Trophic cascades across ecosystems

Copper-Induced Transgenerational Plasticity in Plant Defence Boosts Aphid Fitness

Transgenerational plasticity in plants is an increasingly recognized phenomenon, yet it is mostly unclear whether transgenerational plasticity is relevant to both the fitness of the plant and its interacting species. Using monoclonal strains of the giant duckweed (Spirodela polyrhiza) and its native herbivore, the waterlily aphid (Rhopalosiphum nymphaeae), we assessed whether pre-treating plants with copper excess, both indoors and outdoors, induces transgenerational plasticity in plant defences that alter plant and herbivore fitness. Outdoors, copper pre-treatment tended to increase plant growth rates under recurring copper excess. Indoors, copper pre-treatment either increased or decreased plant growth rates under recurring conditions, depending on the plant genotype. Copper pre-treatment induced anthocyanins that protected plants against copper toxicity, and these elevated levels were transgenerationally retained. Copper pre-treatment also transgenerationally increased the levels of 12-oxo-phytodienoic acid (OPDA), a jasmonate precursor. Nevertheless, aphids grew up to 50% better when the plants were pre-treated with copper. The increased aphid growth was likely caused by transgenerationally elevated OPDA levels, as aphids grew better when jasmonates were externally applied to plants. Taken together, this study shows that transgenerational plasticity is relevant to both plant and herbivore fitness, which highlights the role of transgenerational plasticity in plant evolution and species interactions.

Disentangling small-island multilayer networks: Underlying ecological and evolutionary patterns

This study provides a pioneering analysis of the structural and topological characteristics of one of nature's simplest food webs, using the Montaña Clara islet (Canary Islands) as a case study. Applying a multilayer network approach, which assesses multiple interaction types, we examined plant-animal and plant-fungi interactions during two seasons (humid and dry), comparing this oceanic island food web to one from Na Redona, a small continental island in the Balearic Islands. Data were collected through field observations, flower visitation records, fecal analysis, and DNA metabarcoding of root-associated fungi. The study identified 63 animal species and 367 fungal amplicon sequence variants interacting with 13 plant species, five of which (38%) were structurally significant, as indicated by high multilayer versatility values (>0.5). The network structure was modular, with 23 modules primarily representing single ecological functions, and most species were involved in only one interaction type. Notably, 73% of species shifted roles between interaction layers. Results reveal that Montaña Clara's food web is simpler but more modular and versatile than that of the continental island, aligning with island biogeography theory. The study suggests that the unique biodiversity composition of oceanic islands, particularly islets, influences their ecological network structures.

Fish acting as sinks of methane-derived carbon in Neotropical floodplains

Floodplains function as global hotspots for the natural production of methane. Some of this methane can be oxidized by methanotrophic bacteria and assimilated into their biomass before reaching the atmosphere. Consequently, aquatic invertebrates that feed on methanotrophic bacteria may transfer methane-derived carbon to higher trophic levels in the aquatic food chain. Our objective was to investigate the proportion of methane-derived carbon in the biomass of apex fish across 34 lakes from four major Neotropical floodplains (Amazon, Pantanal, Araguaia, and Paraná) using stable isotopes of carbon (δ13C). We found that methane-derived carbon contributed between 5 % and 16 % to the biomass of 37 apex fish species, providing, for the first time, evidence of the fish's role in the methane cycle in the Neotropics. Consumers in the Amazon and Pantanal floodplains, the largest and most significant regions for methane production, exhibited higher levels of methane-derived carbon in their biomass (11.06 ± 2.87 % and 9.84 ± 3.08 %, respectively). These results underscore the role of aquatic consumers in mitigating methane emissions in floodplains, as methane oxidation and assimilation are linked to reduced emissions. Therefore, conserving fish assemblages in floodplains through strategies that maintain the natural dynamics of these ecosystems is essential for controlling natural methane emissions.

The trophic distribution of biomass in ecosystems with co-occurring wildlife and livestock

Trophic interactions regulate populations, but anthropogenic processes influence primary productivity and consumption by both herbivore and carnivore species. Trophic ecology studies often focus on natural systems such as protected areas, even though livestock globally comprise the majority of terrestrial vertebrate biomass. Here we explore spatial and temporal patterns in the distribution of biomass between plants, and large herbivores and carnivores (> 10 kg) in Norwegian rangelands, including both wildlife and livestock. We find high spatial variation in the relationship between plant and herbivore biomass, with both positive and negative divergence in observed biomass from expectations based on primary productivity. Meanwhile, despite recent partial recoveries in carnivore densities across Norway, carnivore biomass is still lower than expected based on herbivore biomass, even if livestock are excluded from the estimation. Our study highlights how temporal trends in both herbivores and carnivores reflect policy development. The role of livestock husbandry and wildlife management is thus key in determining realised biomass distributions in anthropogenically influenced ecosystems.

Narrow Dietary Niche With High Overlap Between Snow Leopards and Himalayan Wolves Indicates Potential for Resource Competition in Shey Phoksundo National Park, Nepal

Understanding species' dietary ecology and interspecific interactions is crucial for multi-species conservation planning. In Central Asia and the Himalayas, wolves have recolonized snow leopard habitats, raising considerable concern about resource competition between these apex predators. Using micro-histological analysis of prey species remains (e.g., hair) in their fecal samples, we determined the prey composition, dietary niche breadth, and the extent of diet overlap between these two apex predators in Shey Phoksundo National Park, Nepal. We analyzed 152 scat samples collected along 89 survey transects from April to June 2021. Our findings reveal a significant overlap in their diets (Pianka's index = 0.93), with snow leopard and wolf scats containing the remains of 11 and 10 prey species, respectively. However, the interspecific difference in prey selection was apparent, with significant deviations between observed and expected prey use indicating non-random prey selection relative to availability: Snow leopards exhibited a higher occurrence of wild prey items in their diet (55.28%), primarily blue sheep (Pseudois nayaur) (24.83%), whereas wolves relied predominantly on domestic livestock (67.89%), with goats (Capra hircus) accounting for over one-fourth of their diet (29.15%). Yaks (Bos grunniens) comprised a significant portion of the biomass consumed by both predators, with higher for wolves (43.68%) than snow leopards (36.47%). Overall, the narrow dietary niche breadth with high overlap indicates potential resource competition between snow leopards and wolves. However, a comprehensive understanding of resource competition will require further study on other axes of niche partitioning, including habitat and time. Nevertheless, the region's low prey richness means that, with increasing human influence, any reduction in wild prey or increase in livestock could intensify competition between snow leopards and wolves, which could have implications for livestock depredation.

Detecting the effect of intensive agriculture on Odonata diversity using citizen science data

Agricultural areas represent one of the major ecosystems of the world. Intensification of agricultural practices produced openfields characterized by low biological diversity. Nevertheless, the distance up to which intensive agricultural fields alter surrounding natural systems is rarely quantified. We determined the spatial scale at which agricultural landscapes alter the diversity of Odonates, a key taxon in wetland ponds, and we tested to what extent citizen science data can be used reliably for this purpose. We compiled 7731 observations made in a portion of the region Centre-Val-de-Loire (France) over 10 years by naturalists on 729 water bodies to analyze the effect of agricultural landscapes (mainly wheat, rapeseed, sunflower) on the species richness of both damselflies and dragonflies in lentic systems. Sixty species were reported over the 10-year period. For dragonflies, intensive agricultural landscapes best explained their richness at the scales of 800 and 1600 m for overall and autochthonous species, respectively, when using the full dataset. The spatial scale was smaller for damselflies, at 200 m for both overall and autochthonous species. These distances were not severely impacted when constraining the data to consider several biases. Multimodel averaging showed that the proportion of intensive agriculture decreased species richness, despite the potential biases inherent to an imperfect database acquired by citizens. This imperfect citizen dataset allows to infer the lowest effect size of agriculture on species richness. Quantitatively, this effect was more important for autochthonous species. Interestingly, both relatively rare taxa and common or generalist species can be under threat in intensive agricultural landscapes, calling for more ecotoxicological studies. The influence of agricultural practices from a distance implies that conservation and management plans of wetland ponds should consider the landscape ecological characteristics and not only the pond features. Conservation efforts focusing too locally on a site may be undermined because intensive agriculture from a distance limits the potential for the site to recover highly diverse communities. These distant effects should be integrated by policy-makers when deciding which wetland pond should benefit from a conservation plan or which conservation action may be planned, implementing, for instance, buffer zones and/or ecological corridors composed of natural vegetation.

Variability in Precipitation Weakens Sexual Selection for Nuptial Gifts in Spiders

AbstractEnvironmental conditions (i.e., climatic variation) can strongly influence the cost and benefits of reproductive traits. Yet there is still no consensus on whether changing environmental conditions strengthen or relax sexual selection. Evidence from the literature suggests that highly variable environments can limit mate choice and investment in sexual traits, hence relaxing sexual selection pressures. Here, we tested this hypothesis using the nuptial gift-giving spider Paratrechalea ornata, in which males can either wrap nutritive (fresh prey) or worthless (prey leftovers) items in silk. We examined changes in males' sexual trait and female choice among six populations living under different climatic conditions. We found that large variation in precipitation limits female choice, potentially favoring the spread of deceptive worthless gifts. In populations under highly variable conditions and with the highest frequencies of worthless gifts (70%), males offering such gifts acquire longer mating durations than those offering nutritive gifts. In contrast, in populations with less variable conditions and the lowest frequencies of worthless gift (36%), females shortened mating duration to males offering worthless gifts. Our findings are consistent with the prediction that highly variable environmental conditions relax sexual selection.

On the structure of species-function participation in multilayer ecological networks

Understanding how biotic interactions shape ecosystems and impact their functioning, resilience and biodiversity has been a sustained research priority in ecology. Yet, traditional assessments of ecological complexity typically focus on species-species interactions that mediate a particular function (e.g., pollination), overlooking both the synergistic effect that multiple functions might develop as well as the resulting species-function participation patterns that emerge in ecosystems that harbor multiple ecological functions. Here we propose a mathematical framework that integrates various types of biotic interactions observed between different species. Its application to recently collected data of an islet ecosystem-reporting 1537 interactions between 691 plants, animals and fungi across six different functions (pollination, herbivory, seed dispersal, decomposition, nutrient uptake, and fungal pathogenicity)-unveils a non-random, nested structure in the way plant species participate across different functions. The framework further allows us to identify a ranking of species and functions, where woody shrubs and fungal decomposition emerge as keystone actors whose removal have a larger-than-random effect on secondary extinctions. The dual insight-from species and functional perspectives-offered by the framework opens the door to a richer quantification of ecosystem complexity and to better calibrate the influence of multifunctionality on ecosystem functioning and biodiversity.

Terrestrial land use signals on groundwater fauna beyond current protection buffers

Terrestrial and aquatic ecosystems are tightly linked, with direct implications for applied resource management and conservation. It is well known that human land use change and intensification of terrestrial systems can have large impacts on surface freshwater ecosystems. Contrastingly, the study and understanding of such land use impacts on groundwater communities is lagging behind. Both the impact strength of land use on groundwater communities and the spatial extents at which such interlinkages are operating are largely unknown, despite our reliance on groundwater for drinking water extraction as a key ecosystem service. Here, we analyzed groundwater amphipod occurrence from several hundred shallow groundwater aquifers used for drinking water extraction across a region of varying agricultural intensity and human population density in Switzerland. Despite drinking water extraction sites being generally built at locations with expected minimal aboveground impacts on water quality, we found a direct correlation between land use type and intensity within the surrounding catchment area and the locally measured nitrate concentrations, which is a direct proxy for drinking water quality. Furthermore, groundwater amphipods were more likely to be found at sites with higher forest coverage than at sites with higher crop and intensive pasture coverages, clearly indicating a tight connection between aboveground land use and groundwater biodiversity. Our results indicate that land use type effects on groundwater communities are most relevant and pronounced to spatial scales of about 400-1000 m around the groundwater sampling site. Importantly, the here identified spatial scale is 1.2- to 3-fold exceeding the average extent of currently defined groundwater protection zones. We postulate that incorporating an ecosystem perspective into groundwater management strategies is needed for effective protection of groundwater quality and biodiversity.

Wind energy and insects: reviewing the state of knowledge and identifying potential interactions

In 2023 the wind industry hit a milestone of one terawatt of installed capacity globally. That amount is expected to double within the next decade as billions of dollars are invested in new wind projects annually. Wildlife mortality is a primary concern regarding the proliferation of wind power, and many studies have investigated bird and bat interactions. Little is known about the interactions between wind turbines and insects, despite these animals composing far more biomass than vertebrates. Turbine placement, coloration, shape, heat output, and lighting may attract insects to turbines. Insects attract insectivorous animals, which may be killed by the turbines. Compiling current knowledge about these interactions and identifying gaps in knowledge is critical as wind power grows rapidly. We reviewed the state of the literature investigating insects and wind energy facilities, and evaluated hypotheses regarding insect attraction to turbines. We found evidence of insect attraction due to turbine location, paint color, shape, and temperature output. We provide empirical data on insect abundance and richness near turbines and introduce a risk assessment tool for comparing wind development with suitable climate for insects of concern. This understudied topic merits further investigation as insects decline globally. Compiling information will provide a resource for mitigation and management strategies, and will inform conservation agencies on what insects may be most vulnerable to the expansion of wind technologies.

The disruption of birds' double mutualistic interactions in novel ecosystems

Non-native trees disrupt ecological processes vital to native plant communities. We studied how forests dominated by Acacia dealbata and Eucalyptus globulus affect the role of birds as dual pollinators and seed dispersers in a region heavily impacted by these two non-native species. We compared bird-plant interactions in the native and in the two non-native forest types. We constructed a multilayer regional network for each forest type and evaluated differences in network dissimilarity between networks. We also calculated the bird's importance in connecting processes and variables associated with module diversity. To determine how the networks react to changes in species richness, we did a simulation of species richness gradient and link percentage for each forest type. The number of birds acting both as pollinators and seed dispersers was higher in native than in non-native forests. However, birds in non-native forests still play a crucial role in maintaining the ecological services provided to native plant communities. However, the eucalyptus network exhibited a concerning simplification, forcing bird species to fully exploit the few remaining resources, leaving little room for structural adjustments and limiting the ecosystem's ability to withstand further species loss. These findings highlight how non-native trees may trigger cascading effects across trophic levels.

Effects of livestock on arthropod biodiversity in Iberian holm oak savannas revealed by metabarcoding

Increasing food production while avoiding negative impacts on biodiversity constitutes one of the main challenges of our time. Traditional silvopastoral systems like Iberian oak savannas ("dehesas") set an example, where free-range livestock has been reared for centuries while preserving a high natural value. Nevertheless, factors decreasing productivity need to be addressed, one being acorn losses provoked by pest insects. An increased and focalized grazing by livestock on infested acorns would kill the larvae inside and decrease pest numbers, but increased livestock densities could have undesired side effects on ground arthropod communities as a whole. We designed an experimental setup including areas under trees with livestock exclosures of different ages (short-term: 1-year exclusion, long-term: 10-year exclusion), along with controls (continuous grazing), using DNA metabarcoding (mitochondrial markers COI and 16S) to rapidly assess arthropod communities' composition. Livestock removal quickly increased grass cover and arthropod taxonomic richness and diversity, which was already higher in short-term (1-year exclosures) than beneath the canopies of control trees. Interestingly, arthropod diversity was not highest at long-term exclosures (≥10 years), although their community composition was the most distinct. Also, regardless of treatment, we found that functional diversity strongly correlated with the vegetation structure, being higher at trees beneath which there was higher grass cover and taller herbs. Overall, the taxonomic diversity peak at short term exclosures would support the intermediate disturbance hypothesis, which relates it with the higher microhabitat heterogeneity at moderately disturbed areas. Thus, we propose a rotatory livestock management in dehesas: plots with increased grazing should co-exist with temporal short-term exclosures. Ideally, a few long-term excluded areas should be also kept for the singularity of their arthropod communities. This strategy would make possible the combination of biological pest control and arthropod conservation in Iberian dehesas.

Predation risk and floral rewards: How pollinators balance these conflicts and the consequences on plant fitness

Foraging behavior of pollinators is shaped by, among other factors, the conflict between maximizing resource intake and minimizing predation risk; yet, empirical studies quantifying variation in both forces are rare, compared to those investigating each separately. Here, we discuss the importance of simultaneously assessing bottom-up and top-down forces in the study of plant-pollinator interactions, and propose a conceptual and testable graphical hypothesis for pollinator foraging behavior and plant fitness outcomes as a function of varying floral rewards and predation risk. In low predation risk scenarios, no noticeable changes in pollinator foraging behavior are expected, with reward levels affecting only the activity threshold. However, as predation risk increases we propose that there is a decrease in foraging behavior, with a steeper decline as plants are more rewarding and profitable. Lastly, in high predation risk scenarios, we expect foraging to approach zero, regardless of floral rewards. Thus, we propose that pollinator foraging behavior follows an inverse S-shape curve, with more pronounced changes in foraging activity at intermediate levels of predation risk, especially in high reward systems. We present empirical evidence that is consistent with this hypothesis. In terms of the consequences for plant fitness, we propose that specialized plant-pollinator systems should be more vulnerable to increased predation risk, with a steeper and faster decline in plant fitness, compared with generalist systems, in which pollinator redundancy can delay or buffer the effect of predators. Moreover, whereas we expect that specialist systems follows a similar inverse S-shape curve, in generalist systems we propose three different scenarios as a function not only of reward level but also compatibility, mating-system, and the interplay between growth form and floral display. The incorporation of trade-offs in pollinator behavior balancing the conflicting demands between feeding and predation risk has a promising future as a key feature enabling the development of more complex foraging models.

A Review of the Density, Biomass, and Secondary Production of Odonates

Freshwater insects are highly significant as ecosystem service providers, contributing to provisioning services, supporting services, and cultural services. Odonates are dominant predators in many freshwater systems, becoming top predators in fishless ecosystems. One service that odonates provide is the export of matter and energy from aquatic to terrestrial ecosystems. In this study, we provide a review of the literature aiming to estimate the density, biomass, and secondary production of odonates and discuss to what extent this order of insects is relevant for the fertilization of terrestrial ecosystems. We found published data on 109 species belonging to 17 families of odonates from 44 papers. Odonata larvae are abundant in freshwater systems, with a mean density of 240.04 ± 48.01 individuals m-2 (±SE). Lentic habitats show much higher densities (104.40 ± 55.31 individuals m-2, N = 118) than lotic systems (27.12 ± 5.09, N = 70). The biomass estimations for odonates indicate values of 488.56 ± 134.51 mg m-2 y-1, with similar values in lentic and lotic habitats, which correspond to annual secondary productions of 3558.02 ± 2146.80 mg m-2 y-1. The highest biomass is found in dragonflies of the Aeshnidae, Corduliidae, and Gomphidae families. The available evidence suggests a significant potential contribution of Odonata to the exportation of material from water bodies to land. This is further strengthened by the ability of adult odonates to migrate and to colonize different types of water bodies.

Invasive species drive cross-ecosystem effects worldwide

Invasive species are pervasive around the world and have profound impacts on the ecosystem they invade. Invasive species, however, can also have impacts beyond the ecosystem they invade by altering the flow of non-living materials (for example, nutrients or chemicals) or movement of organisms across the boundaries of the invaded ecosystem. Cross-ecosystem interactions via spatial flows are ubiquitous in nature, for example, connecting forests and lakes, grasslands and rivers, and coral reefs and the deep ocean. Yet, we have a limited understanding of the cross-ecosystem impacts invasive species have relative to their local effects. By synthesizing emerging evidence, here we demonstrate the cross-ecosystem impacts of invasive species as a ubiquitous phenomenon that influences biodiversity and ecosystem functioning around the world. We identify three primary ways by which invasive species have cross-ecosystem effects: first, by altering the magnitude of spatial flows across ecosystem boundaries; second, by altering the quality of spatial flows; and third, by introducing novel spatial flows. Ultimately, the strong impacts invasive species can drive across ecosystem boundaries suggests the need for a paradigm shift in how we study and manage invasive species around the world, expanding from a local to a cross-ecosystem perspective.

The propagation of disturbances in ecological networks

Despite the development of network science, we lack clear heuristics for how far different disturbance types propagate within and across species interaction networks. We discuss the mechanisms of disturbance propagation in ecological networks, and propose that disturbances can be categorized into structural, functional, and transmission types according to their spread and effect on network structure and functioning. We describe the properties of species and their interaction networks and metanetworks that determine the indirect, spatial, and temporal extent of propagation. We argue that the sampling scale of ecological studies may have impeded predictions regarding the rate and extent that a disturbance spreads, and discuss directions to help ecologists to move towards a predictive understanding of the propagation of impacts across interacting communities and ecosystems.

Trophic cascades within and across ecosystems: The role of anti-predatory defences, predator type and detritus quality

Species in one ecosystem can indirectly affect multiple biodiversity components and ecosystem functions of adjacent ecosystems. The magnitude of these cross-ecosystem effects depends on the attributes of the organisms involved in the interactions, including traits of the predator, prey and basal resource. However, it is unclear how predators with cross-ecosystem habitat interact with predators with single-ecosystem habitat to affect their shared ecosystem. Also, unknown is how such complex top-down effects may be mediated by the anti-predatory traits of prey and quality of the basal resource. We used the aquatic invertebrate food webs in tank bromeliads as a model system to investigate these questions. We manipulated the presence of a strictly aquatic predator (damselfly larvae) and a predator with both terrestrial and aquatic habitats (spider), and examined effects on survival of prey (detritivores grouped by anti-predator defence), detrital decomposition (of two plant species differing in litter quality), nitrogen flux and host plant growth. To evaluate the direct and indirect effects each predator type on multiple detritivore groups and ultimately on multiple ecosystem processes, we used piecewise structural equation models. For each response variable, we isolated the contribution of different detritivore groups to overall effects by comparing alternate model formulations. Alone, damselfly larvae and spiders each directly decreased survival of detritivores and caused multiple indirect negative effects on detritus decomposition, nutrient cycling and host plant growth. However, when predators co-occurred, the spider caused a negative non-consumptive effect on the damselfly larva, diminishing the net direct and indirect top-down effects on the aquatic detritivore community and ecosystem functioning. Both detritivore traits and detritus quality modulated the strength and mechanism of these trophic cascades. Predator interference was mediated by undefended or partially defended detritivores as detritivores with anti-predatory defences evaded consumption by damselfly larvae but not spiders. Predators and detritivores affected ecosystem decomposition and nutrient cycling only in the presence of high-quality detritus, as the low-quality detritus was consumed more by microbes than invertebrates. The complex responses of this system to predators from both recipient and adjacent ecosystems highlight the critical role of maintaining biodiversity components across multiple ecosystems.

How collectively integrated are ecological communities?

Beyond abiotic conditions, do population dynamics mostly depend on a species' direct predators, preys and conspecifics? Or can indirect feedback that ripples across the whole community be equally important? Determining where ecological communities sit on the spectrum between these two characterizations requires a metric able to capture the difference between them. Here we show that the spectral radius of a community's interaction matrix provides such a metric, thus a measure of ecological collectivity, which is accessible from imperfect knowledge of biotic interactions and related to observable signatures. This measure of collectivity integrates existing approaches to complexity, interaction structure and indirect interactions. Our work thus provides an original perspective on the question of to what degree communities are more than loose collections of species or simple interaction motifs and explains when pragmatic reductionist approaches ought to suffice or fail when applied to ecological communities.

YOLO object detection models can locate and classify broad groups of flower-visiting arthropods in images

Develoment of image recognition AI algorithms for flower-visiting arthropods has the potential to revolutionize the way we monitor pollinators. Ecologists need light-weight models that can be deployed in a field setting and can classify with high accuracy. We tested the performance of three deep learning light-weight models, YOLOv5nano, YOLOv5small, and YOLOv7tiny, at object recognition and classification in real time on eight groups of flower-visiting arthropods using open-source image data. These eight groups contained four orders of insects that are known to perform the majority of pollination services in Europe (Hymenoptera, Diptera, Coleoptera, Lepidoptera) as well as other arthropod groups that can be seen on flowers but are not typically considered pollinators (e.g., spiders-Araneae). All three models had high accuracy, ranging from 93 to 97%. Intersection over union (IoU) depended on the relative area of the bounding box, and the models performed best when a single arthropod comprised a large portion of the image and worst when multiple small arthropods were together in a single image. The model could accurately distinguish flies in the family Syrphidae from the Hymenoptera that they are known to mimic. These results reveal the capability of existing YOLO models to contribute to pollination monitoring.

Müllerian mimicry among bees and wasps: a review of current knowledge and future avenues of research

Many bees and stinging wasps, or aculeates, exhibit striking colour patterns or conspicuous coloration, such as black and yellow stripes. Such coloration is often interpreted as an aposematic signal advertising aculeate defences: the venomous sting. Aposematism can lead to Müllerian mimicry, the convergence of signals among different species unpalatable to predators. Müllerian mimicry has been extensively studied, notably on Neotropical butterflies and poison frogs. However, although a very high number of aculeate species harbour putative aposematic signals, aculeates are under-represented in mimicry studies. Here, we review the literature on mimicry rings that include bee and stinging wasp species. We report over a hundred described mimicry rings, involving a thousand species that belong to 19 aculeate families. These mimicry rings are found all throughout the world. Most importantly, we identify remaining knowledge gaps and unanswered questions related to the study of Müllerian mimicry in aculeates. Some of these questions are specific to aculeate models, such as the impact of sociality and of sexual dimorphism in defence levels on mimicry dynamics. Our review shows that aculeates may be one of the most diverse groups of organisms engaging in Müllerian mimicry and that the diversity of aculeate Müllerian mimetic interactions is currently under-explored. Thus, aculeates represent a new and major model system to study the evolution of Müllerian mimicry. Finally, aculeates are important pollinators and the global decline of pollinating insects raises considerable concern. In this context, a better understanding of the impact of Müllerian mimicry on aculeate communities may help design strategies for pollinator conservation, thereby providing future directions for evolutionary research.

Otterly delicious: Spatiotemporal variation in the diet of a recovering population of Eurasian otters (Lutra lutra) revealed through DNA metabarcoding and morphological analysis of prey remains

Eurasian otters are apex predators of freshwater ecosystems and a recovering species across much of their European range; investigating the dietary variation of this predator over time and space, therefore, provides opportunities to identify changes in freshwater trophic interactions and factors influencing the conservation of otter populations. Here we sampled feces from 300 dead otters across England and Wales between 2007 and 2016, conducting both morphological analyses of prey remains and dietary DNA metabarcoding. Comparison of these methods showed that greater taxonomic resolution and breadth could be achieved using DNA metabarcoding but combining data from both methodologies gave the most comprehensive dietary description. All otter demographics exploited a broad range of taxa and variation likely reflected changes in prey distributions and availability across the landscape. This study provides novel insights into the trophic generalism and adaptability of otters across Britain, which is likely to have aided their recent population recovery, and may increase their resilience to future environmental changes.

The non-random assembly of network motifs in plant-pollinator networks

Ecological processes leave distinct structural imprints on the species interactions that shape the topology of animal-plant mutualistic networks. Detecting how direct and indirect interactions between animals and plants are organised is not trivial since they go beyond pairwise interactions, but may get blurred when considering global network descriptors. Recent work has shown that the meso-scale, the intermediate level of network complexity between the species and the global network, can capture this important information. The meso-scale describes network subgraphs representing patterns of direct and indirect interactions between a small number of species, and when these network subgraphs differ statistically from a benchmark, they are often referred to as 'network motifs'. Although motifs can capture relevant ecological information of species interactions, they remain overlooked in natural plant-pollinator networks. By exploring 60 empirical plant-pollinator networks from 18 different studies with wide geographical coverage, we show that some network subgraphs are consistently under- or over-represented, suggesting the presence of worldwide network motifs in plant-pollinator networks. In addition, we found a higher proportion of densely connected network subgraphs that, based on previous findings, could reflect that species relative abundances are the main driver shaping the structure of the meso-scale on plant-pollinator communities. Moreover, we found that distinct subgraph positions describing species ecological roles (e.g. generalisation and number of indirect interactions) are occupied by different groups of animal and plant species representing their main life-history strategies (i.e. functional groups). For instance, we found that the functional group of 'bees' was over-represented in subgraph positions with a lower number of indirect interactions in contrast to the rest of floral visitors groups. Finally, we show that the observed functional group combinations within a subgraph cannot be retrieved from their expected probabilities (i.e. joint probability distributions), indicating that plant and floral visitor associations within subgraphs are not random either. Our results highlight the presence of common network motifs in plant-pollinator communities that are formed by a non-random association of plants and floral visitors functional groups.

Tradeoffs and synergies in wetland multifunctionality: A scaling issue

Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale.

Long-term insect censuses capture progressive loss of ecosystem functioning in East Asia

Insects provide critical ecosystem services such as biological pest control, in which natural enemies (NE) regulate the populations of crop-feeding herbivores (H). While H-NE dynamics are routinely studied at small spatiotemporal scales, multiyear assessments over entire agrolandscapes are rare. Here, we draw on 18-year radar and searchlight trapping datasets (2003-2020) from eastern Asia to (i) assess temporal population trends of 98 airborne insect species and (ii) characterize the associated H-NE interplay. Although NE consistently constrain interseasonal H population growth, their summer abundance declined by 19.3% over time and prominent agricultural pests abandoned their equilibrium state. Within food webs composed of 124 bitrophic couplets, NE abundance annually fell by 0.7% and network connectance dropped markedly. Our research unveils how a progressive decline in insect numbers debilitates H trophic regulation and ecosystem stability at a macroscale, carrying implications for food security and (agro)ecological resilience during times of global environmental change.

Experimental evidence for a hidden network of higher-order interactions in a diverse arthropod community

Transcending pairwise interactions in ecological networks remains a challenge.^1,2,3,4,5 Higher-order interactions (HOIs), the modulation of a pairwise interaction by a third species,⁶ are thought to play a particularly important role in stabilizing coexistence and maintaining species diversity.^{7,8,9,10,11,12} However, HOIs have so far only been demonstrated in models^{9,10,11,12,13,14} or isolated experimental systems including only a few interacting species.^7,8,15 Their ubiquity and importance at a community level in the real world remain unknown. We hypothesized that a complex network of HOIs could be constantly modifying pairwise interactions and shaping ecological communities and that consequently the outcome of pairwise interactions would be a product of many influences from distinct sources. Using field experiments, we tested how multiple interactions within a diverse arthropod community associated with the tropical shrub Baccharis dracunculifolia D.C. (Asteraceae) were modified by the removal of ant species or live or hatched insect galls (a non-trophic engineering effect) of the dominant galler species. We revealed an extensive hidden network of HOIs modifying each other and the "visible" pairwise interactions. Most pairwise interactions were affected indirectly by the manipulation of non-interacting taxonomic groups. The pervasiveness of these interaction modifications challenges pairwise approaches to understanding interaction outcomes and could shift our thinking about the structure and persistence of ecological communities. Investigating coexistence mechanisms involving interaction modulation by HOIs may be key to elucidating the underlying causes of the stability and persistence of ecological communities.

Fungivorous nematodes drive microbial diversity and carbon cycling in soil

Soil bacteria and fungi mediate terrestrial biogeochemical cycling, but we know relatively little about how trophic interactions influence their community composition, diversity, and function. Specifically, it is unclear how consumer populations affect the activity of microbial taxa they consume, and therefore the interaction of those taxa with other members of the microbial community. Due to its extreme diversity, studying trophic dynamics in soil is a complex feat. Seeking to address these challenges, we performed a microcosm-based consumer manipulation experiment to determine the impact of a common fungal-feeding nematode (Aphelenchus avenae) on soil microbial community composition, diversity, and activity (e.g., C cycling parameters). Fungivory decreased fungal and bacterial α-diversity and stimulated C and N cycling, possibly via cascading impacts of fungivory on bacterial communities. Our results present experimental evidence that soil trophic dynamics are intimately linked with microbial diversity and function, factors that are key in understanding global patterns in biogeochemical cycling.

Ecological relevance of non-perennial rivers for the conservation of terrestrial and aquatic communities

River conservation efforts traditionally focus on perennial watercourses (i.e., those that do not dry) and their associated aquatic biodiversity. However, most of the global river network is not perennial and thus supports both aquatic and terrestrial biodiversity. We assessed the conservation value of nonperennial rivers and streams (NPRS) in one of Europe's driest regions based on aquatic (macroinvertebrates, diatoms) and terrestrial (riparian plants, birds, and carabid beetles) community data. We mapped the distribution of taxa at 90 locations and across wide environmental gradients. Using the systematic planning tool Marxan, we identified priority conservation sites under 2 scenarios: aquatic taxa alone or aquatic and terrestrial taxa together. We explored how environmental factors (runoff, flow intermittence, elevation, salinity, anthropogenic impact) influenced Marxan's site selection frequency. The NPRS were selected more frequently (over 13% on average) than perennial rivers when both aquatic and terrestrial taxa were considered, suggesting that NPRS have a high conservation value at the catchment scale. We detected an underrepresentation of terrestrial taxa (8.4-10.6% terrestrial vs. 0.5-1.1% aquatic taxa were unrepresented in most Marxan solutions) when priority sites were identified based exclusively on aquatic biodiversity, which points to a low surrogacy value of aquatic taxa for terrestrial taxa. Runoff explained site selection when focusing on aquatic taxa (all best-fitting models included runoff, r²  = 0.26-0.27), whereas elevation, salinity, and flow intermittence were more important when considering both groups. In both cases, site selection frequency declined as anthropogenic impact increased. Our results highlight the need to integrate terrestrial and aquatic communities when identifying priority areas for conservation in catchments with NPRS. This is key to overcoming drawbacks of traditional assessments based only on aquatic taxa and to ensure the conservation of NPRS, especially as NPRS become more prevalent worldwide due to climate change and increasing water demands.

Plant genetic diversity affects multiple trophic levels and trophic interactions

Intraspecific genetic diversity is an important component of biodiversity. A substantial body of evidence has demonstrated positive effects of plant genetic diversity on plant performance. However, it has remained unclear whether plant genetic diversity generally increases plant performance by reducing the pressure of plant antagonists across trophic levels for different plant life forms, ecosystems and climatic zones. Here, we analyse 4702 effect sizes reported in 413 studies that consider effects of plant genetic diversity on trophic groups and their interactions. We found that that increasing plant genetic diversity decreased the performance of plant antagonists including invertebrate herbivores, weeds, plant-feeding nematodes and plant diseases, while increasing the performance of plants and natural enemies of herbivores. Structural equation modelling indicated that plant genetic diversity increased plant performance partly by reducing plant antagonist pressure. These results reveal that plant genetic diversity often influences multiple trophic levels in ways that enhance natural pest control in managed ecosystems and consumer control of plants in natural ecosystems for sustainable plant production.

Can botanic gardens serve as refuges for taxonomic and functional diversity of Odonata? The case of the botanic garden of Castilla-La Mancha (Spain)

In a scenario with declining biodiversity and habitat loss, botanic gardens could serve as refuges for invertebrates, but the opportunities they offer for animal conservation are still poorly understood. Odonata is a good model group for conservation studies, because it includes threatened species and responses to habitat disturbance are well documented. In this study, we assessed the role of the botanic garden of Castilla-La Mancha in Spain as a refuge for members of Odonata by analysing their taxonomic and functional diversity. We explored if the small size of the botanic garden might constrain the taxonomic diversity of Odonata and if low habitat diversity might limit their functional diversity. We sampled adult Odonata from five water bodies along a gradient of human impact and characterized the Odonata communities based on 12 functional traits in Odonata. We used a species-area relationship to control for differences in the size of water bodies. Compared with natural lakes, the Odonata communities contained less species and their functional diversity was lower in the botanic garden ponds, where generalist species were basically hosted. Despite these limitations, the botanic garden ponds hosted the number of species expected for natural water bodies with the moderate surface area and functional diversity, thereby demonstrating that they are a valuable habitat for Odonata in an urban environment. Appropriate management involving the removal of exotic fish and habitat diversification, including creating lotic environments, would increase the taxonomic and functional diversity of Odonata in this urban system.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10201-022-00704-3.

Interactions between two functionally distinct aquatic invertebrate herbivores complicate ecosystem- and population-level resilience

Resilience, the capacity for a system to bounce-back after a perturbation, is critical for conservation and restoration efforts. Different functional traits have differential effects on system-level resilience. We test this experimentally in a lab system consisting of algae consumed by zooplankton, snails, or both, using an eutrophication event as a perturbation. We examined seston settlement load, chlorophyll-a and ammonium concentration as gauges of resilience. We find that Daphnia magna increased our measures of resilience. But this effect is not consistent across ecosystem measures; in fact, D. magna increased the difference between disturbed and undisturbed treatments in seston settlement loads. We have some evidence of shifting reproductive strategy in response to perturbation in D. magna and in the presence of Physa sp. These shifts correspond with altered population levels in D. magna, suggesting feedback loops between the herbivore species. While these results suggest only an ambiguous connection between functional traits to ecosystem resilience, they point to the difficulties in establishing such a link: indirect effects of one species on reproduction of another and different scales of response among components of the system, are just two examples that may compromise the power of simple predictions.

Modeling Mosquitoes and their Potential Odonate Predators Under Different Land Uses

To efficiently face the accelerated landscape transformation and its consequences in restructuring biotic communities and ecosystem services, one first question is which regional systems deserve prioritization for empirical assessments and interventive strategies. For the particular case of vector-borne disease control, we should consider generalist predators exhibiting differential responses to land-use change, as is the case of odonate insects. Thus, our aim was to infer land uses in Mexico where odonates (i.e., damselflies and dragonflies) might have some potential to predate mosquitoes of medical relevance. The study area included the hydrological basins of central Mexico. We modelled 167 species of odonates, four species of mosquitoes, and 51 land-use categories. Inferring spatial co-occurrence patterns from data mining and complex networks, we identified: (1) the ecological network of odonates and mosquitoes and (2) the land uses shared by these two groups. We inferred that 34% of odonate species co-occur with mosquitoes of medical relevance mainly in some preserved-mountain mesophyll cloud forest, high evergreen rainforest, and low tropical dry forest-but also in highly modified-human settlements, irrigation-based and pastures crop fields-land uses with strong human presence. Our findings highlight the relevance of community-regional studies for understanding the public health consequences of landscape change.

Species- and element-specific patterns of metal flux from contaminated wetlands versus metals shed with exuviae in emerging dragonflies

Dragonfly adults and their aquatic immature stages are important parts of food webs and provide a link between aquatic and terrestrial components. During emergence, contaminants can be exported into terrestrial food webs as immature adults fly away or be shed with their exuviae and remain in the wetland. Our previous work established metals accumulating in dragonfly nymphs throughout a contaminated constructed wetland designed to regulate pH and sequester trace metals from an industrial effluent line. Here, we evaluated the concentration and mass of metals leaving the wetland in flying emergents versus remaining in the wetland with the shed exuviae in 10 species of dragonflies belonging to 8 genera. Nine elements (Cu, Zn, Cd, Mn, V, Mg, Fe, Al, Pb) were evaluated that include essential and nonessential elements as well as trace and major metals. Metal concentrations in the emergent body and exuviae can differ by orders of magnitude. Aluminum, Fe, Mn, and Pb were largely shed in the exuviae. Vanadium and Cd were more variable among species but also tended to be shed with the exuviae. In contrast, Cu, Zn, and Mg showed a higher tendency to leave the wetland with an emerging dragonfly. Metals shed in dragonfly exuviae can moderate the transport of metals from contaminated wetlands. Taxonomic- and metal-specific variability in daily metal flux from the wetland depended upon concentration accumulated, individual body mass, and number of individuals emerging, with each factor's relative importance often differing among species. This illustrates the importance of evaluating the mass of metals in an individual and not only concentrations. Furthermore, differences in numbers of each species emerging will magnify differences in individual metal flux when calculating community metal flux. A better understanding of the variability of metal accumulation in nymphs/larvae and metal shedding during metamorphosis among both metals and species is needed.

Chronic Road Salt Exposure Across Life Stages and The Interactive Effects of Warming and Salinity in a Semiaquatic Insect

The salinization of freshwater habitats from winter road salt application is a growing concern. Understanding how taxa exposed to road salt run-off respond to this salinity exposure across life history transitions will be important for predicting the impacts of increasing salinity. We show that Leucorrhinia intacta Hagen, 1861 (Odonata: Libellulidae) dragonflies are robust to environmentally relevant levels of salt pollution across intrinsically stressful life history transitions (hatching, growth, and metamorphosis). Additionally, we observed no carry-over effects into adult dragonfly morphology. However, in a multiple-stressor setting, we see negative interactive effects of warming and salinity on activity, and we found that chronically warmed dragonfly larvae consumed fewer mosquitoes. Despite showing relatively high tolerance to salinity individually, we expect that decreased dragonfly performance in multiple-stressor environments could limit dragonflies' contribution to ecosystem services such as mosquito pest control in urban freshwater environments.

Regard and protect ground-nesting pollinators as part of soil biodiversity

While the Convention on Biological Diversity employs a habitat-oriented definition of soil biodiversity including all kinds of species living in soil, the Food and Agriculture Organization, since 2002 assigned to safeguard soil biodiversity, excludes them by focusing on species directly providing four ecosystem services contributing to soil quality and functions: nutrient cycling, regulation of water flow and storage, soil structure maintenance and erosion control, and carbon storage and regulation of atmospheric composition. Many solitary wasps and 70% of wild bees nest below ground and require protection during this long and crucial period of their lifecycle. Recent research has demonstrated the extent of threats to which ground-nesting pollinators are exposed, for example, chemicals and deep tillage. Ground-nesting pollinators change soil texture directly by digging cavities, but more importantly by their indirect contribution to soil quality and functions: 87% of all flowering plants require pollinators. Without pollinators, soil would lose all ecosystem services provided by these flowering plants, for example, litter, shade, roots for habitats, and erosion control. Above- and belowground biota are in constant interaction. Therefore, and in line with the Convention's definition, the key stakeholder, the Food and Agriculture Organization should protect ground-nesting pollinators explicitly within soil biodiversity conservation.

An ecological study of freshwater ecosystem and its colligation to Odonates assemblages in Ipogun, Southwest Nigeria

BACKGROUND

Odonata (dragonfly and damselfly) are particularly good indicators of freshwater ecosystem health. The constant disturbance of freshwater habitats can result in the reduction of Odonata species diversity. Changes in Odonata biodiversity are influenced by several human activities, such as agriculture, urbanization, input of pollutants in water and construction. This study was carried out to assess the abundance and diversity of Odonata, evaluate the physicochemical characteristics of water, and compare the community structure of Odonata at three selected sites along River Aponmu in Ipogun. Adult odonates were sampled and identified for 11 months using a sweep net, water samples were collected and some parameters were determined during the study period.

RESULTS

A total of 906 specimens representing sixty-four (64) species and sixteen (16) genera in seven (7) families (Coenagrionidae, Lestidae, Platycnemididae, Chlorocyphidae, Calopterygidae, Libellulidae, and Gomphidae) were collected and identified. Of the 906 specimens, Libellulidae had the highest percentage composition (44%) with 395 individuals out of which Trithemis arteriosa (a pollution tolerant species) had the highest number of individuals (225) and Gomphidae had the lowest percentage composition (0.03%) with 1 individual. Most of the species collected are known for their tolerance to disturbed environments. They include Pseudagrion melanicterum, Paragomphus genei, and Orthetrum Julia. Aponmu area had the highest species diversity (H' = 2.312) while Idi area had the least species diversity (H' = 2.021). Alaasin area had the highest Simpson_d value (0.8557) and the best taxa distribution (Evenness = 0.524; Equitability_J = 0.7764) which makes the area more pristine than other sites while Aponmu area had the least distribution (Evenness = 0.3365; Equitability_J = 0.6798). Analysis of variance (ANOVA) result of physicochemical parameters revealed that temperature (°C), pH, Dissolved Oxygen (mg/L), turbidity (NTU), Biochemical Oxygen Demand (mg/L), NO₃ (mg/L), and PO₄ (mg/L) did not show significant difference at the three sites while EC (µS/cm) and TDS (mg/L) which have moderately high mean values indicated significant difference at Aponmu area (p < 0.05). T. arteriosa exhibited a weak negative correlation to both temperature and DO.

CONCLUSIONS

This study has provided information on Odonata assemblage at River Aponmu and infers based on the assemblage that the river may be somewhat polluted at the period the research was carried out. It is therefore recommended that efforts should therefore be taken to discourage water pollution in order to preserve the diversity of these insects and the water quality.

Ecology and extent of freshwater browning - What we know and what should be studied next in the context of global change

Water browning or brownification refers to increasing water color, often related to increasing dissolved organic matter (DOM) and carbon (DOC) content in freshwaters. Browning has been recognized as a significant physicochemical phenomenon altering boreal lakes, but our understanding of its ecological consequences in different freshwater habitats and regions is limited. Here, we review the consequences of browning on different freshwater habitats, food webs and aquatic-terrestrial habitat coupling. We examine global trends of browning and DOM/DOC, and the use of remote sensing as a tool to investigate browning from local to global scales. Studies have focused on lakes and rivers while seldom addressing effects at the catchment scale. Other freshwater habitats such as small and temporary waterbodies have been overlooked, making the study of the entire network of the catchment incomplete. While past research investigated the response of primary producers, aquatic invertebrates and fishes, the effects of browning on macrophytes, invasive species, and food webs have been understudied. Research has focused on freshwater habitats without considering the fluxes between aquatic and terrestrial habitats. We highlight the importance of understanding how the changes in one habitat may cascade to another. Browning is a broader phenomenon than the heretofore concentration on the boreal region. Overall, we propose that future studies improve the ecological understanding of browning through the following research actions: 1) increasing our knowledge of ecological processes of browning in other wetland types than lakes and rivers, 2) assessing the impact of browning on aquatic food webs at multiple scales, 3) examining the effects of browning on aquatic-terrestrial habitat coupling, 4) expanding our knowledge of browning from the local to global scale, and 5) using remote sensing to examine browning and its ecological consequences.

Simultaneously estimating food web connectance and structure with uncertainty

Food web models explain and predict the trophic interactions in a food web, and they can infer missing interactions among the organisms. The allometric diet breadth model (ADBM) is a food web model based on the foraging theory. In the ADBM, the foraging parameters are allometrically scaled to body sizes of predators and prey. In Petchey et al. (Proceedings of the National Academy of Sciences, 2008; 105: 4191), the parameterization of the ADBM had two limitations: (a) the model parameters were point estimates and (b) food web connectance was not estimated.The novelty of our current approach is: (a) We consider multiple predictions from the ADBM by parameterizing it with approximate Bayesian computation, to estimate parameter distributions and not point estimates. (b) Connectance emerges from the parameterization, by measuring model fit using the true skill statistic, which takes into account prediction of both the presences and absences of links.We fit the ADBM using approximate Bayesian computation to 12 observed food webs from a wide variety of ecosystems. Estimated connectance was consistently greater than previously found. In some of the food webs, considerable variation in estimated parameter distributions occurred and resulted in considerable variation (i.e., uncertainty) in predicted food web structure.These results lend weight to the possibility that the observed food web data is missing some trophic links that do actually occur. It also seems likely that the ADBM likely predicts some links that do not exist. The latter could be addressed by accounting in the ADBM for additional traits other than body size. Further work could also address the significance of uncertainty in parameter estimates for predicted food web responses to environmental change.

A hurricane alters the relationship between mangrove cover and marine subsidies

As global change alters the composition and productivity of ecosystems, the importance of subsidies from one habitat to another may change. We experimentally manipulated black mangrove (Avicennia germinans) cover in ten large plots and over five years (2014-2019) quantifying the effects of mangrove cover on subsidies of floating organic material (wrack) into coastal wetlands. As mangrove cover increased from zero to 100%, wrack cover and thickness decreased by ~60%, the distance that wrack penetrated into the plots decreased by ~70%, and the percentage of the wrack trapped in the first six m of the plot tripled. These patterns observed during four "normal" years disappeared in a fifth year following Hurricane Harvey (2017), when large quantities of wrack were pushed far into the interior of all the plots, regardless of mangrove cover. Prior to the storm, the abundance of animals collected in grab samples increased with wrack biomass. Wrack composition did not affect animal abundance or composition. Experimental outplants of two types of wrack (red algae and seagrass) revealed that animal abundance and species composition varied between the fringe and interior of the plots, and between microhabitats dominated by salt marsh versus mangrove vegetation. The importance of wrack to overall carbon stocks varied as a function of autochthonous productivity: wrack inputs (per m² ) based on survey data were greater than aboveground plant biomass in the plots (42 × 24 m) dominated by salt marsh vegetation, but decreased to 5% of total aboveground biomass in plots dominated by mangroves. Our results illustrate that increasing mangrove cover decreases the relative importance of marine subsidies into the intertidal at the plot level, but concentrates subsidies at the front edge of the mangrove stand. Storms, however, may temporarily override mangrove attenuation of wrack inputs. Our results highlight the importance of understanding how changes in plant species composition due to global change will impact marine subsidies and exchanges among ecosystems, and foster a broader understanding of the functional interdependence of adjacent habitats within coastal ecosystems.

Beyond the prey: male spiders highly invest in silk when producing worthless gifts

In the spider Paratrechalea ornata, males have two gift-giving mating tactics, offering either a nutritive (prey) or a worthless (prey leftovers) silk wrapped gift to females. Both gift types confer similar mating success and duration and afford males a higher success rate than when they offer no gift. If this lack of difference in the reproductive benefits is true, we would expect all males to offer a gift but some males to offer a worthless gift even if prey are available. To test this, we allowed 18 males to court multiple females over five consecutive trials. In each trial, a male was able to produce a nutritive gift (a live housefly) or a worthless gift (mealworm exuviae). We found that, in line with our predictions, 20% of the males produced worthless gifts even when they had the opportunity to produce a nutritive one. However, rather than worthless gifts being a cheap tactic, they were related to a higher investment in silk wrapping. This latter result was replicated for worthless gifts produced in both the presence and absence of a live prey item. We propose that variation in gift-giving tactics likely evolved initially as a conditional strategy related to prey availability and male condition in P. ornata. Selection may then have favoured silk wrapping as a trait involved in female attraction, leading worthless gift-giving to invade.

Traits affecting nutrient recycling by mobile consumers can explain coexistence and spatially heterogeneous trophic regulation across a meta-ecosystem

Ecosystems are linked through spatial flows of organisms and nutrients that impact their biodiversity and regulation. Theory has predominantly studied passive nutrient flows that occur independently of organism movement. Mobile organisms, however, commonly drive nutrient flows across ecosystems through nutrient recycling. Using a meta-ecosystem model where consumers move between ecosystems, we study how consumer recycling and traits related to feeding and sheltering preferences affect species diversity and trophic regulation. We show local effects of recycling can cascade across space, yielding spatially heterogeneous top-down and bottom-up effects. Consumer traits impact the direction and magnitude of these effects by enabling recycling to favour a single ecosystem. Recycling further modifies outcomes of competition between consumer species by creating a positive feedback on the production of one competitor. Our findings suggest spatial interactions between feeding and recycling activities of organisms are key to predicting biodiversity and ecosystem functioning across spatial scales.

Impacts of Warming on Reciprocal Subsidies Between Aquatic and Terrestrial Ecosystems

Cross-ecosystem subsidies are important as their recipients often rely on them to supplement in situ resource availability. Global warming has the potential to alter the quality and quantity of these subsidies, but our knowledge of these effects is currently limited. Here, we quantified the biomass and diversity of the invertebrates exchanged between freshwater streams and terrestrial grasslands in a natural warming experiment in Iceland. We sampled invertebrates emerging from the streams, those landing on the water surface, ground-dwelling invertebrates falling into the streams, and those drifting through the streams. Emerging invertebrate biomass or diversity did not change with increasing temperature, suggesting no effect of warming on aquatic subsidies to the terrestrial environment over the 1-month duration of the study. The biomass and diversity of aerial invertebrates of terrestrial origin landing on the streams increased with temperature, underpinned by increasing abundance and species richness, indicating that the greater productivity of the warmer streams may attract more foraging insects. The biomass of ground-dwelling invertebrates falling into the streams also increased with temperature, underpinned by increasing body mass and species evenness, suggesting that soil warming leads to terrestrial communities dominated by larger, more mobile organisms, and thus more in-fall to the streams. The biomass and diversity of terrestrial invertebrates in the drift decreased with temperature, however, underpinned by decreasing abundance and species richness, reflecting upstream consumption due to the higher energetic demands of aquatic consumers in warmer environments. These results highlight the potential for asynchronous responses to warming for reciprocal subsidies between aquatic and terrestrial environments and the importance of further research on warming impacts at the interface of these interdependent ecosystems.

Warming and top predator loss drive direct and indirect effects on multiple trophic groups within and across ecosystems

The interspecific interactions within and between adjacent ecosystems strongly depend on the changes in their abiotic and biotic components. However, little is known about how climate change and biodiversity loss in a specific ecosystem can impact the multiple trophic interactions of different biological groups within and across ecosystems. We used natural microecosystems (tank-bromeliads) as a model system to investigate the main and interactive effects of aquatic warming and aquatic top predator loss (i.e. trophic downgrading) on trophic relationships in three integrated food web compartments: (a) aquatic micro-organisms, (b) aquatic macro-organisms and (c) terrestrial predators (i.e. via cross-ecosystem effects). The aquatic top predator loss substantially impacted the three food web compartments. In the aquatic macrofauna compartment, trophic downgrading increased the filter feeder richness and abundance directly and indirectly via an increase in detritivore richness, likely through a facilitative interaction. For the microbiota compartment, aquatic top predator loss had a negative effect on algae richness, probably via decreasing the input of nutrients from predator biological activities. Furthermore, the more active terrestrial predators responded more to aquatic top predator loss, via an increase in some components of aquatic macrofauna, than more stationary terrestrial predators. The aquatic trophic downgrading indirectly altered the richness and abundance of cursorial terrestrial predators, but these effects had different direction according to the aquatic functional group, filter feeder or other detritivores. The web-building predators were indirectly affected by aquatic trophic downgrading due to increased filter feeder richness. Aquatic warming did not affect the aquatic micro- or macro-organisms but did positively affect the abundance of web-building terrestrial predators. These results allow us to raise a predictive framework of how different anthropogenic changes predicted for the next decades, such as aquatic warming and top predator loss, could differentially affect multiple biological groups through interactions within and across ecosystems.

Intraspecific Morphological Variation in the Dragonfly Erythrodiplax Media (Odonata: Libellulidae) Among South American Grassland Physiognomies

We assessed the intraspecific morphological variation in Erythrodiplax media Borror 1942 (Odonata, Libellulidae) among grassland physiognomies ("Coastal," "Highland," and "Steppic") in the South Brazilian Campos. We measured six morphological traits (total body length, thorax height, length, and width of the fore- and hindwings) from 90 specimens (60 males and 45 females). We tested the effect of the grassland type on the set of traits using one-way MANOVA and principal component analysis (PCA) (separately for each sex). Grassland physiognomy affected the morphology of males and females. In both sexes, the PCA mostly opposed the specimens of the Coastal from the Highland and Steppic grasslands. The first PCA axis separated specimens according to body lengths, thorax heights, and wing width, while the second PCA axis opposed specimens according to wing length and thorax height from specimens with broader wings and longer body lengths. Males from the Coastal had longer body lengths and shorter thorax heights than Highland and Steppic grasslands, while males from the Steppic had longer fore- and hindwings than specimens from the Coastal and Highland grasslands. Females from the Coastal had significantly shorter forewings than specimens from the Steppic grasslands and shorter hindwings than Highland grasslands. Our results are likely explained by the differences in climate and habitat complexity among grassland types and indicate that the processes driving odonate performance vary among grassland biotopes. This study potentially indicates that dragonflies are sensitive to changes in the vegetation structure in South American subtropical grasslands.

Microplastics in terrestrial ecosystems: Moving beyond the state of the art to minimize the risk of ecological surprise

Microplastic (plastic particles measuring <5mm) pollution is ubiquitous. Unlike in other well-studied ecosystems, for example, marine and freshwater environments, microplastics in terrestrial systems are relatively understudied. Their potential impacts on terrestrial environments, in particular the risk of causing ecological surprise, must be better understood and quantified. Ecological surprise occurs when ecosystem behavior deviates radically from expectations and generally has negative consequences for ecosystem services. The properties and behavior of microplastics within terrestrial environments may increase their likelihood of causing ecological surprises as they (a) are highly persistent global pollutants that will last for centuries, (b) can interact with the abiotic environment in a complex manner, (c) can impact terrestrial organisms directly or indirectly and (d) interact with other contaminants and can facilitate their transport. Here, we compiled findings of previous research on microplastics in terrestrial environments. We systematically focused on studies addressing different facets of microplastics related to their distribution, dispersion, impact on soil characteristics and functions, levels of biological organization of tested terrestrial biota (single species vs. assemblages), scale of experimental study and corresponding ecotoxicological effects. Our systematic assessment of previous microplastic research revealed that most studies have been conducted on single species under laboratory conditions with short-term exposures; few studies were conducted under more realistic long-term field conditions and/or with multi-species assemblages. Studies targeting multi-species assemblages primarily considered soil bacterial communities and showed that microplastics can alter essential nutrient cycling functions. More ecologically meaningful studies of terrestrial microplastics encompassing multi-species assemblages, critical ecological processes (e.g., biogeochemical cycles and pollination) and interactions with other anthropogenic stressors must be conducted. Addressing these knowledge gaps will provide a better understanding of microplastics as emerging global stressors and should lower the risk of ecological surprise in terrestrial ecosystems.

A sit-and-wait predator, but not an active-pursuit predator, alters pollinator-mediated selection on floral traits

Indirect species interactions are ubiquitous in nature, often outnumbering direct species interactions. Yet despite evidence that indirect interactions have strong ecological effects, relatively little is known about whether they can shape adaptive evolution by altering the strength and/or direction of natural selection. We tested whether indirect interactions affect the strength and direction of pollinator-mediated selection on floral traits of the bumble-bee pollinated wildflower Lobelia siphilitica. We estimated the indirect effects of two pollinator predators with contrasting hunting modes: dragonflies (Aeshnidae and Corduliidae) and ambush bugs (Phymata americana, Reduviidae). Because dragonflies are active pursuit predators, we hypothesized that they would strengthen pollinator-mediated selection by weakening plant-pollinator interactions (i.e., a density-mediated indirect effect). In contrast, because ambush bugs are sit-and-wait predators, we hypothesized that they would weaken or reverse the direction of pollinator-mediated selection by altering pollinator foraging behavior (i.e., a trait-mediated indirect effect). Specifically, if ambush bugs hunt from plants with traits that attract pollinators (i.e., prey), then pollinators will spend less time visiting those plants, weakening or reversing the direction of selection on attractive floral traits. We did not find evidence that high dragonfly abundance strengthened selection on floral traits via a density-mediated indirect effect: neither pollen limitation (a proxy for the strength of plant-pollinator interactions) nor directional selection on floral traits of L. siphilitica differed significantly between high- and low-dragonfly abundance treatments. In contrast, we did find evidence that ambush bug presence affected selection on floral traits via a trait-mediated indirect effect: ambush bugs hunted from L. siphilitica plants with larger daily floral displays, reversing the direction of pollinator-mediated selection on daily display size. These results suggest that indirect species interactions have the potential to shape adaptive evolution by altering natural selection.