Night-time lighting alters the composition of marine epifaunal communities

Marine benthic communities face multiple anthropogenic pressures that compromise the future of some of the most biodiverse and functionally important ecosystems in the world. Yet one of the pressures these ecosystems face, night-time lighting, remains unstudied. Light is an important cue in guiding the settlement of invertebrate larvae, and altering natural regimes of nocturnal illumination could modify patterns of recruitment among sessile epifauna. We present the first evidence of night-time lighting changing the composition of temperate epifaunal marine invertebrate communities. Illuminating settlement surfaces with white light-emitting diode lighting at night, to levels experienced by these communities locally, both inhibited and encouraged the colonization of 39% of the taxa analysed, including three sessile and two mobile species. Our results indicate that ecological light pollution from coastal development, shipping and offshore infrastructure could be changing the composition of marine epifaunal communities.     

空间和环境因子对黄河口自然和淡水恢复湿地底栖动物群落的差异影响

生物多样性的形成和维持机制是生态学研究的核心问题,其中环境和空间因子在群落构建中的相对重要性是生态学家面临的重要挑战。为探究黄河口湿地底栖动物群落的关键影响因子,及环境和空间因子对底栖动物群落结构的相对调控作用。于2017年10月与2018年5月对黄河口湿地32个样点（淡水恢复湿地19个和自然湿地13个）的底栖动物和水体理化指标进行采集分析。非度量多维标度排序（NMDS）结果显示,黄河口淡水恢复湿地和自然湿地的底栖动物群落结构显著不同。典范对应分析（CCA）表明,影响淡水恢复湿地底栖动物群落结构的环境因子主要为电导率、盐度和氧化还原电位;而自然湿地底栖动物群落结构主要受pH和无机碳的影响;盐度是两类湿地底栖动物群落组成差异的关键因子。变差分解（VPA）结果显示,环境过滤对淡水恢复湿地底栖动物群落起主导作用;在自然湿地中,空间因子对底栖动物群落具有主要的调控作用,同时环境和空间因子的相互作用也至关重要。本研究明确了黄河口的自然和恢复湿地中环境和空间因素对底栖动物群落特征的相对作用,对黄河三角洲河口湿地中生物多样性的保护和生态系统管理提供参考。     

Dry and wet periods drive rapid shifts in community assembly in an estuarine ecosystem

The impacts of changing climate regimes on emergent processes controlling the assembly of ecological communities remain poorly understood. Human alterations to the water cycle in the western United States have resulted in greater interannual variability and more frequent and severe extremes in freshwater flow. The specific mechanisms through which such extremes and climate regime shifts may alter ecological communities have rarely been demonstrated, and baseline information on current impacts of environmental variation is widely lacking for many habitats and communities. Here, we used observations and experiments to show that interannual variation in winter salinity levels in San Francisco Bay controls the mechanisms determining sessile invertebrate community composition during the following summer. We found consistent community changes in response to decadal‐scale dry and wet extremes during a 13‐year period, producing strikingly different communities. Our results match theoretical predictions of major shifts in species composition in response to environmental forcing up to a threshold, beyond which we observed mass mortality and wholesale replacement of the former community. These results provide a window into potential future community changes, with environmental forcing altering communities by shifting the relative influences of the mechanisms controlling species distributions and abundances. We place these results in the context of historical and projected future environmental variation in the San Francisco Bay Estuary.     

Long‐term effects of artificial nighttime lighting and trophic complexity on plant biomass and foliar carbon and nitrogen in a grassland community

The introduction of artificial nighttime lighting due to human settlements and transport networks is increasingly altering the timing, intensity, and spectra of natural light regimes worldwide. Much of the research on the impacts of nighttime light pollution on organisms has focused on animal species. Little is known about the impacts of daylength extension due to outdoor lighting technologies on wild plant communities, despite the fact that plant growth and development are under photoperiodic control. In a five‐year field experiment, artificial ecosystems (“mesocosms”) of grassland communities both alone or in combination with invertebrate herbivores and predators were exposed to light treatments that simulated street lighting technologies (low‐pressure sodium, and light‐emitting diode [LED]‐based white lighting), at ground‐level illuminance. Most of the plant species in the mesocosms did not exhibit changes in biomass accumulation after 5 years of exposure to the light treatments. However, the white LED treatment had a significant negative effect on biomass production in the herbaceous species Lotus pedunculatus. Likewise, the interaction between the white LED treatment and the presence of herbivores significantly reduced the mean shoot/root ratio of the grass species Holcus lanatus. Artificial nighttime lighting had no effect on the foliar carbon or nitrogen in most of the grassland species. Nevertheless, the white LED treatment significantly increased the leaf nitrogen content in Lotus corniculatus in the presence of herbivores. Long‐term exposure to artificial light at night had no general effects on plant biomass responses in experimental grassland communities. However, species‐specific and negative effects of cool white LED lighting at ground‐level illuminance on biomass production and allocation in mixed plant communities are suggested by our findings. Further studies on the impacts of light pollution on biomass accumulation in plant communities are required as these effects could be mediated by different factors, including herbivory, competition, and soil nutrient availability.     

Influence of microclimate and species interactions on the composition of plant and invertebrate communities in alpine northern Norway

We assessed the effects of both biotic processes and abiotic factors on the community composition of vascular plant species and invertebrates at a site in northern Norway. Plant species were assigned to functional (woody versus herbaceous) and biogeographic (boreal versus alpine) groups. Invertebrate species were classified as either herbivore or predator. When species interactions and effects of the abiotic environment were partitioned, boreal species appeared to influence the distribution of alpine species and woody species the distribution of herbaceous species. Analysis of partial correlations indicated that facilitation was the dominant mode of interaction between the two pairs of plant groups. Among abiotic factors, the thermal environment probably influenced all components of the plant and invertebrate communities, except for predatory invertebrates, and wind appeared important in determining the composition of woody and alpine components of the plant community but not the herbaceous component. The composition of the boreal component of the plant community apparently influenced the composition of all invertebrate communities, except for predatory invertebrates. The composition of the woody component of the plant community influenced the composition of both herbivore and predator communities. The alpine plant-community composition influenced predatory invertebrate community composition. Woody plant community composition influenced the composition of both herbivore and predator communities. Our analytic approach, based on two kinds of structural equation models (d-separation and path analysis), provides a useful method for identifying the biotic as well as abiotic factors that influence community structure.     

The ecological impact of city lighting scenarios: exploring gap crossing thresholds for urban bats

As the global population urbanizes, dramatic changes are expected in city lighting and the urban form, which may threaten the functioning of urban ecosystems and the services they deliver. However, little is known about the ecological impact of lighting in different urban contexts. Movement is an important ecological process that can be disrupted by artificial lighting. We explored the impact of lighting on gap crossing for Pipistrellus pipistrellus, a species of bat (Chiroptera) common within UK cities. We aimed to determine whether the probability of crossing gaps in tree cover varied with crossing distance and lighting level, through stratified field surveys. We then used the resulting data on barrier thresholds to model the landscape resistance due to lighting across an entire city and explored the potential impact of scenarios for future changes to street lighting. The level of illumination required to create a barrier effect reduced as crossing distance increased. For those gaps where crossing was recorded, bats selected the darker parts of gaps. Heavily built parts of the case study city were associated with large and brightly lit gaps, and spatial models indicate movement would be highly restricted in these areas. Under a scenario for brighter street lighting, the area of accessible land cover was further reduced in heavily built parts of the city. We believe that this is the first study to demonstrate how lighting may create resistance to species movement throughout an entire city. That connectivity in urban areas is being disrupted for a relatively common species raises questions about the impacts on less tolerant groups and the resilience of bat communities in urban centres. However, this mechanistic approach raises the possibility that some ecological function could be restored in these areas through the strategic dimming of lighting and narrowing of gaps.     

Meta‐community theory and stream restoration: evidence that spatial position constrains stream invertebrate communities in a mine impacted landscape

Mining activities, particularly acid mine drainage, often result in adverse effects on stream diversity and ecosystem functioning, and increased concern about these effects has generated a focus on restoration of mine‐impacted waterways. However, many stream restoration projects have not led to increased stream diversity and ecological recovery. One reason for this failure may be that restoration practitioners focus on local environmental conditions and fail to consider the importance of dispersal as a driver of stream invertebrate composition. To test this hypothesis, we used a meta‐community analysis to compare the influence of the local stream conditions with the regional supply of colonists. Invertebrate communities and physico‐chemical conditions were sampled in 37 streams across a mine‐impact gradient on the Stockton Plateau, West Coast of New Zealand's South Island. We found that pH, temperature, dissolved metals, and sediment significantly influenced invertebrate community composition. Furthermore, the spatial location of streams was a good predictor of stream diversity and invertebrate communities, independent of local environmental conditions. This result indicates an important role for regional dispersal barriers in determining stream invertebrate communities. Consequently, consideration of both the locations and strategic preservation of future colonist source streams and potential dispersal barriers during mine planning would enhance post‐mining restoration.     

Diel patterning in the bacterial community associated with the sea anemone Nematostella vectensis

Microbes can play an important role in the physiology of animals by providing essential nutrients, inducing immune pathways, and influencing the specific species that compose the microbiome through competitive or facilitatory interactions. The community of microbes associated with animals can be dynamic depending on the local environment, and factors that influence the composition of the microbiome are essential to our understanding of how microbes may influence the biology of their animal hosts. Regularly repeated changes in the environment, such as diel lighting, can result in two different organismal responses: a direct response to the presence and absence of exogenous light and endogenous rhythms resulting from a molecular circadian clock, both of which can influence the associated microbiota. Here, we report how diel lighting and a potential circadian clock impacts the diversity and relative abundance of bacteria in the model cnidarian Nematostella vectensis using an amplicon‐based sequencing approach. Comparisons of bacterial communities associated with anemones cultured in constant darkness and in light:dark conditions revealed that individuals entrained in the dark had a more diverse microbiota. Overall community composition showed little variation over a 24‐hr period in either treatment; however, abundances of individual bacterial OTUs showed significant cycling in each treatment. A comparative analysis of genes involved in the innate immune system of cnidarians showed differential expression between lighting conditions in N. vectensis, with significant up‐regulation during long‐term darkness for a subset of genes. Together, our studies support a hypothesis that the bacterial community associated with this species is relatively stable under diel light conditions when compared with static conditions and that particular bacterial members may have time‐dependent abundance that coincides with the diel photoperiod in an otherwise stable community.     

The influence of range‐wide plant genetic variation on soil invertebrate communities

Plant genetic variation can have far‐reaching effects on associated communities and ecosystems. Heritable variation in ecologically relevant plant traits is often non‐randomly distributed across a species’ range and can exhibit geographic clines. In the event of range expansions and migration, previously unfamiliar genotypes may have large impacts on resident communities and ecosystems due to the introduction of novel and heritable phenotypic variation. Here we test the hypothesis that geographic origin of a focal plant genotype has effects on belowground invertebrate communities using a common garden field experiment. We sampled soil invertebrates from 103 Oenothera biennis genotypes, which were collected from across the species’ range and planted into a common garden field experiment at the northern range limit. We enumerated 24 000 individuals from 190 morphospecies and found that the diversity, abundance, and composition of soil invertebrate communities varied greatly among plant genotypes. Despite strong effects of plant genotype, we found few genetic correlations between plant traits and soil invertebrate community variables. However, herbivore damage was strongly related to variation in the soil invertebrate community. Geographic origin of plant genotypes had at most a weak effect on belowground communities. We speculate that predicting the extended effects of population movement on associated communities will require detailed knowledge of the trait variation occurring within focal species across particular environmental gradients.     

Potential Biological and Ecological Effects of Flickering Artificial Light

Organisms have evolved under stable natural lighting regimes, employing cues from these to govern key ecological processes. However, the extent and density of artificial lighting within the environment has increased recently, causing widespread alteration of these regimes. Indeed, night-time electric lighting is known significantly to disrupt phenology, behaviour, and reproductive success, and thence community composition and ecosystem functioning. Until now, most attention has focussed on effects of the occurrence, timing, and spectral composition of artificial lighting. Little considered is that many types of lamp do not produce a constant stream of light but a series of pulses. This flickering light has been shown to have detrimental effects in humans and other species. Whether a species is likely to be affected will largely be determined by its visual temporal resolution, measured as the critical fusion frequency. That is the frequency at which a series of light pulses are perceived as a constant stream. Here we use the largest collation to date of critical fusion frequencies, across a broad range of taxa, to demonstrate that a significant proportion of species can detect such flicker in widely used lamps. Flickering artificial light thus has marked potential to produce ecological effects that have not previously been considered.     

The Impact of Hydrological Restoration on Benthic Aquatic Invertebrate Communities in a New Zealand Wetland

Drainage is a major disturbance affecting wetlands, as drains lower water tables and convert lentic habitats to lotic ones. Consequently, invertebrate communities in drained wetlands are likely to differ from those in unimpacted wetlands. This study investigated the effect of hydrological restoration on invertebrate communities in small drains in a New Zealand fen. Invertebrates were collected over 4 summers from 10 drains within the wetland, one of which was blocked as part of a restoration program. The sampling protocol thus represented a Before‐After Control‐Impact experiment. Invertebrate community composition varied over the 4 years, but variability was greatest in the manipulated drain before and after it was blocked. Relative abundance of the amphipod Paraleptamphopus decreased after blockage, whereas those of the midges Chironomus zelandicus and Tanypodinae increased. Relative abundances of these taxa in control sites were unchanged. Hydraulic restoration thus had a demonstrable impact on the invertebrate communities. The invertebrate community of the blocked drain was compared to that of natural wetlands in undisturbed catchments. Similarity was very low prior to drain blockage, but increased following drain blockage. Invertebrate communities in the restored drain were more similar to those of low pH wetlands than high pH wetlands. Given the goal of restoring the communities to those similar to natural conditions, this was a beneficial result. These results, coupled with studies that showed a decline in the cover of alien pasture grasses around the blocked drain, suggest that drain blockage represents a cost‐effective way of restoring wetland plant and aquatic invertebrate communities, especially where connectivity allows for the natural recruitment of these organisms into restored areas.     

Invertebrate community response to fire and rodent activity in the Mojave and Great Basin Deserts

Recent increases in the frequency and size of desert wildfires bring into question the impacts of fire on desert invertebrate communities. Furthermore, consumer communities can strongly impact invertebrates through predation and top‐down effects on plant community assembly. We experimentally applied burn and rodent exclusion treatments in a full factorial design at sites in both the Mojave and Great Basin deserts to examine the impact that fire and rodent consumers have on invertebrate communities. Pitfall traps were used to survey invertebrates from April through September 2016 to determine changes in abundance, richness, and diversity of invertebrate communities in response to fire and rodent treatments. Generally speaking, rodent exclusion had very little effect on invertebrate abundance or ant abundance, richness or diversity. The one exception was ant abundance, which was higher in rodent access plots than in rodent exclusion plots in June 2016, but only at the Great Basin site. Fire had little effect on the abundances of invertebrate groups at either desert site, with the exception of a negative effect on flying‐forager abundance at our Great Basin site. However, fire reduced ant species richness and Shannon's diversity at both desert sites. Fire did appear to indirectly affect ant community composition by altering plant community composition. Structural equation models suggest that fire increased invasive plant cover, which negatively impacted ant species richness and Shannon's diversity, a pattern that was consistent at both desert sites. These results suggest that invertebrate communities demonstrate some resilience to fire and invasions but increasing fire and spread of invasive due to invasive grass fire cycles may put increasing pressure on the stability of invertebrate communities.     

Outcomes of fungal interactions are determined by soil invertebrate grazers

Saprotrophic fungal community composition, determined by the outcome of competitive mycelial interactions, is one of the many key factors affecting soil nutrient mineralisation and decomposition rates. Fungal communities are not generally predicted to be regulated by top-down factors, such as predation, but rather by bottom-up factors, including resource availability. We show that invertebrate grazers can exert selective pressures on fungal decomposer communities in soil, reversing the outcomes of competitive interactions. By feeding selectively on the cord-forming fungus Resinicium bicolor, isopods prevented the competitive exclusion of Hypholoma fasciculare and Phanerochaete velutina in soil and wood. Nematode populations also reversed the outcomes of competitive interactions by stimulating growth of less competitive fungi. These represent two opposing mechanisms by which soil fauna may influence fungal community composition and diversity. Factors affecting soil invertebrate communities will have direct consequences for fungal-mediated nutrient cycling in woodland soils.     

Pollination by nocturnal Lepidoptera,and the effects of light pollution: a review

1. Moths (Lepidoptera) are the major nocturnal pollinators of flowers. However, their importance and contribution to the provision of pollination ecosystem services may have been under‐appreciated. Evidence was identified that moths are important pollinators of a diverse range of plant species in diverse ecosystems across the world. 2. Moth populations are known to be undergoing significant declines in several European countries. Among the potential drivers of this decline is increasing light pollution. The known and possible effects of artificial night lighting upon moths were reviewed, and suggest how artificial night lighting might in turn affect the provision of pollination by moths. The need for studies of the effects of artificial night lighting upon whole communities of moths was highlighted. 3. An ecological network approach is one valuable method to consider the effects of artificial night lighting upon the provision of pollination by moths, as it provides useful insights into ecosystem functioning and stability, and may help elucidate the indirect effects of artificial light upon communities of moths and the plants they pollinate. 4. It was concluded that nocturnal pollination is an ecosystem process that may potentially be disrupted by increasing light pollution, although the nature of this disruption remains to be tested.     

Grassland invertebrate assemblages in managed landscapes: Effect of host plant and microhabitat architecture

Abstract Grasslands are often considered as two‐dimensional habitats rather than complex, multilayered habitats. However, native grasslands are complex habitats, with multiple layers of annual and perennial grasses, sedges, shrubs and mosses. Vegetation complexity, including plant type, quality and three‐dimensional structure is important for providing a variety of food and habitat resources for insects. Grazing by domestic livestock can affect these processes through the loss or fragmentation of habitats, as well as altering the vertical and horizontal vegetation structure. This study aimed to investigate the role of host plants and microhabitat architecture for determining foliage invertebrate assemblages. Different plant species supported distinct invertebrate assemblages and less complex host plants supported fewer invertebrate individuals and species. Manipulations of plant architecture changed the species composition of invertebrates, with most species found in more complex vegetation. This study illustrates the importance of host diversity and pasture complexity for invertebrate communities. Management practices that encourage a heterogeneous environment with diverse and structurally complex pastures should also sustain a more diverse and functional invertebrate assemblage.     

Habitat‐specific invertebrate responses to hydrological variability,anthropogenic flow alterations,and hydraulic conditions

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Invertebrate DNA metabarcoding reveals changes in communities across mine site restoration chronosequences

Invertebrate biomonitoring can reveal crucial information about the status of restoration projects; however, it is routinely underused because of the high level of taxonomic expertise and resources required. Invertebrate DNA metabarcoding has been used to characterize invertebrate biodiversity but its application in restoration remains untested. We use DNA metabarcoding, a new approach for restoration assessment, to explore the invertebrate composition from pitfall traps at two mine site restoration chronosequences in southwestern Australia. Invertebrates were profiled using two cytochrome oxidase subunit 1 assays to investigate invertebrate biodiversity. The data revealed differences between invertebrate communities at the two mines and between the different age plots of the chronosequences. Several characteristic taxa were identified for each age within the chronosequence, including springtails within the youngest sites (Order: Collembola) and millipedes within the oldest and reference sites (Order: Julida). This study facilitates development of a molecular “toolkit” for the monitoring of ecological restoration projects. We suggest that a metabarcoding approach shows promise in complementing current monitoring practices that rely on alpha taxonomy.     

Community Associations of Chalk Grassland Leafhoppers (Hemiptera: Auchenorrhyncha): Conclusions for Habitat Conservation

Due to their confinement to specific hostplants or restricted habitat types, Auchenorrhyncha have the potential to make suitable biological indicators to measure the quality of chalk grassland under different management practices for nature conservation. The Auchenorrhyncha data from a study designed to identify the factors influencing the invertebrate diversity of chalk grasslands in southern England was used to evaluate the potential use of this group of insects as biological indicators. Between 1998 and 2002 altogether 81 chalk grassland sites were sampled. Vegetation structure and composition were recorded, and Auchenorrhyncha were sampled at each site on three occasions in each of two seasons using a ‘Vortis’ suction sampler. Auchenorrhyncha assemblages were then linked to the different grassland plant communities occurring on chalk soils according to the British National Vegetation Classification (NVC). Altogether 96 Auchenorrhyncha species were recorded during the study. Using data on the frequency and dominance of species, as is commonly done for plant communities, it was possible to identify the preferential and differential species of distinct Auchenorrhyncha assemblages. Significant differences between the Auchenorrhyncha assemblages associated with the various chalk grassland plant communities of the NVC were observed down to a level of sub-communities. We conclude that data on Auchenorrhyncha assemblages can provide valuable information for the setting of conservation management priorities, where data on floristic composition alone may not be sufficient, providing additional information on aspects of vegetation structure and condition.     

Assessment of Littoral Benthic Invertebrate Communities at the Land–Water Interface in Lakes Recovering from Severe Acid- and Metal-Damage

Benthic invertebrate communities within confluence sites, or areas of sediment deposition, are shaped by the input of catchment products including coarse woody debris, organic and inorganic particulates, and contaminants, but these sites also appear to be potential “hotspots” where recolonization of severely damaged ecosystems begins. Two species of leaf packs and a sweep netting technique were used to assess benthic invertebrate communities across a gradient of 14 confluence sites in 3 recovering lakes near the copper and nickel smelters in Sudbury, Canada. Environmental variables including delta habitat composition, delta area and length, and composition of deposited materials were used to detect spatial patterns in littoral benthic invertebrate communities. Benthic invertebrate community relationships with water chemistry were also assessed. Partial redundancy analysis (pRDA) showed that all sampling methods detected similar gradients of increasing invertebrate community richness and diversity as area and length of the sediment delta and the surface organic matter abundance increased. Two-way nested ANOVAs showed significant differences (p < .05) in taxa richness and diversity metrics among sites. Of the three methods, the benthic invertebrate community measurements from the birch leaf packs provided the strongest correlations with measures of organic matter inputs or habitat characteristics of the confluence zones. These correlations suggest that tree planting in riparian areas, or organic matter or macrophyte additions to littoral zones, may enhance littoral benthic invertebrate richness and diversity in acid and metal damaged lakes.     

How do patch quality and spatial context affect invertebrate communities in a natural moss microlandscape?

Globally, moss associated invertebrates remain poorly studied and it is largely unknown to what extent their diversity is driven by local environmental conditions or the landscape context. Here, we investigated small scale drivers of invertebrate communities in a moss landscape in a temperate forest in Western Europe. By comparing replicate quadrats of 5 different moss species in a continuous moss landscape, we found that mosses differed in invertebrate density and community composition. Although, in general, richness was similar among moss species, some invertebrate taxa were significantly linked to certain moss species. Only moss biomass and not relative moisture content could explain differences in invertebrate densities among moss species. Second, we focused on invertebrate communities associated with the locally common moss species Kindbergia praelonga in isolated moss patches on dead tree trunks to look at effects of patch size, quality, heterogeneity and connectivity on invertebrate communities. Invertebrate richness was higher in patches under closed canopies than under more open canopies, presumably due to the higher input of leaf litter and/or lower evaporation. In addition, increased numbers of other moss species in the same patch seemed to promote invertebrate richness in K. praelonga, possibly due to mass effects. Since invertebrate richness was unaffected by patch size and isolation, dispersal was probably not limiting in this system with patches separated by tens of meters, or stochastic extinctions may be uncommon. Overall, we conclude that invertebrate composition in moss patches may not only depend on local patch conditions, in a particular moss species, but also on the presence of other moss species in the direct vicinity.