4%). Sesquiterpenes (ca.19%) were mainly β-cubebene (1.8%), β-caryophyllene (1.7%), α humulene (1.7%) and β-farnesene (1.7%). Diterpenes (1.4%) were present in few concentrations mainly at one population. Data projection on axes of principal component analysis from P. pinea samples showed significant geographic polymorphism between Tunisian populations. This suggests that, using an appropriate wide-range sample of P. pinea populations, terpenes could be used to study the genetic diversity of P. pinea. This species has never shown a noticeable genetic variability using microsatellites, fatty acids or allozymes.

Sprouting, succession and tree species diversity in a South African coastal dune forest

Abstract:Sprouting may play a significant role in maintenance of plant diversity where prevailing disturbance frequency and severity allows. When disturbance frequency and severity decrease, strong sprouters may be outcompeted. As a result, species composition and diversity may change. This study was carried out to investigate the relationship between sprouting, succession and species diversity in a coastal dune forest that currently suffers from low-severity, chronic disturbance due to sea winds and loose sand substrate. Historically, the site was occupied by shifting cultivators who left the site about 80 y ago. Data on trees that were at least 1.3 m tall from 42 sample plots measuring 20 × 20 m were used. The plots were ranked in order of advancement of succession using the first axis of Principal Components Analysis of forest structural variables. Regeneration pattern was examined using analysis of stem diameter frequency distribution. Abundance and regeneration of strong basal sprouters, incidence of basal sprouting and species diversity decreased with advancement of succession. Only a few species could regenerate under the canopy of late-successional sites. Basal sprouts decreased with advancement of succession whereas trunk sprouts increased. These results suggest that maintenance of high species diversity may need a level of disturbance that allows regeneration and maintenance of strong basal sprouters.

Lead, mercury and cadmium content in bottom sediments, reed (Phragmites australis) beds and great pond snails (Lymnaea stagnalis) in fishponds and the role of littoral zones in their accumulation

We studied the contents of cadmium (Cd), lead (Pb) and mercury (Hg) in common reed (Phragmites australis), great pond snails (Lymnaea stagnalis), and in littoral bottom sediments in 18 fishponds in two regions of the Czech Republic. We also assessed the impact of environmental factors on heavy metal accumulation in these three components of littoral ecosystem. Cadmium and lead values were significantly higher in bottom sediments (median values 0.70 and 13.4 mg·kg-1) than in reed (0.014 and 0.51 mg·kg-1) and snails (0.074 and 0.81 mg·kg-1). Cadmium values in reed stems positively correlated with Cd values in great pond snails (Spearman’s rank correlation, rS = 0.62; p < 0.05). Cadmium and lead contents in reed stems positively correlated with each other (rS = 0.56; p < 0.05). The mercury values in snails (0.043 mg·kg-1) were higher than in sediments (0.040 mg·kg-1) and these were higher than in reed stems (0.010 mg·kg-1). We also found higher mercury contents in reed stems and higher cadmium contents in great pond snails in eastern compared to western parts of investigated ponds. Based on the principal component analysis (PCA) performed on heavy metal values, relative reed beds rate in the pond perimeter was negatively correlated with the sample scores on the first PCA axis and the orientation of sampling site and fish stock density negatively correlated with the second PCA axis. Our results proved the important role of littoral sediments in Cd, Pb and Hg accumulation, and the suitability of great pond snails for mercury stress biomonitoring in fishponds. In conclusion, littoral reed beds play a very important role in toxic element uptake in fishponds. The results contribute to the understanding of heavy metal cycles and their accumulation in fishponds under semi-natural conditions and in less affected landscape, and can be used as reference values for comparison with more damaged sites.

Controls on at‐a‐station hydraulic geometry in steep headwater streams, Colorado, USA

AbstractDetailed hydraulic measurements were made in nine step‐pool, five cascade and one plane‐bed reach in Fraser Experimental Forest, Colorado to better understand at‐a‐station hydraulic geometry (AHG) relations in these channel types. Average values for AHG exponents, m (0·49), f (0·39), and b (0·16), were well within the range found by other researchers working in steep gradient channels. A principal component analysis (PCA) was used to compare the combined variations in all three exponents against five potential control variables: wood, D84, grain‐size distribution (σ), coefficient of variation of pool volume, average roughness‐area (projected wetted area) and bed gradient. The gradient and average roughness‐area were found to be significantly related to the PCA axis scores, indicating that both driving and resisting forces influence the rates of change of velocity, depth and width with discharge. Further analysis of the exponents showed that reaches with m > b + f are most likely dominated by grain resistance and reaches below this value (m < b + f) are dominated by form resistance. Copyright © 2010 John Wiley & Sons, Ltd.

On the role of natural water level fluctuation in structuring littoral benthic macroinvertebrate community composition in lakes

We used traditional hydrologic endpoints and extracted novel water‐level fluctuation (WLF) characteristics through principal components analysis (PCA), to determine the relationship between WLF and rocky littoral benthic macroinvertebrate (BMI) richness in 16 boreal lakes. Yearly WLF amplitude (maximum minus minimum water levels) ranged from 35.9 cm to 157.5 cm. Using PCA we derived a new variable D80‐D210 (31 March minus 01 August) as a surrogate for change in mean water level and potential habitat squeeze (loss). Analyses of BMI richness with several physicochemical variables, including water quality (8), habitat variability (4), lake and basin morphology (6), land classification (28), water temperature (8), hydrology (9), and PCA axes (10) resulted in only three significant relationships. We found a classic species‐area relationship, as BMI richness increases with increasing lake area (r2 = 0.38linear, r2 = 0.69unimodal). Similarly, as littoral slope increases macroinvertebrate richness decreases (r2 = 0.32linear). Most importantly, lower water levels, quantified using D80‐D210, have higher macroinvertebrate richness (r2 = 0.38linear). Together these results suggest that a habitat squeeze in littoral areas is the direct result of lower mean water levels and that relatively small changes in natural WLF can be associated with changes in BMI communities.

Evaluating the Illinois Stream Valley Segment Model as an Effective Management Tool

Stream habitat assessments are conducted to evaluate biological potential, determine anthropogenic impacts, and guide restoration projects. Utilizing these procedures, managers must first select a representative stream reach, which is typically selected based on several criteria. To develop a consistent and unbiased procedure for choosing sampling locations, the Illinois Department of Natural Resources and the Illinois Natural History Survey have proposed a technique by which watersheds are divided into homogeneous stream segments called valley segments. Valley segments are determined by GIS parameters including surficial geology, predicted flow, slope, and drainage area. To date, no research has been conducted to determine if the stream habitat within a valley segment is homogeneous and if different valley segments have varying habitat variables. Two abutting valley segments were randomly selected within 13 streams in the Embarras River watershed, located in east-central Illinois. One hundred meter reaches were randomly selected within each valley segment, and a transect method was used to quantify habitat characteristics of the stream channel. Habitat variables for each stream were combined through a principal components analysis (PCA) to measure environmental variation between abutting valley segments. A multivariate analysis of variance (MANOVA) was performed on PCA axes 1-3. The majority of abutting valley segments were significantly different from each other indicating that habitat variability within each valley segment was less than variability between valley segments (5.37 ≤ F ≤ 245.13; P ≤ 0.002). This comparison supports the use of the valley segment model as an effective management tool for identifying representative sampling locations and extrapolating reach-specific information.

Establishing environmental flow regimes in a Mediterranean watershed based on a regional classification

Summary Environmental flow estimation in regulated rivers has become a major issue for watershed management in Mediterranean countries. The lack of regional environmental flow guidelines to protect ecological values of rivers, especially when the environmental flows must be determined at many locations in large basins, has led to the establishment of very simplistic criteria to fix instream flow needs in rivers. These simple hydrological methodologies ignore the site-specific characteristics of natural systems, and therefore should not be used for management practices when maintaining sustainable river ecosystems. We provide different methodological approaches to establish an environmental flow regime for regulated rivers at regional or watershed levels in both gauged and ungauged rivers, depending on the availability of site-specific empirical data and desired accuracy of the results. The types of selected approaches include simple environmental flow values interpolation from calculated values at a discrete set of points with available data, and the development of environmental flow prediction models based on a previous stream-flow classification and regionalization process. A total of 51 hydrological and physical watershed characteristic variables were defined at 46 gauging stations. Variables were classified in five groups, and a Principal Component Analysis (PCA) was conducted on each group of variables in order to reduce the dimension of the data set. Identified PCA axes were used in a Cluster analysis to find similarities among the gauging stations. Results revealed four homogeneous regions in the Ebro watershed, where environmental flow values may be predicted from variables such as the flow equalled or exceeded 347 days per year (Q 347 ), or the average for the period of record of minimum mean monthly flows.

The role of plant traits and their plasticity in the response of pasture grasses to nutrients and cutting frequency.

Although plant functional traits (PFTs) appear to be important indicators of species' responses to land use changes, there is no clear understanding of how the variations in traits and their plasticity determine variations in species performance. This study investigated the role of functional shoot traits and their plasticity for variation in above-ground net primary productivity (ANPP) due to changes in N supply and in cutting frequency for 13 native perennial C(3) grass species. Monocultures of the grass species were grown in a fully factorial block design combining plant species, cutting frequency and N supply as factors. Four major trait associations were obtained by reducing the dimensions of 14 PFTs with a principal component analysis (PCA).Variations in species' productivity in response to an increase in cutting frequency was mainly explained by traits linked to the first PCA axis, opposing high plant stature from lower shoot cellulose and lignin contents and high leaf N content. Variation in species productivity in response to change in N supply was mainly explained by a set of predictor variables combining traits (average flowering date) and a trait's plasticity (tiller density per unit land area and leaf dry matter content, i.e. mg dry matter g fresh mass(-1)). These traits involved are linked to the second PCA axis ('nutrient acquisition-conservation'), which opposes distinct strategies based on response to nutrient supply. Variations in ANPP of species in response to an increase in cutting frequency and a decrease in N supply are controlled by a group of traits, rather than by one individual trait. Incorporating plasticity of the individual traits into these trait combinations was the key to explaining species' productivity responses, accounting for up to 89 % of the total variability in response to the changes in N supply.

Intra- and inter- correlative responses among fruits physical traits, seedling growth parameters and fruit and nut proximate qualities of the Nigerian shea nut tree (Vitellaria paradoxa c. f. Haertn)

Seedling growth of Vitellaria paradoxa C. F. Gaertn (shea nut tree) is extremely slow. Identification of any nut trait that shows positive and significant relationship with vigorous seedling growth could therefore, be an important selection index. Besides, fruit preferences among indigenous peoples are associated with high pulp proximate quality while highly valued nut has strong relationship with fat content. Thus, intra- and inter- correlative responses among fruits physical traits, seedling growth parameters and fruit and nut proximate qualities of V. paradoxa were studied. Agronomically important seedling characters of nine provenances across Nigeria’s savanna zone were also examined with principal components analysis (PCA). Results indicated that the first three PCA axes retained explained 96.3% of total variability among seedling provenances, revealing that leaf area, seedling girth, plant height and number of leaves are more promising traits for shea seedling classification in Nigeria. Multiple correlation analysis showed that nut length had high and significant linkage with number of leaves, leaf width, leaf area and seedling girth. Nut width also correlated positively with leaf length, leaf area and seedling girth (P

Responses of Chironomid larvae (insecta, Diptera) to ecological quality in Mediterranean river mesohabitats (South Italy)

AbstractChironomid larvae and pupae were studied in selected Mediterranean rivers with the aim of identifying pool and riffle taxa assemblages and of analysing their response to ecological quality gradients. Macroinvertebrate samples were collected in six Italian rivers along a pool‐riffle sequence in three seasons following a multihabitat sampling technique. Chironomids were identified as genus/species, other macroinvertebrates as family/genus. The main physico‐chemical, hydromorphological and geographical data were collected. Samples were ascribed to five quality classes according to the STAR_ICM index. Based on Chironomid taxa, principal component analysis (PCA) axis 1 represented an organic pollution gradient, axis 2 represented seasonality. Pool and riffle samples were significantly different according to taxa assemblages. Similar results were obtained with PCA based on the whole macrobenthic community. Indicator value (IndVal) analysis facilitated the detection of the Chironomid indicators of high/good quality pools (e.g. Conchapelopia pallidula, Rheopelopia ornata, Epoicocladius ephemerae) and riffles (Tvetenia calvescens, Eukiefferiella gracei). The Berger–Parker dominance index based on Chironomid assemblages in pools was correlated to PCA axis 1 and performed well in discriminating between quality classes. In riffles, no correlations to PCA axes were detected and a wide overlap between quality classes was present. Thus, assessment in the analysed river type may focus on pool mesohabitat as this seems to represent best the ecological gradient of sites. Copyright © 2009 John Wiley & Sons, Ltd.

Metal (Fe, Zn, Cu, Pb and Cd) concentration patterns in components of a macrophyte-based coastal lagoon ecosystem

Information on the metal biological fate in macrophyte-based coastal lagoons is provided; this information can contribute to the assessment of the environmental effects of metal pollution and to the development of predictive models for rational management of coastal lagoons. Iron, Zn, Cu, Pb and Cd concentrations in the dominant invertebrate and fish species of Monolimni Lagoon, Mediterranean Sea, as well as in potential major sources for metal accumulation in these animals (water, sediments, angiosperms, seaweeds), were measured. Principal Component Analysis (PCA) was conducted using metal concentrations in invertebrates and fishes. All five metal concentrations loaded significantly on the first PCA axis; however, Zn and Cu loadings were less significant than Cd and even less than Fe and Pb ones. The samples of deposit-feeding invertebrates were separated from those of the rest of the organisms (browsing, herbivorous and carnivorous invertebrates, carnivorous gobies and muscle tissues of detritivorous mullets) along the first PCA axis. Deposit-feeding invertebrates displayed the highest Fe and Pb contents, and in general, the highest or comparatively high Cd, Zn and Cu ones. Carnivorous gobies showed comparatively high Zn contents and carnivorous shrimps the highest Cu ones, while muscle tissues of detritivorous mullets had low metal loads. In addition, there was no essential increase in metal concentrations corresponding to the increasing trophic level (autotrophs, to herbivores, to carnivores). Our findings suggest that (a) the variability in Fe, Pb and Cd contents in invertebrates and gobies depends at least to some extent on interspecific differences in feeding habits—deposit feeders accumulated the highest metal amounts probably due to high rates of uptake from sediments, (b) the variability in Zn and Cu concentrations in these organisms depends also on other interspecific differences apart from those in feeding habits, (c) metal accumulation in mullet muscle tissues does not depend markedly on feeding habits and (d) the trophic transfer of macrophyte-bound metals to the coastal lagoon food web is of relatively minor importance.

Evaluation of anatomical characters and the question of hybridization with domestic cats in the wildcat population of Thuringia, Germany

Germany’s large population of wildcats (Felis silvestris silvestris) can be clearly distinguished from domestic cats on the basis of morphological characters. However, an examination of 71 specimens from Thuringia also illustrates the risks involved in using only a few such characters. The most reliable tool for identification in the field are three pelage characters (distinctness of tail bands, stripes on the nape and stripes on the shoulder). Only two morphological characters (intestine length and cranial volume) are unambiguous and demonstrate no overlap in distribution between domestic cats and wildcats. A linear discriminant analysis with forward selection of variables showed that only five skull variables are necessary to distinguish all four groups (subspecies × sex). Additionally, the high degree of correlation between most of the 49 variables examined (as indicated by Pearson’s r correlation matrix) speaks against the utility of measuring such high numbers of characters in the future. Principal component analysis (PCA) enabled the subspecies to be separated clearly. The first PCA axis was highly correlated with variables characterizing overall body size, thus separating male and female into wildcats and domestic cats. Even when the chief differentiating characters are missing, the PCA still resulted in a good separation of subspecies. None of the genetically determined hybrids could have been deciphered unambiguously using the morphological characters still intact after a road death. Hybridization seems to occur whenever wildcats change their ecological function and become field cats. The impulse to hybridize seems to come much more from the wildcat side than the side of feral cats, and deforestation represents the major threat to the wildcat.

Zinco total e disponível em amostras de perfis de solos do estado de São Paulo

Em amostras dos horizontes A e B de vinte e oito perfis de unidades de solos representativas do Estado de São Paulo fez-se a determinação de zinco usando os extratores DTPA pH 7,3 (ZnDTPA); Mehlich-1 (ZnM1); HCl 0,1 mol L-1 (ZnHCl); EDTA (ZnEDTA); e, NH4OAc 1 mol L-1 (ZnAc). O teor total de zinco nas amostras de solo estava alto, entretanto, notou-se somente uma pequena fração na forma disponível. O zinco total foi mais influenciado pelo teor de óxido de ferro (r=0,75). Para os teores considerados biodisponíveis, o pH foi o componente mais importante com coeficientes de correlação que variaram de 0,52 (ZnDTPA) a 0,66 (ZnAc). A análise dos componentes principais (PCA) revelou que os dois primeiros componentes principais explicaram 66% da variação, mostrando a associação entre os seguintes atributos dos solos: silte, pH, cálcio, magnésio, valor T, sílica, óxido de ferro, ZnT, ZnDTPA, ZnM1, ZnHCl e ZnEDTA, em que havia valores superiores a 0,63 no F1. No F2 ficou demonstrada a associação entre os teores de argila, areia fina e óxido de alumínio. Foi observada ambiguidade nos F1 e F2 para a areia grossa. Concluiu-se que: a maioria das amostras de solo apresenta potencial para o aparecimento de deficiência de zinco em curto e médio prazos e aPCA foi eficiente no agrupamento de solos originários de mesmo material de origem, indicando que as formas de Zn analisadas são influenciadas positivamente pelos teores de silte, Ca, Mg, sílica e Fe2O3, pH e valor T.

Evaluating the Effects of Enteric Helminths on Epigamic Characters of Male Wild Turkeys (Meleagris gallopavo) in Southeastern Kansas, U.S.A.

Costs associated with the production of epigamic characters might make them honest indicators of a male's fitness. The Hamilton–Zuk hypothesis suggests epigamic characters might be indicators of a male's heritable resistance to parasites, predicting a negative correlation between parasite abundance and the elaboration of epigamic characters. Principal component analysis (PCA) of the epigamic characters of 35 male wild turkeys from a zone of Rio Grande (Meleagris gallopavo intermedia) and Eastern (Meleagris gallopavo silvestris) subspecies hybridization revealed variation in characters that covaried with body size (beard length and spur size) and characters that varied independent of body size (snood length and skullcap width), which have the potential for indicating heritable resistance. None of the PCA axes was correlated with mean enteric helminth abundances, suggesting that helminth parasites are not affecting the vigor of male wild turkeys in southeastern Kansas, U.S.A., and apparently, have not exerted selective pressure in the recent past to advertise resistance.

Impact of reservoirs and channelization on lowland river macroinvertebrates: A case study from Central Europe

In order to assess and compare the ecological impacts of channelization and shallow lowland reservoirs, macroinvertebrate communities of a lowland metapotamal river below reservoirs with epilimnial release were studied. The study was carried out in the Dyje River (Czech Republic) at five sites located from 1.5 to 22.5 km downstream of the reservoir outfall. The five sites differed in the degree of channel modification from natural muddy banks to riprap regulation. Seven samples were collected during the years 1998 and 1999 at each site using a semiquantitative method. The data were processed using multivariate analyses and methods for assessing the ecological and functional structure of communities. Altogether, 261 species of benthic macroinvertebrates were recorded including several rare and threatened taxa. Based on the results of principal component analysis (PCA), most of the variability within the species data (the first PCA axis) was explained by the degree of channel modification, from natural muddy banks with aquatic vegetation to a man-made riprap. The second axis was strongly correlated with current velocity. The sites differed in species richness, total abundances, proportion of individual functional feeding groups, pattern of the distribution of the current preference groups, and values of several biotic indexes, all of which also corresponded to the degree of channel modification. Thus, the morphological man-made modifications of the river channel were found to be the main factor affecting lowland river macroinvertebrates and their biodiversity. Our results suggest that the biggest threat to benthic macroinvertebrate diversity of lowland rivers comes from channelization. The impact of reservoirs can be completely overwhelmed by the impact of channelization, especially when muddy banks with aquatic vegetation present a substantial part of habitat diversity and significantly contribute to the total species pool.

Spectral characteristics of plant communities from salt marshes: A case study from Chongming Dongtan, Yangtze estuary, China

The spectral reflectance of recently formed salt marshes at the mouth of the Yangtze River, which are undergoing invasion by Spartina alterniflora, were assessed to determine the potential utility of remotely sensed data in assessing future invasion and changes in species composition. Following a review of published research on remote sensing of salt marshes, 53 locations along three transects were sampled for paired data on plant species composition and spectral reflectance using a FieldSpec™ Pro JR Field Portable Spectroradiometer. Spectral data were processed concerning reflectance, and the averaged reflectance values for each sample were reanalysed to correspond to a 12-waveband bandset of the Compact Airborne Spectral Imager. The spectral data were summarised using principal components analysis (PCA) and the relationships between the vegetation composition, and the PCA axes of spectral data were examined. The first PCA axis of the reflectance data showed a strong correlation with variability in near infrared reflectance and ‘brightness’, while the second axis was correlated with visible reflectance and ‘greenness’. Total vegetation cover, vegetation height, and mudflat cover were all significantly related to the first axis. The implications of this in terms of the ability of remote sensing to distinguish the various salt marsh species and in particular the invasive species S. alterniflora were discussed. Major differences in species with various physiognomies could be recognised but problems occurred in separating early colonising S. alterniflora from other species at that stage. Further work using multi-seasonal hyperspectral data might assist in solving these problems.

Macroinvertebrate Communities and Habitat Structure in Least-Impacted Hill Streams of Central Portugal

ABSTRACT We surveyed macroinvertebrate communities in 31 hill streams in the Vouga River and Mondego River catchments in central Portugal. Despite applying a “least-impacted” criterion, channel and bank management was common, with 38% of streams demonstrating channel modification (damming) and 80% with evidence of bank modification. Principal component analysis (PCA) at the family and species level related the macroinvertebrates to habitat variables derived at three spatial scales—site (20 m), reach (200 m), and catchment. Variation in community structure between sites was similar at the species and family level and was statistically related to pH, conductivity, temperature, flow, shade, and substrate size at the site scale; channel and bank habitat and riparian vegetation and land-use at the reach scale; and altitude and slope at the catchment scale. While the effects of river management were apparent in various ecologically important habitat features at the site and reach scale, a direct relationship with macroinvertebrate assemblages was only apparent between the extent of walled banks and the secondary PCA axis described by species data. The strong relationship between catchment scale variables and descriptors of physical structure at the reach and site scale suggests that catchment-scale parameters are valuable predicators of macroinvertebrate community structure in these streams despite the anthropogenic modifications of the natural habitat.

Community analysis of Belarusian lakes: correlations of species diversity with hydrochemistry

Our purpose was to explore relationships of freshwater planktonic and benthic community species richness with water chemistry parameters using a dataset of biological, chemical, and physical data from 550 lakes. This was done using multivar- iate (ordination), graphical, and correlation analyses. Although the lakes are rather similar in location (Belarus) and in being mostly eutrophic, they do show variations in water chemistry. We ordinated lakes by water chemistry variables, and then looked for correlations between the ordination axes and species richness in 10 taxonomic groups: Cyanobac- teria, Chlorophyta, Bacillariophyta, Cladocera, Copepoda, Rotatoria, Mollusca, Trichoptera, Chiro- nomidae, and aquatic macrophytes. The first four Principal Components Analysis (PCA) axes explained about 67% of the total variability in water chemistry. The axes represent water hardness (DIC, dissolved inorganic carbon), organic content (DOC, dissolved organic carbon), nutrients, and chlorides and sulfates. The PCA ordination revealed environ- mental gradients, but not the distinctive clusters of lakes. Species richness was most strongly correlated with the first PCA axis (DIC), which accounted for 29% of the total variation in water chemistry. Species richness was positively correlated with DIC for eight of 10 taxonomic categories. The second PCA axis (DOC), which accounted for 20% of total variation in water chemistry, was correlated with species richness in the three phytoplankton groups, and with chiron- omid species richness. The third PCA axis (nutrients, especially nitrogen, 11%) was correlated with species richness of copepoda, chironomids, and macrophytes. The fourth PCA axis (chloride and sulfate) accounted for only 7% of the total variance in water chemistry, and was significantly negatively correlated with species richness of rotifers, molluscs, and chirono- mids. In addition to these linear correlations, there were several significant non-linear relationships. DIC variables showed curvilinear (hump-shaped) relation- ship with benthos (all groups combined) and especially with molluscs, and DOC variables—with phytoplankton and benthos. Each community, and often separate taxonomic groups within community have their own optimal ranges of chemical concen- trations, and various water chemistry variables showed significant curvilinear relationships with biodiversity, suggesting that the diversity of different