Multivariate Ordination Methods Research Articles

Pogonoloma macrorhizum (Basidiomycota, Agaricales) in Slovak landscape: a distinct fungus of Quercus cerris stands transitional in space and time

The lack of precise data on the environmental requirements of the conspicuous fungus with a northern distribution limit in Slovakia, Pogonoloma macrorhizum, initiated our study. Its identity was verified by sequencing of ITS and 28 S nrDNA regions. The analysis of trophic status by stable-isotope ratio of carbon and nitrogen suggested that the species is probably ectomycorrhizal. For the seventeen sampling sites, environmental data were obtained and information on landscape development and management were retrieved from historical maps and aerial orthophotographs. All these parameters were analysed by multivariate ordination methods. In Slovakia, P. macrorhizum is found in thermophilous to mesophilous stands on acidic soils with a pH ranging from 4.1 to 6.2. These habitats are dominated by Quercus cerris, with non-frequent tree taxa of Carpinus betulus and Quercus petraea agg. The key environmental drivers shaping the habitat of P. macrorhizum were identified as time since deforestation, with the presence of old Q. cerris individuals (former solitary trees of pastures) and soil characteristics. The fungus appears to be a species of transitional habitats historically affected by grazing. These transitions occur between thermophilic and mesophilic sites, including oak forest communities, dry steppic grasslands and forest edges, as well as spontaneously overgrown pastures and forests with a closed canopy. It is regrettable that the Q. cerris stands in Slovakia are under threat, particularly because of felling and the lack of grazing in forests. Furthermore, recent silvicultural practices have resulted in the replacement of oaks (Quercus spp.) by hornbeam (Carpinus betulus) and the formation of closed stands.

Radular teeth of Conus (Mollusca: Neogastropoda: Conidae) from the Red Sea: comparative morphology and character analysis

ABSTRACT Hypodermic needle-like radular teeth characterise predatory gastropods of the genus Conus. They inject neurotoxins that disable their prey, which is then swallowed whole. Until now, these structures have received limited use in assessing the range of intraspecific variation within and interspecific differences among closely related species. However, radular tooth characters deserve greater attention, especially because they conform more closely with molecular phylogenetic data than do more conventionally used external shell characters. This report describes radular tooth morphology of 16 Conus species from the Egyptian coast of the Red Sea, representing the three commonest feeding guilds in the genus: vermivores (12 species), piscivores (2) and molluscivores (2), and provides SEM images of all. This study gives the first description of the radula teeth of C. (Virroconus) sinaiensis. Multivariate ordination methods applied to quantitative characters separate the vermivorous species mainly into two distinct groups and distinguish between the closely related species C. (Virgiconus) flavidus and C. (Virgiconus) frigidus, confirming the ability of these methods to assess intraspecific variation within and interspecific differences between closely related species. Similar studies supported by molecular markers in other Conus species groups are needed to further test phylogenetic hypotheses of relationships throughout the genus.

Recent and future distribution of the alien Chinese pond mussel Sinanodonta woodiana (Lea, 1834) on the European continent

The alien freshwater mussel Sinanodonta woodiana (Lea, 1834) has rapidly spread throughout Europe over the past decades. This species can cope with a broad range of environmental conditions and has a high reproductive capacity making S. woodiana a successful invader. Due to its negative effects on native freshwater mollusk communities and parasitized fish it is critical to identify suitable habitats where S. woodiana may persist and how these habitats may be altered under future climate projections. We applied multivariate ordination methods to analyze the space-time relationship and a maximum entropy approach (MaxEnt) to predict the recent (1970–2000) and future (2041–2060 and 2081–2100) distribution of S. woodiana using environmental and climate variables for the European continent. After first sightings in 1979 there were only a few new locations and findings which increased unevenly and exponentially to a maximum of about 100 new locations per year followed by decline during the last few years. Under recent climate condition, 2.3% of European watersheds are predicted as highly suitable habitat for S. woodiana and located in the temperate climate zone between 40°N and 60°N. Suitable habitat was associated with lowland watersheds characterized by fluviatile deposits and agriculture. Elevation, the distance between water bodies, land cover and mean temperature of the coldest quarter were the main factors influencing the modeling results. For future climate scenarios, highly suitable habitat increased to 2.4% by the middle of this century and decreased to 2.2% by the end of the century under the ‘least radiative forcing’ scenario. For the intermediate and high radiative forcing in 2050 and 2100, highly suitable habitat decreased to 2.2% and 1.7% and to 2.2% and 2.2%, respectively. Results from our study can be used as a baseline to better understand potential invasion pathways, identify high risk areas, and to initiate early detection and rapid response strategies.

Multivariate mapping of ontogeny, taphonomy and phylogeny to reconstruct problematic fossil taxa.

Exceptionally preserved fossils of soft-bodied organisms provide unique evidence of evolutionary history, but they are often contentious; different approaches frequently produce radically different reconstructions of taxa and their affinities. Conflict arises due to difficulties in disentangling the three non-independent factors that underlie all morphological variation within and between fossils: ontogeny, taphonomy and phylogeny. Comparative data from extant organisms can be extremely powerful in this context, but is often difficult to apply given the multi-dimensionality of anatomical variation. Here, we present a multivariate ordination method using discrete morphological character data from modern taxa at different ontogenetic and taphonomic stages (semaphoront and 'semataphonts'). Analysing multiple axes of morphological variation simultaneously allows us to visualize character combinations that are likely to exist in fossil specimens at intersecting stages of growth and decay, and thus constrain interpretation of fossils. Application to early vertebrates finds variation in fossil specimens to be accounted for by all three axes: primarily decay in Mayomyzon, ontogeny in Priscomyzon and phylogeny in 'euphaneropoids' and Palaeospondylus. Our demonstration of empirical multi-factorial variation underscores the power of multivariate approaches to fossil interpretation, especially non-biomineralized taxa. As such, this conceptual approach provides a new method for resolving enigmatic taxa throughout the fossil record.

Trait–environment relationships of hydroids (Cnidaria: Hydrozoa) across large spatial and environmental gradients in the Atlantic Ocean

AbstractAimThe aim was to test trait–environment relationships in hydroids across large spatial and environmental gradients and to evaluate associations between traits, environmental variables, space and phylogeny.LocationAtlantic Ocean and adjacent polar seas.Time periodPresent day.Major taxa studiedHydrozoa.MethodsTrait–environment relationships and their spatial and phylogenetic contexts were assessed in hydroids by using a combination of a fourth‐corner test and extended‐RLQ approach, in a multivariate ordination method that uses five matrices: (1) species across sites, (2) environmental data across sites, (3) traits across species, (4) latitude and longitude for each site, and (5) phylogenetic distance among species. We based our analyses on 3680 records of 431 species distributed at 1440 sites, 16 species traits, nine environmental variables and a phylogenetic tree of the studied species.ResultsHydroid traits are significantly correlated with environmental variables and geographical space, and hydroid phylogeny is correlated with the environment and geographical space. More evidently, we observed an increased presence of larger species (taller, more branched, with greater base diameter and polysiphonic) at sites richer in nitrate and silicate, with higher dissolved oxygen, lower temperatures, lower salinities and lower current velocities. The observation of phylogenetically related species with similar traits and distributions corroborates that historical processes interact with the environment in determining community assembly and explaining patterns of distribution of species traits.Main conclusionsSeveral environmental variables combined affect the distribution of hydroid traits, which are also influenced by spatial and historical factors. In the first analysis of its kind for hydrozoans, we have provided an overview of how hydroids are distributed across environments according to their traits and revealed the spatial and phylogenetic components of these trait–environment relationships.

Nonmetric multidimensional scaling and probabilistic ecological risk assessment of trace metals in surface sediments of Daya Bay (China) using diffusive gradients in thin films

This research is one main objective to assess combined toxicity of trace metal mixtures in aquatic biota in coastal sediments. Coastal sediments around the world are a major reservoir of trace metals from industrial wastewater discharge. Our case study site, Daya Bay in southern China, was selected because it has been under severe man-made impacts. Diffusive gradients in thin films (DGT) technique has proven to be a good method for measuring the bioavailability of trace metals. The bioavailability and distribution of trace metals in surface sediments were investigated along with their possible biological risks. The average bioavailable (DGT-labile) concentrations (μg/L) were 0.44 (V), 0.51 (Cr), 52.49 (Mn), 0.10 (Co), 1.36 (Ni), 0.74 (Cu), 14.53 (Zn), 0.97 (As), 0.14 (Se), 6.73 (Mo), 0.17 (Cd), 0.27 (Sb), 0.10 (W), and 1.32 (Pb). Nonmetric multidimensional scaling (NMS) is a robust multivariate ordination method that makes no assumptions about the distribution of the underlying data. NMS was used to explore that DGT-labile concentrations of trace metals were influenced by sediment properties. NMS results indicated that most DGT- labile trace metals influenced by sediment properties. Risk assessment of single trace metal toxicity revealed that risk quotient (RQ) values for Mn, Cu, Zn and Pb significantly exceeded 1, demonstrating that the toxic effects of these trace metals should be not ignored. The probabilistic ecological risk assessment for integral toxicity of one mixture of 14 trace metals revealed that Daya Bay surface sediments had a low probability (9.04 %) of adverse effects on aquatic biota.

РАСПРЕДЕЛЕНИЕ МОЛЛЮСКА ИЗ РОДА GYRAULUS (GASTROPODA, PLANORBIDAE) В СРЕДНЕМ ПРИТОКЕ САРАТОВСКОГО ВОДОХРАНИЛИЩА

Background.The Volga basin has been studied unevenly from an ecological point of view. The region of the Upper Volga can be rightly considered the best studied area. While the Lower Volga remains less investigated despite its significant influence on the complex of interrelated social, economic and ecological problems. The most informative assessment for the state of aquatic ecosystems is the state of macrozoobenthos which has various advantages over other approaches, first of all, consisting in species diversity and structure of bottom communities. Freshwater mollusks are one of their numerous groups. In the Volga basin there are representatives of two classes: Gastropoda and Bivalvia. Therefore, the aim of the work is to reveal the peculiarities of Gyraulusalbus distribution in the Samara River and to establish quantitative characteristics in different sections with different ecological conditions. Materials and methods. The study of malacofauna from the source to the river mouth was carried out in the Samara River. A total of 17 stations belonging to different sections were examined. Samples were taken during the low-water period. Near the shore, samples were collected using a hydrobiological scraper (blade length 0.2 m) and a quantitative frame. In deep water using Eckman-Burgey dredge (1/40 m2) with two replicates. The collected material was fixed with 95% ethanol solution, which was replaced with 70% after one week. Statistical processing was performed using Statistica 10.0, Microsoft Excel 2010 and in the R 4.0.5 programming environment and its vegan package. Results.SnailG. albus were recorded by us in sections of the river from its source to its mouth. Specimens of the species were recorded exclusively in the thickets of higher aquatic vegetation. Occurrence of the snail in the river biotopes was low and amounted to only 42% of all investigated stations. This is largely due to the natural rapid flow of water at most sites and hence the small area of macrophytes, which are important for the development of the species. The species prefers low-flow or standing water bodies, so the presence of a small reservoir on the river favored the quantitative indicators of the species in the river, reaching its peak just in this biotope. Morphological variability of the species' shells had no significant differences in the sections of the watercourse. The assessment of the influence of the most significant abiotic and biotic factors on the distribution of G. albus in the Samara River, fallen by the multivariate ordination method revealed three significantly correlated environmental variables: dissolved oxygen concentration, macrophyte area, and salinity level. Conclusions. The results of the study added to the existing gaps in the current composition and distribution of freshwater malacofauna in the region. A number of features of quantitative indicators reflecting features of G. albus habitat in conditions of lotic ecosystems were revealed.

Habitat occupancy by semi‐aquatic reptiles on an aridity gradient in the western Mediterranean

AbstractThe influence of aquatic and riparian habitats on the composition of the local herpetofauna has not been studied extensively. We used redundancy analysis and multivariate ordination methods to evaluate the occurrence of semi‐aquatic reptiles in south‐eastern France, the Iberian Peninsula, and Morocco where the climate transitions from humid temperate to subtropical desert. All the semi‐aquatic reptile species present in this region were studied, including two native turtles (Emys orbicularis and Mauremys leprosa), three native snakes (Natrix astreptophora, N. helvetica, and N. maura), and one introduced turtle (Trachemys scripta). We hypothesized that these species will vary in their responses to differences in the composition of riparian habitats (vegetative community and relative proportion of trees, shrubs, grasses, water and bare ground surface) along the aridity gradient in the region. We found that the habitat niche marginality and niche breadth varied widely across species and climatic regions, although most of the species display a greater habitat niche breadth in the transitional semi‐arid belt. Mauremys leprosa and N. maura were the more generalist species, occupying a wide range of freshwater habitats, including streams associated with impoverished vegetation communities, characteristic of the arid southern Mediterranean region.

Gradient analysis of soil-plant interactions from the alpine-nival ecotone to the snowline on slopes of the Central Great Caucasus (Kazbegi Region, Georgia)

Alpine ecosystems are especially sensitive to climatic changes which affect the relationships among glaciers, snow, vegetation and soils. Our aim was to examine how the variation in the abiotic environment affected soil properties and plant species distribution at regional and local scales. We sampled soil and vegetation along two transects set on the opposite-facing slopes (North versus South), from the alpine-nival ecotone to the snowline (Central Great Caucasus, Kazbegi, Georgia). We measured also soil temperature and controlled for the slope inclination. Multivariate ordination methods were used to link abiotic factors, soil properties and plant species distribution along the gradients. We found that ordination models were better resolved when soil properties were used as environmental variables instead of abiotic ones such as elevation, inclination and slope aspect. Soil pH and plant available potassium were the best predictors of plant species distribution in these habitats. We conclude that the models that account for the role of soils as a mediator between the abiotic environment and vegetation can more accurately describe plant species distribution at local and regional scales: a potentially important amendment with implications for the monitoring of the effects of climate change on vegetation at least in high mountain systems.

Environmental factors influencing the distribution of habitat types in the highlands of the Kamnik − Savinja Alps

In this work, we investigated the relationship between habitat types (HTs) and selected environmental factors in the highlands at altitudes of 1800–2558 m in the Kamnik-Savinja (KS) Alps in Slovenia. For 275 sampling sites, we identified seven HTs in their typical form and 11 ecotones, and provided field and modelled data for 14 environmental factors. HTs-environment relationships were analysed using multivariate ordination methods. In addition, binomial generalised linear mixed models were applied to reveal the influence of environmental factors on the occurrence of most frequent HTs in the study area [Outer Alpine Pinus mugo scrub (EUNIS code F2.4/Natura 2000 code 4070*), Southern rusty sedge grasslands (E4.413/6170), Cushion sedge carpets (E4.433/6170) and Fine calcareous screes (H2.43/8120)]. Results showed that certain modelled data (e.g. average annual air temperature) combined with field measurements (e.g. inclination, soil surface and soil moisture) can be effective predictors of most representative HTs in the study area, and thus useful for further refining of monitoring. Our study contributes to the knowledge and understanding of the relationships between environmental conditions and the occurrence of highland HTs in KS Alps, which probably concerns a great part of the Alpine highlands. Such knowledge is essential for assessing credible long-term conservation planning.

Habitat Partitioning and Overlap by Large Lacertid Lizards in Southern Europe

South-western Europe has a rich diversity of lacertid lizards. In this study, we evaluated the occupancy patterns and niche segregation of five species of lacertids, focusing on large-bodied species (i.e., adults having >75 mm snout-vent length) that occur in south-western Europe (Italian to the Iberian Peninsula). We characterized the niches occupied by these species based on climate and vegetation cover properties. We expected some commonality among phylogenetically related species, but also patterns of habitat segregation mitigating competition between ecologically equivalent species. We used multivariate ordination and probabilistic methods to describe the occupancy patterns and evaluated niche evolution through phylogenetic analyses. Our results showed climate niche partitioning, but with a wide overlap in transitional zones, where segregation is maintained by species-specific responses to the vegetation cover. The analyses also showed that phylogenetically related species tend to share large parts of their habitat niches. The occurrence of independent evolutionary lineages contributed to the regional species richness favored by a long history of niche divergence.

Variable soil pH can drive changes in slope aspect preference of plants in alpine desert of the Central Great Caucasus (Kazbegi district, Georgia)

Alpine deserts are noteworthy habitats in temperate high mountain systems such as the Caucasus. Botanically this biome is well studied, yet little is known about its vegetation patterns in quantitative terms, whilst the role of soil pH in species distributions is particularly unexplored. Here we describe and quantitatively analyse vegetation patterns and soil pH in an alpine desert along elevation range (3000–4000 m a.s.l.) on two contrasting slope aspects (N versus S) of Mt. Kazbegi, the Central Greater Caucasus, Georgia. We sampled vegetation with standardized stratified-random design and collected soil samples for measuring pH; the collected data were analyzed using multivariate ordination methods. Overall, 63 species were recorded and, as expected, strong dependence of species distribution on elevation and between slopes was observed. However, we also found that soil pH increased monotonically and more steeply on N than on S slope, and many relatively abundant species changed their preference to slope aspect from N to S in parallel with the increasing difference in soil pH between N and S slopes. Our results suggest that the observed shift in slope preference from N to S, at least in part, can be explained by the differences in soil pH gradient between N and S slopes.

Engineering Analysis of Plant and Fungal Contributions to Bioretention Performance

While the use of bioretention for stormwater management is widespread, data about the impacts of plants and microorganisms on long-term treatment efficacy remain region-specific. To help address this knowledge gap for the Pacific Northwest region of the United States, we installed twelve under-drained bioretention mesocosms built to Washington State Department of Ecology stormwater management standards in an urban watershed in Seattle, WA that included a busy portion of Interstate 5. Six mesocosms were planted with Pacific ninebark (Physocarpus capitatus) and six were inoculated with the wine cap mushroom (Stropharia rugoso-annulata) resulting in four replicated factorial treatments. Because region-specific studies must be mindful of the prevailing regulatory framework, all mesocosms used the Washington State Department of Ecology design standard soil: a blend of 60% sand and 40% compost by volume, despite the known leaching problems with high compost volume fraction soils. Five water quality sampling events over 15 months of continuous stormwater loading were analyzed for dozens of water quality parameters. Multiple linear regression analyses of treatment differences over the 400-day loading period illustrate that incorporating fungi into the wood mulch slowed the release of total and ortho-phosphorus from the bioretention soil; however net export of phosphorus from this compost rich media continued through 400 days of loading for all treatments. Multivariate ordination methods illustrate that time and temperature dramatically affect performance of this media, but the impact of planting and fungal inoculation had marginal detectible effects on overall water quality during the study timeframe. These results demonstrate that future studies of this media blend must plan for at least one year of nutrient and metal leaching before the time-dependent heterogenous variance introduced by these exports will no longer pose an obstacle to analysis of other performance changing factors. The results highlight important physical and chemical considerations for this media blend, and the opportunity for continued research on the use of fungal inoculated mulch application as a new ecological engineering tool for reducing phosphorus leaching from soils.

Sequence clustering threshold has little effect on the recovery of microbial community structure.

Analysis of microbial community structure by multivariate ordination methods, using data obtained by high-throughput sequencing of amplified markers (i.e., DNA metabarcoding), often requires clustering of DNA sequences into operational taxonomic units (OTUs). Parameters for the clustering procedure tend not to be justified but are set by tradition rather than being based on explicit knowledge. In this study, we explore the extent to which ordination results are affected by variation in parameter settings for the clustering procedure. Amplicon sequence data from nine microbial community studies, representing different sampling designs, spatial scales and ecosystems, were subjected to clustering into OTUs at seven different similarity thresholds (clustering thresholds) ranging from 87% to 99% sequence similarity. The 63 data sets thus obtained were subjected to parallel DCA and GNMDS ordinations. The resulting community structures were highly similar across all clustering thresholds. We explain this pattern by the existence of strong ecological structuring gradients and phylogenetically diverse sets of abundant OTUs that are highly stable across clustering thresholds. Removing low-abundance, rare OTUs had negligible effects on community patterns. Our results indicate that microbial data sets with a clear gradient structure are highly robust to choice of sequence clustering threshold.

Biodiversity analyses for risk assessment of genetically modified potato

Abstract An environmental risk assessment for the introduction of genetically modified crops includes assessing the consequences for biodiversity. In this study arthropod biodiversity was measured using pitfall traps in potato agro-ecosystems in Ireland and The Netherlands over two years. We tested the impact of site, year, potato genotype, and fungicide management regime on arthropod community composition. Three potato genotypes were compared: the cultivar Desiree, susceptible to the late blight pathogen Phytophthora infestans, a genetically modified cisgenic clone of Desiree resistant to P. infestans and the cultivar Sarpo Mira, also resistant to late blight. We aimed to test several ways to measure biodiversity in the context of risk assessment by using both univariate biodiversity indices and multivariate ordination methods, categorizing the pitfall trap catch by taxonomic or functional category. The Shannon-Wiener and Simpson biodiversity indices both showed strong differences between sites, years and potato genotypes, but showed no effects of the fungicide management regime. The effect of genotype was due to cultivar differences between Desiree and Sarpo Mira rather than between the GM-event (A15-31) and its isogenic comparator Desiree. Multivariate permutation analyses and RDA ordination confirmed these findings and also showed interactions between year, site and either genotype or treatment. The added value of the multivariate analysis was that it provided information on the specific arthropod groups or taxa that contributed to community structure. Multivariate analyses are recommended for use as a sensitive method to compare functionally important arthropod groups driving community structure within the framework of environmental risk assessments, or for the process of indicator species selection.

Detect and exploit hidden structure in fatty acid signature data

AbstractEstimates of predator diet composition are essential to our understanding of their ecology. Although several methods of estimating diet are practiced, methods based on biomarkers have become increasingly common. Quantitative fatty acid signature analysis (QFASA) is a popular method that continues to be refined and extended. Quantitative fatty acid signature analysis is based on differences in the signatures of prey types, often species, which are recognized and designated by investigators. Similarly, predator signatures may be structured by known factors such as sex or age class, and the season or region of sample collection. The recognized structure in signature data inherently influences QFASA results in important and typically beneficial ways. However, predator and prey signatures may contain additional, hidden structure that investigators either choose not to incorporate into an analysis or of which they are unaware, being caused by unknown ecological mechanisms. Hidden structure also influences QFASA results, most often negatively. We developed a new method to explore signature data for hidden structure, called divisive magnetic clustering (DIMAC). Our DIMAC approach is based on the same distance measure used in diet estimation, closely linking methods of data exploration and parameter estimation, and it does not require data transformation or distributional assumptions, as do many multivariate ordination methods in common use. We investigated the potential benefits of the DIMAC method to detect and subsequently exploit hidden structure in signature data using two prey signature libraries with quite different characteristics. We found that the existence of hidden structure in prey signatures can increase the confusion between prey types and thereby reduce the accuracy and precision of QFASA diet estimates. Conversely, the detection and exploitation of hidden structure represent a potential opportunity to improve predator diet estimates and may lead to new insights into the ecology of either predator or prey. The DIMAC algorithm is implemented in the R diet estimation package qfasar.

Планктонные и донные сообщества высокоминерализованных рек бассейна оз. Эльтон: статистический анализ зависимостей

На примере экосистемы высокоминерализованных рек бассейна гипергалинного оз. Эльтон проанализированы изменения таксономической структуры донных и планктонных сообществ в условиях экстремальных факторов среды. Показано,что под воздействием резких природно-климатических колебаний идёт постоянная перестройка таксономической структуры составляющих гидроэкосистему сообществ. Для многомерного статистического анализа использованы многолетние данные гидробиологической съёмки макрозообентоса, мейобентоса и зоопланктона на 15 станциях 5 солёных рек разного уровня минерализации и соответствующий блок из 19 абиотических показателей. Проверены гипотезы о причинах и закономерностях изменения видовой структуры гидросообществ в условиях воздействия экстремальных факторов (уровень минерализации, температура, эвтрофирование). Установлено, что структуры планктонных и донных сообществ достаточно хорошо коррелируют между собой, следовательно, тесно связаны. Эта связь обусловливается взаимно согласованной реакцией на изменение факторов водной среды и биотическими взаимодействиями, что объясняет снижение коэффициентов матричной корреляции Мантеля между ценозами гидробионтов и гидрохимическими показателями. Для выявления планктонных и донных сообществ, развивающихся в сходных биотопах в условиях перекрывающихся экологических ниш, использованы методы кластерного анализа. Осуществлено целенаправленное графическое проецирование таксонов изучаемых гидросообществ и биотопов в пространстве факторов среды. Определена роль абиотических показателей для оценки особенностей развития популяций макрозообентоса, мейобентоса и зоопланктона. Выполнен сравнительный анализ изменения видового разнообразия сообществ с использованием обобщённых энтропий Реньи. При взаимодействии планктонных и донных сообществ солёных рек выявлена высокая доля по генезису композиционно «взаимопроникающих» экологических групп.

Morphological variation and modularity in the mandible of three Mediterranean dolphin species

Geometric morphometric studies of dolphins have traditionally concentrated on the skull, while the mandible and its modularity have been little explored. We investigated the mandible variability and modularity in three strictly related Mediterranean dolphins: Stenella coeruleoalba, Delphinus delphis and Tursiops truncatus. The aims were to describe the interspecific differences in the size and shape of the mandible as a whole, and of its structural modules, and to detect the influence of adaptive pressures on trait variation. Data were collected on 96 specimens from the Mediterranean Sea. Eight and 10 two-dimensional landmarks were recorded respectively in the lateral and medial sides of the mandible. After General Procrustes Analysis (GPA) transformation, measurement error, sexual dimorphism and ontogenetic allometry were first investigated to allow further pooling of samples. Univariate analysis of variance (ANOVA) of centroid size was used to evaluate size differences among the species; multivariate ordination, classification and clustering methods were used to investigate interspecific variation of shape variables. Different subsets of landmarks representing distinct mandibular subunits were tested for modular integration through the RV coefficient; two-block partial least squares statistics was used to explore the patterns of covariation between modules. Size and shape differences in the whole mandible of the three species evidenced a clear morphological divergence of Tursiops truncatus and a close similarity of Stenella coeruleoalba and Delphinus delphis. The analysis of modularity identified the corpus and the ramus, with its internal foramen, as distinct modules. The corpus and ramus patterns of variation could discriminate between T. truncatus vs. the other two species. The mandibular foramen was the only trait able to discriminate each species, and the corresponding shape differences were related to selective pressures toward the differentiation of communication patterns.

Long-term microphytoplankton variability patterns using multivariate analyses: ecological and management implications.

Microphytoplankton data along the southern Tunisian coasts have been monitored weekly since 1995. This study used the data collected during the period 2000-2007 to determine the temporal variability patterns and to characterize the geographical structures of microphytoplankton populations. The methodological approach consisted in isolating the temporal variability common to all sampled sites and in analyzing the "residual" site-specific component. Multivariate ordination methods were used to determine the seasonal and interannual variability. The temporal pattern shared by all sites was highlighted and the seasonal cycle of the most frequent phytoplankton communities contrasted the diatoms winter-spring species to the dinoflagellates summer-fall species. Multitable comparison allowed the identification of three areas exhibiting similar phytoplankton population variability. The results, despite the coastal location of sampling sites, indicated that hydrodynamic and geomorphologic properties of the different areas as well as anthropogenic activities play a key role in the structure of the phytoplankton communities.

Impactos dos métodos de colheita da cana-de-açúcar sobre a macrofauna do solo em área de produção no Espírito Santo – Brasil

The objective of this study was to evaluate the effects of harvesting methods on the macrofauna, a known indicator of soil quality that detects changes in the system and indicates management alternatives. The experimental design was randomized blocks with six replications, with each block consisting of four parcels that corresponded to treatments green cane (CC), burnt cane (CQ), green cane – burnt cane (CC-Q) and burnt cane – green cane (CQ-C). Samples were collected in February and July 2010. The animals were divided into major taxonomic groups and accounted. Were evaluated ecological indexes (Shannon, Pielou and richness) and average total density of individuals and groups. Data were analyzed by the nonparametric statistical tools by Friedman or Signal test at 5%. To check relationships between soil fauna and environmental variables, was used a multivariate conditional ordination method, the redundancy analysis (RDA). The index richness was more efficient than the total average density to evaluate the influence of cane harvesting systems, with the highest values related to areas harvested without burning. Further, the occurrence of key groups in the areas harvested without burning configures the establishment of a trophic web. There was dominance of the social group Formicidae in all treatments.