Ecological Players Research Articles

Disruption of pollination by herbivores is rescued by nectar yeasts

Abstract Attracting pollinators to achieve successful reproduction is a key challenge for wild plants that may be disturbed by complex multispecies interactions in nature. Pairwise plant–pollinator interactions have traditionally been studied for decades, while ignoring other ecological players may obscure a comprehensive understanding on how plants recruit partners or combat enemies in the pollination process. Hence, integrated studies considering the inherent complexity of ecological interactions are needed, which may open up new perspectives for deciphering intricate systems and predicting ecological consequences. We examined the presence of nectar yeasts using a combination of high‐throughput sequencing, cultivation and microscopy and quantified floral herbivory by evaluating the incidence of flowers with visible holes in 13 natural populations of Iris bulleyana in the Hengduan Mountains of southwest China during 2017–2022. We combined yeast inoculation and herbivore manipulation treatments to illustrate the isolated and combined impacts of two contrasting nectarivorous organisms, the ascomycetous yeast Metschnikowia reukaufii and adult sawflies, on pollinator visitation and plant reproductive success in two populations. In the lab, we first employed gas chromatography–mass spectrometry to profile the volatile metabolites of yeast‐inoculated nectar relative to control, followed by a behavioural bioassay to test the preference of honeybees for these microbial volatiles. Yeasts commonly inhabited floral nectar and insect herbivores frequently bit holes in the perianth tube to consume nectar and nectaries. Nectar yeasts indirectly facilitated plant reproduction through increased pollinator visits, probably because of microbial metabolism as honeybees preferred nectar volatiles produced by yeasts in behavioural bioassays. Insect herbivores increased total floral visits but reduced legitimate visits by inducing legitimate‐to‐robbing behavioural changes of honeybees, thus leading to lower seed production. The detrimental effect of herbivory was mitigated by the presence of yeasts, which diminished the relative proportion of robbing visits and thereby ‘rescued’ flowers from reproductive failure. Synthesis: Overall, we found contrasting effects of non‐pollinator species, including both micro‐ and macro‐organisms, on plant–pollinator interactions in a biodiversity hotspot, where pollination deficit may be a ubiquitous phenomenon. Our findings suggest that both microbial and herbivory effects are likely to be important in explaining the exact causes of pollen limitation in species‐rich areas, highlighting the biological context dependence of species interactions in natural ecosystems.

Habitat use of five sympatric predatory reef fishes at a remote island in the south-western Atlantic.

Density-dependent mechanisms and habitat use are important drivers of marine spatial distribution in complex ecosystems such as coral or rocky reefs. In the last decade, a few studies have assessed habitat use by reef fishes in nearshore and coastal environments along the Brazilian coast. Serranidae (groupers and sea basses) are regarded as excellent models for understanding habitat use patterns due to their diversity, long lifespan, wide distribution, morphological and functional diversity, and behavioural complexity. Their trophic position in the food web, from meso- to top-predators, grants them critical roles as top-down population controllers. Herein, we present the first assessment of habitat use by five sympatric Serranidae in a Brazilian oceanic island, Trindade. The model species selected for this assessment were the coney (Cephalopholis fulva), the rock hind (Epinephelus adscensionis), the greater soapfish (Rypticus saponaceus), the Creole-fish (Paranthias furcifer) and the hybrid between C. fulva and P. furcifer. Our findings revealed that the species showed specific associations with topographic characteristics related to shelter from predation, reproduction and feeding. Habitat use in Trindade was similar to that observed in nearshore coastal environments (where the hybrid is absent). The present work contributes to the knowledge of habitat use and niche partitioning among key species, which is a valuable tool to subsidize effective conservation initiatives such as designing marine protected areas focusing on the behaviour and habitat use of key ecological players.

Resolving the Microalgal Gene Landscape at the Strain Level: a Novel Hybrid Transcriptome of Emiliania huxleyi CCMP3266.

Microalgae are key ecological players with a complex evolutionary history. Genomic diversity, in addition to limited availability of high-quality genomes, challenge studies that aim to elucidate molecular mechanisms underlying microalgal ecophysiology. Here, we present a novel and comprehensive transcriptomic hybrid approach to generate a reference for genetic analyses and resolve the microalgal gene landscape at the strain level. The approach is demonstrated for a strain of the coccolithophore microalga Emiliania huxleyi, which is a species complex with considerable genome variability. The investigated strain is commonly studied as a model for algal-bacterial interactions and was therefore sequenced in the presence of bacteria to elicit the expression of interaction-relevant genes. We applied complementary PacBio Iso-Seq full-length cDNA and poly(A)-independent Illumina total RNA sequencing, which resulted in a de novo-assembled, near-complete hybrid transcriptome. In particular, hybrid sequencing improved the reconstruction of long transcripts and increased the recovery of full-length transcript isoforms. To use the resulting hybrid transcriptome as a reference for genetic analyses, we demonstrate a method that collapses the transcriptome into a genome-like data set, termed "synthetic genome" (sGenome). We used the sGenome as a reference to visually confirm the robustness of the CCMP3266 gene assembly, to conduct differential gene expression analysis, and to characterize novel E. huxleyi genes. The newly identified genes contribute to our understanding of E. huxleyi genome diversification and are predicted to play a role in microbial interactions. Our transcriptomic toolkit can be implemented in various microalgae to facilitate mechanistic studies on microalgal diversity and ecology. IMPORTANCE Microalgae are key players in the ecology and biogeochemistry of our oceans. Efforts to implement genomic and transcriptomic tools in laboratory studies involving microalgae suffer from the lack of published genomes. In the case of coccolithophore microalgae, the problem has long been recognized; the model species Emiliania huxleyi is a species complex with genomes composed of a core and a large variable portion. To study the role of the variable portion in niche adaptation, and specifically in microbial interactions, strain-specific genetic information is required. Here, we present a novel transcriptomic hybrid approach, and generated strain-specific genome-like information. We demonstrate our approach on an E. huxleyi strain that is cocultivated with bacteria. By constructing a "synthetic genome," we generated comprehensive gene annotations that enabled accurate analyses of gene expression patterns. Importantly, we unveiled novel genes in the variable portion of E. huxleyi that play putative roles in microbial interactions.

Lead Drives Complex Dynamics of a Conjugative Plasmid in a Bacterial Community.

Plasmids carrying metal resistance genes (MRGs) have been suggested to be key ecological players in the adaptation of metal-impacted microbial communities, making them promising drivers of bio-remediation processes. However, the impact of metals on plasmid-mediated spread of MRGs through selection, plasmid loss, and transfer is far from being fully understood. In the present study, we used two-member bacterial communities to test the impact of lead on the dispersal of the IncP plasmid pKJK5 from a Pseudomonas putida KT2440 plasmid donor and two distinct recipients, Variovorax paradoxus B4 or Delftia acidovorans SPH-1 after 4 and 10 days of mating. Two versions of the plasmid were used, carrying or not carrying the lead resistance pbrTRABCD operon, to assess the importance of fitness benefit and conjugative potential for the dispersal of the plasmid. The spread dynamics of metal resistance conveyed by the conjugative plasmid were dependent on the recipient and the lead concentration: For V. paradoxus, the pbr operon did not facilitate neither lead resistance nor variation in plasmid spread. The growth gain brought by the pbr operon to D. acidovorans SPH-1 and P. putida KT2440 at 1 mM Pb enhanced the spread of the plasmid. At 1.5 mM Pb after 4 days, the proteomics results revealed an oxidative stress response and an increased abundance of pKJK5-encoded conjugation and partitioning proteins, which most likely increased the transfer of the control plasmid to D. acidovorans SPH-1 and ensured plasmid maintenance. As a consequence, we observed an increased spread of pKJK5-gfp. Conversely, the pbr operon reduced the oxidative stress response and impeded the rise of conjugation- and partitioning-associated proteins, which slowed down the spread of the pbr carrying plasmid. Ultimately, when a fitness gain was recorded in the recipient strain, the spread of MRG-carrying plasmids was facilitated through positive selection at an intermediate metal concentration, while a high lead concentration induced oxidative stress with positive impacts on proteins encoding plasmid conjugation and partitioning.

Identification of Reticulitermes Subterranean Termites (Blattodea: Rhinotermitidae) in the Eastern United States Using Inter-Simple Sequence Repeats.

In the eastern United States, there are nine species of subterranean termites in three genera: Reticulitermes (six species), Coptotermes (two species), and Prorhinotermes (one species). These species serve as important ecological players by decomposing cellulose material, and some are important structural pests. Many of these species are difficult to discriminate morphologically and require examining the reproductive or soldier castes, which can be difficult to collect. While some genetic tools have been developed for species identification, they are often expensive and time-consuming. To help facilitate identification, we developed a more cost-effective and rapid genetic method to identify Reticulitermes species by screening 10 PCR primers that amplified inter-simple sequence repeats (ISSRs) in other termite species. From these, one primer was amplified in all five focal Reticulitermes species and contained conserved, species-specific fragments. We further screened this identification method on samples of each species covering a diversity of mitochondrial DNA haplotypes and localities. This identification method utilizing ISSRs can be used to quickly identify five species of Reticulitermes subterranean termites in the eastern United States in a matter of hours, providing a useful technique for pest management as well as future ecological research.

Differing thermal sensitivities in a host–parasitoid interaction: High, fluctuating developmental temperatures produce dead wasps and giant caterpillars

Abstract Insect parasitoids, and the arthropod hosts they consume during development, are important ecological players in almost all environments across the globe. As ectothermic organisms, both parasitoid and host are strongly impacted by environmental temperature. If thermal tolerances differ between host insect and parasitoid, then the outcome of their interaction will be determined by the ambient temperature. As mean temperatures continue to rise and extreme temperatures become more frequent, we must determine the effect of high temperature stress on host–parasitoid systems to predict how they will fare in the face of climate change. The majority of studies conducted on host–parasitoid systems focus on either performance under constant temperature or a fixed metric of thermal tolerance (CTmax) for individual organisms. However, performance at constant temperatures is not predictive of performance under ecologically relevant, fluctuating temperatures and measurements of thermal thresholds provide little information regarding the effects of temperature throughout development. We address this by testing the effects of increasing mean temperature in both constant and fluctuating (±10°C) environments throughout development on the performance of the parasitoid wasp Cotesia congregata and its lepidopteran larval host, Manduca sexta. The growth of M. sexta was influenced by mean temperature, diurnal fluctuations and parasitization status. Caterpillar growth rate increased with increasing mean temperature, but decreased in response to diurnal fluctuations and parasitization by C. congregata wasps. Wasp survival decreased with increasing mean temperature and with diurnal fluctuations. The effect of diurnal fluctuations was stronger at higher mean temperatures. Diurnal fluctuations at our highest mean temperature treatment (30 ± 10°C) resulted in complete wasp mortality, and parasitized hosts displayed abnormal physiology, wherein they failed to exhibit wasp emergence, did not enter the prepupal stage, continued to feed and grew up to twofold larger than a normal, unparasitized caterpillar. Our results indicate hosts and parasitoids in this system have different thermal tolerances during development; the parasitoid wasp suffered complete mortality at a temperature regime that is mildly stressful for the unparasitized caterpillar host species. Our findings suggest C. congregata will suffer more severely under increasing temperatures than M. sexta, with cascading trophic and ecological effects. A free Plain Language Summary can be found within the Supporting Information of this article.

DNA Metabarcoding for the Characterization of Terrestrial Microbiota-Pitfalls and Solutions.

Soil-borne microbes are major ecological players in terrestrial environments since they cycle organic matter, channel nutrients across trophic levels and influence plant growth and health. Therefore, the identification, taxonomic characterization and determination of the ecological role of members of soil microbial communities have become major topics of interest. The development and continuous improvement of high-throughput sequencing platforms have further stimulated the study of complex microbiota in soils and plants. The most frequently used approach to study microbiota composition, diversity and dynamics is polymerase chain reaction (PCR), amplifying specific taxonomically informative gene markers with the subsequent sequencing of the amplicons. This methodological approach is called DNA metabarcoding. Over the last decade, DNA metabarcoding has rapidly emerged as a powerful and cost-effective method for the description of microbiota in environmental samples. However, this approach involves several processing steps, each of which might introduce significant biases that can considerably compromise the reliability of the metabarcoding output. The aim of this review is to provide state-of-the-art background knowledge needed to make appropriate decisions at each step of a DNA metabarcoding workflow, highlighting crucial steps that, if considered, ensures an accurate and standardized characterization of microbiota in environmental studies.

Seaweeds through time: Morphological and ecological analysis of Proterozoic and early Paleozoic benthic macroalgae

Benthic marine macroalgae or seaweeds are key ecological players in oceans today and have been since the Proterozoic. To date, however, morphological and evolutionary patterns for Precambrian macroalgae have been documented only in rather broad terms. To refine our understanding in this critical interval, we updated a dataset of Proterozoic to early Paleozoic noncalcified macroalgal fossils preserved as macroscopic carbonaceous compressions. The data were analyzed using non-parametric multidimensional scaling (NMDS) and functional-form group (FFG) approaches, in order to characterize morphological and ecological evolutionary patterns of these macroalgae. At the broadest scale, the results show progressive increases in thallus size, morphospace range, and aspects of ecological complexity such as canopy heights, surface area/volume ratios, and functional-form groups through time. These trends, however, are not always monotonous. In particular, significant increases in Proterozoic macroalgal morphological diversity and maximum size appear to have occurred in the Neoproterozoic (Tonian and Ediacaran periods, respectively). Analysis of Ediacaran macroalgal assemblages shows that macroalgae broadly follow the Ediacara-like fossil assemblages, with a significant drop in most studied metrics in the terminal Ediacaran stage (~550–539 Ma). The latter event occurs during the Kotlinian crisis experienced by Ediacara-type macro-organisms, highlighting the possibility that this extinction event during the Ediacaran-Cambrian transition affected both macroalgae and Ediacara-type macro-organisms. Our analysis also confirms an Ordovician increase in the morphological and ecological diversity of macroalgae.

Neglected but Potent Dry Forest Players: Ecological Role and Ecosystem Service Provision of Biological Soil Crusts in the Human-Modified Caatinga

Biological soil crusts (biocrusts) have been recognized as key ecological players in arid and semiarid regions at both local and global scales. They are important biodiversity components, provide critical ecosystem services, and strongly influence soil-plant relationships, and successional trajectories via facilitative, competitive, and edaphic engineering effects. Despite these important ecological roles, very little is known about biocrusts in seasonally dry tropical forests. Here we present a first baseline study on biocrust cover and ecosystem service provision in a human-modified landscape of the Brazilian Caatinga, South America's largest tropical dry forest. More specifically, we explored (1) across a network of 34 0.1 ha permanent plots the impact of disturbance, soil, precipitation, and vegetation-related parameters on biocrust cover in different stages of forest regeneration, and (2) the effect of disturbance on species composition, growth and soil organic carbon sequestration comparing early and late successional communities in two case study sites at opposite ends of the disturbance gradient. Our findings revealed that biocrusts are a conspicuous component of the Caatinga ecosystem with at least 50 different taxa of cyanobacteria, algae, lichens and bryophytes (cyanobacteria and bryophytes dominating) covering nearly 10% of the total land surface and doubling soil organic carbon content relative to bare topsoil. High litter cover, high disturbance by goats, and low soil compaction were the leading drivers for reduced biocrust cover, while precipitation was not associated Second-growth forests supported anequally spaced biocrust cover, while in old-growth-forests biocrust cover was patchy. Disturbance reduced biocrust growth by two thirds and carbon sequestration by half. In synthesis, biocrusts increase soil organic carbon (SOC) in dry forests and as they double the SOC content in disturbed areas, may be capable of counterbalancing disturbance-induced soil degradation in this ecosystem. As they fix and fertilize depauperated soils, they may play a substantial role in vegetation regeneration in the human-modified Caatinga, and may have an extended ecological role due to the ever-increasing human encroachment on natural landscapes. Even though biocrusts benefit from human presence in dry forests, high levels of anthropogenic disturbance could threaten biocrust-provided ecosystem services, and call for further, in-depth studies to elucidate the underlying mechanisms.

Mycobiome diversity: high-throughput sequencing and identification of fungi.

Fungi are major ecological players in both terrestrial and aquatic environments by cycling organic matter and channelling nutrients across trophic levels. High-throughput sequencing (HTS) studies of fungal communities are redrawing the map of the fungal kingdom by hinting at its enormous - and largely uncharted - taxonomic and functional diversity. However, HTS approaches come with a range of pitfalls and potential biases, cautioning against unwary application and interpretation of HTS technologies and results. In this Review, we provide an overview and practical recommendations for aspects of HTS studies ranging from sampling and laboratory practices to data processing and analysis. We also discuss upcoming trends and techniques in the field and summarize recent and noteworthy results from HTS studies targeting fungal communities and guilds. Our Review highlights the need for reproducibility and public data availability in the study of fungal communities. If the associated challenges and conceptual barriers are overcome, HTS offers immense possibilities in mycology and elsewhere.

Insight on the bacterial ecology in membrane bioreactor: Operational conditions effect over dominant ecological players

A bench‐scale bioreactor was operated under two different technologies of membrane bioreactor and hybrid moving bed bioreactor‐membrane bioreactor at hydraulic retention time 6–16 h, sludge retention time 6–24 days, and mixed liquor suspended solids 3400–7800 mg L−1. Analyses of their bacterial community structures showed marked differences between the two technologies for global communities but not for dominant phylotypes, and the domination of different bacterial phylotypes for the different operational conditions. Tetrasphaera genus was ubiquitous (1.1%–19.2% relative abundance) in both bioprocesses. Fodinibacter (0.04%–7.75%) was found to positively correlate with other dominant phylotypes, highlighting the relevance of Intrasporangiaceae family in membrane‐based technologies. Oligotypes distribution of dominant phylotypes showed that certain strains were favored at all operational conditions. Linkage with operational conditions determined that the presence/absence of carriers deeply impacted the relative abundance of dominant phylotypes. The results are relevant to discern the effect of operational conditions over bacterial communities in membrane‐based technologies. © 2018 American Institute of Chemical Engineers AIChE J, 65: 536–548, 2019

Environmental drivers influencing stonefly assemblages along a longitudinal gradient in karst lotic habitats

Stoneflies are among the most sensitive aquatic insect taxa and therefore arguably the best indicator of the excellent, i.e. pristine, ecological status of surface streams. Karst habitats are one of the most exciting freshwater habitats in terms of biological-geological interplay. They, in turn, support a biodiversity far superior to surrounding freshwater habitats and hence these habitats are designated as biodiversity hotspots. Our study deals with both of these crucial ecological players. We studied stonefly assemblages, their microhabitat preferences and emergence patterns along a karst oligotrophic hydrosystem. The sampling was conducted monthly from March 2007 to December 2008 using pyramid-type emergence traps set in various habitats and associated microhabitats (e.g. springs, rivers, streams, tufa barriers × moss, angiosperm, cobble, sand, silt substrates). Favorable environmental conditions, such as a wide range of karst habitat types with low water temperature and high oxygen concentration, resulted in high stonefly species richness (31 recorded species). Water temperature and pH had the highest influence on stonefly assemblages. Species richness and diversity decreased in a downstream direction. We recorded a longitudinal shift from crenal-epirhithral to epirhithral-metarhithral assemblages with some hyporhithral and potamal elements. Upstream sites were dominated by shredders, while downstream sites had a higher proportion of gatherers-collectors. Several species showed a significant preference for a specific microhabitat type in accordance with their feeding strategies and food availability. The majority of recorded species exhibited univoltine life cycles slow or fast.

Seasonal rather than spatial variability drives planktonic and benthic bacterial diversity in a microtidal lagoon and the adjacent open sea.

Coastal lagoons are highly productive ecosystems, which are experiencing a variety of human disturbances at increasing frequency. Bacteria are key ecological players within lagoons, yet little is known about the magnitude, patterns and drivers of diversity in these transitional environments. We carried out a seasonal study in the Venice Lagoon (Italy) and the adjacent sea, to simultaneously explore diversity patterns in different domains (pelagic, benthic) and their spatio-temporal variability, and test the role of environmental gradients in structuring assemblages. Community composition differed between lagoon and open sea, and between domains. The dominant phyla varied temporally, with varying trends for the two domains, suggesting different environmental constraints on the assemblages. The percentage of freshwater taxa within the lagoon increased during higher river run-off, pointing at the lagoon as a dynamic mosaic of microbial taxa that generate the metacommunity across the whole hydrological continuum. Seasonality was more important than spatial variability in shaping assemblages. Network analyses indicated more interactions between several genera and environmental variables in the open sea than the lagoon. Our study provides evidences for a temporally dynamic nature of bacterial assemblages in lagoons and suggests that an interplay of seasonally influenced environmental drivers shape assemblages in these vulnerable ecosystems.

Are Elephants the Most Disastrous Agricultural Pests or the Agents of Ecological Restorations?

Human-elephant interactions occur in the areas where people coexist with elephants. It happens in the communities neighbouring core wildlife protected areas. Human and elephants have coexisted since the beginning of agriculture. The relationship between humans and elephants has deteriorated since humans have increased their dependence on domesticated herbivores and encroached into elephant habitats. The interactions usually result in human deaths, elephant deaths, house demolitions, crop damage and secondary impacts. However, crop damage is the most reported negative impacts from the interactions. In this article, we reviewed the current situation of humanelephant interactions, extent, and nature of elephants' destruction, the contribution of elephants to ecological restorations and players in rural poverty alleviation. We also provided a conclusion on whether elephants are disastrous pests or agents of ecological restoration. Due to the exceptional anatomical, physiological and behavioural features, people perceive elephants as the most disastrous pests and merciless killers. In a similar way, secondary impacts, such as the unfairness of compensation schemes and intangible conservation benefits, influence negative perceptions and attitudes of people towards elephants. Elephants as agents of ecological restoration provide socio-economic benefits to humans through forest management because the seed dispersal of about 400 species of timber and nontimber forest species depend on the digestive tract of elephants. The livelihoods of about 1 billion poor people in the world depend on forests. On the other hand, elephants are not as destructive as other pests such as rodents, wild boars, and starlings, and they are not as killers as hippopotamus and crocodiles. When the positive and negative impacts of human-elephant interactions are summed up, conservation benefits provided to humans usually exceed conservation costs. The mismanagement of elephants leads to increasing negative impacts, if properly managed; elephants may provide significant contributions to environmental conservation and rural poverty alleviation.

Improved mixing efficiency and biomass productivity of Ettlia sp. in co-cultivation system with loaches

Maintaining a homogeneous cell suspension has been identified as a key parameter for higher biomass productivity of microalgae cultivation systems. This study proposes an alternative mixing method where microalgae are co-cultivated with loaches to improve the mixing efficiency and microalgal biomass productivity. The highly settleable microalga, Ettlia sp. showed a stable temporal cell concentration at the specified sampling sites when co-cultivated with 10 loaches, whereas it sank to the bottom of a 20L rectangular vessel (20cm deep) within 12h in a water-pump-assisted mixing system. As a consequence of the better mixing efficiency in the co-cultivation system, biomass and lipid productivities of co-cultivation system were 66.9±8.3mg/L/day and 14.7±1.0mg/L/day, respectively, and were about 57.6% and 32.4% higher than the results from the water-pump-assisted mixing system. In addition, when the co-cultivation systems were cultured under various depth conditions (10, 16, 20, 40, 60, 80cm deep) to determine the maximum areal biomass and lipid productivity, the system showed the highest biomass productivity with a depth of around 16–20cm, while the lipid content and productivity were sharply lowered at this depth. The introduction of loaches also altered the microbial community structure of the co-cultivation systems. Therefore, these results suggest that the co-cultivation of loaches can be used as an efficient mixing method, while also introducing new ecological players, the loaches themselves and associated microorganisms, which can improve the sustainability of microalgae cultivation systems.

Environmental drivers of ectomycorrhizal communities in Europe's temperate oak forests.

Ectomycorrhizal fungi are major ecological players in temperate forests, but they are rarely used in measures of forest condition because large-scale, high-resolution, standardized and replicated belowground data are scarce. We carried out an analysis of ectomycorrhizas at 22 intensively monitored long-term oak plots, across nine European countries, covering complex natural and anthropogenic environmental gradients. We found that at large scales, mycorrhizal richness and evenness declined with decreasing soil pH and root density, and with increasing atmospheric nitrogen deposition. Shifts in mycorrhizas with different functional traits were detected; mycorrhizas with structures specialized for long-distance transport related differently to most environmental variables than those without. The dominant oak-specialist Lactarius quietus, with limited soil exploration abilities, responds positively to increasing nitrogen inputs and decreasing pH. In contrast, Tricholoma, Cortinarius and Piloderma species, with medium-distance soil exploration abilities, show a consistently negative response. We also determined nitrogen critical loads for moderate (9.5-13.5 kg N/ha/year) and drastic (17 kg N/ha/year) changes in belowground mycorrhizal root communities in temperate oak forests. Overall, we generated the first baseline data for ectomycorrhizal fungi in the oak forests sampled, identified nitrogen pollution as one of their major drivers at large scales and revealed fungi that individually and/or in combination with others can be used as belowground indicators of environmental characteristics.

A little bit of light goes a long way: the role of phototrophs on mercury cycling

Among toxic metals, mercury (Hg) is a global priority contaminant due to the biomagnification of the most toxic form methylmercury (MeHg) in food webs, even in remote regions, such as the high Arctic. The importance of Hg as a chemical of major concern to human health was underscored by the recent adoption of the Minamata Convention on Mercury, a legally binding treaty that requires government agencies be equipped to monitor processes affecting global mercury transport and cycling. For several decades now, field and laboratory experiments have shown that phototrophs can directly interact with Hg and affect its speciation and fate. While an important body of work on the role of chemotrophic microbes on Hg cycling has been undertaken, the role of phototrophs is too often overlooked. Strikingly, what is known about phototroph-Hg interactions pertains mostly to oxygenic phototrophs with relatively little being known about anoxygenic phototrophs. Ongoing environmental change will no doubt affect the physical and chemical properties of aquatic ecosystems, which in turn will alter all phototrophic community dynamics. How these changes will affect the Hg cycle represent an important knowledge gap. After synthesizing what is currently known about chemotrophic Hg transformations, we describe the current state of knowledge on what is known about how phototrophs (bacteria and algae) affect Hg cycling (i.e., alteration of Hg redox state, Hg scavenging, potential for methylation) as well as describe the cellular and molecular targets of Hg toxicity in phototrophs. We discuss these interactions in an evolutionary context and provide recommendations for future research directions.

Role of non-established plants in determining biotic homogenization patterns in Pacific Oceanic Islands

Numerous organisms have been relocated by human agency among remote regions of the world. One of the consequences of alien invasions (and associated native extinctions) is that the taxonomic similarity between areas trends to increase, a process called biotic homogenization. This process is studied in plants using naturalized species, while the role of non-established (but nevertheless present) plants is not investigated. Here we evaluate if adding the non-established component to the pool of alien plants modifies similarity patterns recorded in a preceding study of biotic homogenization in six Oceanic Islands of the South-eastern Pacific. Although our analyses confirm previous findings of floristic homogenization for these Islands, the effect of adding the non-established component results in several changes. By consideration of only naturalized plants we detected two cases of increased similarity (i.e. floristic homogenization), while the other 13 comparisons yielded non-significant changes. By adding non-established plants, four pairs of Islands show increased similarity, while in one case there is decreased similarity (i.e. floristic differentiation). These results support the hypothesis that non-established species can modify qualitative and quantitative trends of floristic change, revealing the complexity of biotic change. Although discrimination between only native and naturalized species appears reasonable for some groups, among plants it becomes a critical decision because of the importance of non-established species as ecological players and as purveyors of early information on future biotic change.

Conservation of protists: is it needed at all?

Protists have scarcely been considered in traditional perspectives and strategies in environmental management and biodiversity conservation. This is a remarkable omission given that these tiny organisms are highly diverse, and have performed as key ecological players in evolutionary theatres for over a billion years of Earth history. Protists hold key roles in nearly all ecosystems, notably as participants in fluxes of energy and matter through foodwebs that centre on their predation on microbes. In spite of this, they have been largely ignored in conservation issues due to a widespread, naive belief that protists are ubiquitous and cosmopolitanously distributed. Nevertheless, recent research shows that many protists have markedly restricted distributions. These range from palaeoendemics (Gondwanan-Laurasian distribution) to local endemics. Our ignorance about the ultimate and proximate causes of such acute disparities in scale-dependent distributions of protists can be flagged as a singular reason to preserve these more cryptic participants in ecological and evolutionary dynamics. This argument is disturbing when one considers anthropogenic modifications of landscapes and the very poorly understood roles of protists in ecological processes in soils, not least in agroecolandscapes and hydrological systems. Major concerns include host specific symbiotic, symphoric and parasitic species which become extinct, unseen and largely unknown, alongside their metazoan hosts; change or loss of habitats; massive change or loss of type localities; and losses of unique genetic resources and evolutionary potential. These concerns are illustrated by examples to argue that conservation of protists should be integral to any strategy that traditionally targets vascular plants and animals. The ongoing decline in research capacity to inventory and classify protist diversity exemplifies a most acute symptom of the failures, at local, national and international levels, to support scientific responses to the biodiversity crisis. Responsible responses to these severe problems need to centre on the revival of natural history as the core discipline in biology.

Host plant genetics affect hidden ecological players: links amongPopulus, condensed tannins, and fungal endophyte infection

Recent studies have shown effects of host plant genetics on community and ecosystem processes, which makes understanding the impacts of genetically based traits on hidden or non-apparent organisms more important. Here we examined links among genetic variation in hybrid cottonwoods, plant phytochemistry, and twig fungal endophytes (i.e., a common hidden organism). We found three major patterns: (1) twig fungal endophyte infection was positively related to the introgression of Fremont cottonwood (Populus fremontii S. Wats.) RFLP genetic markers, (2) condensed tannin concentration in twig bark tissue was negatively correlated to the introgression of Fremont genetic markers, and (3) fungal endophyte infection was negatively related to condensed tannin concentration in twig bark. These data demonstrate that plant genotype can impact hidden ecological players (i.e., fungal endophytes) resulting in community and ecosystem consequences.Key words: ecological genetics, fungal endophytes, hidden players, hybridization, Populus, tannins.