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Livestock grazing is often perceived as being detrimental to the quality and functioning of dryland ecosystems. For example, a study in a semiarid Kenyan savanna proposed that cattle form bare spaces throughout the landscape, which indicate ecosystem degradation. Other studies, conducted in north‐eastern Spain, where climatic conditions range between semiarid and Mediterranean subhumid, reported that sheep and goat trails have increased the emergence of rill erosion processes. Sometimes, this negative perception is extended to include wild, large ungulate herbivores as well. Here, we challenge this perception by highlighting the generally nonadverse and even ameliorative impacts of moderate animal rate on geoecosystem functioning of hilly drylands. Specifically, trampling routes (also known as treading paths, livestock terracettes, cattle trails, migration tracks, cowtours, etc.) formed across hillslopes by grazing animals—being either domesticated livestock or native large herbivores—transform the original two‐phase vegetation mosaic of shrubby patches and interpatch spaces into a three‐phase mosaic. The animal routes increase the complexity of ecosystem, by strengthening the spatial redistribution of water and soil resources at the patch scale and decreasing hydrological connectivity at the hillslope scale. As a consequence, the animal routes improve functioning of hilly drylands and increase their resilience to long‐term droughts and climatic change. Therefore, instead of viewing the animal routes as degraded spots, they should be perceived at a wider perspective that allows to properly understand their overall role in sustaining dryland geoecosystems., Livestock animals and wild ungulates form trampling routes across the landscape, transforming the original two‐phase vegetation mosaic into a three‐phase mosaic. The routes increase the complexity of ecosystems and decrease hydrological connectivity at the hillslope scale, thus improving ecological functioning and sustaining dryland durability under long‐term droughts and climatic change.

Different conceptions of disturbance differ in the degree to which they appeal to mechanisms that are general and equivalent, or species‐, functional group‐, or interaction‐specific. Some concepts of disturbance, for example, predict that soil disturbances and herbivory have identical impacts on species richness via identical mechanisms (reduction in biomass and in competition). An alternative hypothesis is that the specific traits of disturbance agents (small mammals) and plants differentially affect the richness or abundance of different plant groups. We tested these hypotheses on a degu (Octodon degus) colony in central Chile. We ask whether native and non‐native forbs respond differently to degu bioturbation on runways versus herbivory on grazing lawns. We ask whether this can explain the increase in non‐native plants on degu colonies. We found that biopedturbation did not explain the locations of non‐native plants. We did not find direct evidence of grazing increasing non‐native herbs either, but a grazing effect appears to be mediated by grass, which is the dominant cover. Further, we provide supplementary evidence to support our interpretation that a key mechanism of non‐native spread is the formation of dry soil conditions on grazing lawns. Thus, ecosystem engineering (alteration of soil qualities) may be an outcome of disturbances, in which each interacts with specific plant traits, to create the observed pattern of non‐native spread in the colony. Based on these results, we propose to extend Jentsch and White (Ecology, 100, 2019, e02734) concept of combined pulse/ disturbance events to the long‐term process duality of ecosystem engineering/ disturbance., Non‐native plant species accumulate on the centers of native degu (Octodon degus) colonies. We show that this is the result of the interaction and accumulation of two kinds of disturbances (biopedturbation and herbivory) with different effects on plant species over time. Although disturbance is usually represented as different from, or indeed opposite to, ecosystem engineering, we show that ecosystem engineering best explains the outcome of these two disturbances over time.

Facilitative interactions between co-occurring species sustain diverse communities and constitute a vital functional component of coastal marine ecosystems. In seagrass ecosystems, facilitation ensures the survival and resilience of this important habitat. As seagrass meadows are in decline, innovative restoration strategies incorporating facilitative interactions could open new avenues in marine restoration. Here, we investigated the interactions between eelgrass Zostera marina and the Baltic clam Macoma balthica, and tested whether clams could enhance early survival and biomass increase of transplanted eelgrass shoots in the northern Baltic Sea. We measured eelgrass responses to differing densities of clams, as well as porewater ammonium (NH4+) and phosphate (PO43-) concentrations in field and aquarium experiments. Overall, survival of transplanted plots was high, independent of clam density. Specifically, we found that clams facilitated eelgrass above- and below-ground biomass in low porewater nutrient conditions, potentially through nutrient release, but inhibited growth in high-nutrient conditions, particularly where clams were added at high densities. Our results show the important role of infaunal bivalves for nutrient fluxes within seagrass meadows. Most notably, we highlight the importance of considering and testing context- and density-dependency when studying interspecific interactions, as clams could both benefit and hamper Zostera biomass increase. This becomes particularly crucial when incorporating such interactions in a restoration context.

In this article we summarize the development of vehicles for penetrating living cells, tissue and organisms with nucleic acids (DNA and RNA) and proteins that damage or repair DNA. The purpose in doing so is to provide an assessment of the potential for these technologies to unintentionally cause harm to human health or the environment or to be re-tasked with an intention to cause harm. Two new types of biological-molecule-based products are being developed for use in medicine, agriculture and food production or preservation. The first type are genetically modified organisms, such as those that express bio-pesticides. They produce molecules and that are difficult to alter at scale after release. Products of this type are usually evaluated by both food and environmental regulators. The second type comprises topical chemical or physical agents. Most of these are in pre-commercial testing phase. Topically applied products use nucleic acids and/or proteins wherein the active biological is transferred by contact, ingestion or inhalation. From a survey of the research and patent literature we suggest that chemical formulations and physical manipulations that can be used to ferry nucleic acid and protein cargo into cells, tissues or organisms could be assembled de novo or repurposed from existing commercial products and loaded with proteins and/or nucleic acids designed using publicly available genome sequences. Biological actives may evade risk assessment and regulatory review because they are often excluded from the category of hazardous chemicals and are actively being excluded as agents of genetic modification. This emerging gap in oversight could lead to either dual use appropriation or unintended harm to human health or the environment.

In grassland ecosystems, burrowing mammals create disturbances, providing habitat for animal species and increasing plant community diversity. We investigated whether seedling assemblages on Richardson’s ground squirrel Urocitellus richardsonii mounds result from seed rearrangement or environmental changes that favor germination of certain species over others. To test whether ground squirrels rearrange the seed bank by burrowing, we compared seed compositions among mounds, burrows, and undisturbed soil. To test whether ground squirrels change environmental conditions, we compared soil nitrate and bare ground cover on and off mounds. We also compared seedlings that germinated on mounds with seedlings that germinated on artificial disturbances from which we removed aboveground vegetation. Soil nitrate and bare ground cover were significantly higher on mounds than artificial disturbances. While seed richness and abundance did not differ among mounds, burrows, and undisturbed soil, seedling richness was reduced on mounds relative to artificial disturbances. Burrowing disturbance favors seedlings that can capitalize on bare ground availability but are less able to immobilize nitrate, as opposed to perennial species that immobilize more nitrate but take longer to establish. Our results suggest that Richardson’s ground squirrels act as ecosystem engineers, although future research following succession on ground squirrel mounds is necessary to understand how they influence plant communities past the seedling stage.

Species that facilitate others under stressful conditions are often ecosystem engineers: organisms that modify or create physical habitat. However, the net effect of an engineering species on another depends on both the magnitude of the direct interactions (e.g., competition or predation) and the specific environmental context. We used a laboratory system to isolate the trophic and engineering impacts of a predator, the nematode Caenorhabditis remanei, on its prey, Escherichia coli under different levels of environmental stress. We predicted that under stressful surface conditions the nematodes would positively impact their prey by creating burrows which protected the bacteria. Colony plate counts of E. coli indicated that there was a stress‐induced change in the net impact of nematodes on bacteria from neutral to positive. Predator engineering in the form of burrowing allowed larger bacteria populations to survive. We conclude that even in a simple two‐species system a predator can positively impact prey via ecosystem engineering.

Field measurements of bed elevation and related wave events were performed within a tidal marsh, on two cordgrass species, Spartina anglica (exotic) and Spartina maritima (native), in the Bay of Arcachon (SW France). Bed- and water-level time series were used to infer on the sediment behavior patterns from short to long term. A consistent response was found between the bed-level variation and the wave forcing, with erosion occurring during storms and accretion during low energy periods. Such behavior was observed within the two species, but the magnitude of bed-level variation was higher within the native than the exotic Spartina. These differences, in the order of millimeters, were explained by the opposite allocation of biomass of the two species. On the long term, the sedimentation/erosion patterns were dominated by episodic storm events. A general sediment deficit was observed on the site, suggested by an overall bed-level decrease registered within both species. However, further verification of within species variation needs to be considered when drawing conclusions. Despite possible qualitative limitations of the experimental design, due to single point survey, this work provides original and considerable field data to the understanding the different species ability to influence bed sediment stabilization and their potential to build marsh from the mudflat pioneer stage. Such information is valuable for coastal management in the context of global change.

Megafaunal extinctions are recurring events that cause evolutionary ripples, as cascades of secondary extinctions and shifting selective pressures reshape ecosystems. Megafaunal browsers and grazers are major ecosystem engineers, they: keep woody vegetation suppressed; are nitrogen cyclers; and serve as seed dispersers. Most angiosperms possess sets of physiological traits that allow for the fixation of mutualisms with megafauna; some of these traits appear to serve as exaptation (preadaptation) features for farming. As an easily recognized example, fleshy fruits are, an exaptation to agriculture, as they evolved to recruit a non-human disperser. We hypothesize that the traits of rapid annual growth, self-compatibility, heavy investment in reproduction, high plasticity (wide reaction norms), and rapid evolvability were part of an adaptive syndrome for megafaunal seed dispersal. We review the evolutionary importance that megafauna had for crop and weed progenitors and discuss possible ramifications of their extinction on: (1) seed dispersal; (2) population dynamics; and (3) habitat loss. Humans replaced some of the ecological services that had been lost as a result of late Quaternary extinctions and drove rapid evolutionary change resulting in domestication. Introduction Lost Seed-Dispersal Services - Small-Seeded Grains and Legumes - Large Fleshy Fruiting Plants Loss of Herbivory and Disturbance Regimes Plant Domestication - Exaptation Traits Supporting Domestication Anthropogenic Ecosystem Services

Beavers have influenced the world&rsquo, s ecosystem for millions of years. Their dams create ponds and wetlands that provide a large range of hydraulic and ecological benefits to the natural world, including mitigation against flooding and improving water quality. As beavers are now being reintroduced to many parts of the world, it is important to fully understand the impact of their dams on the flow characteristics of the water-courses on which they are built. This paper investigates the relationship between the physical properties of a model beaver dam and its fundamental hydraulics and pollutant dispersion characteristics. The first objective of this paper was to develop a modelling framework to relate discharge to flow-depth for dams with a combination of porous and impermeable sections. The second objective was to utilize a similar framework to predict the down-stream concentration distribution of an up-stream pollution event passing through such systems. The ability to model these parameters for dams with variable lengths of porous and impermeable sections is important as the porosity of beaver dams can vary with depth, depending on which sections are constructed from branches, rocks, or compacted mud. The analysis and modelling developed in this paper show that a single, general relationship can be obtained between discharge and flow-depth regardless of the presence of sections that are both porous or impermeable, provided the relative depths of these sections are known and accounted for. It is also shown that the Nominal Residence Time and the Advection Dispersion Equation can be used to predict pollutant transport in such systems. These two equations have previously been shown to have limitations when applied to some complex systems, so demonstrating they can be applied to a porous dam with combinations of porous and impermeable sections at the relative discharges investigated is noteworthy.

Background The nuclear genomes of eukaryotes vary enormously in size, with much of this variability attributable to differential accumulation of transposable elements (TEs). To date, the precise evolutionary and ecological conditions influencing TE accumulation remain poorly understood. Most previous attempts to identify these conditions have focused on evolutionary processes occurring at the host organism level, whereas we explore a TE ecology explanation. Results As an alternative (or additional) hypothesis, we propose that ecological mechanisms occurring within the host cell may contribute to patterns of TE accumulation. To test this idea, we conducted a series of experiments using a simulated asexual TE/host system. Each experiment tracked the accumulation rate for a given type of TE within a particular host genome. TEs in this system had a net deleterious effect on host fitness, which did not change over the course of experiments. As one might expect, in the majority of experiments TEs were either purged from the genome or drove the host population to extinction. However, in an intriguing handful of cases, TEs co-existed with hosts and accumulated to very large numbers. This tended to occur when TEs achieved a stable density relative to non-TE sequences in the genome (as opposed to reaching any particular absolute number). In our model, the only way to maintain a stable density was for TEs to generate new, inactive copies at a rate that balanced with the production of active (replicating) copies. Conclusions From a TE ecology perspective, we suggest this could be interpreted as a case of ecosystem engineering within the genome, where TEs persist by creating their own “habitat”.

The decline of open habitats in Europe, such as semi-natural grasslands and heathlands, has caused a general decline in biodiversity, which has been well documented for butterflies. Current conservation practices often involve grazing by domestic livestock to maintain suitable butterfly habitats. The extent to which wild ungulates may play a similar role remains largely unknown. Through their rooting activity, wild boar could be effective to reduce grass encroachment and restore pioneer microhabitats that are vital to many grassland insects in temperate climates. Here, we assessed the microhabitat requirements of Pyrgus malvae, an endangered butterfly of heathland and grassland habitats in the Netherlands, with special attention for the influence of wild boar rooting. To date, oviposition site selection of this species has concentrated on calcareous grasslands, whereas we also include heathlands. Overall, larval occupancy was higher in warm, open and sparsely vegetated microhabitats, which supports earlier findings. In heathland, microhabitat occupancy was positively affected by bryophyte and litter cover. In heath-grassland mosaic, microhabitat occupancy was also influenced by bryophyte and litter cover, but in addition low grass cover increased occupancy by favouring host plants. In grassland, only low grass cover and host plant cover determined microhabitat quality. Across all habitats, occupied microhabitats were characterized by lower vegetation as well as higher average daytime temperatures than unoccupied microhabitats. We discovered that wild boar play an important role in reducing grass cover by shallow rooting in grass patches, thereby increasing host plant availability. Hence, wild boar may have an added value in maintaining and restoring P. malvae microhabitats in grassland habitats in addition to grazing by domestic livestock., Journal of Insect Conservation, 22 (1), ISSN:1366-638X, ISSN:1572-9753

Burial of aboveground plant litter by animals reduces the amount available for surface transport and places it into a different environment, affecting decomposition rates and fluxes of organic matter to adjacent ecosystems. Here we show that in a Southwestern Atlantic salt marsh the burrowing crab Neohelice granulata buries aboveground plant litter at rates (0.5–8 g m−2 day−1) comparable to those of litter production (3 g m−2 day−1). Buried litter has a low probability (0.6%) of returning to the marsh surface. The formation of burrow excavation mounds on the marsh surface is responsible for most litter burial, whereas litter trapped in burrows was an order of magnitude lower than rates of burial under excavation mounds. Crab exclusion markedly increased surface litter accumulation (3.5-fold in just 21 days). Tides with the potential to transport significant amounts of surface litter are infrequent; hence, most litter is buried before it can be transported elsewhere or decomposes on the surface. Crab litter burial can account for the observed low levels of surface litter accumulation in this ecosystem and likely drives organic matter transformation and export. The impacts of ecosystem engineering by this crab species are therefore substantial and comparable in magnitude to the large effects found for tropical crabs and other litter-burying organisms, such as anecic earthworms. Fil: Gutierrez, Jorge Luis Ceferino. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; Argentina. Cary Institute of Ecosystem Studies; Estados Unidos. Grupo de Investigación y Educación en Temas Ambientales (GrIETA) - Estación Biológica Las Brusquitas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Jones, Clive G.. Cary Institute of Ecosystem Studies; Estados Unidos Fil: Ribeiro, Pablo Damián. Grupo de Investigación y Educación en Temas Ambientales (GrIETA) - Estación Biológica Las Brusquitas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencia Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Findlay, Stuart E. G.. Cary Institute of Ecosystem Studies; Estados Unidos Fil: Groffman, Peter M.. Cary Institute of Ecosystem Studies; Estados Unidos. City University of New York; Estados Unidos

We report wild octopuses (Octopus tetricus) living at high density at a rock outcrop, the second such site known. O. tetricus are often observed as solitary individuals, with the species known to exist at similar densities and exhibiting complex social behaviors at only one site other than that described here. The present site was occupied by 10–15 octopuses on eight different days. We recorded frequent interactions, signaling, mating, mate defense, eviction of octopuses from dens, and attempts to exclude individuals from the site. These observations demonstrate that high-density occupation and complex social behaviors are not unique to the earlier described site, which had been affected to some extent by remains of human activity. Behavior at this second site confirms that complex social interactions also occur in association with natural substrate, and suggest that social interactions are more wide spread among octopuses than previously recognized. This work was supported by The University of Sydney, and by Alaska Pacific University from donations by the Pollock Conservation Consortium. Findings and conclusions presented by the authors are their own and do not necessarily reflect the views or positions of the supporting organizations.

Recent empirical evidence suggests that herbicides have damaging effects on non-target organisms in both natural and semi-natural ecosystems. The African mound building termite, Macrotermes bellicosus, is an important beneficial insect that functions as an ecosystem engineer due to its role in the breakdown of dead and decaying materials. Here, we examined the effects of 2,4-D amine salt (2,4-D) and atrazine based herbicides viz. Vestamine® and Ultrazine® on the survival and locomotion response of M. bellicosus. Worker termites were treated with a range of concentrations of Vestamine® (the recommended concentration: 6.25 ml per 500 ml of water, 0.25- and 0.5-fold below the recommended concentration and distilled water as control) and Ultrazine® (the recommended concentration: 3.75 ml per 500 ml of water, 0.25-, 0.5-, 2.0- and 4-fold of the recommended concentration and distilled water as control) for 24 hours for the mortality test, and allowed to run for 15 seconds for the locomotion trial. All concentrations of both Vestamine® and Ultrazine® were highly toxic to worker termites and mortality increased as the concentration and time after treatment increased. For both herbicides, concentrations far less than the recommended rates caused 100% mortality. The speed of termites was significantly influenced by both Vestamine® and Ultrazine® as termites exposed to all tested concentrations of the herbicides exhibited reduced running speed than the control. These findings suggest that beneficial insects, especially M. bellicosus may experience high mortality (up to 100%) and reduced mobility if they are sprayed upon or come in contact with plant materials that have been freshly sprayed with (less or more than) the recommended concentrations of Vestamine® and Ultrazine®. The findings of our study calls for the reassessment of the usage of 2,4-D and atrazine based herbicides in weed control in termite and other beneficial insect populated habitats.

Propagule dispersal is an integral part of the life cycle of seagrasses; important for colonising unvegetated areas and increasing their spatial distribution. However, to understand recruitment success, seed dispersal and survival in habitats of different complexity remains to be quantified. We tested the single and synergistic effects of three commonly distributed ecosystem engineers-eelgrass (Zostera marina), oysters (Magellana gigas) and blue mussels (Mytilus edulis)-on trapping of Z. marina seeds in a hydraulic flume under currents. Our results suggest that seed retention increases with habitat complexity and further reveal insights into the underlying mechanisms. In eelgrass canopy, trapping occurred mostly through direct blocking of a seed's pathway, while trapping in bivalve patches was mainly related to altered hydrodynamics in the lee side, i.e. behind each specimen. With increasing flow velocity (24-30 cm s-1 in eelgrass canopy, 18-30 cm s-1 in bivalve patches), modifications of the sediment surface through increased turbulence and erosive processes became more important and resulted in high seed trapping rates. Furthermore, we show that while monospecific patches of seagrass and bivalves had different trapping optima depending on flow velocities, intermixing resulted in consistently high trapping rates throughout the investigated hydrodynamic gradient. Our results highlight the importance of positive interactions among ecosystem engineers for seed retention and patch emergence in eelgrass.

We addressed the implications of limb loss and regeneration for multispecies interactions and their impacts on ecosystem engineering in freshwater stream environments.We included regenerative and nonregenerative crayfish as well as fish predators in a 2 × 2 factorial design to assess the effects on water turbidity of interactions between crayfish ecosystem engineers differing in regenerative status and their fish predators.We demonstrated that crayfish limb loss and predation risks lead to more turbidity in field and mesocosm conditions. Moreover, ongoing regeneration of crayfish increased turbidity, while fish presence seemed to hinder crayfish turbidity‐inducing behaviors (such as tail‐flipping and burrowing) in the mesocosm experiment.We confirmed that greater numbers of crayfish produce a greater amount of turbidity in situ in streams.Although mechanical burrowing crayfish capacities may depend on crayfish burrowing classification (primary, secondary, or tertiary), our work emphasizes the implication for turbidity levels of crayfish autotomy in freshwater streams., We addressed the implications of limb loss and regeneration for multispecies interactions and their impacts on ecosystem engineering in freshwater stream environments. We demonstrated that crayfish limb loss and predation risks lead to more turbidity in field and mesocosm conditions. Although mechanical burrowing crayfish capacities may depend on crayfish burrowing classification (primary, secondary, or tertiary), our work emphasizes the implication for turbidity levels of crayfish autotomy in freshwater streams.

Beavers (Castor fiber, Castor canadensis) are one of the most influential mammalian ecosystem engineers, heavily modifying river corridor hydrology, geomorphology, nutrient cycling, and ecosystems. As an agent of disturbance, they achieve this first and foremost through dam construction, which impounds flow and increases the extent of open water, and from which all other landscape and ecosystem impacts follow. After a long period of local and regional eradication, beaver populations have been recovering and expanding throughout Europe and North America, as well as an introduced species in South America, prompting a need to comprehensively review the current state of knowledge on how beavers influence the structure and function of river corridors. Here, we synthesize the overall impacts on hydrology, geomorphology, biogeochemistry, and aquatic and terrestrial ecosystems. Our key findings are that a complex of beaver dams can increase surface and subsurface water storage, modify the reach scale partitioning of water budgets, allow site specific flood attenuation, alter low flow hydrology, increase evaporation, increase water and nutrient residence times, increase geomorphic heterogeneity, delay sediment transport, increase carbon, nutrient and sediment storage, expand the extent of anaerobic conditions and interfaces, increase the downstream export of dissolved organic carbon and ammonium, decrease the downstream export of nitrate, increase lotic to lentic habitat transitions and aquatic primary production, induce ‘reverse’ succession in riparian vegetation assemblages, and increase habitat complexity and biodiversity on reach scales. We then examine the key feedbacks and overlaps between these changes caused by beavers, where the decrease in longitudinal hydrologic connectivity create ponds and wetlands, transitions between lentic to lotic ecosystems, increase vertical hydraulic exchange gradients, and biogeochemical cycling per unit stream length, while increased lateral connectivity will determine the extent of open water area and wetland and littoral zone habitats, and induce changes in aquatic and terrestrial ecosystem assemblages. However, the extent of these impacts depends firstly on the hydro-geomorphic landscape context, which determines the extent of floodplain inundation, a key driver of subsequent changes to hydrologic, geomorphic, biogeochemical, and ecosystem dynamics. Secondly, it depends on the length of time beavers can sustain disturbance at a given site, which is constrained by top down (e.g. predation) and bottom up (e.g. competition) feedbacks, and ultimately determines the pathways of river corridor landscape and ecosystem succession following beaver abandonment. This outsized influence of beavers on river corridor processes and feedbacks is also fundamentally distinct from what occurs in their absence. Current river management and restoration practices are therefore open to re-examination in order to account for the impacts of beavers, both positive and negative, such that they can potentially accommodate and enhance the ecosystem engineering services they provide. It is hoped that our synthesis and holistic framework for evaluating beaver impacts can be used in this endeavor by river scientists and managers into the future as beaver populations continue to expand in both numbers and range.

Insights from biome-wide experiments can improve efficacy of landscape-scale ecological restoration projects. Such insights enable implementers to set temporal and geographical benchmarks and to identify key drivers of success during the often decades-long restoration trajectory. Here we report on a biome-wide experiment aimed at informing the ecological restoration of thousands of hectares of degraded subtropical thicket dominated by the succulent shrub, Portulacaria afra (spekboom). Restoration using spekboom truncheons has the potential to sequester, for a semi-arid region, large amounts of ecosystem carbon, while regenerating a host of associated ecosystem services. This study evaluates, after about three years post-propagation, the effects of spekboom truncheon size and treatment on survivorship in 40 fence-enclosed (0.25 ha) plots located in target habitat across the entire spekboom thicket biome. In each plot, locally harvested spekboom truncheons, comprising eight size/treatment combinations, were planted in replicated rows of between 24 and 49 individuals, depending on treatment. The experiment assessed the role of truncheon size, spacing, application of rooting hormone and watering at planting on survivorship percentage as an indicator of restoration success. All eight combinations recorded extreme minimum survivorship values of zero, while the range of extreme maximum values was 70-100%. Larger truncheons (>22.5 mm diameter) had almost double the survivorship (ca. 45%) than smaller truncheons (< 15 mm) (ca. 25%). Planting large, untreated truncheons at 1 m intervals—as opposed to 2 m intervals recommended in the current restoration protocol—resulted in no significant change in survivorship. The application of rooting hormone and water at planting had no significant effect on restoration success for both large and small truncheons. While our results do not provide an evidence base for changing the current spekboom planting protocol, we recommend research on the financial and economic costs and benefits of different propagation strategies in real-world contexts.

Funding: This work was funded by the John Templeton Foundation Grant 60501, “Putting the Extended Evolutionary Synthesis to the Test”. It also received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland, (https://www.masts.ac.uk)) and their support is gratefully acknowledged. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. DMP received funding from MASTS, funded by the Scottish Funding Council (grant reference HR09011), and AJW received funding under the MASTS small grant scheme (grant reference SG433). Intertidal systems are complex and dynamic environments with many interacting factors influencing biochemical characteristics and microbial communities. One key factor are the actions of resident fauna, many of which are regarded as ecosystem engineers because of their bioturbation, bioirrigation and sediment stabilising activities. The purpose of this investigation was to elucidate the evolutionary implications of the ecosystem engineering process by identifying, if any, aspects that act as selection pressures upon microbial communities. A mesocosm study was performed using the well characterised intertidal ecosystem engineers Corophium volutator, Hediste diversicolor, and microphytobenthos, in addition to manual turbation of sediments to compare effects of bioturbation, bioirrigation and stabilisation. A range of sediment functions and biogeochemical gradients were measured in conjunction with 16S rRNA sequencing and diatom taxonomy, with downstream bacterial metagenome function prediction, to identify selection pressures that incited change to microbial community composition and function. Bacterial communities were predominantly Proteobacteria, with the relative abundance of Bacteroidetes, Alphaproteobacteria and Verrucomicrobia being partially displaced by Deltaproteobacteria, Acidobacteria and Chloroflexi as dissolved oxygen concentration and redox potential decreased. Bacterial community composition was driven strongly by biogeochemistry; surface communities were affected by a combination of sediment functions and overlying water turbidity, and subsurface communities by biogeochemical gradients driven by sediment reworking. Diatom communities were dominated by Nitzschia laevis and Achnanthes sp., and assemblage composition was influenced by overlying water turbidity (manual or biogenic) rather than direct infaunal influences such as grazing. Publisher PDF

Ecosystem engineering species create, modify, and/or maintain the characteristics of the environment. The polychaete Phragmatopoma caudata builds large sand reefs in the intertidal region of the Brazilian coast with high structural complexity, favoring the increase of diversity and interactions among the species associated. However, there are no studies concerning the association of polychaetes with crustacean macrofauna in the northeastern Brazil ecoregion, leaving an information gap on baseline biodiversity. Our aim was to analyze the effect of P. caudata colonies (PC) on the local diversity of macrocrustaceans compared to the rocky shore (RS) microhabitat. Monthly collections were carried out in low tide from September 2015 to August 2016 on 10 × 10 m quadrants for fauna and environmental variables (temperature and salinity) samples. In each microhabitat, the capture effort was two hours by two researchers. We collected 3,390 individuals, 60% associated with the colonies of PC and 40% with the RS. The PC obtained higher Shannon diversity, Pielou evenness and species richness coupled with milder water temperature and salinity conditions (minor air exposure during tide), compared to the RS that obtained greater species dominance and more extreme abiotic conditions (major air exposure). The Porcellanidae family stood out because all its species were highly abundant and had high occurrence in the colonies. The tropical Brazil porcelain crab Pachycheles greeleyi was dominant in both microhabitats (major dominance in PC). The structural complexity in the reefs of PC promoted higher availability of niches for the species, as more shelter for the resident species and refugium for temporary species with preference for more complex microhabitats. Conservation managers should prioritize the health of these colonies and subsequent species that constitute important ecosystemic and fishery resources.

Biogenic reefs constructed by the tube-building ecosystem engineer Lanice conchilega (Terrebilidae, Polychaeta) have profound structuring impacts on the benthic environment in that they alter the biogeochemical and physical properties of the sediment. This study provides new insights into the functioning and effects on food webs of L. conchilega reefs in intertidal sediments using linear inverse models to quantify the carbon flows in the food webs in the presence and absence of the tubeworm. The inverse food web models were based on an empirical dataset from 2 study sites, which provided biomass and stable isotope data, and information on general physiological constraints from the literature. Results of the model showed that the carbon input into reef food webs (mean ± SE; 191 ± 50 mmol C m -2 d -1 ) is ca. 40 times higher compared to bare sand areas (5 ± 2 mmol C m -2 d -1 ) and is mainly derived from organic matter (OM) in the water column. Most of the OM input towards these reefs is consumed by suspension-feeding macrofauna, particularly L. conchilega ; however, the worm is not an important source of carbon for other macrofaunal organisms. The ratio of OM input to primary production indicates that the OM needs to be produced in an area at least 15 times larger than the reef area, demonstrating significant OM ‘focussing’ within the reef food web. The reef structures created by L. conchilega act as a trap for OM, resulting in an overall higher macrofaunal biomass and much more diverse food webs than in the absence of the tubeworm.

Niche construction refers to the modification of selective environments by organisms. Theoretical and empirical studies of niche construction are increasing in importance as foci in evolutionary ecology. This special edition presents theoretical and empirical research that illustrates the significance of niche construction to the field. Here we set the scene for the following papers by (1) discussing the history of niche construction research, (2) providing clear definitions that distinguish niche construction from related concepts such as ecosystem engineering and the extended phenotype, (3) providing a brief summary of the findings of niche construction research, (4) discussing the contribution of niche construction and ecological inheritance to (a) expanded notions of inheritance, and (b) the extended evolutionary synthesis, and (5) briefly touching on some of the issues that underlie the controversies over niche construction. Publisher PDF

Physical properties, distribution, and abundance of natural hard substrates are important variables modulating the potential distribution of sessile aquatic species. In this study, we analyze the effects of the geological origin of different rock types common in intertidal environments of Argentina on the recruitment success of the nonindigenous Pacific oyster Crassostreagigas, accounting for spatial and interannual variation. A series of experiments showed that although recruitment occurs on all of the five most widespread hard substrates in the region (i.e., pelitic mudstone, limestone, conglomeradic sabulitic sandstone, gray sandstone, and volcanic rock) it is significantly higher on pelitic mudstone. Accounting for the geographic distribution of these substrate types along the coast of Argentina, it is concluded that the Valdés Peninsula and central San Jorge Gulf areas, where pelitic mudstone outcrops are the dominant intertidal hard substrate, are the regions with highest potential for C. gigas intertidal reef formation. Pelitic mudstone displayed the highest mean values of specific heat and porosity as well as high values of luminosity. Fil: Carrasco, Mauro Fabián. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Tecnología E Innovación Productiva del Chubut; Argentina. Universidad de Chubut; Argentina Fil: Venerus, Leonardo Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: Weiler, Nilda Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina Fil: Baron, Pedro Jose. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina

While positive interactions have been well documented in plant and sessile benthic marine communities, their role in structuring mobile animal communities and underlying mechanisms has been less explored. Using field removal experiments, we demonstrated that a large vertebrate herbivore (cattle; Bos tarurs ) and a much smaller invertebrate (ants; Lasius spp.), the two dominant animal taxa in a semi-arid grassland in Northeast China, facilitate each other. Cattle grazing led to higher ant mound abundance compared with ungrazed sites, while the presence of ant mounds increased the foraging of cattle during the peak of the growing season. Mechanistically, these reciprocal positive effects were driven by habitat amelioration and resource (food) enhancement by cattle and ants (respectively). Cattle facilitated ants, probably by decreasing plant litter accumulation by herbivory and trampling, allowing more light to reach the soil surface leading to microclimatic conditions that favour ants. Ants facilitated cattle probably by increasing soil nutrients via bioturbation, increasing food (plant) biomass and quality (nitrogen content) for cattle. Our study demonstrates reciprocal facilitative interactions between two animal species from phylogenetically very distant taxa. Such reciprocal positive interactions may be more common in animal communities than so far assumed, and they should receive more attention to improve our understanding of species coexistence and animal community assembly.

Habitat forming ‘ecosystem engineers’ such as kelp species create complex habitats that support biodiverse and productive communities. Studies of the resilience and stability of ecosystem engineers have typically focussed on the role of external factors such as disturbance. However, their population dynamics are also likely to be influenced by internal processes, such that the environmental modifications caused by engineer species feedback to affect their own demography (e.g. recruitment, survivorship). In numerous regions globally, kelp forests are declining and experiencing reductions in patch size and kelp density. To explore how resilience and stability of kelp habitats is influenced by this habitat degradation, we created an array of patch reefs of various sizes and supporting adult Ecklonia radiata kelp transplanted at different densities. This enabled testing of how sub-canopy abiotic conditions change with reductions in patch size and adult kelp density, and how this influenced demographic processes of microscopic and macroscopic juvenile kelp. We found that ecosystem engineering by adult E. radiata modified the environment to reduce sub-canopy water flow, sedimentation, and irradiance. However, the capacity of adult kelp canopy to engineer abiotic change was dependent on patch size, and to a lesser extent, kelp density. Reductions in patch size and kelp density also impaired the recruitment, growth and survivorship of microscopic and macroscopic juvenile E. radiata, and even after the provisioning of established juveniles, demographic processes were impaired in the absence of sufficient adult kelp. These results are consistent with the hypothesis that ecosystem engineering by adult E. radiata facilitates development of juvenile conspecifics. Habitat degradation seems to impair the ability of E. radiata to engineer abiotic change, causing breakdown of positive intraspecific feedback and collapse of demographic functions, and overall, leading to reductions in ecosystem stability and resilience well before local extirpation.

The twig-girdler beetle Oncideres albomarginata chamela (Chemsak and Giesbert) (Cerambycidae: Lamiinae) detaches branches of Spondias purpurea L. (Sapindales: Anacardiaceae) that fall on the forest floor or remain suspended on vegetation. Many wood-boring beetles also oviposit in these branches and larval development creates cavities that are abandoned when the adults emerge. The objective of this study was to evaluate the role of wood-boring beetles as facilitators by creating new habitats for arthropods, and test for vertical stratification and temporal variation of arthropods associated with S. purpurea branches that were previously engineered by O. albomarginata chamela in a tropical dry forest (TDF) in Jalisco, Mexico. In order to determine the effects of vertical strata and seasons on branch colonization by arthropods, we placed 60 branches on the forest floor (ground stratum) and 60 were placed in trees (vegetation stratum) from February to April (dry season), and from August to October 2016 (rainy season), for 240 branch samples in total. We collected 8,008 arthropods, which included 7,753 ants (14 species) and 255 nonsocial arthropods (80 species) from 13 different orders. We observed a greater arthropod abundance in the branches in the vegetation stratum in the dry season compared with the rainy season, whereas the richness and abundance of arthropods in the ground stratum were greater in the rainy season compared with the dry season. We concluded that wood-boring beetles are important habitat facilitators for arthropods, and that the vertical position of branches and the seasonal variations in TDFs differently affect the colonization of the abandoned cavities by arthropods.

The accumulation of the widely-used antibacterial and antifungal compound triclosan (TCS) in freshwaters raises concerns about the impact of this harmful chemical on the biofilms that are the dominant life style of microorganisms in aquatic systems. However, investigations to-date rarely go beyond effects at the cellular, physiological or morphological level. The present paper focuses on bacterial biofilms addressing the possible chemical impairment of their functionality, while also examining their substratum stabilization potential as one example of an important ecosystem service. The development of a bacterial assemblage of natural composition – isolated from sediments of the Eden Estuary (Scotland, UK) – on non-cohesive glass beads (