Global warming is expected to have direct effects on species through their sensitivity to temperature, and also via their biotic interactions, with cascading indirect effects on species, communities, ...and entire ecosystems. To predict the community-level consequences of global climate change we need to understand the relative roles of both the direct and indirect effects of warming. We used a laboratory experiment to investigate how warming affects a tropical community of three species of Drosophila hosts interacting with two species of parasitoids over a single generation. Our experimental design allowed us to distinguish between the direct effects of temperature on host species performance, and indirect effects through altered biotic interactions (competition among hosts and parasitism by parasitoid wasps). Although experimental warming significantly decreased parasitism for all host-parasitoid pairs, the effects of parasitism and competition on host abundances and host frequencies did not vary across temperatures. Instead, effects on host relative abundances were species-specific, with one host species dominating the community at warmer temperatures, irrespective of parasitism and competition treatments. Our results show that temperature shaped a Drosophila host community directly through differences in species' thermal performance, and not via its influences on biotic interactions.
•Functionally diverse dung beetle assemblages deliver multiple ecosystem services.•Dung removal may not be fully representative of overall dung beetle functioning.•Activity of tunnelling dung beetles ...stimulates soil fauna feeding activity.
Dung beetles mediate a variety of important ecosystem services in both natural and human-modified habitats. These services are associated with the exploitation of dung by beetles for breeding and feeding, with different functional groups using dung in different ways. While many studies have considered how individual ecosystem functions and services (primarily dung removal and seed dispersal) are affected by changes in dung beetle diversity, fewer studies have considered the consequences for multiple functions and services. We used manipulative experiments to evaluate the functional efficiency of three species of dung beetles, each representing one of the three functional groups present in temperate Europe. Standardising beetle biomass, we compared single-species treatments to a three-species mixture containing each of the species in equal biomass. We then measured three ecosystem services relevant in supporting pasture-based livestock production systems: dung removal, soil fauna activity, and soil aeration. The presence of dung beetles significantly elevated all three ecosystem services. However, delivery of each service peaked under different treatments, indicating that no single-species assemblage can provide maximum functioning across multiple services. For all three services, the three-species polyculture provided a level of functioning indistinguishable from the most efficient single-species treatment. Our results highlight the importance of considering multiple functions and services when assessing the relationship between biodiversity and ecosystem functioning, and suggest that the conservation of functional richness within dung beetle communities could play an important role in securing the delivery of multiple ecosystem services.
1. Fundamental ecological research is both intrinsically interesting and provides the basic knowledge required to answer applied questions of importance to the management of the natural world. The ...100th anniversary of the British Ecological Society in 2013 is an opportune moment to reflect on the current status of ecology as a science and look forward to high-light priorities for future work. 2. To do this, we identified 100 important questions of fundamental importance in pure ecology. We elicited questions from ecologists working across a wide range of systems and disciplines. The 754 questions submitted (listed in the online appendix) from 388 participants were narrowed down to the final 100 through a process of discussion, rewording and repeated rounds of voting. This was done during a two-day workshop and thereafter. 3. The questions reflect many of the important current conceptual and technical pre-occupations of ecology. For example, many questions concerned the dynamics of environmental change and complex ecosystem interactions, as well as the interaction between ecology and evolution. 4. The questions reveal a dynamic science with novel subfields emerging. For example, a group of questions was dedicated to disease and micro-organisms and another on human impacts and global change reflecting the emergence of new subdisciplines that would not have been foreseen a few decades ago. 5. The list also contained a number of questions that have perplexed ecologists for decades and are still seen as crucial to answer, such as the link between population dynamics and life-history evolution. 6. Synthesis. These 100 questions identified reflect the state of ecology today. Using them as an agenda for further research would lead to a substantial enhancement in understanding of the discipline, with practical relevance for the conservation of biodiversity and ecosystem function.
Documenting which species interact within ecological communities is challenging and labor intensive. As a result, many interactions remain unrecorded, potentially distorting our understanding of ...network structure and dynamics. We test the utility of four structural models and a new coverage-deficit model for predicting missing links in both simulated and empirical bipartite networks. We find they can perform well, although the predictive power of structural models varies with the underlying network structure. The accuracy of predictions can be improved by ensembling multiple models. Augmenting observed networks with mostlikely missing links improves estimates of qualitative network metrics. Tools to identify likely missing links can be simple to implement, allowing the prioritization of research effort and more robust assessment of network properties.
Parasitoids are key regulators of the population dynamics of their arthropod hosts, are integral to the structure and dynamics of food webs, and provide ecosystem services by suppressing agricultural ...pests. Despite their ecological and functional importance, relatively few studies have considered the effects of a warming climate on host–parasitoid interactions.
The three primary modes through which parasitoids might respond to a warming climate are by (i) shifting distributions into cooler environments, (ii) altering phenology, and (iii) adjusting to persist
in situ
through phenotypic plasticity or evolutionary adaptation.
Here, we focus on examples of altered distributions and phenology in response to climate warming. We suggest that the responses of parasitoids to elevated temperatures and the population dynamic consequences for their hosts will be linked to two key traits: the dispersal ability of both partners, and the host specificity of parasitoids.
Effects of climate warming on host–parasitoid interactions will be complicated by interactions with other co‐occurring environmental changes, such as elevated carbon dioxide and nitrogen, and to interactions with competitors, mutualists, and antagonists. These factors will complicate efforts to generate predictive models of host–parasitoid interactions, for example in the context of the ecosystem service of biological pest control.
Studies investigating how biodiversity affects ecosystem functioning increasingly focus on multiple functions measured simultaneously ("multifunctionality"). However, few such studies assess the role ...of species interactions, particularly under alternative environmental scenarios, despite interactions being key to ecosystem functioning. Here we address five questions of central importance to ecosystem multifunctionality using a terrestrial animal system. (1) Does the contribution of individual species differ for different ecosystem functions? (2) Do inter-species interactions affect the delivery of single functions and multiple functions? (3) Does the community composition that maximizes individual functions also maximize multifunctionality? (4) Is the functional role of individual species, and the effect of interspecific interactions, modified by changing environmental conditions? (5) How do these roles and interactions change under varying scenarios where ecosystem services are weighted to reflect different societal preferences? We manipulated species' relative abundance in dung beetle communities and measured 16 functions contributing to dung decomposition, plant productivity, nutrient recycling, reduction of greenhouse gases, and microbial activity. Using the multivariate diversity–interactions framework, we assessed how changes in species identity, composition, and interspecific interactions affected these functions in combination with an environmental driver (increased precipitation). This allowed us to identify key species and interactions across multiple functions. We then developed a desirability function approach to examine how individual species and species mixtures contribute to a desired state of overall ecosystem functioning. Species contributed unequally to individual functions, and to multifunctionality, and individual functions were maximized by different community compositions. Moreover, the species and interactions important for maintaining overall multifunctionality depended on the weight given to individual functions. Optimal multifunctionality was context-dependent, and sensitive to the valuation of services. This combination of methodological approaches allowed us to resolve the interactions and indirect effects among species that drive ecosystem functioning, revealing how multiple aspects of biodiversity can simultaneously drive ecosystem functioning. Our results highlight the importance of a multifunctionality perspective for a complete assessment of species' functional contributions.
Reasons for restricted and nonuniform glaciation over High‐Mountain Asia (HMA) during the global last glacial maximum (LGM; ~28‐23 ka) have been intensively studied but remain elusive. Using a ...1‐km‐resolution ice sheet model, we show that glaciers across HMA exhibit high region variability in glaciation. Glaciers in western and southern HMA are the most sensitive to climate change and those in the interior are the least sensitive. Our model broadly reproduces the restricted glaciation across HMA during the LGM, although it overestimates the extent of glaciation over western and southern HMA as compared with reconstructions. Modeled decreases in precipitation hampers glacier growth over northern HMA, while insufficient cooling hampers glacier advance over eastern HMA for the LGM. Both reduced precipitation and insufficient cooling inhibit large‐scale glaciation over inner HMA. Moreover, climatic conditions conducive to glaciation across the entire HMA include a reduction in temperature of ~10 °C and an increase in precipitation, unlikely to have occurred during any Quaternary glacial maximum.
Plain Language Summary
Presently, High‐Mountain Asia (HMA) is home to the largest mass of glaciers outside the polar regions and known as the Earth's Third Pole. During the global last glacial maximum (LGM; ~28–23 ka), geological evidence points to restricted and nonuniform glaciation over HMA, in stark contrast to the expanded ice sheets across high latitudes of Northern Hemisphere. However, it remains elusive why was there no large‐scale ice sheet over HMA during the LGM. Using a 1‐km‐resolution ice sheet model, we highlight the climate sensitivity of glaciers across HMA showing highly region variability in glaciation and revealing that insufficient cooling and/or precipitation decrease constrained glaciation over HMA during the LGM.
Key Points
The 1‐km‐resolution model broadly reproduces the restricted and nonuniform glaciation over HMA in the LGM
The climate sensitivity of glaciers across HMA shows high region variability in glaciation
Insufficient cooling and/or precipitation decrease constrained glaciation over HMA in the LGM, but the dominant factor is region dependent
Biting flies (Diptera) transmit pathogens that cause many important diseases in humans as well as domestic and wild animals. The networks of feeding interactions linking these insects to their hosts, ...and how they vary geographically and in response to human land-use, are currently poorly documented but are relevant to understanding cross-species disease transmission. We compiled a database of biting Diptera-host interactions from the literature to investigate how key interaction network metrics vary latitudinally and with human land-use. Interaction evenness and H2' (a measure of the degree of network specificity) did not vary significantly with latitude. Compared to near-natural habitats, interaction evenness was significantly lower in agricultural habitats, where networks were dominated by relatively few species pairs, but there was no evidence that the presence of humans and their domesticated animals within networks led to systematic shifts in network structure. We discuss the epidemiological relevance of these results and the implications for predicting and mitigating future spill-over events.
Pollinators are declining globally, with climate change implicated as an important driver. Climate change can induce phenological shifts and reduce floral resources for pollinators, but little is ...known about its effects on floral attractiveness and how this might cascade to affect pollinators, pollination functions and plant fitness.
We used an in situ long‐term drought experiment to investigate multiple impacts of reduced precipitation in a natural Mediterranean shrubland, a habitat where climate change is predicted to increase the frequency and intensity of droughts. Focusing on three insect‐pollinated plant species that provide abundant rewards and support a diversity of pollinators (Cistus albidus, Salvia rosmarinus and Thymus vulgaris), we investigated the effects of drought on a suite of floral traits including nectar production and floral scent. We also measured the impact of reduced rainfall on pollinator visits, fruit set and germination in S. rosmarinus and C. albidus.
Drought altered floral emissions of all three plant species qualitatively, and reduced nectar production in T. vulgaris only. Apis mellifera and Bombus gr. terrestris visited more flowers in control plots than drought plots, while small wild bees visited more flowers in drought plots than control plots. Pollinator species richness did not differ significantly between treatments. Fruit set and seed set in S. rosmarinus and C. albidus did not differ significantly between control and drought plots, but seeds from drought plots had slower germination for S. rosmarinus and marginally lower germination success in C. albidus.
Synthesis. Overall, we found limited but consistent impacts of a moderate experimental drought on floral phenotype, plant reproduction and pollinator visits. Increased aridity under climate change is predicted to be stronger than the level assessed in the present study. Drought impacts will likely be stronger and this could profoundly affect the structure and functioning of plant–pollinator networks in Mediterranean ecosystems.
Résumé
Le changement climatique est une des causes importantes du déclin des pollinisateurs. Il peut notamment provoquer une réduction de la production de ressources florales et des décalages phénologiques entre les périodes de floraison et d'activité des pollinisateurs. Cependant les effets du changement climatique sur l'attractivité des fleurs, et les conséquences sur les interactions plantes‐pollinisateurs, les fonctions de pollinisation et la reproduction des plantes restent peu connus.
Nous avons mené une expérimentation in situ simulant une intensification de la sécheresse à long terme pour mesurer les multiples impacts de la réduction des précipitations dans une communauté végétale Méditerranéenne caractéristique de la garrigue écorchée. Dans cet habitat, les prédictions climatiques se caractérisent par une augmentation de la fréquence et de l'intensité des épisodes de sécheresse. Nous avons centré nos mesures sur trois espèces parmi les plus abondantes et fournissant la plus grande quantité de ressources florales pour les pollinisateurs (Cistus albidus, Salvia rosmarinus et Thymus vulgaris). Nous avons mesuré un ensemble de trait floraux, y compris la production de nectar et l'émission d'odeurs florales sur les plantes en conditions de sécheresse ou sous précipitations naturelles (contrôle). Nous avons également mesuré l'effet de la réduction des précipitations sur les visites des pollinisateurs, la production de fruits et la germination chez S. rosmarinus et C. albidus.
La réduction des précipitations a provoqué une altération des odeurs florales des trois espèces de plantes, ainsi qu'une réduction de la production de nectar chez T. vulgaris. Apis mellifera et Bombus gr. terrestris ont visité plus de fleurs dans les parcelles contrôle que dans les parcelles en conditions de sécheresse, alors que les petites abeilles sauvages ont montré un comportement opposé. La richesse spécifique des pollinisateurs n'était pas significativement différente entre les deux traitements. Finalement, la production de fruits et de graines de S. rosmarinus et C. albidus n'étaient pas significativement modifiées par le traitement. Enfin, les graines issues de plantes en conditions de sécheresse ont germé légèrement plus lentement chez S. rosmarinus, et avec un taux de germination légèrement plus faible chez C. albidus.
Synthèse. Globalement, la réduction des précipitations, relativement modérée, a provoqué des effets limités mais consistants sur les traits floraux, ainsi que sur les visites des pollinisateurs et sur la reproduction des plantes. L'intensification prédite des épisodes de sécheresse dans cette région est plus importante que celle testée dans cette étude. Les impacts seront donc probablement plus forts, avec des conséquences possibles importantes sur la structure et le fonctionnement des réseaux de pollinisation dans les écosystèmes méditerranéens.
In the Mediterranean Basin, climate change is causing an intensification of drought intensity and frequency. Our community‐level in situ measures showed that drought altered floral scent with changes in plant–pollinator interactions and limited impacts on plant reproduction. We discuss why the context of our study—an exceptionally wet year—may have led to limited effects of drought. (A) Sampling of floral scent in the study site equipped with rainfall exclusion plots and control plots. (B, C) Two wild bee species of small body size and (D) Apis mellifera, the managed honeybee, which has a large body size, collecting floral resources on Salvia rosmarinus.
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