Secondary Dispersal Research Articles

Improving the performance of diesel engines fueled with water-fuel emulsion

Due to unique properties, production and operation features, water-fuel emulsion (WFE) could be considered as one of the most promising type of alternative fuels for diesel engines. Experimental research showed that comparing to traditional diesel fuel, application of water-fuel emulsion allows to reduce nitrogen oxides and soot emissions, which is due primarily to a decrease in the level of maximum temperatures in the engine cylinder, as well as a more uniform distribution of fuel over the combustion chamber volume thanks to its secondary dispersion (micro-explosion phenomena). To control the stability of water-fuel emulsion properties during engine operation it is recommended to install water content sensor in the fuel supply system.

Identifying the source populations supplying a vital economic marine species for the New Zealand aquaculture industry

Aquaculture of New Zealand’s endemic green-lipped mussel (Perna canaliculus) is an industry valued at NZ$ 336 M per annum and is ~ 80% reliant on the natural supply of wild mussel spat harvested at a single location—Te Oneroa-a-Tōhē—Ninety Mile Beach (NMB)—in northern New Zealand. Despite the economic and ecological importance of this spat supply, little is known about the population connectivity of green-lipped mussels in this region or the location of the source population(s). In this study, we used a biophysical model to simulate the two-stage dispersal process of P. canaliculus. A combination of backward and forward tracking experiments was used to identify primary settlement areas and putative source populations. The model was then used to estimate the local connectivity, revealing two geographic regions of connectivity in northern New Zealand, with limited larval exchange between them. Although secondary dispersal can double the dispersal distance, our simulations show that spat collected at NMB originate from neighbouring mussel beds, with large contributions from beds located at Ahipara (southern end of NMB). These results provide information that may be used to help monitor and protect these important source populations to ensure the ongoing success of the New Zealand mussel aquaculture industry.

SUSTAINABLE DEVELOPMENT OF LIGHTWEIGHT RECYCLED ALUMINIUM COMPOSITES

In the present work, three composites have been developed by reinforcing Mild Steel (MS) chips in the amounts of 1 wt. %, 2 wt. % 3 wt. % respectively to recycled Aluminium chips through a manual stir-casting process. The developed composites were hot rolled at 200 ℃ to 50% reduction to increase the strength further. The microstructure showed that adding MS chips leads to grain refinement in the matrix due to the promotion of instantaneous nucleation. Further, it was observed that the composite developed by reinforcing 2 wt. % MS chips exhibited better grain refinement and the smallest grain size among the others, which also exhibited the highest hardness and compression strength of 83 Hv and 563 MPa, respectively, which are 26% and 15.3%, respectively, compared to the unreinforced alloy. This improvement in the strength can be attributed to the improved grain refinement, uniform distribution of MS powder in the matrix, formation of secondary phase and dispersion strengthening. However, beyond 2 wt. % addition of MS chips, the grain size started to grow, leading to a decline in the hardness and compression strength. Further, all the hot-rolled samples exhibited better properties than their counterparts. However, the variation trend in properties after hot rolling remained the same as the composite with 2 wt% MS chips showing the highest hardness and compression strength of 106 Hv and 722 MPa, respectively.

Inflated Ovary May Increase the Dispersal Ability of Three Species in the Cold Deserts of Central Asia.

Among the diaspores of angiosperms an inflated ovary (IO) is a novel morphological trait, but no studies have evaluated its effects on dispersal. The primary aim of this study was to determine the effect of the IO on diaspore dispersal in three cold desert species (Carex physodes, Calligonum junceum, and Sphaerophysa salsula). Various morphological features and the mass of fruits and seeds of each species were measured. The role of an IO in diaspore dispersal by wind and water was determined by comparing responses of intact (inflated) IOs and flattened fruits and seeds. Mature diaspores of three species were dispersed by wind, and the IO significantly increased dispersal distance in the field and at different wind speeds in the laboratory. The floating time on water was greater for inflated fruits than flattened fruits and seeds. Since the seed remains inside the IO until after dispersal is completed, the IO of the three species enhances diaspore dispersal. This is the first detailed study on how an IO increases diaspore/seed dispersal. Furthermore, after primary dispersal by wind, secondary dispersal can occur via wind or surface runoff of water, and each method is enhanced by the presence of an IO.

Understanding and Describing London Dispersion Effects in ­Transition-Metal-Catalyzed C–H Activations

AbstractTransition-metal-catalyzed C–H activation has emerged as a powerful strategy for molecular synthesis with unique levels of resource economy. Weak secondary dispersion interactions were found to play an essential role in these transformations in terms of kinetic efficacy and selectivity. This Account summarizes our group’s recent progress in the rationalization and quantification of London dispersion effects within the transition-metal-catalyzed C–H activation.1 Introduction2 Annulation Reactions3 Alkylation Reactions4 Arylation Reactions5 Olefination Reactions6 Oxygenation Reactions7 Conclusion

Active pollination in a functionally dioecious Ficus species: An interplay between pollinator behaviour and floral morphology

Active pollination has evolved four times in brood site pollination mutualisms. When pollination is active, the pollinator's behaviour specifically evolves to ensure flower fertilisation. In functionally dioecious Ficus species, the male figs host pollinating wasp larvae, while wasps cannot breed in the female figs because the styles are longer than the wasp ovipositor. Here we investigate the dioecious Ficus hispida. We show that in male figs, every time the wasp has laid an egg into a pistillate flower, it removes one pollen grain from its pollen pockets and places it on the hypopygium. When the wasp inserts its ovipositor into the next flower, the pollen grain is deposited deep within the style. Each ovipositor insertion results in flower pollination and insect oviposition. Because of systematic pollination of the flowers into which the eggs are laid, the wasp larvae benefit from feeding on fertilised endosperm while no seed are produced. In female figs, after probing a flower, the wasp presents pollination behaviour only every five visits. However, if it does occur, this behaviour lasts longer than in male figs and results in the deposition of on average 10 pollen grains on the hypopygium. The exposed sticky papillae on the stigmatic surface collect pollen from the hypopygium and pollen tubes may grow to neighbouring stigmas, ensuring secondary dispersal and efficient ovule fertilisation. Overall, our study demonstrates that the floral morphology of male figs facilitates precise pollen deposition, beneficial for the wasp progeny, while the floral morphology of female figs compensates for wasp pollination behaviour that is not selected in those figs. We conclude that the morphology of the arena in which interactions with its pollinator are played out is the result of selection on the plant to maximize its male and female fitness. Incidentally, this morphology stabilises the mutualistic interaction.

Forest conversion into pasture selects dung beetle traits at different biological scales depending on species pool composition.

The conversion of forests into open areas has large effects on the diversity and structure of native communities. The intensity of these effects may vary between regions, depending on the existence of native species adapted to open habitats in the regional pool or the time since habitat change.We assess the differences in species richness and functional diversity of dung beetle communities (Coleoptera: Scarabaeinae) between native forests and novel pasturelands of the Atlantic Forest and the Cerrado, two biomes with contrasting histories of human occupation in Brazil. We conducted standardized surveys in seven forest fragments and adjacent pastures in each region and measured 14 traits in individuals collected in each type of habitat at each particular site. We calculated functional richness, functional evenness, functional divergence, and community-weighted mean of traits for each area, and analyzed individual variation through nested variance decomposition and Trait Statistics.Communities were richer and more numerous at the Cerrado. We did not find any consistent relationship between functional diversity and forest conversion beyond the changes in species diversity. Although landscape changes were more recent at the Cerrado, the colonization of the new habitat by native species already adapted to open habitats lessens the functional loss in this biome. This indicates that habitat change's effects on trait diversity depend on the regional species pool rather than on time since land conversion.Forest conversion effects were primarily due to internal filtering. The effects of external filtering only appear at the intraspecific variance level, with contrasting differences between the Cerrado, where traits related to relocation behavior and size are selected, and the Atlantic Forest, where selection operates for traits related to relocation behavior and flight. These results evidence the importance of considering individual variance to address the responses of dung beetle communities to forest conversion.

Vegetation Patterns in the Hyperbolic Klausmeier Model with Secondary Seed Dispersal

This work focuses on the dynamics of vegetation stripes in sloped semi-arid environments in the presence of secondary seed dispersal and inertial effects. To this aim, a hyperbolic generalization of the Klausmeier model that encloses the advective downhill transport of plant biomass is taken into account. Analytical investigations were performed to deduce the wave and Turing instability loci at which oscillatory and stationary vegetation patterns arise, respectively. Additional information on the possibility of predicting a null-migrating behavior was extracted with suitable approximations of the dispersion relation. Numerical simulations were also carried out to corroborate theoretical predictions and to gain more insights into the dynamics of vegetation stripes at, close to, and far from the instability threshold.

Effects of anthropogenic disturbances on diaspore removal by ants: A meta-analysis

Anthropogenic changes in natural landscapes are identified as a major driver of biodiversity loss worldwide. Consequently, important ecosystem functions, such as seed dispersal by animals, can be lost, which threaten the stability of essential ecological processes. Given the current scenario of large seed disperser's loss, secondary dispersal by ants has been identified as an important alternative to mitigate the impacts caused by human changes. However, empirical evidence shows contradictory effects of anthropogenic disturbances on diaspore removal by ants. Here, we conducted a global meta-analysis from 22 studies (65 comparisons) comparing diaspore removal by ants in disturbed versus preserved areas to investigate general trends to different anthropogenic disturbances. Specifically, we evaluate: (i) the effects of anthropogenic disturbances on diaspore removal by ants comparing temperate and tropical regions, and (ii) comparing different disturbance types (agriculture related disturbances, fragmentation, mining, fire, etc.) on diaspore removal by ants. We found an overall negative effect of anthropogenic disturbances on diaspore removal by ants (26% decrease), both in temperate and tropical regions (38% and 19% decrease, respectively). In addition, diaspore removal by ants responded negatively to disturbances related to fragmentation (24% decrease) and mining (83% decrease). However, we found no evidence of effects in areas subjected to agricultural processes (0.9% decrease). Our findings suggest that human disturbances might compromise crucial early stages to the natural regeneration in ecosystems such the seed dispersal.

Global expansion of a solitary‐social tropical spitting spider shaped by multiple long‐distance dispersals

The spitting spider Scytodes fusca is a species complex well known for its unusual hunting technique which involves spitting a venomous sticky silken substance over its prey. Previous studies supposed that S. fusca was native to Central and South America but had expanded to the tropics of almost every continent. We aimed to test the hypothesis of a Neotropical origin for this spider followed by a secondary dispersal to other regions, and to discuss how population expansion occurring in the tropics was driven. We investigated the population structure and spatiotemporal biogeography of the species complex through the culmination of 22 years of comprehensive global sampling using the mitochondrial and nuclear loci (COI, 16S, 18S, 28S, H3 and ITS2). The S. fusca species complex is divided into two clades. One clade comprises the haplotypes from Australasian regions and a haplotype from Baja Peninsula, Mexico. The other is composed of the haplotypes from all analyzed regions including Asia, Australia, the Americas and Madagascar. Populations from the Americas and Madagascar exhibit a lower genetic diversity compared with the Australasian population, and both have different population demographic histories. The initial divergence within the species complex started during the early Miocene. Diversifications of both clades occurred during the late Miocene. One haplotype was recently and widely dispersed into Southeast Asia, South Asia, Australia, the Americas and Madagascar. Our results elucidate the history of the global spread of the S. fusca species complex, suggesting a Malay Archipelago origin, two expansion routes and its multiple dispersals into the Americas. These stem from a common native source population, as well as from Australia, Fiji, French Polynesia or Turks and Caicos bridgeheads. Our data support the view that the expansion of the S. fusca species complex from Australasia to America and Madagascar was facilitated by long‐distance jump dispersal events.

The dingo (Canis familiaris) as a secondary disperser of mycorrhizal fungal spores

Context Many mycorrhizal fungi are vital to nutrient acquisition in plant communities, and some taxa are reliant on animal-mediated dispersal. The majority of animals that disperse spores are relatively small and have short-distance movement patterns, but carnivores – and especially apex predators – eat many of these small mycophagists and then move greater distances. No studies to date have assessed the ecosystem services carnivores provide through long-distance spore dispersal. Aims In this study, we aimed to investigate whether Australia’s free-ranging dogs (Canis familiaris), including dingoes, act as long-distance spore dispersers by predating smaller mycophagous animals and then secondarily dispersing the fungi consumed by these prey species. Methods To answer this question, we collected dingo scats along 40 km of transects in eastern Australia and analysed the scats to determine the presence of fungal spores and prey animals. Using telemetry and passage rate data, we then developed a movement model to predict the spore dispersal potential of dingoes. Key results We found 16 species of mammalian prey to be eaten by dingoes, and those dingo scats contained spores of 14 genera of mycorrhizal fungi. These fungi were more likely to appear in the scats of dingoes if primary mycophagist prey mammals had been consumed. Our model predicted dingo median spore dispersal distance to be 2050 m and maximum dispersal potential to be 10 700 m. Conclusions Our study indicates that dingoes are providing a previously overlooked ecosystem service through the long-distance dispersal of mycorrhizal fungi. Many of the fungi found in this study form hypogeous (underground) fruiting bodies that are unable to independently spread spores via wind. Because dingoes move over larger areas than their prey, they are especially important to these ecosystem functions. Implications Our novel approach to studying an overlooked aspect of predator ecology is applicable in most terrestrial ecosystems. Similar modelling approaches could also be employed to understand the dispersal potential of both primary and secondary spore dispersers globally. Because this study highlights an unrecognised ecosystem service provided by dingoes, we hope that it will stimulate research to develop a more comprehensive understanding of other apex predators’ ecosystem functions.

海草床种子扩散过程及种子库形成机制研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 海草床种子扩散过程及种子库形成机制研究进展 DOI: 10.5846/stxb202108262396 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划(2019YFE0121500);国家自然科学基金委-山东联合基金(U2006215);唐仲英基金会 A review on seed dispersal process and mechanism of seed bank formation of seagrass meadows Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:海草是唯一一类可以完全生活在海水中的高等被子植物,具有重要的生态服务功能和巨大的经济价值。但受气候变化和人类活动的双重影响,海草床退化趋势日益严峻。海草床生态系统受到外界胁迫后的稳定性和恢复能力很大程度上依赖于有性繁殖即种子繁殖,当胁迫造成海草死亡等不可逆转的伤害时,通过沉积物种子库能够进行种群维持和自我更新,因此研究海草种子扩散过程及种子库形成机制对海草生态系统稳定性的维持具有重要意义。综述了海草生活史类型、种子繁殖特征、种子扩散过程及影响因素、种子库形成机制等。在此基础上总结了目前研究存在的几方面不足和未来展望:1)不同环境胁迫条件对海草有性繁殖努力的影响研究;2)海草种子二次扩散的影响因素和扩散机制研究;3)沉积物沉降和再悬浮对种子扩散和截留的影响研究;4)环境因素变化下种子库的潜在分布和海草适宜生境预测与模拟。本研究以期为海草床生态系统的保护恢复研究提供理论参考。 Abstract:Seagrasses are the only higher angiosperms fully living in marine environments, which have important ecosystem service functions and enormous economic value. However, in recent years, the structure and function of seagrass ecosystems have been threatened by multiple global stressors caused by human activities and climate change, resulting in the continuous degradation of seagrasses. The stability and resilience of the seagrass ecosystem under external stress depend highly on its sexual reproduction, i.e., seed reproduction. When stressors cause irreversible damage to seagrasses, population maintenance and self-renewal could occur through sediment seed banks. Therefore, it is crucial to study the dispersal processes of seeds and the mechanism of seed bank formation, which play a key role in maintaining seagrass ecosystem stability. This paper reviews the life-history types, seed reproductive characteristics, seed dispersal processes and their influencing factors and seed bank formation of seagrass. On the basis of these understandings, we further proposed that future studies should focus on: 1) sexual reproductive efforts of seagrass under different environmental stress conditions; 2) the influencing factors and mechanism of secondary dispersal of seagrass seeds; 3) the influence of sediment deposition and resuspension on seed dispersal and retention processes; 4) prediction and simulation of the potential distribution of seagrasses and suitable habitat of seed bank under changing environments. This study is expected to provide theoretical references for the protection and restoration of seagrass meadow ecosystems. 参考文献 相似文献 引证文献

Effects of biocrusts on surface roughness and seed secondary dispersal of shrubs and grasses on the Loess Plateau, China

Effects of biocrusts on surface roughness and seed secondary dispersal of shrubs and grasses on the Loess Plateau, China

Effects of dung beetle activity on tropical forest plants

Dung beetles are recognized as providers of important ecosystem functions, most of which are derived from the removal of vertebrate dung from the soil surface. These insects occur in nearly all terrestrial biomes but are most diverse in the humid tropics. Several of the ecological functions attributed to dung beetles are related to their direct and indirect interactions with plants. Among these functions, the secondary dispersal of seeds defecated by mammals has received the most attention in tropical forests. Nonetheless, while several aspects of secondary seed dispersal by dung beetles are relatively well understood, others remain understudied or have not been addressed at all. Thus, a broad generalization about the effects of secondary seed dispersal by dung beetles on plant fitness remains somewhat elusive. Furthermore, other effects of dung beetle activity on tropical plants have received very little attention. A few studies have shown that through their behaviors of dung burial and soil-excavation, dung beetles can shape seed bank structure and dynamics. Also, though numerous greenhouse studies and field experiments in agricultural lands and temperate grasslands have shown that dung beetle activity increases plant nutrient uptake and yield, it is uncertain whether such effects are common in tropical forests. Here, we review and synthesize our current knowledge on how dung beetles affect tropical forest plants by dispersing defecated seeds, shaping the structure and dynamics of seed banks, and influencing the performance of understory seedlings. We focus on the Neotropics, where most studies on the effects of dung beetles on tropical forest plants have been carried out, but we also show results from other regions and biomes, to present a more general picture of these beetle-plant interactions. Throughout the review we emphasize aspects that need more research to allow generalizations and point out those questions that remain unanswered. We hope that this review will stimulate more research about the fascinating interactions between dung beetles and plants in tropical ecosystems.

Soil disturbance impacts on ant‐diaspore multilayer networks in a tropical savanna

Abstract1. Current anthropogenic disturbances have changed natural environments, broadly impacting ecosystem services and functions. Here, the authors focused on the secondary dispersal of diaspores by ants, which serve an important ecological function in the natural regeneration of degraded habitats.2. The authors experimentally studied the effects of vegetation suppression and soil disturbance on (i) diaspore removal, (ii) the quality of secondary removal, and (iii) the structure of interaction networks between ants and diaspores. The authors tested whether the disturbance affected the species richness of seed removers, diaspore removal rate, removal distance and time, and removal effectiveness. Additionally, the authors tested whether the structure of ant‐diaspore networks, that is, specialisation, modularity and robustness, is altered by soil disturbance. To do that, the authors studied three degraded and three preserved areas in the Brazilian Cerrado.3. The authors observed 25 ant species interacting with the diaspores. Disturbance did not affect ant species richness, removal distance or removal rate, but ants took twice as long to remove the diaspores in the preserved habitat. The frequency of interaction networks was higher in the preserved habitat, and the effectiveness of species in removing the diaspores differed between habitats. Surprisingly, the authors observed that ants considered effective dispersers mostly occurred in degraded habitats, highlighting the potential of myrmecochory in the regeneration of impacted environments.4. The findings point to the potential of ants in acting as secondary seed dispersal, improving the restoration of areas highly impacted by soil disturbance. Moreover, this study contributes to understanding the effects of anthropogenic disturbances on ecological interactions and ecosystem functions.

The distinct fruit size and physical defense promote divergent secondary seed dispersal strategies of three oak species

Secondary seed dispersal is one of the most important factors contributing to the co-existence of plant species. Variations in fruit properties including fruit size, physical defense and chemical composition influence seed foraging and secondary dispersal, but the details remain unclear. Here, we focused on three common nut-bearing tree species (Quercus aliena Blume, Q. dentata Thunb., and Q. variabilis Blume), which often co-occur in mixed deciduous forest in northern China. We estimated their acorn properties and evaluated their effects on the secondary dispersal patterns. We found similar chemical profiles but different acorn sizes and physical defense among these three species. Moreover, we detected distinct secondary seed dispersal strategies in relation to their acorn properties: Q. dentata produced the smallest-sized acorns with the lowest physical defense, which had shorter dispersal range but the highest survival rate; Q. variabilis generated the largest-sized acorns with the highest physical defense, which suffered the lowest survival rate but benefited from the longer dispersal range; and an intermediate survival rate existed in Q. alienawith the intermediate-sized acorns. In addition, Père David’s rock squirrel (Sciurotamias davidianus Milne-Edwards, Sciuridae) and brown rat (Rattus norvegicus Berkenhout, Muridae) are secondary seed dispersal agents for three oak species. Brown rats not only disperse more acorns than Père David’s rock squirrels, they also create different dispersal distance for the acorns of three species, which enhance three species’ niche separation. Our results therefore revealed that differentiations in acorn properties have derived distinct trade-offs in secondary seed dispersal strategies, likely facilitating the coexistence of the three examined species.

Lift-off velocity of diaspores during secondary wind dispersal varies with particle size of the underlying surface matrix

Lift-off velocity of diaspores during secondary wind dispersal varies with particle size of the underlying surface matrix

The genetic history of the Southern Arc: A bridge between West Asia and Europe.

By sequencing 727 ancient individuals from the Southern Arc (Anatolia and its neighbors in Southeastern Europe and West Asia) over 10,000 years, we contextualize its Chalcolithic period and Bronze Age (about 5000 to 1000 BCE), when extensive gene flow entangled it with the Eurasian steppe. Two streams of migration transmitted Caucasus and Anatolian/Levantine ancestry northward, and the Yamnaya pastoralists, formed on the steppe, then spread southward into the Balkans and across the Caucasus into Armenia, where they left numerous patrilineal descendants. Anatolia was transformed by intra-West Asian gene flow, with negligible impact of the later Yamnaya migrations. This contrasts with all other regions where Indo-European languages were spoken, suggesting that the homeland of the Indo-Anatolian language family was in West Asia, with only secondary dispersals of non-Anatolian Indo-Europeans from the steppe.

How individual, social, and ecological conditions influence dispersal decisions in malevervet monkeys.

Dispersal between social groups reduces the risk of inbreeding and can improve individuals'reproductive opportunities. However, this movement has costs, such as increased risk of predation and starvation, loss of allies and kin support, and increased aggression associated with entering the new group. Dispersal strategies, such as the timing of movement and decisions on whether to transfer alone or in parallel with a peer, involve different costs and benefits. We used demographic, behavioral, hormonal, and ecological data to examine the causes and consequences of 36 dispersal events from 29 male vervet monkeys (Chlorocebus pygerythrus) at Lake Nabugabo, Uganda. Adult males'secondary dispersal coincided with the conception season in females, and males improved their potential access to females by moving to groups with higher female-to-male sex ratios and/or by increasing their dominance rank. Males that dispersed with a peer had lower fecal glucocorticoid and androgen metabolite levels than lone dispersers.Subadult males were not more likely to engage in parallel dispersals compared to adult males. Dispersal was also used as a mechanism to avoid inbreeding, but changes in hormone levels did not seem to be a trigger of dispersal in our population. Our findings illustrate the complex individual strategies used during dispersal, how many factors can influence movement decisions, as well as the value of dominance and hormone analyses for understanding these strategies.

Influence of secondary dispersal by ants on invasive processes of exotic species with fleshy fruits

Influence of secondary dispersal by ants on invasive processes of exotic species with fleshy fruits