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Effects of dragonflies on pollinators.a, Photograph of a dragonfly (female Erythemis simplicicollis) consuming a bee-fly pollinator (Bombylius sp. (Diptera: Bombyliidae)) at our study site. Photo by M.W.McC. b, Results from the experiment comparing pollinator visitation rates in pairs of large-mesh cages placed around a H. fasciculatum shrub, one with a dragonfly (female E. simplicicollis) in it, and one as a control. Overall, visitation was much lower in the cage with the dragonfly than in the control cage (paired t-test: t = -3.5, P = 0.007).
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Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift habitats during their life cycles and provide potent condu...
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... near adult dragon- flies. At our study site, over a seven-day period, we observed several predation events by two common species of dragonflies (Anax junius and Erythemis simplicicollis) 24 known to attack large insect species including pollinators; four of eight of those observed predation events were on pollinators (bees, moths and flies; Fig. 5a). To examine the behavioural influence of dragonfly presence on polli- nator visitation, we put cages around naturally occurring H. fasci- culatum near a pond with fish; the mesh size allowed free access by most pollinators but precluded escape by enclosed E. simplicicollis. We found that fewer visitors entered cages containing ...
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... cages containing dragonflies than control cages (paired t-test: t ¼ 24.2, P ¼ 0.002), and visitors that did enter cages with dragonflies foraged on fewer flowers than visitors that entered cages not containing dragonflies (t ¼ 23.8, P ¼ 0.009). This resulted in H. fasciculatum flowers receiving fewer overall visits in the presence of a dragonfly (Fig. ...
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... Se ha sugerido que este parámetro puede reflejar factores que influyen en la forma y tamaño corporal, como la velocidad del caudal, para enfrentar o adherirse a corrientes rápidas (Fenoglio et al. 2020). Organismos con dietas ricas en energía, como los depredadores, tienden a tener relaciones longitud-peso distintas a los detritívoros, reforzando la idea de que tanto el tipo de hábitat como las estrategias tróficas juegan roles importantes en las proporciones corporales (Knight et al. 2005;Fenoglio et al. 2020). No obstante, para evaluar esta última hipótesis, son necesarios trabajos en distintas localidades de la ecorregión subantártica de Magallanes. ...
RESUMEN La biomasa es un parámetro clave en ecología, ya que proporciona información sobre el funcionamiento de los ecosistemas. Las estimaciones de longitud-peso se han utilizado ampliamente debido a sus procedimientos relativamente simples y directos. En este estudio, realizamos la primera evaluación de las relaciones longitud-peso para 25 especies de insectos acuáticos presentes en la ecoregión sub-Antártica chilena. Nuestros resultados indican que existe una fuerte correlación lineal entre el peso y el tamaño de los organismos, tal como indican los altos coeficientes de determinación. Encontramos valores bajos de b para la mayoría de los organismos estudiados, lo que podría indicar mudas recientes y/o grado de quitinización incompleta, o predominancia de estados de desarrollo iniciales. Si bien los parámetros estimados de las regresiones lineales y no lineales fueron similares a los reportados en otros estudios, es importante señalar que se debe evitar la extrapolación de datos desde otras áreas dada las particularidades inherentes de cada sistema. Esperamos que nuestros resultados fomenten la generación y recopilación de datos longitud-peso, ya que representan información importante sobre la biomasa y la producción secundaria, parámetros clave de la diversidad funcional.
... Most considered projects involved landscape scale restoration of different habitats including ponds. This makes a lot of sense given that fluxes of nutrients and energy in landscapes cross barriers between aquatic and terrestrial habitats (Knight et al. 2005;Nummi et al. 2011;Lewis-Phillips et al. 2020). In addition, amphibious pond species, like most aquatic insects and amphibians, also have terrestrial habitat requirements and, vice versa, many typical terrestrial species and species interactions, such as plant-pollinator networks, benefit from the presence of ponds (e.g. ...
Pond ecosystems harbour substantial biodiversity and contribute to several ecosystem services as nature‐based solutions (NbS). Pond restoration and creation projects have been initiated to address these trends, yet while some insights are published, many remain within the expertise of practitioners and are not easily accessible. Moreover, papers synthesizing findings from multiple such projects to derive broad, universal conclusions are very much lacking. Here, we contacted pond creation and restoration practitioners that worked on recent pond restoration projects in Europe using a questionnaire. We reported which practices are currently most common and identified where current good practices might need to be modified. As expected, most projects targeted and monitored species and habitats protected under the European Union Birds Directive and Habitats Directive. Most projects focused on species as conservation targets, rather than the promotion of specific Natura 2000 habitats, pond ecosystem services or NbS. Several challenges were highlighted including funding limitations and stakeholder engagement difficulties. Recommendations included amending legal frameworks, improving connectivity among pondscapes for effective biodiversity conservation and implementing more systematic monitoring. This work illustrates how consultation of practitioners as stakeholders can generate insights that may remain hidden in typical monitoring reports.
... This spider species offers several opportunities to research these eco-evolutionary processes. Individuals live in riparian habitats which are known to be highly variable with unpredictable conditions that can lead to floods (Lytle 2002;Iwata et al. 2003;Sanzone et al. 2003;Knight et al. 2005;Hagen and Sabo 2014). Given the nature of the environment, prey availability is unpredictable and potentially interacts with mate competition which increases progressively throughout the mating season (see below). ...
Environmental conditions together with agents of sexual selection (i.e., mate competition) regulate the expression of mating tactics. Likewise, alternative tactics arise when resources needed for reproduction are limited. These tactics are commonly performed by less competitive males (e.g. small size) and restricted to low frequencies in the population. Exceptionally, in the gift-giving spider Paratrechalea ornata the deceptive tactic frequencies can range between 0 and 80% throughout the mating season. Males offer nutritive gifts (prey wrapped in silk), but they can very often wrap inedible items offering worthless gifts as an alternative tactic. The gift is presented by males during courtship, and females can only recognize the content, and therefore the deception, once they have accepted the mating. Although, receiving food gifts have a positive effect on females’ fecundity, producing and offering it can be costly for males. We tested the hypothesis that the frequency shifts in worthless gift-giving are the result of the interaction between prey availability, post-copulatory competition and individual size altering the benefits and costs associated with each gift type. In the field, we found that the deceptive tactic is performed by all males regardless of their size. Small and medium males mostly produced worthless gifts under low prey availability and high post-copulatory competition; whereas large males were not affected by prey availability, producing worthless gifts only under low post-copulatory competition. To further understand how mate competition affects less competitive males, we disentangled the potential effects on medium size males by conducting experiments with constant prey availability. We found that under post-copulatory competition, males increased the production of worthless gifts compared to males exposed to pre-copulatory or no competition. In this treatment all males acquired a mating, though with reduced mating duration. Altogether, our findings support that post-copulatory competition limits the deceptive gift-giving tactic, creating the observed shifts in the frequencies throughout the mating season.
... For these species, agricultural practices can directly influence the habitats used during both their terrestrial and aquatic life periods, thereby altering the services that these species can provide (Priyadarshana & Slade, 2023;Raitif et al., 2019). Aquatic species may also trigger cascading effects onto adjacent crop productivity, as shown in a system with fishes, dragonflies, and pollinators (Knight et al., 2005). In this example, the presence of predatory fish in ponds near crops indirectly improves crop pollination efficiency because fish predate on dragonfly larvae, thereby decreasing the predation pressure of winged dragonflies on pollinator insects in the nearest crop fields adjacent to the pond. ...
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.
... There are often substantial knowledge gaps in how individuals, energy and matter interact across scales and between ecosystem domains (Pichon et al., 2024), but these have potential to generate powerful feedbacks and emergent phenomena (e.g. Knight et al. 2005, Kamaru et al. 2024, Pichon et al., 2024. If we are to understand emerging ecological patterns then, it stands to reason that we have to be able to elucidate the sign and magnitude of those cross-scale and cross-domain feedback loops (Pichon et al., 2024). ...
The myriad interactions among individual plants, animals, microbes and their abiotic environment generate emergent phenomena that will determine the future of life on Earth. Here, we argue that holistic ecosystem models – incorporating key biological domains and feedbacks between biotic and abiotic processes and capable of predicting emergent phenomena – are required if we are to understand the functioning of complex, terrestrial ecosystems in a rapidly changing planet. We argue that holistic ecosystem models will provide a framework for integrating the many approaches used to study ecosystems, including biodiversity science, population and community ecology, soil science, biogeochemistry, hydrology and climate science. Holistic models will provide new insights into the nature and importance of feedbacks that cut across scales of space and time, and that connect ecosystem domains such as microbes with animals or above with below ground. They will allow us to critically examine the origins and maintenance of ecosystem stability, resilience and sustainability through the lens of systems theory, and provide a much-needed boost for conservation and the management of natural environments. We outline our approach to developing a holistic ecosystem model – the Virtual Ecosystem – and argue that while the construction of such complex models is obviously ambitious, it is both feasible and necessary.
... Heavy metal exposure can lead to developmental abnormalities and decreased fertility, altered feeding habits and predator avoidance behaviours can decrease survival rates. The introduction of heavy metals can induce oxidative stress in aquatic organisms, leading to cellular damage and increased vulnerability to diseases (Knight, T. M. [41]. [43]. ...
Heavy metals, which include lead (Pb), mercury (Hg), cadmium (Cd), chromium (Cr), arsenic (As), nickel (Ni)and zinc (Zn), serve as persistent environmental pollutants that pose significant risks to aquatic ecosystems and human health. This review article provides a comprehensive analysis of the toxicological effects of heavy metals on fish, underscoring the pathways of exposure, biological implications, and methodologies for mitigating toxicity. We examine the sources of heavy metal contamination, such as industrial discharges, agricultural runoff, domestic sewage, and mining activities, which contribute to the accumulation of these deleterious substances in aquatic environments. The review clarifies the processes through which heavy metals penetrate fish tissues and the resulting physiological and biochemical alterations, including bioaccumulation, toxicity, oxidative stress, growth inhibition, and behavioral changes. The manuscript details various analytical methodologies employed to detect and quantify heavy metals in fish tissues, while also addressing the difficulties associated with monitoring and assessing contamination levels. Moreover, we evaluate the ecological consequences of heavy metal accumulation in fish populations and the potential risks posed to human health through the consumption of contaminated fish products. The review further considers recent innovations in bioremediation techniques, such as the use of microbial and phytoremediation systems, aimed at alleviating heavy metal pollution in aquatic environments. By synthesizing existing research findings and identifying areas where knowledge is lacking, this review seeks to provide a valuable resource for researchers, policymakers, and environmental advocates. It underscores the necessity for continuous monitoring, more rigorous regulatory frameworks, and novel remediation strategies to address the ongoing challenge of heavy metal toxicity in fish, thereby safeguarding both aquatic ecosystems and public health.
... At the same time, the depletion of conspicuous emerging insects, may also impact S. antinorii, but probably to a lesser degree, because S. antinorii can rely on many other terrestrial preys (Table 2). However, it is likely that the influence of fish extends beyond shrews and aquatic macroinvertebrates to encompass and impoverish the entire insectivore community living along the shoreline (Baxter et al., 2004;Knight et al., 2005;Epanchin et al., 2010). For example, the alterations of insect subsidies induced by fish (e.g., reduced emergence of conspicuous insects) can lead to a reduction of terrestrial invertebrate predators such as spiders (Baxter et al., 2004), which constitute a significant portion of the diet of S. antinorii (Table 2). ...
Widespread fish introductions into originally fishless mountain lakes have had severe consequences for native biota, including aquatic macroinvertebrates, which provide important food subsidies for terrestrial and semiaquatic insectivores like shrews (Fam. Soricidae). Since both fish and shrews rely on aquatic macroinvertebrates as food, whether in their larval or imaginal stage, we investigated if fish presence had adverse effects on shrews. Baited tubes were deployed to monitor the presence/absence of shrews by collecting their scats in lakes with and without fish in the western Italian Alps. Only two species, the Valais shrew (Sorex antinorii) and the Eurasian water shrew (Neomys fodiens), were found inhabiting the lakes' edges, where they fed on aquatic insect subsidies. The results indicate a significant pattern of exclusion between shrews and introduced fish. This negative association was especially evident in the presence of large-bodied fish (i.e., salmonids), but also of small fish (i.e., cyprinids). Consistently, compared to naturally fishless lakes, those with fish exhibit a lower availability of aquatic prey, representing a significant portion of the diet of both shrew species. Overall, our findings suggest that the impact on shrews may be mediated by a complex interplay of competition and predation between fish and shrews. Fish impacts may extend beyond the lakes to insectivorous mammals in surrounding areas. We recommend that the potential benefits to species and habitats reliant on aquatic subsidies be considered and integrated into conservation and restoration plans, and that these findings be communicated to the public to foster greater support for restoration efforts.
... Invertebrates are the most diverse animal group, including a wide variety of feeding habits and ecological functions, connecting ecosystem compartments (Knight et al., 2005). Current terrestrial ecosystems have been shaped by these organisms, either as primary consumers or predators in "green" food webs, establishing resource-based mutualistic interactions with plants or as detritivores in "brown" food webs (Kitching et al., 2020;Eisenhauer & Hines 2021). ...
Climate change represents the greatest challenge for humanity in the 21st century, especially concerning the need to reconcile increased food and energy production with the conservation of ecosystems. The Brazilian Cerrado, the second-largest ecoregion in South America, is recognized as a global biodiversity hotspot and a great center for grain, animal protein, and hydroelectric power production. This doctoral thesis investigates the origin and extent of climate change currently affecting this ecoregion, as well as its potential impacts on biodiversity. This document consists of five chapters, with the key
findings presented across three scientific papers. The first paper demonstrated that the Cerrado is becoming significantly hotter and drier. The massive conversion of native vegetation to pasture and cropland plays a key role in driving regional climate change by reducing evapotranspiration during the dry season, leading to pronounced warming and decreased relative humidity. The second article described a significant reduction in rainfall and frequency of rainy days in the northern and central Cerrado regions for all periods except at the beginning of the dry season. Our results indicate a clear trend of dry season lengthening and intensification, resulting in widespread environmental and social impacts that transcend the Cerrado boundaries. These findings are associated with the intensification of the South Atlantic Subtropical Anticyclone, which has been shifting atmospheric circulation and raising regional subsidence. The third article reviews the climate change in the Cerrado and projects possible impacts on different taxonomic groups of terrestrial biodiversity. Over the past 5,000 years, the Cerrado’s predictable temperature and water cycles shaped species' life history strategies and community structure. Climate change is now reshaping ecological communities, leading to biotic homogenization. The impacts of climate change on society and biodiversity are already wide, and its mitigation will require the replacement of the current agricultural production model in the Cerrado by more sustainable practices.
... Given the plant species where Odonata have been recorded, with very large floating flowers (waterlilies), it is likely that dragonflies and damselflies just perch on flowers as a support, with no particular purpose to visit them. In addition, their impact on pollination is probably more detrimental than beneficial, as they are known to predate valuable pollinators such as bees (Knight et al. 2005). In summary, Odonata appear to be less good candidates for pollination, justifying a more specific interest in ETP, Megaloptera and Diptera in our following discussion. ...
The substantial loss of insects we are experiencing today has been highlighted all over the world. There is a growing concern about the global decline of pollinators and its impact on terrestrial and agricultural ecosystems, but the focus of scientists towards bees remains the rule. Therefore, the role of other insect taxa in pollination is still overlooked. Our review focused on some of these neglected pollinating taxa, the winged aquatic insects, i.e., insects with an aquatic larval stage such as Ephemeroptera, Trichoptera, Plecoptera (ETP), Megaloptera and some aquatic Diptera. We first documented the visitors of aquatic and wetland flowering plants, anticipating a greater presence of aquatic insects on these plants compared to terrestrial pollinators. Secondly, we documented plant visits, pollen found in gut contents and pollen transfers performed by aquatic insects. Our results revealed a surprisingly low proportion of aquatic insects visiting both aquatic and wetland plants, suggesting a potential gap in the literature. The scarcity of articles dedicated to pollen transfer by aquatic insects also indicates that they are fewly considered in ecological studies. While the role of aquatic insects in pollination is not well documented in the literature, records of their flower visits and pollen found on them or in their gut contents do exist and are promising clues to consider them as effective pollinators. Future research is needed to provide new insights into the importance of winged aquatic insects for the reproductive success of plants, which could also be an argument for the importance of wetland conservation.
... Double mutualisms rely on positive but unstable feedback loops between ecological functions [19,84], and the loss of a single link can disrupt these loops with severe consequences for network stability and all participating species. When merging different mutualistic networks, species that connect both networks tend to exhibit positive correlations (e.g. a generalist pollinator also acts as a generalist disperser), which implies that perturbations could easily propagate through the entire network [85]. This effect was particularly pronounced in non-native networks, as they were not only structurally simple and had fewer resources but also held a smaller community of double mutualists. ...
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.
