Secondary Dispersal Research Articles

Seed dispersal of anemochoric Abies alba Mill.: lessons learned from seed tracking, seed trap experiments and genetic parentage assignment of seedlings

Several methods are used to estimate the spatial pattern of seed dispersal. However, each method has specific shortcomings that limit the accuracy and reliability of the resulting dispersal models. In this study we compared seed shadows of the anemochoric species Abies alba Mill. obtained from (1) phenomenological models derived from seed trapping data and inverse modelling, (2) ballistic models based on wind speed at canopy height and an exponential wind profile and (3) empirical models parameterised from seed-tracking data. In addition, we checked whether the empirical model coupled with multiannual wind characteristics provides a dispersal pattern concordant with the gene shadow obtained from parentage assignment between seedlings and overstorey trees. The seed trap and seed-tracking experiments were conducted in 2013 and 2015 with contrasting wind conditions in five study plots located in the Krynica Forest Experimental Station in southern Poland. Genetic data originated from 16 mature stands with dominant A. alba . The study revealed that the distances reached by single seeds strongly vary at the same wind speed at canopy height. The ballistic model overestimated the flight distances of A. alba seeds. Similarly, the empirical model calibrated on data that disregarded seeds trapped in the crowns of neighbouring conifer trees predicted longer flight distances than those derived from the seed trap experiments. The gene shadow obtained from the parentage analysis suggests dispersal patterns concordant with those anticipated by the empirical model based on the seed-tracking experiments, with a possible shift towards an increased proportion of seeds landing close to the source. It was concluded that in dense canopies collisions with canopy elements during seed flight and secondary dispersion of seeds trapped in the canopy zone may considerably shorten the travel distances of A. alba seeds .

Fine-scale habitat heterogeneity and vole runways influence seed dispersal in Plagiobothrys nothofulvus.

Seed dispersal allows plants to colonize new sites and contributes to gene flow among populations. Despite its fundamental importance to ecological and evolutionary processes, our understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. This is particularly true for the majority of plant species that are considered to have gravity as their primary dispersal mechanism. The potential for long-distance movement of gravity-dispersed seeds by secondary dispersal vectors is rarely evaluated. We employ whole-genome assays of maternally inherited cpDNA in Plagiobothrys nothofulvus to resolve patterns of genetic variation due to effective (realized) seed dispersal within a 16 hectare prairie that is characterized by a mosaic of habitat types. We evaluate the effects of microgeographic landscape features extracted from micro-UAV aerial surveys on patterns of seed dispersal using landscape genetics methods. We found evidence of high resistance to seed-mediated gene flow (effective dispersal) within patches of Plagiobothrys nothofulvus, and strong genetic structure over distances of less than 20 m. Geographic distance was a poor predictor of dispersal distance, while landscape features had stronger influences on patterns of dispersal (distance and direction of seed movement). Patterns of dispersal were best predicted by the combined distribution of flower patches, habitat type, and the network of vole runways, with the latter explaining the largest proportion of variation in the model. Our results suggest that primary dispersal occurs mostly within microhabitats and infrequent secondary dispersal may occur over longer distances due to the activity of small mammals and other vertebrates.

Influence of the physiological condition of bivalve recruits on their post-settlement dispersal potential

Secondary dispersal (= migration) of bivalves occurs after metamorphosis and is a key recruitment process that can radically change patterns of primary settlement. An example of secondary dispersal is active migration behavior of bivalve recruits such as in bysso-pelagic drift. We hypothesize that these active migrations represent an energy cost for recruits and that the ability to actively migrate will depend upon the recruit’s physiological profile (quantity and quality of energy reserves). In lab experiments, we hatched 4 batches of recruits ofVenus verrucosawith different physiological profiles by varying rearing temperature and diet composition. We then introduced these recruits into a fall velocity tube (5 m height) to estimate their vertical fall velocity as a proxy of their dispersal potential: slower fall velocity implies enhanced dispersal potential. We also compared alive vs. passive (dead) recruits to assess behavioral differences. Fall velocity increased logarithmically with recruit volume for each treatment, and no differences between active and passive individuals were observed for batches reared at 20°C with a mixture ofTisochrysis luteaandChaetoceros gracilis. By contrast, active recruits in 2 other treatments (T. luteaat 20°C and a mix ofC. gracilisandT. luteaat 15°C) significantly decreased their fall velocity regardless of their volume. Moreover, the ability of recruits to control their fall velocity by their behavior was correlated with triglyceride content. Recruits with the highest energy reserves had the greatest capacity to decrease their fall velocity, which suggests a major role of physiological conditions on potential secondary dispersal. We also used a benthic flume to test the substrate selection ability of recruits depending on their physiological profile and found no differences between physiologically different batches. However,V. verrucosarecruits preferred fine sediments, unlike adults, which live mainly in coarse sediment habitats; such difference in substrate preference suggests potential secondary migrations between nursery and adult areas.

Laser puncture of symptomatic primary iris pigment epithelial cyst causing hemeralopia: a rare case

Primary iris pigment epithelium cysts involve posterior surface of the iris and can occur at pupillary margin or anterior ciliary body. They may be stationary or progressive and sometimes regress spontaneously. These cyst can occasionally lead to angle-closure glaucoma, plateau iris syndrome and secondary pigment dispersion syndrome. A steadily growing cyst may disturb the vision by covering the visual axis and provoke an increase in intraocular pressure (IOP) or even inflammation if it touches the corneal endothelium. There are multiple management options in complicated situations. We report a case of a 17-year-old girl with unusual complaints of hemeralopia and dark-brown discolouration of pupils in both eyes. On examination, she had multiple pigment epithelial iris cysts at the pupillary margins, which were punctured with Nd:Yag laser, and the response was improvement in vision and hemeralopia without any pigment dispersion or IOP changes.

Calonectria pseudonaviculata Conidia Dispersal and Implications for Boxwood Blight Management

We investigated Calonectria pseudonaviculata conidial dispersal from sporulating lesions on boxwood leaves and sporulating cultures on half-strength PDA (1/2 PDA). Botrytis cinerea-infected blossoms were used as a control. Dispersal of C. pseudonaviculata or Botrytis conidia was confirmed by capture using an Allergenco air sampler at 15 liters/min and by microscopic observation of conidia and C. pseudonaviculata growth on 15-cm-diameter 1/2 PDA Petri dishes. C. pseudonaviculata conidia were not dispersed by either dry or moist air currents directed at conidia and conidiophores from 2 mm away at air speeds of 19.8 m/s for 10 min or by a fine mist with water droplets (mean diameter 20 µm) with air speeds of 1.7 m/s. C. pseudonaviculata spores were dispersed by splash of water droplets at air speeds of 9.0 to 19.8 m/s. C. pseudonaviculata conidia released from phialides by water could not be wind dispersed after the water had evaporated. Secondary water dispersal was reduced because conidia strongly adhered to a surface after drying. Boxwood leaves dropped from heights of 15, 33, or 66 cm landed with more than 60% of leaves facing abaxial surface up. The cupped shape of most boxwood leaves may result in the abaxial surface with sporulation facing up. That orientation may also aid in retention of water films to wet and release conidia for splash dispersal. This is consistent with observations of increased disease severity in lower boxwood canopies and reinforces suggestions for best management practices including mulching and pruning lower branches to reduce the incidence and severity of disease.

ПЕРСПЕКТИВИ ВІДКЛАДІВ НАДЗАПЛАВНИХ ТЕРАС ДНІСТРА НА ЗОЛОТУ МІНЕРАЛІЗАЦІЮ

The article clarifies the stratigraphic binding and origin of silicon nodules, which served as the main raw material for the manufacture of tools for mammoth hunters of the Mezhyrich Late Paleolithic site. In archaeological publications, these nodules are often mentioned to be confined to the "Vyrzhikovsky layer" (the Albian layer of the Lower Cretaceous), which was formed under continental conditions and consists of sand-clay (kaolin, in particular) deposits. The analysis of the necessary conditions and possible mechanisms for the formation of silicon nodules indicates the erroneousness of such ideas. Most likely, the source of silicon raw materials was the marine deposits of the Cenomanian (Upper Cretaceous), or, in accordance with the modern stratigraphic division of the Mesozoic-Cenozoic sequence, deposits of the Burim suite (upper Albian – lower Cenomanian). The paleogeographic setting, sedimentological conditions and lithological composition of the "Vyrzhikovsky layer" did not ensure the formation of silicon nodules in it in the form of inclusions. The latter are diagenetic in origin and could only form in the thickness of carbonate rocks, free of clay minerals. The region of Kaniv dislocations was the optimal region from the silicon production point of view, which was determined: firstly, by the tectonic dislocation of the sedimentary sequence, which contributed to the removal of deposits containing silicon nodules in the thickness of younger rocks; secondly,the erosion activity of temporary streams, which brought these deposits to the level of the denudation cut-off. The most convenient place for collecting flints was not the outcrop of bedrock in ravines but the cones of their removal, which overlook the floodplains of the Dnipro and Ros'. The possibility of collecting flint in the immediate vicinity of the Mezhirich site, in the ravines and gullies between the Ros and Rosava rivers, does not find confirmation, since the chalk deposits here lie much lower than the local erosion base and are not exposed by ravines. Therefore, the leading role in the formation of the raw material supply of the Late Paleolithic site of Mezhirich was played by the region adjacent to the Kaniv mountains of the alluvial-proluvial plain.Despite long-term geological study of the Dniester River basin, we still have no clear evidences about gold-bearing potentiality of this area as well as origin of gold. The leading role of geological, geochemical and mineralogical criteria is proved for defining the prospects of substantial gold deposits finding within the Dniester river basin. Gold was found here in the crystalline basement and in the sedimentary cover rocks. Study of mineralogy and lithology of the terraces above the flood-plain and typomorphic peculiarities of native gold shows that palaeogeographic conditions and alimentation zones of debris vary at the different tectonic stages of this area development. Gold-bearing potential of the Pliocene-Quaternary sediments in the Dniester River basin is related to the Pliocene (VI-IX terraces above the flood-plain) and Quaternary (I-V terraces above the flood-plain) terraces complex of the Dniester river, as well as this river and its inflows recent alluvia. Our study of the Mid-flow part of the Dniester river basin allow to conclude that native gold was found in geologocal strata of all ages, from Proterozoic up to the recent alluvium. This fact points the necessity of further prospecting to find the mother lodes of gold. Our field study, samples analyses made as well as publications observation allow highlighting the principal directions of further prospecting and evaluation works. The main among that are: 1) comprehensive study of river Dniester alluvia and its terraces complex (previously VI–VII terraces), that will allow to specify their material composition, to assess real gold-bearing potential and to define the history of denudation areas changes; 2) lithogeochemical prospecting of primary and secondary dispersion haloes to clear the principal gold-bearing regularities; 3) definition of prospect plots within the area described; 4) modern analytical approach study of typomorphic peculiarities of native gold from alluvia and terrace deposits to define its ore formational affinity and mineral type.

Post-Dispersal Seed Removal in a Large-Seeded Palm by Frugivore Mammals in Western Ecuador

Post-dispersal seed removal by ground-foraging frugivores promotes secondary dispersal of large seeds, reducing seed predation and increasing recruitment and regeneration. We studied how habitat disturbance influences seed removal patterns in the large-seeded palm Phytelephas aequatorialis within three habitats forming a continuum of disturbance (agroforestry system, disturbed forest, and less-disturbed forest) using seed removal experiments and camera trapping. We tested whether seed removal rates, and both richness and composition of seed remover communities varied between the habitats. On average, 15 seeds were removed under each tree in the agroforestry system over seven days, which was significantly lower compared to the disturbed forest (18) and the less-disturbed forest (19). Eight mammal species were identified removing seeds in the three habitats. On average, one mammal species removed seeds at each station in the agroforestry system, which was significantly lower than the two species observed in the two forests. The composition of seed remover communities was significantly different between the three habitats. Our results suggest that the loss of forest cover in the agroforestry system has reduced the richness of seed removers, which subsequently caused decreased removal rates. Nevertheless, this habitat could still maintain effective seed dispersal events because spiny rats were important seed removers. Our camera trap data should be taken as preliminary because we could only identify less than half of the animals responsible for seed removal. This study highlights the importance of medium- and large-sized rodents for the removal and effective dispersal of large seeds in disturbed tropical habitats.

Responses of secondary wind dispersal to environmental characteristics and diaspore morphology of seven Calligonum species

AbstractSecondary diaspore dispersal by wind, that is, wind‐driven movement along the ground surface (GS), is important for the structure and dynamics of plant populations and communities. However, how wind velocity (WV), GS, and diaspore morphology influence diaspore secondary dispersal by wind are unclear. We used a wind tunnel and video camera to measure the threshold of WV (TWV) and diaspore velocities (DV) of secondary diaspore dispersal. Diaspores of seven Calligonum species with different appendages (wings, bristles, membranous balloon, and wings + thorns) were used to determine the TWV and DV under variable wind speed (4, 6, 8, and 10 m s‐1) and four GSs (cement, sand, loam, and gravel). GS and diaspore morphological traits explained 37.1 and 18% of diaspore TWV, respectively. Meanwhile, WV, GS, and diaspore morphological traits explained 62.4, 13.6, and 3.2% of DV, respectively. An increasing trend was shown for TWV, and a decreasing trend was shown for DV in the order of cement, sand, loam, and gravel surfaces. Spherical and light diaspores had low TWV and high DV, whereas winged and heavy diaspores had high TWV and low DV. Our results indicated that adaptive features of diaspore appendages might be the result of selection for primary dispersal or secondary dispersal. The mechanism of diaspore secondary dispersal is important for understanding the recovery of degraded sand dunes and providing theoretical support for restoration practices.

Effect of environmental conditions and phenology in the dispersal of secondary Erysiphe necator conidia in a vineyard

An integrated powdery mildew management strategy to identify the principal moments of secondary Erysiphe necator conidia dispersal in a vineyard based on aerobiological, phenological and meteorological data was developed. An adaptation of the physiological P-days model was conducted to obtain a descriptive equation for the prediction of the advantageous meteorological conditions for Erysiphe necator conidia dispersal in the vineyards of the Ribeiro Designation of Origin area. Moreover, a regression model was developed to predict the conidia concentration as a function of the weather and aerobiological variables with the highest influence on airborne E. necator spores. Additionally, phenological observations were conducted during the vegetative cycle of Vitis vinifera, with the aim to identify the most susceptible phenological stages to powdery mildew infection by relating them with the detected atmospheric spore concentrations. The study was carried out from 2008 to 2018 in an experimental vineyard. The E. necator spores were trapped using a Lanzoni VPPS-2000 sampler and the phenological observations were conducted following the BBCH standardized scale. The highest total fungal spore amount per season in the atmosphere of the vineyard was detected in 2013 with 4828 spores m-3, while the lowest amount was recorded in 2009 with 883 spores m-3. In general, the highest daily airborne spore concentrations were detected during the Flowering (stage 6) or in the previous and next stages, whereas the maximum total spore amount by stage was recorded during Development of Fruits (stage 7). The proposed threshold of P-days for potential secondary infections in the Ribeiro D.O. ranges from 120 to 160 P-days. The combination of aerobiological, phenological and meteorological data provides us a useful tool for the knowledge of the Erysiphe necator conidia dispersal behaviour bringing agricultural practices closer to a sustainable system.

Molecular Aspects of Film Formation of Partially Cross-Linked Water-Borne Secondary Dispersions that Show Skin Formation upon Drying

In a previous publication [Macromolecules 2019, 52, 5245–5254], we described the synthesis of surfactant-free latex dispersions of nanoparticles (NPs) based on emulsification of a preformed proprie...

Strong dispersal limitation in postfire regeneration of Baker cypress, a rare serotinous conifer.

Dispersal capacity primarily determines the spatial establishment patterns that drive range expansions and contractions in tree species. Seedling establishment in Baker cypress (Hesperocyparis bakeri [(Jeps.) Bartel]) relies predominantly on fire events, due to its cone serotiny, shade intolerance, and small seeds that require the optimal conditions of fire-exposed, mineral soil seedbeds. We quantified the density and spatial distribution of post-disturbance seedlings following the 2014 Eiler Fire in northern California and compared the observed recruitment to predictions from a mechanistic seed dispersal model. Postfire recruitment was dense, averaging 11 seedlings/m2 , and occurred primarily in the first year after fire. We estimated the mean descent velocity of the wingless seeds as ~4 m/s, the highest value reported for any putatively wind-dispersed tree species. The rapid seed descent contributed to markedly spatially constrained recruitment. Most seedlings (~81%) established within 5 m of the parent tree, and 94% established within 10 m. The maximum observed dispersal distance was 48.5 m; dispersal distance scaled linearly with canopy height. Distributions of modeled seed dispersal distance and observed seedling establishment in Baker cypress did not differ, demonstrating that wind disperses seeds a short distance because of the lack of a wing, and secondary dispersal appeared to be minimal at this recently burned site. If seed dispersal is solely reliant on wind, migration in response to rapid climate change will be impeded and potentially present difficulties in sustaining populations of this and other obligate seeder species with equally constrained dispersal.

Phylogeny and biogeography of the Brazilian–Guiana Shield endemic Corymbophanes clade of armoured catfishes (Loricariidae)

AbstractNumerous rivers, interrupted by large waterfalls and extensive rapids, drain the geologically ancient Guiana Shield Highlands. We describe a new armoured catfish genus and two new species endemic to the upper Ireng and Kuribrong rivers, respective tributaries of the Amazon and Essequibo basins in western Guiana. Corymbophanes ameliae sp. nov. is distinguished by having vermiculations on the abdomen, bands on the caudal fin, the anal fin i,5 and narrow caudal peduncle. Yaluwak primus gen. & sp. nov. is distinguished by having evertible cheek odontodes, a plated snout, a tall caudal peduncle and absence of adipose fin and iris operculum. We present a new molecular phylogenetic analysis inclusive of these and several related genera that suggests that the Corymbophanes clade (Araichthys, Corymbophanes, Cryptancistrus, Guianancistrus, Hopliancistrus and Yaluwak) originated in the Guiana Shield with secondary dispersal to the Brazilian Shield. Within the Guiana Shield, relationships among Corymbophanes and Yaluwak are consistent with geodispersal between drainages via headwater capture, although an uplift-mediated relictual distribution cannot be ruled out. ND2 haplotype structure among C. ameliae populations suggests that ichthyofaunal diversity on the Guiana Shield escarpment is shaped not only by inter-, but also intrafluvial barriers to gene flow.

Multiple introductions and secondary dispersion of Tubastraea spp. in the Southwestern Atlantic

Accidental introduction through ballast water and biofouling are currently the main factors responsible for spreading non-indigenous species in the marine realm. In the Southwestern Atlantic, two scleractinian corals, Tubastraea coccinea and T. tagusensis, have been introduced by opportunistic colonization in 1980 and are now widespread along more than 3,500 km of coastline. To better understand the invasion process and the role of vectors in spreading these species, we sampled 306 and 173 colonies of T. coccinea and T. tagusensis from invaded sites, possible vectors and one native population. Analyses revealed a higher diversity of multi-locus genotypes (MLGs) on vectors, suggesting that they were contaminated prior to their arrival in the Southwestern Atlantic, and a high proportion of clones at invaded sites, with few genotypes spread over ~2,000 km. This broad distribution is most likely a result of secondary introductions through the transport of contaminated vectors. Results also suggest the occurrence of multiple invasions, mainly in the northernmost sites. In summary, clonality, secondary introductions, and multiple invasions are the main reasons for the broad spread and invasive success of Tubastraea spp. in the Southwestern Atlantic. Consequently, the correct control of vectors is the most effective approach for management and prevention of new invasions.

Dispersal behaviour of African wild dogs in Kenya

AbstractDispersal behaviour plays a key role in social organisation, demography and population genetics. We describe dispersal behaviour in a population of African wild dogs (Lycaon pictus) in Kenya. Almost all individuals, of both sexes, left their natal packs, with 45 of 46 reproductively active “alpha” individuals acquiring their status through dispersal. Dispersal age, group size and distance did not differ between males and females. However, only females embarked on secondary dispersal, probably reflecting stronger reproductive competition among females than males. When dispersing, GPS‐collared wild dogs travelled further than when resident, both in daylight and by night, following routes an order of magnitude longer than the straight‐line distance covered. Dispersers experienced a daily mortality risk three times that experienced by adults in resident packs. The detailed movement data provided by GPS‐collars helped to reconcile differences between dispersal patterns reported previously from other wild dog populations. However, the dispersal patterns observed at this and other sites contrast with those assumed in published demographic models for this endangered species. Given the central role of dispersal in demography, models of wild dog population dynamics need to be updated to account for improved understanding of dispersal processes.

Intersexual conflict influences female reproductive success in a female-dispersing primate

In group-living mammals, individual efforts to maximize reproductive success result in conflicts and compromises between the sexes. Females utilize counterstrategies to minimize the costs of sexual coercion by males, but few studies have examined the effect of such behaviors on female reproductive success. Secondary dispersal by females is rare among group-living mammals, but in western gorillas, it is believed to be a mate choice strategy to minimize infanticide risk and infant mortality. Previous research suggested that females choose males that are good protectors. However, how much female reproductive success varies depending on male competitive ability and whether female secondary dispersal leads to reproductive costs or benefits has not been examined. We used data on 100 females and 229 infants in 36 breeding groups from a 20-year long-term study of wild western lowland gorillas to investigate whether male tenure duration and female transfer rate had an effect on interbirth interval, female birth rates, and offspring mortality. We found that offspring mortality was higher near the end of males’ tenures, even after excluding potential infanticide when those males died, suggesting that females suffer a reproductive cost by being with males nearing the end of their tenures. Females experience a delay in breeding when they dispersed, having a notable effect on birth rates of surviving offspring per female if females transfer multiple times in their lives. This study exemplifies that female counterstrategies to mitigate the effects of male-male competition and sexual coercion may not be sufficient to overcome the negative consequences of male behavior.SignificanceIndividual reproductive success is maximized through conflicts and compromises between the sexes in social mammals. In species with high dimorphism, females can experience sexual coercion by males and develop counterstrategies to reduce these costs. We studied this link in western lowland gorillas, which exhibit female secondary dispersal, a strategy that is believed to reflect female choice for the protective abilities of males. We found that females are faced with the dilemma of staying with a silverback at the end of his tenure and risk higher infant mortality versus dispersing and suffering reproductive delays and lower birth rates. This study shows that female reproductive strategies, namely dispersal, used to counter the effects of sexual coercion by males are not sufficient to overcome the negative consequences of male behavior.

Multiple External Seed Dispersers Challenge the Megafaunal Syndrome Anachronism and the Surrogate Ecological Function of Livestock

The dispersal of many large-seeded plants is thought to have been handicapped by the extinction of megafauna in the late Pleistocene, and due to the ongoing defaunation of the largest of the extant dispersers. Oversized fruits defined as “megafaunal” provide variable amounts of flesh even though many of them cannot be ingested entirely, nor their seeds defecated, by any extant vertebrate. This apparent mismatch lead to the hypothesis of anachronisms involving extinct megafauna as dispersal-mediated selective agents on fruit traits shaped through endozoochory. It has been suggested that free-ranging livestock partially supply the dispersal functions previously provided by those globally or regionally extinct species. However, there is little knowledge on the role of livestock as a surrogate for megafauna dispersal agents relative to living wild dispersers. Here, we focus on seed dispersal of six palm species (Attalea eichleri, Attalea barreirensis, Attalea speciosa, Attalea princeps, Mauritia flexuosa, Acrocomia totai) with large fruits that conform to the so-called “megafaunal syndrome”. Data on seed dispersal were obtained by observations and camera trapping in the Cerrado, Pantanal and Amazonia biomes in Bolivia and Brazil. Rich communities of wild seed dispersers differing among palm species and study areas were recorded, including rodents, monkeys, canids and a wide variety of birds, especially parrots. Long-distance primary dispersal was mainly conducted by parrots, while multiple species acted as short- and medium-distance secondary dispersers. Among livestock, dispersal was limited to seeds of A. totai and A. princeps moved by several species through stomatochory and endozoochory (mainly regurgitation). These results show that the large seeds can be efficiently dispersed externally by a wide array of present-day vertebrates of variable size but much smaller than extinct megafauna and livestock. A knowledge gap of the natural history of these and other plants with oversized fruits assumed to be maladapted for contemporary dispersal may have been partially favoured by neglecting some key disperser guilds (e.g. parrots) and dispersal mechanisms (e.g. ectoozochory). The evaluation of historic and ongoing defaunation of key external dispersers is advocated to understand the influence of actual (rather than putative) dispersers on contemporary frugivore-plant mutualistic interactions.

Round goby movement patterns in a non-navigable river

Understanding non-native species dispersal is vital for their future management. The round goby (Neogobius melanostomus) has greatly extended its range since the 1990s, with commercial shipping being the main vector. However, our knowledge regarding their secondary dispersal from points of introduction is surprisingly limited. In this study, a series of field experiments were undertaken on a mid-sized river to assess goby dispersal patterns within an established population, following a simulated release of a large number of propagules, or at a simulated invasion front. Most of the established population remained stationary and just a few individuals undertook long-distance dispersal (principally upstream). Mean distance travelled was 1.1 m·day−1 (max. 29.6 m·day−1). While site fidelity appeared to last for most of the year (including winter), it was surprisingly relaxed during the spawning season. Concentrated release of a large number of propagules resulted in appreciably greater movement rates than in the established population, with upstream movement again dominating. In general, smaller, mostly male fish tended to move further and appeared as first colonizers in uninvaded areas.

Seed Morphology of Ruellieae Species (Acanthaceae) in Brazil and Its Taxonomic Implications

Abstract—Ruellieae is a highly diverse tribe of Acanthaceae in Brazil, and morphological studies of its seeds have revealed important information about the systematics of the tribe. We analyzed the seed morphology of Brazilian species of Ruellieae, using stereoscopic, light, and scanning electron microscopy. The best-sampled genus was Ruellia (53 species), followed by Dyschoriste (seven), and Hygrophila (three); including external groups, a total of 65 species of Ruellieae (68 of Acanthaceae) were sampled. We observed capsular fruits with explosive dehiscence, important for autochory, and discoid seeds covered by hygroscopic and mucilaginous trichomes. The characters most relevant to the taxonomy of the groups were fruit shape, number of ovules, and the distribution, shape, and number of rings on the seed trichomes, the latter two addressed here for the first time. Those characters proved useful for discriminating and characterizing the sampled genera within Ruellieae, and especially the infrageneric clades of Ruellia. Based on the morphological patterns observed, we provide a key for those taxa, and suggest the infrageneric placement of unclassified Ruellia species: R. hypericoides and Ruellia sp. 4 for the clade “Ebracteolati” s. l., Ruellia spp. 2 and 3 for “R. inflata,” Ruellia sp. 1 for “Euruellia” s. s., and R. anamariae for the clade “Blechum.” In a broader context, we corroborate the finding that partial loss of seed trichomes is exclusive to one of the two large lineages of Neotropical Ruellia (lineage II). The hygroscopic and mucilaginous trichomes of Ruellieae seeds play important roles in water retention, germination, protection, and secondary dispersal, and we discuss some aspects of secondary hydrochory and epizoochory on medium- and long-range dispersal of Ruellieae, including transatlantic distances.

Achieving Secondary Dispersion of Modified Nanoparticles by Hot-Stretching to Enhance Dielectric and Mechanical Properties of Polyarylene Ether Nitrile Composites

Enhanced dielectric and mechanical properties of polyarylene ether nitrile (PEN) are obtained through secondary dispersion of polyaniline functionalized barium titanate (PANI-f-BT) by hot-stretching. PANI-f-BT nanoparticles with different PANI content are successfully prepared via in-situ aniline polymerization technology. The transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopic instrument (XPS) and Thermogravimetric analysis (TGA) results confirm that the PANI layers uniformly enclose on the surface of BaTiO3 nanoparticles. These nanoparticles are used as functional fillers to compound with PEN (PEN/PANI-f-BT) for studying its effect on the mechanical and dielectric performance of the obtained composites. In addition, the nanocomposites are uniaxial hot-stretched by 50% and 100% at 280 °C to obtain the oriented nanocomposite films. The results exhibit that the PANI-f-BT nanoparticles present good compatibility and dispersion in the PEN matrix, and the hot-stretching endows the second dispersion of PANI-f-BT in PEN resulting in enhanced mechanical properties, crystallinity and permittivity-temperature stability of the nanocomposites. The excellent performances of the nanocomposites indicate that a new approach for preparing high-temperature-resistant dielectric films is provided.

Investigating Molecular Exchange between Partially Cross-Linked Polymer Particles Prepared by a Secondary Dispersion Process

We recently described a new approach to surfactant-free latex dispersions prepared by emulsification of a partially neutralized linear acrylic acid-containing styrene-acrylic copolymer without the ...