Single Assemblage Research Articles

Rarefaction and extrapolation with beta diversity under a framework of Hill numbers: The iNEXT.beta3D standardization

AbstractBased on sampling data, we propose a rigorous standardization method to measure and compare beta diversity across datasets. Here beta diversity, which quantifies the extent of among‐assemblage differentiation, relies on Whittaker's original multiplicative decomposition scheme, but we use Hill numbers for any diversity order q ≥ 0. Richness‐based beta diversity (q = 0) quantifies the extent of species identity shift, whereas abundance‐based (q > 0) beta diversity also quantifies the extent of difference among assemblages in species abundance. We adopt and define the assumptions of a statistical sampling model as the foundation for our approach, treating sampling data as a representative sample taken from an assemblage. The approach makes a clear distinction between the theoretical assemblage level (unknown properties/parameters of the assemblage) and the sampling data level (empirical/observed statistics computed from data). At the assemblage level, beta diversity for N assemblages reflects the interacting effect of the species abundance distribution and spatial/temporal aggregation of individuals in the assemblage. Under independent sampling, observed beta (= gamma/alpha) diversity depends not only on among‐assemblage differentiation but also on sampling effort/completeness, which in turn induces dependence of beta on alpha and gamma diversity. How to remove the dependence of richness‐based beta diversity on its gamma component (species pool) has been intensely debated. Our approach is to standardize gamma and alpha based on sample coverage (an objective measure of sample completeness). For a single assemblage, the iNEXT method was developed, through interpolation (rarefaction) and extrapolation with Hill numbers, to standardize samples by sampling effort/completeness. Here we adapt the iNEXT standardization to alpha and gamma diversity, that is, alpha and gamma diversity are both assessed at the same level of sample coverage, to formulate standardized, coverage‐based beta diversity. This extension of iNEXT to beta diversity required the development of novel concepts and theories, including a formal proof and simulation‐based demonstration that the resulting standardized beta diversity removes the dependence of beta diversity on both gamma and alpha values, and thus reflects the pure among‐assemblage differentiation. The proposed standardization is illustrated with spatial, temporal, and spatiotemporal datasets, while the freeware iNEXT.beta3D facilitates all computations and graphics.

Dispersed spore assemblages from the Lower Devonian Rañeces - La Vid groups of Northern Spain: Palaeogeographical implications

Dispersed spore assemblages are described from the Early Devonian (late Lochkovian-late Emsian) Rañeces Group (Asturias) and equivalent La Vid Group (Leon) of Northern Spain. The lower part of both groups consists predominantly of limestone and yields only impoverished palynological assemblages. However, the upper parts contain more clastic sediments and yield rich assemblages of well preserved palynomorphs. These are dominated by marine forms but also include abundant spores. Sixty-two spore taxa are reported from the Valporquero Formation (Leon). These all belong to a single assemblage that can be equated with the lindlarensis-sextantii Assemblage Zone (mid-early late Emsian age) erected in northern Gondwana. The sequences are independently age constrained by conodont and invertebrate macrofossil evidence and the ages derived from these studies are concordant with the assigned spore zones. The Spanish spore assemblages are from deposits that accumulated around the Armorican Terrane Assemblage (ATA), a group of islands that lay between the continents of Laurussia and Gondwana. Jacaard Index analysis indicates that the Valporquero Formation spore assemblage is endemic, and not closely related to those previously described from Laurussia or Gondwana, although it has more in common with the latter. This suggests that the Armorican Terrane Assemblage was widely separated from both Laurussia and Gondwana, but was located closer to and had more connectivity with Northern Gondwana.

Knotting the Humanimal Assemblage. Race, Animals, and Art in Post-socialist Belgrade

The aim of this article is to show how ontic difference between humans and animals is produced and maintained through weaving and knotting various bodies and flows of matter – the humanimal assemblage. Race and effects of capitalism play decisive roles in the formation of such differences and include humans, postsocialist condition, investment urbanism, state apparatus, non-human beings, artworks, etc. Those humans who are defined as non-white are socially produced as spatio-temporally closer to animals in the whole spectrum of material-semiotic registers. By close reading of the installation Gypsies and Dogs and the event of a death of a dog to which I was a witness, I show the ways in which art plays an important role in this humanimal assemblage, together with the institutions that surround it and enable its production. Using concepts created by Deleuze and Guattari together with Afropessimist thought, I show that humanimal assemblage produces ontological rigidity in the Roma people and their relation with the companion dogs, as well as ethnic Serbs and their dogs as pets. Each human-animal relation is an effect and constitutive part of humanimal assemblage that forcefully relates human and nonhuman animals and other bodies and flows of matter. By thinking transversally, we can see that racialization, postsocialist condition, nascent neoliberal capitalist order, and artworld function to capture flows of matter, singularities-in-constitution, and tie them together in a single assemblage. In conclusion, the knots of the humanimal assemblage need to be unraveled by critical attention to the moments of ontological heterogenesis, which is grounded neither in ontological plasticity nor ontological rigidity.

Using citizen science to test for acoustic niche partitioning in frogs

The acoustic niche hypothesis proposes that to avoid interference with breeding signals, vocal species should evolve to partition acoustic space, minimising similarity with co-occurring signals. Tests of the acoustic niche hypothesis are typically conducted using a single assemblage, with mixed outcomes, but if the process is evolutionarily important, a pattern of reduced acoustic competition should emerge, on average, over many communities. Using a continental-scale dataset derived from audio recordings collected by citizen scientists, we show that frogs do partition acoustic space. Differences in calls were predominately caused by differences in spectral, rather than temporal, features. Specifically, the 90% frequency bandwidths of observed frog assemblages overlapped less than expected, and there was greater distance between dominant frequencies than expected. To our knowledge, this study is the first to use null models to test for acoustic niche partitioning over a large geographic scale.

Coordination of phage genome degradation versus host genome protection by a bifunctional restriction-modification enzyme visualized by CryoEM

Restriction enzymes that combine methylation and cleavage into a single assemblage and modify one DNA strand are capable of efficient adaptation toward novel targets. However, they must reliably cleave invasive DNA and methylate newly replicated unmodified host sites. One possible solution is to enforce a competition between slow methylation at a single unmodified host target, versus faster cleavage that requires multiple unmodified target sites in foreign DNA to be brought together in a reaction synapse. To examine this model, we have determined the catalytic behavior of a bifunctional type IIL restriction-modification enzyme and determined its structure, via cryoelectron microscopy, at several different stages of assembly and coordination with bound DNA targets. The structures demonstrate a mechanism in which an initial dimer is formed between two DNA-bound enzyme molecules, positioning the endonuclease domain from each enzyme against the other's DNA and requiring further additional DNA-bound enzyme molecules to enable cleavage.

Detection of Giardia intestinalis assemblages A and B among children from three villages in the West Delta region, Egypt using assemblage specific primers.

Giardia intestinalis is a common diarrheagenic parasite infecting children globally. It has been classified into eight morphologically identical but genetically distinct genotypes. Human infection is mainly associated with A and B assemblages with variable geographical distribution. The present work aimed to study the epidemiology of assemblages A and B in children inhabiting different areas in Lower Egypt. Stool samples were collected from 315 children and examined microscopically for parasitic infections. Giardia positive samples were genotyped using tpi assemblage specific primers. The prevalence of Giardia was 18.1% among the examined children. Mixed assemblages A and B was more common (47.4%) than single assemblage B (36.8%) or A (15.8%). The distribution of different genotypes was significantly associated with the residence area, animal contact, and handwashing habits. A non-significant association was observed between Giardia assemblages and the clinical manifestations. Assemblage B is the predominant genotype among Egyptian children. The distribution of different Giardia assemblages is strongly associated with the studied area and the habits of its people.

Elastoplastic Analysis of Ultimate Bearing Capacity for Multilayered Thick-Walled Cylinders Under Internal Pressure

The elastoplastic analysis based on the unified strength theory was performed to evaluate the ultimate bearing capacity of double- and multilayered thick-walled cylinders. The theory provides a new concept and method for the analysis of thick-walled cylinders. The solutions derived herein are widely applicable and can quantitatively account for different tension-compression strength values and mean principal stress. The fundamental solutions for single radii, assemblage pressure, and shrink range are derived with the yield condition of the theory. The traditional existing elastoplastic results by the Tresca or von Mises yield criteria can be seen as a particular case of the new solutions that can overcome shortcomings. The strength parameter, tension-compression strength ratio, radii ratio, and combined cylinder layers were taken as major theory variables for the unified solutions. The new solutions are versatile and can be adapted to the existing formulas, to more accurately calculate the structural stress conditions. The strength theory effect due to adopting different yield criteria is quite significant, which cannot be underestimated.

Upper Miocene molluscs of Monti Livornesi (Tuscany, Italy): Biotic changes across environmental gradients

The upper Miocene mollusc assemblages of Monti Livornesi, used as a means to study the nature of Mediterranean benthic communities at the edge of the Messinian salinity crisis, are framed in a high-resolution stratigraphic scheme and quantitatively approached by the study of historical museum collections and modern samples. Instead of a single assemblage from either Tortonian or Messinian age, as previously thought, this fauna comes from three consecutive shallowing-upward depositional sequences bounded by regional unconformities, the Luppiano (upper Tortonian-lowermost Messinian), Rosignano and Raquese units (early Messinian). Facies analysis, taphonomy and quantitative paleoecology show that the Luppiano assemblage is characterised by aragonitic species from a eutrophic brackish-water shallow marine muddy bottom, the Rosignano assemblage by calcitic species from an oligotrophic coarse-grained seafloor close to a coral reef and the Raquese assemblage from an open-marine muddy bottom. Published comparisons between Miocene and Pliocene faunal lists should be considered only crude estimates of faunal change until more is known about the distribution of species along paleoenvironmental gradients. The analysis of Miocene and Pliocene abundance data allows us to frame the Monti Livornesi molluscs along carbonate-siliciclastic and water depth gradients and to reach a better understanding of the effects of salinity crisis on the Mediterranean biota.

An endemic microphytoplankton assemblage from Middle Devonian Iberia and its paleogeographical significance

Diverse microphytoplankton assemblages, including 72 taxa belonging to 27 genera of acritarchs and prasinophyte phycomata, have been recovered from Middle Devonian rocks in northern Spain, revealing an endemic flora dissimilar to coeval assemblages. These deposits are of early Givetian age and consist of the laterally equivalent Naranco, Huergas and Gustalapiedra formations of Asturias, León and Palencia provinces. At the time, Iberia was part of the Armorican Terrane Assemblage, a comparatively isolated island chain positioned between Laurussia and Gondwana. The studied formations represent a marine transect across a nearshore–offshore gradient and consist of a large clastic unit sandwiched between extensive carbonate deposits. This clastic unit incorporates the Kačák Event, an important global extinction event associated with marine anoxia. Herein, the suite of generally well-preserved microphytoplankton assemblages is described and their stratigraphical and biogeographical importance are considered. The microphytoplankton represents a single assemblage deposited in a short interval and is interpreted as being endemic. The assemblage is only moderately similar to contemporary assemblages from Laurussia and Gondwana and, although certain characteristic Middle Devonian taxa are present, other common species such as Arkonites bilixus and Tyligmasoma alargada are absent. While no unique taxa are found here, the taxa which are present represent a particular combination of species not seen elsewhere. Certain taxa appear which may have discordant temporal ranges, though no major inferences can be made from them as only two taxa both occur in significant numbers and have a confident identification. This assemblage adds to our knowledge of phytoplankton palaeobiogeography, representing a significantly endemic assemblage within the generally cosmopolitan microphytoplankton flora of the Middle Devonian.

An endemic flora of dispersed spores from the Middle Devonian of Iberia

AbstractDiverse assemblages of dispersed spores have been recovered from Middle Devonian rocks in northern Spain, revealing a significant endemism in the flora. Middle Devonian Iberia was part of a relatively isolated island complex (Armorican Terrane Assemblage), separated by considerable tracts of ocean from Laurussia to the north‐west and Gondwana to the south‐east. The Middle Devonian deposits of the Cantabrian Zone of northern Spain are entirely marine and comprise a thick clastic unit sandwiched between extensive carbonate units. The clastic unit, the laterally equivalent Naranco, Huergas and Gustalapiedra formations of Asturias, León and Palencia provinces, represents a nearshore‐offshore transect across a marine shelf. This unit is also believed to encompass the Kačák Event, an important global extinction event. The recovered palynomorphs include marine (phytoplankton, chitinozoans, scolecodonts) and terrestrial (spores) assemblages. These are abundant and well preserved, although of variable thermal maturity. Here, we describe the dispersed spores and consider their significance as regards biostratigraphy, palaeophytogeography and Kačák Event interpretation. The dispersed spores represent a single assemblage assignable to the lemurata–langii Assemblage Zone (lemurata Subzone) indicating a probable early (but not earliest) Givetian age. Signs of endemism include various taxa known only from this region, some taxa appearing to have discordant ranges compared with elsewhere, and the absence from Iberia of certain prominent taxa characteristic of coeval assemblages elsewhere, such as those with grapnel‐tipped processes. The abrupt interruption of carbonate deposition, with a change to rapid deposition of thick clastic deposits, provides support for a monsoonal cause of the Kačák Event.

Using Torulaspora delbrueckii killer yeasts in the elaboration of base wine and traditional sparkling wine

For still wines, killer strains of Torulaspora delbrueckii can be used instead of non-killer strains to improve this species' domination during must fermentation, with an ensured, reliable impact on the final wine quality. The present work analysed the usefulness of these killer yeasts for sparkling-wine making. After the first fermentation, the foaming capacity of T. delbrueckii base wines was very low compared to Saccharomyces cerevisiae base wines. Significant positive correlations of foaming parameters were found with the amounts of C4–C16 ethyl esters and proteins, and negative with some anti-foaming alcohols produced by each yeast species. There were, however, no evident positive effects of polysaccharides on those parameters. The organoleptic quality of the T. delbrueckii base wines was judged inappropriate for sparkling-wine making, so that the following second-fermentation experiments only used a single assemblage of S. cerevisiae base-wines. While second fermentation was completed with inoculation of S. cerevisiae (both alone and mixed with T. delbrueckii) to yield dry sparkling wines with high CO2 pressure, single inoculation with T. delbrueckii did not complete this fermentation, leaving sweet wines with poor CO2 pressure. Yeast death due to CO2 pressure was much greater in T. delbrueckii than in S. cerevisiae, making any killer effect of S. cerevisiae over T. delbrueckii irrelevant because no autolysed cells were found during the first days of mixed-inoculated second fermentation. Nonetheless, the organoleptic quality of the mixed-inoculated sparkling wines was better than that of wines single-inoculated with S. cerevisiae, and showed no deterioration in foam quality. This seemed mainly to be because T. delbrueckii increased the amounts of ethyl propanoate and some acids (e.g., isobutyric and butanoic), alcohols (e.g., 3‑ethoxy‑1‑propanol), and phenols (e.g., 4‑vinylguaiacol). For these sparkling wines, no significant correlations between foaming parameters and aroma compounds were found, probably because the differences in foaming parameter values among these wines were fairly small. This is unlike the case for the base wines for which there were large differences in these parameters, which facilitated the analysis of the influence of aroma compounds on base-wine foamability.

Assemblage of Urban Small Parcels in Three Different Scales with the Emphasize on the Citizenship Participation, Case Study: Tehran - Iran

During recent years, several experiences have been executed for interfering in inefficient urban fabrics, all of them had been forced on the basis of centralized intervention approach; determining a territory as the project range, funding sources, ownership, execution, utilization, is a single process , the attribution of which could be found in several cases in the country. The important point in this regards which determines the future strategies is the performance process and method. The global examples and local experiences show that all approaches, plans and executive plans should be developed and materialized on the basis of “people participation” principle. This procedure is executable in various forms; reinforcement of existing buildings, renovation of single parcel and assemblage of small sized parcels are the methods that play important role in this process. The present paper studies different scales of “assemblage” as one of the methods of housing renovation and by using analytic hierarchy model AHP method proves that assemblage in urban block scale by citizenship participation could serve both as a tool for improving land distribution pattern, and, providing new opportunities for the city to develop. The indexes that are used in this survey were selected by literature review and attribution to several executive plan cases.

Deciphering the enigma of undetected species, phylogenetic, and functional diversity based on Good-Turing theory.

Estimating the species, phylogenetic, and functional diversity of a community is challenging because rare species are often undetected, even with intensive sampling. The Good-Turing frequency formula, originally developed for cryptography, estimates in an ecological context the true frequencies of rare species in a single assemblage based on an incomplete sample of individuals. Until now, this formula has never been used to estimate undetected species, phylogenetic, and functional diversity. Here, we first generalize the Good-Turing formula to incomplete sampling of two assemblages. The original formula and its two-assemblage generalization provide a novel and unified approach to notation, terminology, and estimation of undetected biological diversity. For species richness, the Good-Turing framework offers an intuitive way to derive the non-parametric estimators of the undetected species richness in a single assemblage, and of the undetected species shared between two assemblages. For phylogenetic diversity, the unified approach leads to an estimator of the undetected Faith's phylogenetic diversity (PD, the total length of undetected branches of a phylogenetic tree connecting all species), as well as a new estimator of undetected PD shared between two phylogenetic trees. For functional diversity based on species traits, the unified approach yields a new estimator of undetected Walker etal.'s functional attribute diversity (FAD, the total species-pairwise functional distance) in a single assemblage, as well as a new estimator of undetected FAD shared between two assemblages. Although some of the resulting estimators have been previously published (but derived with traditional mathematical inequalities), all taxonomic, phylogenetic, and functional diversity estimators are now derived under the same framework. All the derived estimators are theoretically lower bounds of the corresponding undetected diversities; our approach reveals the sufficient conditions under which the estimators are nearly unbiased, thus offering new insights. Simulation results are reported to numerically verify the performance of the derived estimators. We illustrate all estimators and assess their sampling uncertainty with an empirical dataset for Brazilian rain forest trees. These estimators should be widely applicable to many current problems in ecology, such as the effects of climate change on spatial and temporal beta diversity and the contribution of trait diversity to ecosystem multi-functionality.

The Bruneau Woodpile: A Miocene Phosphatized Fossil Wood Locality in Southwestern Idaho, USA

The Bruneau Woodpile site has long been popular among fossil collectors; however, the deposit has received scant attention from scientists. Our research reveals that the fossilized wood was deposited ca. 6.85 Ma, within the Chalk Hills Formation, and was mineralized with carbonate-fluorapatite. The diverse assemblage of conifers and hardwoods is representative of the warm temperate forests that flourished in southwest Idaho, USA during the late Miocene. Limb and trunk fragments preserved in a single thin sandstone bed appear to represent woody debris that was transported by streams. One possible explanation is that wood, pumice, and sandy volcaniclastic sediment arrived separately as a result of ordinary stream action, and later were combined into a single assemblage during a subsequent high-energy sedimentation event. We favor an alternate hypothesis: a catastrophic event (e.g., a windstorm) damaged trees on slopes bordering the ancient lake. Branches and small trunk fragments were carried by wind and rain into local streams and ponds where they became waterlogged. After a delay that allowed pumice and wood to become saturated, storm water transported these materials, along with finer volcaniclastic sediment, into a lake. The resulting density current produced a fining-upward sedimentary cycle where wood was preserved in the lowest, coarsest stratum.

Multilocus genotyping of Giardia duodenalis isolates from breeding cattery cats in Japan.

ObjectivesThe present study reports the multilocus genotyping of Giardia duodenalis isolates from cats maintained in breeding catteries in Japan and discusses their potential for zoonotic transmission.MethodsA total of 41 faecal samples positive for Giardia-specific antigen were procured from cats maintained in five breeding catteries and subjected to PCR to amplify four gene loci, namely small subunit ribosomal RNA (SSU rRNA), glutamate dehydrogenase (gdh), beta-giardin (bg) and triose phosphate isomerase (tpi ). The PCR-amplified DNA fragments were sequenced to determine the G duodenalis genotypes (synonym for assemblages).ResultsThe most commonly occurring single assemblage was assemblage F (68.3%; n = 28/41), followed by assemblage A (12.2%; n = 5/41) and assemblage C (2.4%; n = 1/41). The mixed assemblages were identified as follows: assemblages F and A (9.8%; n = 4/41), assemblages F and C (4.9%; n = 2/41) and assemblages C and D (2.4%; n = 1/41). Additional sub-genotyping of assemblage A isolates based on three of the sequenced loci (gdh, bg and tpi ) revealed that all eight isolates were identified as sub-assemblage AI and/or AII.Conclusions and relevanceThe present study is the first to report the detection of dog-adapted assemblages C and D in feline isolates from Japan. In addition, zoonotic sub-assemblage AI and human-adapted sub-assemblage AII were also identified. Thus, we concluded that the risk of transmission of G duodenalis from breeding cattery cats to humans is considerable and cannot be ignored.

The genus Trochodendroides (Cercidiphyllaceae) in the Cretaceous floras of North-East of Russia

The genus Trochodendroides, recognized by its ovate or elliptical leaves with palmate brochidodromous venation, is well represented in the late Albian-Maastrichtian floras of North-East of Russia. The study of recently collected materials and revision of previous data allow us to introduce one new species (T. montana P. Alekseev, sp. nov.) and to offer 6 new combinations (T. ochotica (Vachr. et Herman) Golovn. et Gnilovskaya, comb. nov., T. barykovensis (Moiseeva) Golovn., comb. nov., T. gigantea (Moiseeva) Golovn., comb. nov., T. terranea (Moiseeva et Herman) Golovn., comb. nov., T. campanica (Abramova) Golovn. et Yudova, comb. nov., T. crenata (Herman) Golovn., comb. nov.). The new names were proposed for two species (T. samyliniae P. Alekseev, nom. nov., T. magadanica Golovn., nom. nov.). The diagnoses of 10 species are emended. The species Trochodendroides pekulneensis Philipp. and Zizyphus anadyrensis Philipp. are joined under the name Trochodendroides pekulneensis Philipp. emend. Yudova. The species Zizyphus microphylla Philipp. and Trochodendroides armanensis Philipp. are joined under the name T. magadanica Golovn. The species Macclintockia ochotica Vachr. et Herman and Trochodendroides longifolia Golovn. are joined under the name Trochodendroides ochotica (Vachr. et Herman) Golovn. et Gnilovskaya. In the whole, 21 species are recognized in the Late Cretaceous floras of North-East of Russia. Their stratigraphic and geographic ranges were analized. The systematic and morphology diversity of Trochodendroides was comparatively low in the late Albian–Turonian and the findings of these leaves are rare. During the Coniacian this genus reached the highest systematic and morphologic diversity. In the Santonian the abundance of Trochodendroides leaves was decreasing. In this time the lanceolate or narrow-ovate leaf morphotypes were most usual. The abundance of Trochodendroides leaves was increased again in the Campanian and decreasing in the Maastrichtian. Between 21 species, 18 species were distributed only in North-East of Russia. Many species were recorded only in single floristic assemblage. Species T. deminii and T. sachalinensis were characterised by wide stratigraphic ranges (from the late Albian to the Maastrichtian and from the Coniacian to the Campanian consequently).

New interpretation of the Gran Dolina-TD6 bearing Homo antecessor deposits through sedimentological analysis

Gran Dolina is a cavity infilled by at least 25 m of Pleistocene sediments. This sequence contains the TD6 stratigraphic unit, whose records include around 170 hominin bones that have allowed the definition of a new species, Homo antecessor. This fossil accumulation was studied as a single assemblage and interpreted as a succession of several human home bases. We propose a complete stratigraphic context and sedimentological interpretation for TD6, analyzing the relationships between the sedimentary facies, the clasts and archaeo-palaeontological remains. The TD6 unit has been divided into three sub-units and 13 layers. Nine sedimentary facies have been defined. Hominin remains appear related to three different sedimentary facies: debris flow facies, channel facies and floodplain facies. They show three kinds of distribution: first a group of scattered fossils, then a group with layers of fossils in fluvial facies, and third a group with a layer of fossils in mixed fluvial and gravity flow facies. The results of this work suggest that some of these hominin remains accumulated in the cave by geological processes, coming from the adjacent slope above the cave or the cave entry, as the palaeogeography and sedimentary characteristics of these allochthonous facies suggest.

Body mass distributions along successional gradients in epigeic carabid beetle fauna (Coleoptera: Carabidae)

Background and purpose: Body mass distributions may be related to the stage of succession of a habitat and provide with information for assessing successional processes. Therefore, body mass distributions of carabid assemblages were studied in three research areas, which were post-industrial areas near the city of Belchatow (Central Poland) planted with different tree and shrub species, moist and wet forest stands in the Puszcza Knyszynska forest (Northeastern Poland), and beech stands in the Ruhr valley (Western Germany) in order to analyze the changes in body mass distributions within single assemblages along successional gradients. Materials and Methods: For each carabid assemblage, the mean individual biomass (MIB) as well as MIB standard deviation (SD) and coefficient of variation (CV) were calculated. SD and CV were plotted against the age of study sites and MIB values, respectively. Analyses of Covariance (ANCOVA) were carried out with SD and CV as dependent variables and the age of study sites and MIB as covariates. Results: SD was low at young stages of succession, but increased rapidly and plateaued at advanced stages in beech but not in wet forest stands. Accordingly, CV was low at very young stages of succession, showing a rapid increase and subsequent decrease in the beech stands, whereas in the wet stands it stayed on a constant level. ANCOVA revealed significant differences in SD and CV between the research areas and significant changes with age or MIB, but, with the exception of CV as dependent variable and MIB as covariate, interactions were also significant. Conclusions: The results of the study suggest that data on body mass distributions within single carabid assemblages may be useful in the assessment and comparison of successional stages and processes between different habitat types.

Species traits and catchment‐scale habitat factors influence the occurrence of freshwater mussel populations and assemblages

Summary Conservation of freshwater unionid mussels presents unique challenges due to their distinctive life cycle, cryptic occurrence and imperilled status. Relevant ecological information is urgently needed to guide their management and conservation. We adopted a modelling approach, which is a novel application to freshwater mussels to enhance inference on rare species, by borrowing data among species in a hierarchical framework to conduct the most comprehensive occurrence analysis for freshwater mussels to date. We incorporated imperfect detection to more accurately examine effects of biotic and abiotic factors at multiple scales on the occurrence of 14 mussel species and the entire assemblage of the Tar River Basin of North Carolina, U.S.A. The single assemblage estimate of detection probability for all species was 0.42 (95% CI, 0.36–0.47) with no species‐ or site‐specific detection effects identified. We empirically observed 15 mussel species in the basin but estimated total species richness at 21 (95% CI, 16–24) when accounting for imperfect detection. Mean occurrence probability among species ranged from 0.04 (95% CI, 0.01–0.16) for Alasmidonta undulata, an undescribed Lampsilis sp., and Strophitus undulatus to 0.67 (95% CI, 0.42–0.86) for Elliptio icterina. Median occurrence probability among sites was <0.30 for all species with the exception of E. icterina. Site occurrence probability generally related to mussel conservation status, with reduced occurrence for endangered and threatened species. Catchment‐scale abiotic variables (stream power, agricultural land use) and species traits (brood time, host specificity, tribe) influenced the occurrence of mussel assemblages more than reach‐ or microhabitat‐scale features. Our findings reflect the complexity of mussel ecology and indicate that habitat restoration alone may not be adequate for mussel conservation. Catchment‐scale management can benefit an entire assemblage, but species‐specific strategies may be necessary for successful conservation. The hierarchical multispecies modelling approach revealed findings that could not be elucidated by other means, and the approach may be applied more broadly to other river basins and regions. Accurate measures of assemblage dynamics, such as occurrence and species richness, are required to create management plans for effective conservation.

COMPOSICIÓN Y ESTRUCTURA DEL ENSAMBLAJE DE CRUSTÁCEOS BRACHYURA DE LA PLATAFORMA CONTINENTAL DE LA GUAJIRA COLOMBIANA Y SU RELACIÓN CON LA PROFUNDIDAD Y LAS CARACTERÍSTICAS DEL SEDIMENTO

Brachyura crustaceans composition and structure assemblage along be continental shelf of La Guajira and its variation according to depth gradient and sediment characteristics were determined. 44 bottom drag samples were taken at 10 and 50 m depth using a semi globe demersal net, during March and April 2005. 83 species belonging to 21 families were identified; the most important families due to their abundance of specimens and amount of species were Goneplacidae, Portunidae, and Mithracidae; and dominant species were Glyptoplax smithii, with, 12.53 % of total abundance; Portunus spinicarpus, 7.42 % and Nemausa cornuta, 6.84 %. The non-metric multidimensional scaling analysis (NMDS) did not show any well defined sampling station clusters, but meaningful statistical differences were found in the assemblage structure according to depth gradient and the different kinds of sediments. The ANOSIM tests and the ordination analysis (NMDS) pointed out that there is a single assemblage that varies gradually with depth, and to a lesser degree by physical sediments characteristics. The ordination (NMDS) also reveals that the assemblage is more heterogeneous at 10 m than at 50 m depth, possibly as a result of the larger environmental variability close to the coast, in comparison with the environmental stability that characterizes deeper zones.