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1.
A frequent observation in plant–animal mutualistic networks is that abundant species tend to be more generalised, interacting with a broader range of interaction partners than rare species. Uncovering the causal relationship between abundance and generalisation has been hindered by a chicken‐and‐egg dilemma: is generalisation a by‐product of being abundant, or does high abundance result from generalisation? Here, we analyse a database of plant–pollinator and plant–seed disperser networks, and provide strong evidence that the causal link between abundance and generalisation is uni‐directional. Specifically, species appear to be generalists because they are more abundant, but the converse, that is that species become more abundant because they are generalists, is not supported by our analysis. Furthermore, null model analyses suggest that abundant species interact with many other species simply because they are more likely to encounter potential interaction partners. 相似文献
2.
Paul J. CaraDonna Laura A. Burkle Benjamin Schwarz Julian Resasco Tiffany M. Knight Gita Benadi Nico Blüthgen Carsten F. Dormann Qiang Fang Jochen Fründ Benoit Gauzens Christopher N. Kaiser‐Bunbury Rachael Winfree Diego P. Vzquez 《Ecology letters》2021,24(1):149-161
Most studies of plant–animal mutualistic networks have come from a temporally static perspective. This approach has revealed general patterns in network structure, but limits our ability to understand the ecological and evolutionary processes that shape these networks and to predict the consequences of natural and human‐driven disturbance on species interactions. We review the growing literature on temporal dynamics of plant–animal mutualistic networks including pollination, seed dispersal and ant defence mutualisms. We then discuss potential mechanisms underlying such variation in interactions, ranging from behavioural and physiological processes at the finest temporal scales to ecological and evolutionary processes at the broadest. We find that at the finest temporal scales (days, weeks, months) mutualistic interactions are highly dynamic, with considerable variation in network structure. At intermediate scales (years, decades), networks still exhibit high levels of temporal variation, but such variation appears to influence network properties only weakly. At the broadest temporal scales (many decades, centuries and beyond), continued shifts in interactions appear to reshape network structure, leading to dramatic community changes, including loss of species and function. Our review highlights the importance of considering the temporal dimension for understanding the ecology and evolution of complex webs of mutualistic interactions. 相似文献
3.
YVE E. A. GADELHA DENISE LANGE WESLEY DÁTTILO BENEDITO C. LOPES 《Ecological Entomology》2017,42(6):827-837
- Several studies have recently focused on the structural pattern of plant–insect interaction networks. However, insects and plants have dynamic cycles and differ in their level of specialisation over time, space, and scales. Thus, it is expected that sap‐sucking insects, such as treehoppers, and plants will not share similar patterns of interactions in all phenological stages of the plants.
- It was postulated that phenological stages of the host plant could change the structure of plant–treehopper networks, which will be more specialised during the reproductive stage than during the vegetative stage, mainly because of high concentrations of toxic compounds in the flowers. Here, quantitative metrics derived from graph theory were used to describe, for the first time, the changes in the structure of plant–treehopper interactions during the phenological stages of the host plants in Brazilian Atlantic Forest.
- The results revealed high temporal turnover of plant–treehopper interactions, and high similarity in the treehopper composition between the phenological stages. In both phenological stages, plant–treehopper networks exhibited a modular and non‐nested pattern. However, during the reproductive stage, the results showed lower species richness of plants and treehoppers, and higher levels of network specialisation compared with the vegetative phase.
- These findings demonstrate that the organisation of the same ecological interaction can change throughout plant phenology. In short, it was shown that the phenological phases of the host plants can constitute a remarkable mechanism that shapes plant–treehopper interaction networks in a tropical rainforest.
4.
Diego P. Vázquez Rodrigo Ramos‐Jiliberto Pasquinell Urbani Fernanda S. Valdovinos 《Ecology letters》2015,18(4):385-400
The strength of species interactions influences strongly the structure and dynamics of ecological systems. Thus, quantifying such strength is crucial to understand how species interactions shape communities and ecosystems. Although the concepts and measurement of interaction strength in food webs have received much attention, there has been comparatively little progress in the context of mutualism. We propose a conceptual scheme for studying the strength of plant–animal mutualistic interactions. We first review the interaction strength concepts developed for food webs, and explore how these concepts have been applied to mutualistic interactions. We then outline and explain a conceptual framework for defining ecological effects in plant–animal mutualisms. We give recommendations for measuring interaction strength from data collected in field studies based on a proposed approach for the assessment of interaction strength in plant–animal mutualisms. This approach is conceptually integrative and methodologically feasible, as it focuses on two key variables usually measured in field studies: the frequency of interactions and the fitness components influenced by the interactions. 相似文献
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Biological invasions can alter direct and indirect interactions between species, generating far-reaching changes in ecological networks that affect key ecological functions. We used model and real fruit assays to show that the invasion and formation of high-density supercolonies by the yellow crazy ant (YCA), Anoplolepis gracilipes, disrupt frugivory by endemic birds on Christmas Island, Indian Ocean. The overall handling rates of model fruits by birds were 2.2–2.4-fold lower in ant-invaded than in uninvaded rainforest, and pecking rates by two bird species declined by 2.6- and 4.5-fold, respectively. YCAs directly interfered with frugivory; their experimental exclusion from fruiting displays increased fruit handling threefold to sixfold, compounding indirect effects of ant invasion on resources and habitat structure that influence bird abundances and behaviours. This invasive ant, whose high densities are sustained through mutualism with introduced scale insects, rapidly decreases fruit handling by endemic island birds and may erode a key ecological function, seed dispersal. Because most other invasive ant species form expansive, high-density supercolonies that depend in part on association with hemipteran mutualists, the effects that we report here on avian frugivore–plant associations may emerge across their introduced ranges. 相似文献
8.
Susana Chamorro Ruben Heleno Jens M. Olesen Conley K. McMullen Anna Traveset 《Annals of botany》2012,110(7):1489-1501
Background
Despite the importance of the Galápagos Islands for the development of central concepts in ecology and evolution, the understanding of many ecological processes in this archipelago is still very basic. One such process is pollination, which provides an important service to both plants and their pollinators. The rather modest level of knowledge on this subject has so far limited our predictive power on the consequences of the increasing threat of introduced plants and pollinators to this unique archipelago.Scope
As a first step toward building a unified view of the state of pollination in the Galápagos, a thorough literature search was conducted on the breeding systems of the archipelago''s flora and compiled all documented flower–visitor interactions. Based on 38 studies from the last 100 years, we retrieved 329 unique interactions between 123 flowering plant species (50 endemics, 39 non-endemic natives, 26 introduced and eight of unknown origin) from 41 families and 120 animal species from 13 orders. We discuss the emergent patterns and identify promising research avenues in the field.Conclusions
Although breeding systems are known for <20 % of the flora, most species in our database were self-compatible. Moreover, the incidence of autogamy among endemics, non-endemic natives and alien species did not differ significantly, being high in all groups, which suggests that a poor pollinator fauna does not represent a constraint to the integration of new plant species into the native communities. Most interactions detected (approx. 90 %) come from a single island (most of them from Santa Cruz). Hymenopterans (mainly the endemic carpenter bee Xylocopa darwinii and ants), followed by lepidopterans, were the most important flower visitors. Dipterans were much more important flower visitors in the humid zone than in the dry zone. Bird and lizard pollination has been occasionally reported in the dry zone. Strong biases were detected in the sampling effort dedicated to different islands, time of day, focal plants and functional groups of visitors. Thus, the existing patterns need to be confronted with new and less biased data. The implementation of a community-level approach could greatly increase our understanding of pollination on the islands and our ability to predict the consequences of plant invasions for the natural ecosystems of the Galápagos. 相似文献9.
Paula J. Peeters 《Austral ecology》2002,27(6):658-671
Abstract Significant correlations were found between herbivorous insect densities and leaf constituent levels across 18 species of understorey shrub in an Australian forest. In general, insect densities were positively correlated with nitrogen and water and negatively correlated with fibre and its constituents (cellulose and lignin), but not all insect guilds were significantly correlated with all leaf constituents. When mature leaf traits were considered, total herbivore density among plant species was most strongly correlated with levels of nitrogen and water. However, when insects were divided into functional guilds, only densities of sucking insects were significantly correlated with mature leaf nitrogen and water, whereas chewing insect densities were significantly correlated with mature leaf fibre and lignin. Low leaf nitrogen levels were recorded for all plants surveyed (among the lowest reported for woody angiosperms), and many plant species also had high levels of leaf fibre. These features are characteristic of Australian forests and have been linked to the generally nutrient‐poor soils of this continent. Levels of new leaf nitrogen (% fresh weight) were generally less than or equal to levels of mature leaf nitrogen (% fresh weight). Hence the new leaf preference of several herbivore guilds could not be explained by higher levels of leaf nitrogen. However, significant negative correlations were found between chewer densities and levels of leaf fibre, cellulose and lignin for new and mature leaves, suggesting that higher levels of fibre, cellulose and lignin in mature leaves may be contributing more strongly to the new leaf preference of chewers than leaf nitrogen levels. Despite the significant correlations between leaf constituent levels and the densities of individual guilds, multivariate analyses found no significant relationship between leaf constituent levels and the taxonomic or guild composition of herbivorous insect assemblages. 相似文献
10.
Madhav P. Thakur Vera Quast Nicole M. van Dam Nico Eisenhauer Christiane Roscher Arjen Biere Ainhoa Martinez‐Medina 《Oikos》2019,128(8):1136-1146
Plants form mutualistic relationship with a variety of belowground fungal species. Such a mutualistic relationship can enhance plant growth and resistance to pathogens. Yet, we know little about how interactions between functionally diverse groups of fungal mutualists affect plant performance and competition. We experimentally determined the effects of interaction between two functional groups of belowground fungi that form mutualistic relationship with plants, arbuscular mycorrhizal (AM) fungi and Trichoderma, on interspecific competition between pairs of closely related plant species from four different genera. We hypothesized that the combination of two functionally diverse belowground fungal species would allow plants and fungi to partition their symbiotic relationships and relax plant–plant competition. Our results show that: 1) the AM fungal species consistently outcompeted the Trichoderma species independent of plant combinations; 2) the fungal species generally had limited effects on competitive interactions between plants; 3) however, the combination of fungal species relaxed interspecific competition in one of the four instances of plant–plant competition, despite the general competitive superiority of AM fungi over Trichoderma. We highlight that the competitive outcome between functionally diverse fungal species may show high consistency across a broad range of host plants and their combinations. However, despite this consistent competitive hierarchy, the consequences of their interaction for plant performance and competition can strongly vary among plant communities. 相似文献
11.
Susan Hodgson Catherine de Cates Joshua Hodgson Neil J. Morley Brian C. Sutton Alan C. Gange 《Ecology and evolution》2014,4(8):1199-1208
To date, it has been thought that endophytic fungi in forbs infect the leaves of their hosts most commonly by air‐borne spores (termed “horizontal transmission”). Here, we show that vertical transmission from mother plant to offspring, via seeds, occurs in six forb species (Centaurea cyanus, C. nigra, Papaver rhoeas, Plantago lanceolata, Rumex acetosa, and Senecio vulgaris), suggesting that this may be a widespread phenomenon. Mature seeds were collected from field‐grown plants and endophytes isolated from these, and from subsequent cotyledons and true leaves of seedlings, grown in sterile conditions. Most seeds contain one species of fungus, although the identity of the endophyte differs between plant species. Strong evidence for vertical transmission was found for two endophyte species, Alternaria alternata and Cladosporium sphaerospermum. These fungi were recovered from within seeds, cotyledons, and true leaves, although the plant species they were associated with differed. Vertical transmission appears to be an imperfect process, and germination seems to present a bottleneck for fungal growth. We also found that A. alternata and C. sphaerospermum occur on, and within pollen grains, showing that endophyte transmission can be both within and between plant generations. Fungal growth with the pollen tube is likely to be the way in which endophytes enter the developing seed. The fact that true vertical transmission seems common suggests a more mutualistic association between these fungi and their hosts than has previously been thought, and possession of endophytes by seedling plants could have far‐reaching ecological consequences. Seedlings may have different growth rates and be better protected against herbivores and pathogens, dependent on the fungi that were present in the mother plant. This would represent a novel case of trans‐generational resistance in plants. 相似文献
12.
Ant–plant mutualisms are usually regarded as driven by ants defending plants against herbivores in return for plant‐produced food rewards and housing. However, ants may provide additional services. In a review of published studies on ant–pathogen–plant interactions, we investigated whether ants’ extensive hygiene measures, including the use of ant‐produced antibiotics, extend to their host plants and reduce plant pathogen loads. From 30 reported species combinations, we found that the presence of ants lead to reduced pathogen levels in 18 combinations and to increased levels in 6. On average, ants significantly reduced pathogen incidence with 59%. This effect size did not differ significantly from effect sizes reported from meta‐analyses on herbivore protection. Thus, pathogen and herbivore protection could be of equal importance in ant–plant mutualisms. Considering the abundance of these interactions, ecological impacts are potentially high. Furthermore, awareness of this service may stimulate the development of new measures to control plant diseases in agriculture. It should be noted, though, that studies were biased toward tropical ant–plant symbioses and that the literature in the field is limited at present. Future research on plant pathogens is needed to enhance our understanding of ant–plant mutualisms and their evolution. 相似文献
13.
A long-standing but controversial hypothesis assumes that carnivorous plants employ aggressive mimicry to increase their prey capture success. A possible mechanism is that pitcher plants use aggressive mimicry to deceive prey about the location of the pitcher''s exit. Specifically, species from unrelated families sport fenestration, i.e. transparent windows on the upper surfaces of pitchers which might function to mimic the exit of the pitcher. This hypothesis has not been evaluated against alternative hypotheses predicting that fenestration functions to attract insects from afar. By manipulating fenestration, we show that it does not increase the number of Drosophila flies or of two ant species entering pitchers in Sarracenia minor nor their retention time or a pitcher''s capture success. However, fenestration increased the number of Drosophila flies alighting on the pitcher compared with pitchers of the same plant without fenestration. We thus suggest that fenestration in S. minor is not an example of aggressive mimicry but rather functions in long-range attraction of prey. We highlight the need to evaluate aggressive mimicry relative to alternative concepts of plant–animal communication. 相似文献
14.
- Host specificity of a guild of sucking insects tapping leaf mesophyll cells (Auchenorrhyncha: Typhlocybinae) was surveyed for the first time in the tropics, on 65 woody species from a lowland rainforest in Papua New Guinea (PNG).
- Typhlocybinae species were host specific, feeding on 1–3 (median 1) plant species. Their assemblages did not functionally connect populations of different plant species, as an overwhelming majority (> 99%) of tree species pairs coexisting in the same forest did not share any typhlocybine species.
- Cell‐sucking typhlocybines were more specialised than phloem‐ and xylem‐sucking Auchenorrhyncha. Typhlocybines were also more specialised in PNG than on trees in temperate Europe, even after standardisation for different phylogenetic diversity of tropical and temperate trees.
- The cell‐sucking guild was species poor, with 0–5 (median 1) typhlocybine species per tree species. Their distribution among tree species conformed to a Poisson distribution, suggesting that tropical typhlocybine assemblages are not saturated with species.
- Early succession plants supported a higher number of typhlocybine species than primary forest hosts but this preference could not be explained by successional trends in specific leaf area, foliar nitrogen content, wood density, tree abundance, or tree size.
- The effective specialisation of typhlocybines on 65 plant species E = 0.79 was extrapolated to the entire known flora of PNG and used to estimate that there may be at least 2775 typhlocybine species in PNG, in comparison to the global total of only 4508 taxonomically described species, including merely 40 from PNG.
15.
Plant fitness is affected by herbivory, and in moist tropical forests, 70 percent of herbivore damage occurs on young leaves. Thus, to understand the effects of herbivory on tropical plant fitness, it is necessary to understand how tropical young leaves survive the brief, but critical, period of susceptibility. In this study, we surveyed three species of Inga during young leaf expansion. Three classes of toxic secondary metabolites (phenolics, saponins, and tyrosine), extrafloral nectar production, leaf area, and extrafloral nectary area were measured at randomly assigned young leaf sizes. In addition, all defenses were compared for potential trade‐offs during leaf expansion. No trade‐offs among defenses were found, and the concentration of all defenses, except tyrosine, decreased during leaf expansion. We suggest that plants continued to increase phenolic and saponin content, but at a rate that resulted in decreasing concentrations. In contrast, tyrosine content per leaf steadily increased such that a constant concentration was maintained regardless of young leaf size. Nectar production remained constant during leaf expansion, but, because young leaf area increased by tenfold, the investment in extrafloral nectar per leaf area significantly decreased. In addition, nectary area did not change during leaf expansion and therefore the relative size of the nectary significantly decreased during young leaf expansion. These results support the predictions of the optimal defense hypothesis and demonstrate that the youngest leaves have the highest investment in multiple defenses, most likely because they have the highest nitrogen content and are most susceptible to a diversity of herbivores. 相似文献
16.
Volatile organic compounds (VOCs) emitted by plant roots can influence the germination and growth of neighbouring plants. However, little is known about the effects of root VOCs on plant–herbivore interactions of neighbouring plants. The spotted knapweed (Centaurea stoebe) constitutively releases high amounts of sesquiterpenes into the rhizosphere. Here, we examine the impact of C. stoebe root VOCs on the primary and secondary metabolites of sympatric Taraxacum officinale plants and the resulting plant‐mediated effects on a generalist root herbivore, the white grub Melolontha melolontha. We show that exposure of T. officinale to C.stoebe root VOCs does not affect the accumulation of defensive secondary metabolites but modulates carbohydrate and total protein levels in T. officinale roots. Furthermore, VOC exposure increases M. melolontha growth on T. officinale plants. Exposure of T. officinale to a major C. stoebe root VOC, the sesquiterpene (E)‐β‐caryophyllene, partially mimics the effect of the full root VOC blend on M. melolontha growth. Thus, releasing root VOCs can modify plant–herbivore interactions of neighbouring plants. The release of VOCs to increase the susceptibility of other plants may be a form of plant offense. 相似文献
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Fernanda S. Valdovinos 《Ecology letters》2019,22(9):1517-1534
Plant–animal mutualistic networks sustain terrestrial biodiversity and human food security. Global environmental changes threaten these networks, underscoring the urgency for developing a predictive theory on how networks respond to perturbations. Here, I synthesise theoretical advances towards predicting network structure, dynamics, interaction strengths and responses to perturbations. I find that mathematical models incorporating biological mechanisms of mutualistic interactions provide better predictions of network dynamics. Those mechanisms include trait matching, adaptive foraging, and the dynamic consumption and production of both resources and services provided by mutualisms. Models incorporating species traits better predict the potential structure of networks (fundamental niche), while theory based on the dynamics of species abundances, rewards, foraging preferences and reproductive services can predict the extremely dynamic realised structures of networks, and may successfully predict network responses to perturbations. From a theoretician's standpoint, model development must more realistically represent empirical data on interaction strengths, population dynamics and how these vary with perturbations from global change. From an empiricist's standpoint, theory needs to make specific predictions that can be tested by observation or experiments. Developing models using short‐term empirical data allows models to make longer term predictions of community dynamics. As more longer term data become available, rigorous tests of model predictions will improve. 相似文献
19.
Catherine R.C. Unabia 《Invertebrate Biology》2011,130(2):100-114
Abstract. The endemic Hawaiian gastropod Smaragdia bryanae is a specialized marine herbivore that uses the endemic seagrass Halophila hawaiiana as both food and habitat. These small neritids, their grazing scars, and their egg capsules are found year‐round on seagrass leaves, where they feed on protoplast contents released as the sharp outer‐lateral teeth of the snail's radula puncture leaf epidermal cells; the contents of these cells are likely swept into the mouth by the long, wispy cusps of the marginal teeth. Structural differences from the typical neritid radula include elongated outer‐lateral teeth with two sharply pointed cusps, delicate marginal teeth reduced in both size and number, and a compressed central section. Snails grazed on leaves of H. hawaiiana steadily in laboratory culture, and grew and reproduced on this diet. In laboratory choice experiments, snails did not graze the thalli of any of six macroalgal species growing near seagrass where snails were collected, and strongly preferred occupying seagrass. Seagrass samples from five field sites on Oahu and one on Maui showed from 30% to 94% of leaves damaged, with 11% of the total leaf standing area grazed. Snails are smaller (mean length 2.74±0.32 mm, mean width 2.15±0.17 mm, n=217) than the width of the leaves of H. hawaiiana (mean 3.24±1.26 mm, n=790). The snails associate constantly with their host, despite the scattered distribution, small patch size, and variability of the seagrass resource, demonstrated by a sevenfold range in the leaf area index (mean 1.11±0.61 cm2 blade surface cm?2, n=31) among samples. Damage on grazed leaves (mean 8.21±7.05 mm2 per leaf, or 16.5% of leaf surface, n=511) is concentrated in the apical and central epithelia between the midrib and the marginal veins, where snails may access cells with thinner walls and few fibers. Details of the grazing interaction between these extant species in Hawai'i shed light on the ecological specialization of members of the genus Smaragdia to seagrasses over geological time. 相似文献
20.
Megan E. Frederickson 《Ecology letters》2020,23(2):409-411
Whether natural selection favours ‘cheating’ in mutualisms is hotly debated. Gano‐Cohen et al. (2019a) report a negative correlation between fitness and mutualist quality in rhizobia, suggesting that rhizobia evolve to cheat. However, reanalysis of their data shows that the correlation is an artefact of unequal sampling across populations. 相似文献