Dispersal Ability Research Articles

Effect of hydrophilic silica nanoparticles on foam properties of mixtures of silicone and hydrocarbon surfactants

Foams stabilized by nanoparticles (NPs) and surfactants have great application prospects in the development of fluorine-free firefighting foams. In the present study, hydrophilic SiO2 NPs, a nonionic silicone surfactant (CoatOsil-77), and a zwitterionic hydrocarbon surfactant (BS-12) were used to prepare mixed dispersions to investigate effect of NPs on properties of fluorine-free foams. The interactions between NPs and surfactants, foaming ability, and foam stability of the mixed dispersions were investigated. Results indicate that the surface activity, conductivity, and foaming ability of the mixed dispersions decreased with increasing NP concentration. The addition of NPs has a remarkable impact on foam stability of the mixed dispersions. The presence of NPs at a NP concentration above 2% leads to enhancement of foam stability by delaying foam drainage and coarsening. This study provides theoretical guidance for the application of NPs in fluorine-free foams.

Decomposing dark diversity affinities of species and sites using Bayesian method: What accounts for absences of species at suitable sites?

Abstract Locally observed biodiversity always consists of only a fraction of its site‐specific species pool. Why some suitable species are absent, shaping dark diversity of that site, is a basic yet increasingly crucial question in the face of global biodiversity degradation. The ultimate processes underlying dark diversity associate with either dispersal or persistence limitations, or both. These two limitations in turn link to several characteristics of individual species and sites, making it challenging to detect the exact factors contributing to dark diversity in a particular metacommunity. Here, we propose a metric, dark diversity affinity (DDA), which measures the tendencies of individual species to be absent from suitable sites and of individual sites to miss suitable species. We developed a Bayesian model interrelating four types of datasets: metacommunity matrix of species presences in sites, species‐sites suitability matrix, species functional traits and site characteristics. In the model, DDA operates as an adjustment bridging the disparity between site‐specific suitability and observed presence/absence of each species at each site. Furthermore, DDA can be related to individual properties of species and sites through logistic regression sub‐models. We demonstrated our framework using nine empirical datasets of vertebrate, invertebrate and vascular plant metacommunities. We show the decomposed roles of species traits and site characteristics in defining DDA and, therefore, dark diversity in metacommunities. In the empirical datasets, various functional traits, which related to morphology, reproduction, dispersal ability, population attributes, resource specificity and life history, significantly affected species‐level DDA, while site characteristics regarding habitat types and attributes, resource availability, pollution, and edaphic and water conditions influenced DDA at the site level. Our framework provides a concept and methodological toolbox that allows identification of the processes underlying dark diversity and advances both the theory of community ecology and biodiversity conservation. Conservation actions can be more successful by knowing whether species loss in a particular metacommunity is associated to some species traits or site characteristics and what their relative contributions are.

Preparation and Characterization of Modified Kaolin by a Mechanochemical Method.

A mechanochemical approach was utilized to prepare modified kaolin, and the hydrophobic modification of kaolin was realized. The study aims to investigate the changes in particle size, specific surface area, dispersion ability, and adsorption performance of kaolin. The structure of kaolin was analyzed using infrared spectroscopy, scanning electron microscopy, and X-ray diffraction, and the alterations to the kaolin microstructure were thoroughly researched and discussed. The results demonstrated that this modification method can effectively improve the dispersion and adsorption capacities of kaolin. Mechanochemical modification can increase the specific surface area of kaolin particles, reduce their particle size, and improve their agglomeration behavior. The layered structure of the kaolin was partially destroyed, the degree of order was debased, and the activity of its particles was enhanced. Furthermore, organic compounds were adsorbed on the surface of the particles. The appearance of new infrared peaks in the modified kaolin's infrared spectrum suggested that the kaolin has undergone a chemical modification process, introducing new functional groups.

Ultrasmall Coordination Polymer Nanodots Fe‐Quer Nanozymes for Preventing and Delaying the Development and Progression of Diabetic Retinopathy

AbstractDiabetic retinopathy (DR) is the most prevalent type of retinal vasculopathy and the most widespread cause of preventable blindness in adults. Excessive increases in reactive oxygen species (ROS) and vascular endothelial growth factor are major initiators and drivers of DR progression, respectively. However, current DR treatment options remain limited, particularly for early DR. Nanotechnology‐mediated antioxidant strategies are gaining increasing popularity to treat ocular diseases. Quercetin has excellent ROS scavenging efficiency but poor stability and low bioavailability in physiological environments. In this study, ultrasmall Fe‐Quer nanozymes (NZs) formed by coupling quercetin with low‐toxic iron ions are reported that can mimic the activities of three important antioxidant enzymes, superoxide dismutase, catalase, and peroxidase, thereby exhibiting excellent water dispersion and efficient ROS scavenging ability. In vitro and in vivo assays validate the effects of Fe‐Quer NZs against inflammation, oxidative stress damage, microvascular leakage, and angiogenesis, particularly their vascular protective effect in early DR. Transcriptomic analysis further reveals a potential multitarget‐specific therapeutic mechanism of Fe‐Quer NZs against DR. These observations open avenues for Fe‐Quer NZs, composed of molecules of a natural product and metal ions with artificial NZ activity, as microvascular protective agents for DR and other ROS‐related diseases.

Study on the dispersion performance and mechanism of polycarboxylate superplasticizer by the long side‐chain dicarboxyl terminated

AbstractThe steric hindrance formed by polyether side chains is the key factor determining the dispersion performance of polycarboxylate superplasticizer (PCE). While with the increase of the side chain length, the coiled conformation of side chain will prevent the dispersion ability of PCE from being further improved. In this work, the methallyl polyoxyethylene ether (HPEG) was esterified with tricarballylic acid (TA) to obtain dicarboxyl terminated macromonomer, and further used to synthesize polycarboxylate (PCETA). The fluidity tests show that compared with ordinary PCE‐B2400 with short side chain, the dispersion performance of PCETA‐2400 was slightly improved. While for the PCEs with long side chain, the dispersion ability of PCETA‐4000 was significantly improved than that of ordinary PCE‐B4000. The adsorption layer thickness of PCETA‐4000 adsorbed on the surface of SiO2 sphere measured by dynamic light scattering is 7.93 nm, which is 1.3 times that of PCE‐B4000. Due to electrostatic repulsion between the carboxylic groups, the stretching of long side‐chain forms stronger steric hindrance and enhancing the dispersion of cement particles. In addition, PCETA also shows good slump retention and clay resistance properties, and it is an excellent multi‐functional concrete admixture with great application potential.

Post-glacial range formation of temperate forest understorey herbs - Insights from a spatio-temporally explicit modelling approach.

Our knowledge of Pleistocene refugia and post-glacial recolonization routes of forest understorey plants is still very limited. The geographical ranges of these species are often rather narrow and show highly idiosyncratic, often fragmented patterns indicating either narrow and species-specific ecological tolerances or strong dispersal limitations. However, the relative roles of these factors are inherently difficult to disentangle. Central and south-eastern Europe. 17,100 BP - present. Five understorey herbs of European beech forests: Aposeris foetida, Cardamine trifolia, Euphorbia carniolica, Hacquetia epipactis and Helleborus niger. We used spatio-temporally explicit modelling to reconstruct the post-glacial range dynamics of the five forest understorey herbs. We varied niche requirements, demographic rates and dispersal abilities across plausible ranges and simulated the spread of species from potential Pleistocene refugia identified by phylogeographical analyses. Then we identified the parameter settings allowing for the most accurate reconstruction of their current geographical ranges. We found a largely homogenous pattern of optimal parameter settings among species. Broad ecological niches had to be combined with very low but non-zero rates of long-distance dispersal via chance events and low rates of seed dispersal over moderate distances by standard dispersal vectors. However, long-distance dispersal events, although rare, led to high variation among replicated simulation runs. Small and fragmented ranges of many forest understorey species are best explained by a combination of broad ecological niches and rare medium- and long-distance dispersal events. Stochasticity is thus an important determinant of current species ranges, explaining the idiosyncratic distribution patterns of the study species despite strong similarities in refugia, ecological tolerances and dispersal abilities.

Fragmentation shapes nest density and social structure but not genetic diversity of Temnothorax crassispinus (Formicidae)

AbstractHuman activities affect biodiversity by reducing the area of habitats, altering their shape, and increasing their isolation. Ants are particularly sensitive to habitat fragmentation, as it may locally change abiotic conditions, the availability of food and nest sites, the abundance of mutualists, competitors and predators, and also restrict gene flow between patches. As a result, the genetic population and colony structure of ants is expected to show signs of fragmentation. In the present study, we investigated the impact of fragmentation on the ant Temnothorax crassispinus in 45 forest patches across the Franconian Jura, Germany. Based on 283 colonies, of which 156 were genetically analyzed, we evidenced the presence of two putative distinct genetic clusters in the study area. Both the nest densities and the presence of queen were impacted by the number of adjacent forest patches within 400 m around the focal patch, but neither by patch shape nor patch size. We could not detect any effect of fragmentation on the genetic diversity, probably because the high dispersal abilities of T. crassispinus counterbalance any detrimental genetic consequences of fragmentation. Nevertheless, fragmentation still impacts the species density as well as the social structure of its colonies. Further investigations regarding the drivers of occurrence at a finer spatial scale might clarify the role of edge effects on the occurrence of this species.

Traits shaping urban tolerance in birds differ around the world

As human density increases, biodiversity must increasingly co-exist with urbanization or face local extinction. Tolerance of urban areas has been linked to numerous functional traits, yet few globally consistent patterns have emerged to explain variation in urban tolerance, which stymies attempts at a generalizable predictive framework. Here, we calculate an Urban Association Index (UAI) for 3,768 bird species in 137 cities across all permanently inhabited continents. We then assess how this UAI varies as a function of ten species-specific traits and further test whether the strength of trait relationships vary as a function of three city-specific variables. Of the ten species traits, nine were significantly associated with urban tolerance. Urban-associated species tend to be smaller, less territorial, have greater dispersal ability, broader dietary and habitat niches, larger clutch sizes, greater longevity, and lower elevational limits. Only bill shape showed no global association with urban tolerance. Additionally, the strength of several trait relationships varied across cities as a function of latitude and/or human population density. For example, the associations of body mass and diet breadth were more pronounced at higher latitudes, while the associations of territoriality and longevity were reduced in cities with higher population density. Thus, the importance of trait filters in birds varies predictably across cities, indicating biogeographic variation in selection for urban tolerance that could explain prior challenges in the search for global patterns. A globally informed framework that predicts urban tolerance will be integral to conservation as increasing proportions of the world's biodiversity are impacted by urbanization.

Simulating the dynamics of dispersal and dispersal ability in fragmented populations with mate-finding Allee effects.

We consider the spatial propagation and genetic evolution of model populations comprising multiple subpopulations, each distinguished by its own characteristic dispersal rate. Mate finding is modeled in accord with the assumption that reproduction is based on random encounters between pairs of individuals, so that the frequency of interbreeding between two subpopulations is proportional to the product of local population densities of each. The resulting nonlinear growth term produces an Allee effect, whereby reproduction rates are lower in sparsely populated areas; the distribution of dispersal rates that evolves is then highly dependent upon the population's initial spatial distribution. In a series of numerical test cases, we consider how these dynamics affect lattice-like arrangements of population fragments, and investigate how a population's initial fragmentation determines the dispersal rates that evolve as a habitat is colonized. First, we consider a case where initial population fragments coincide with habitat islands, within which death rates differ from those that apply outside; the presence of inhospitable exterior regions exaggerates Allee effect-driven reductions in dispersal ability. We then examine how greater distances separating adjacent population fragments lead to more severe reductions in dispersal ability. For populations of a fixed initial magnitude, fragmentation into smaller, denser patches leads not only to greater losses of dispersal ability, but also helps ensure the population's long-term persistence, emphasizing the trade-offs between the benefits and risks of rapid dispersal under Allee effects. Next, simulations of well-established populations disrupted by localized depopulation events illustrate how mate-finding Allee effects and spatial heterogeneity can drive a population's dispersal ability to evolve either downward or upward depending on conditions, highlighting a qualitative distinction between population fragmentation and habitat heterogeneity. A final test case compares populations that are fragmented across multiple scales, demonstrating how differences in the relative scales of micro- and macro-level fragmentation can lead to qualitatively different evolutionary outcomes.

The role of niche breadth in oak phylogeography: Quercus glaucoides as a study case

AbstractAimThe extent of genetic diversity and its distribution among populations have been associated with species attributes such as mating system, dispersal ability and geographic range size. Another attribute that could contribute to intraspecific phylogeographic patterns is niche breadth, but this has rarely been tested. Here, we ask whether a Mexican oak with a comparatively narrow climatic niche breadth has distinct genetic diversity patterns compared to other codistributed oaks with a broader climatic niche.LocationMexico.TaxonQuercus glaucoides M. Martens & Galeotti (Fagaceae).MethodsDescriptors of genetic diversity and structure were calculated for 21 Q. glaucoides populations using chloroplast DNA (cpDNA) and nuclear microsatellites (nSSRs). Historical demographic dynamics were inferred with approximate Bayesian computation (ABC) and past potential distribution models. To test for an association between niche breadth and phylogeographic patterns, we used genetic diversity and differentiation values of Q. glaucoides plus those previously published for 10 other Mexican oak taxa. Niche breadth was estimated for all taxa and linear regressions were performed.ResultsGenetic diversity calculated from nSSRs (HO = 0.539; HE = 0.714) was among the lowest and cpDNA differentiation (NST = 0.88) was the highest so far obtained for comparable Mexican oaks. Moderate changes in demographic size and distribution shifts throughout the last glacial cycle were inferred, explaining some of the observed genetic patterns. A positive correlation of HO and a negative correlation of NST with niche breadth were detected across taxa.Main ConclusionsDistinct phylogeographic patterns in Q. glaucoides could be explained because a narrower niche may cause lower historical effective population sizes and more fragmented distributions in comparison to species with a wider niche breadth, even with similar range sizes. Our results indicate that niche breadth would be an interesting ecological attribute to be included in future comparative phylogeographic studies.

Structure-Performance Relationships of Complexing Agents on the Chemical Mechanical Polishing of 6063 Aluminum Alloy

Aluminum alloy has wide applications in many industries due to its unique properties. Chemical mechanical polishing (CMP) is commonly used to treat aluminum alloy to generate mirror-finish surface. In this study, the effects of pH and H2O2 concentration on the CMP of 6063 aluminum alloy were studied. Better CMP performance was obtained in basic media with 1.0 wt% H2O2. Moreover, complexing agents with different structures and functional groups were evaluated for the CMP of Al-alloy, and their structure-performance relationship was systematically studied. It was found that complexing power, steric hindrance and electrostatic repulsion of complexing agents were important factors determining material removal rate and surface roughness. The complexing agent with high complexing power can favor the dissolution and Al substrate. The complexing agent with large steric hindrance and high charge density can form a stable boundary layer on the surface of substrate and improve its dispersion ability, thereby improving MRR and surface quality. In addition, the amino functional groups of complexing agents exist in the form of neutral molecules at pH 10, which is inferior to carboxyl complexing agents due to their poor static repulsion. XPS analysis confirmed the anchoring of carboxylate anions on the sample surface.

Preparation and Structural Behavior of High-Performance PBO Fibers

To improve the dispersion ability of monomers in the high-viscosity PBO pre-polymerization system, a new large-capacity mixing paddle for PBO pre-polymerization reaction was designed. Through simulated calculation, it was found that the new mixing paddle has good dispersion effect and produced PBO polymer whose intrinsic viscosity was 37.5 dL/g, number-average molecular weight was 92700, and degree of polymerization was 396. Then the PBO fibers were prepared by the dry jet wet spinning technique. The morphology analysis showed that the PBO fibers were well formed, with a diameter of 14 µm. The infrared spectrum analysis verified the structure of PBO fibers. The mechanical test showed that the tensile strength of PBO fibers was 5.04-5.76 GPa and the elongation at break was 3.93% - 4.54%, which means they have good mechanical properties.

Post-glacial colonization of the Fennoscandian coast by a plant parasitic insect with an unusual life history.

Species that exhibit very peculiar ecological traits combined with limited dispersal ability pose a challenge to our understanding of ecological and evolutionary mechanisms. This is especially true when they have managed to spread over long distances, overcome physical barriers, and colonize large areas. Climate and landscape changes, trophic web relations, as well as life history all interact to shape migration routes and present-day species distributions and their population genetic structures. Here we analyzed the post-glacial colonization of northern Europe by the gall midge Contarinia vincetoxici, which is a monophagous parasite on the perennial herb White swallowwort (Vincetoxicum hirundinaria). This insect not only has a narrow feeding niche but also limited dispersal ability and an exceptionally long dormancy. Gall midge larvae (n = 329) were collected from 16 sites along its distribution range in Denmark, Sweden, and Finland. Using microsatellite loci and knowledge of the species and the regions' history, we investigated the role of landscape change, host plant distribution, insect population dynamics, and life history in shaping the population genetic structure of the insect. We devoted particular interest to the role of the insect's presumed poor dispersal capacity in combination with its exceptionally extended diapause. We found significant levels of local inbreeding (95% highest posterior density interval = 0.42-0.47), low-level within-population heterozygosity (mean H E = 0.45, range 0.20-0.61) with private alleles in all populations except two. We also found significant (p < .001) regional isolation-by-distance patterns, suggesting regularly recurring mainly short-distance dispersal. According to approximate Bayesian computations, C. vincetoxici appears to have colonized the study area via wind-aided flights from remote areas approximately 4600-700 years before present when the land has gradually risen above the sea level. Extremely long dormancy periods have allowed the species to "disperse in time", thereby aiding population persistence despite generally low census population sizes.

Heterogeneity in the isolation of patches may be essential for the action of metacommunity mechanisms

The spatial isolation gradient of communities and the gradient in the species dispersal ability are recognized as determinants of biodiversity in metacommunities. In spite of this, mean field models, spatially explicit models, and experiments were mainly focused on idealized spatial arrangements of communities leaving aside the combining role of dispersal and isolation gradients in metacommunity processes. Consequently, we have an incipient understanding of the role of the real spatial arrangement of communities on biodiversity patterns. We focus on six metacommunities for which confident information about the spatial arrangement of water bodies is available. Using coalescent metacommunity models and null models that randomize the location of water bodies, we estimated the potential effect of the landscape on biodiversity and its dependence on species dispersal ability. At extremely low or high dispersal abilities, the location of ponds does not influence diversity because different communities are equally affected by the low or high incoming dispersal. At intermediate dispersal abilities, peripheral communities present a much lower richness and higher beta diversity than central communities. Moreover, metacommunities from real landscapes host more biodiversity than randomized landscapes, a result that is determined by the heterogeneity in the geographic isolation of communities. In a dispersal gradient, mass effects systematically increase the local richness and decrease beta diversity. However, the spatial arrangement of patches only has a large importance in metacommunity processes at intermediate dispersal abilities, which ensures access to central locations but limits dispersal in isolated communities. The ongoing reduction in spatial extent and simplification of the landscape may consequently undermine the metacommunity processes that support biodiversity, something that should be explicitly considered in preserving and restoring strategies.

Preparation of micro-calcite powder using fine-bubble assisted carbonation as toothpaste material

ABSTRACTIntroduction: Calcite (CaCO3) is typically used in commercial toothpaste with particle size ranges from 1-12 μm. In the latest study, calcite was synthesized by using Ca(OH)2 precursor from natural resources However, the resulting particle size does not match the size of the toothpaste filler. This study aims to prepare micro-calcite via fine-bubble assisted carbonation as toothpaste material. Methods: The calcite powder was prepared from Ca(OH)2 analytical grade powder utilizing the fine-bubble carbonation process with the Ca(OH)2 concentration and initial pH variation. The study was started by making a Ca(OH)2 suspension with a concentration of 0.25, 0.5, 0.75, 1 and 1.25 M using 2.000 ml methanol as a solvent. 0.5 M NaH2PO4 solutions were utilized to adjust the initial pH of 0.5 M Ca(OH)2 suspension into 8, 9, and 10. The suspensions were aerated using CO2 fine-bubble for two hours to produce CaCO3 samples. All precipitated CaCO3 particles were characterized by PSA, Zeta-Potential, and FTIR measurements. Results: The calcite phase was identified from the FTIR transmittance. Aragonite or vaterite phase was not observed in the samples. PSA result shows the size of CaCO3 particles from samples 0.25 M to 1.25 M are as follows 3.03, 3.23, 2.79, 3.70, 0.99 μm respectively. Meanwhile, the particle sizes of CaCO3 in samples with a pH of 8, 9 and 10 are 3.00, 2.03 and 2.50 μm respectively. The zeta potential shows the value ranges from -23.2 mV to -11.9 mV, indicating fair dispersion ability. Conclusion: The fine bubble assisted carbonation method in this study helps in producing calcite in micron size that could be used as alternative fillers for toothpaste.Keywords: calcite, fine-bubble, carbonation, particle size, toothpaste

Has riparian woody vegetation a positive effect on dispersal and distribution of mayfly, stonefly and caddisfly species?

During their adult life stage most EPTs (Ephemeroptera, Plecoptera and Trichoptera) disperse by flying following the riparian corridor. Although it is likely that riparian forest fosters EPT dispersion, this has not been empirically tested in a larger dataset yet and several additional open questions remain. First, it is unclear if the effect of riparian vegetation on EPT community differs and depends on the spatial scale. Second, it is not assessed how the effect of riparian vegetation on EPTs is and how it changes depending on other environmental stressors. Third, the effect potentially depends on riparian vegetation characteristics such as trees species composition and cover.We analysed 98 sites in lowland and lower mountain streams in Northrhine Westfalia, Germany, at two longitudinal and two lateral spatial scales. At each site we calculated the EPT community dispersal ability and quantified other environmental stressors as well as deciduous and coniferous woody cover in the riparian buffer. Generalised Linear Models were used to identify the conditions under which woody riparian vegetation has a significant effect on EPT community dispersal ability.Our results confirmed that the share of weak dispersers increased with deciduous woody riparian cover in low mountain streams, indicating a potential positive effect of natural riparian forest on landscape connectivity. This relationship was only observed at the regional longitudinal scale irrespective of the lateral spatial scale. Tree species composition was relevant as coniferous forests did not contribute to this effect. Finally, there was some indication that the positive effect of deciduous riparian forest occurs at a moderate woody cover and levels off at higher values.This highlights the role of riparian forests not only as habitat but also dispersal corridor in river management and the need to preserve and restore natural woody riparian vegetation to improve EPT communities and macroinvertebrates ecological status.

The pattern of photosynthetic response and adaptation to changing light conditions in lichens is linked to their ecological range

Epiphytic lichens constitute an important component of biodiversity in both deforested and forest ecosystems. Widespread occurrence is the domain of generalist lichens or those that prefer open areas. While, many stenoecious lichens find shelter only in a shaded interior of forests. Light is one of the factors known to be responsible for lichen distribution. Nevertheless, the effect of light intensity on photosynthesis of lichen photobionts remain largely unknown. We investigated photosynthesis in lichens with different ecological properties in relation to light as the only parameter modified during the experiments. The aim was to find links between this parameter and habitat requirements of a given lichen. We applied the methods based on a saturating light pulse and modulated light to perform comprehensive analyses of fast and slow chlorophyll fluorescence transient (OJIP and PSMT) combined with quenching analysis. We also examined the rate of CO2 assimilation. Common or generalist lichens, i.e. Hypogymnia physodes, Flavoparmelia caperata and Parmelia sulcata, are able to adapt to a wide range of light intensity. Moreover, the latter species, which prefers open areas, dissipates the excess energy most efficiently. Conversely, Cetrelia cetrarioides considered an old-growth forest indicator, demonstrates definitely lower range of energy dissipation than other species, although it assimilates CO2 efficiently both at low and high light. We conclude that functional plasticity of the thylakoid membranes of photobionts largely determines the dispersal abilities of lichens and light intensity is one of the most important factors determining the specificity of a species to a given habitat.

Experimental and molecular dynamics simulation of hard asphalt microstructure

To better design and application of hard asphalt, the conventional properties tests, SARA composition experiments, 1H NMR experiments, and elemental analysis were carried out for five types of hard asphalt and three types of virgin asphalt, and correlation analysis was performed. Systemic molecular dynamics were applied to reveal the microstructure characteristics by producing the density map and the mean square Displacement. The results indicated that the resins component and the number of saturated carbon in the molecular structure are closely related to the high-temperature performance. Meanwhile, the aromatics component and the number of branches connected to the aromatics rings in the molecular system are closely related to the low-temperature performance. Short, unordered planar accumulations dominate the asphalt microstructure. The variation coefficient of the density map follows the same trend as the CII values when characterizing the dispersion ability of the resins and aromatics components. The variation coefficient shows that the saturates components have more significant aggregation behavior than the asphaltenes component. The viscous behavior of asphalt cannot be directly characterized by microstructural distribution but requires further attention to the intermolecular forces within the microstructure.

A systematic revision of the South African Gymnobisiidae (Pseudoscorpiones: Neobisioidea).

The South African fauna of Gymnobisiidae pseudoscorpions is revised. Originally containing only three species in a single genus (Gymnobisium Beier, 1931), results of this study show that there are eight distinct species of the genus within South Africa, five of which are new to science, namely G. capense sp. nov., G. cuneatum sp. nov., G. hogsbackense sp. nov., G. megalodontum sp. nov. and G. prionotogladiatum sp. nov. Three of these, namely G. cuneatum sp. nov., G. hogsbackense sp. nov., and G. inukshuk Harvey and Giribet, 2016 (which is a rare troglobite), are short-range endemics and threatened by habitat loss. Most of the other species, with the exception of G. quadrispinosum (Tullgren, 1907), have small distribution ranges. They are predominantly found inhabiting moist leaf litter of indigenous forests along the coastal provinces, indicating either a low dispersal ability or high niche specificity in these pseudoscorpions. The lack of dense, shaded vegetation between isolated forest patches seems to act as a dispersal barrier for many of the species.

Diversity and structure of feather mite communities on seabirds from the north–east Atlantic and Mediterranean Sea

The richness and structure of symbiont assemblages are shaped by many factors acting at different spatial and temporal scales. Among them, host phylogeny and geographic distance play essential roles. To explore drivers of richness and structure of symbiont assemblages, feather mites and seabirds are an attractive model due to their peculiar traits. Feather mites are permanent ectosymbionts and considered highly host-specific with limited dispersal abilities. Seabirds harbour species-rich feather mite communities and their colonial breeding provides opportunities for symbionts to exploit several host species. To unravel the richness and test the influence of host phylogeny and geographic distance on mite communities, we collected feather mites from 11 seabird species breeding across the Atlantic Ocean and Mediterranean Sea. Using morphological criteria, we identified 33 mite species, of which 17 were new or recently described species. Based on community similarity analyses, mite communities were clearly structured by host genera, while the effect of geography within host genera or species was weak and sometimes negligible. We found a weak but significant effect of geographic distance on similarity patterns in mite communities for Cory’s shearwaters Calonectris borealis. Feather mite specificity mainly occurred at the host-genus rather than at host-species level, suggesting that previously inferred host species-specificity may have resulted from poorly sampling closely related host species. Overall, our results show that host phylogeny plays a greater role than geography in determining the composition and structure of mite assemblages and pinpoints the importance of sampling mites from closely-related host species before describing mite specificity patterns.