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211 results for “mutualists”
Data from: From structure to function in mutualistic interaction networks: topologically important frugivores have greater potential as seed dispersers
1. Networks of mutualistic interactions between animals and plants are considered a pivotal part of ecological communities. However, mutualistic networks are rarely studied from the perspective of species-specific roles, and it remains to be established whether those animal species more relevant for network structure also contribute more to the ecological functions derived from interactions. 2. Here, we relate the contribution to seed dispersal of vertebrate species with their topological role in frugivore-plant interaction networks. For one year in two localities with remnant patches of Colombian tropical dry forest, we sampled abundance, morphology, behavior, and fruit consumption from fleshy-fruited plants of various frugivore species. 3. We assessed the network topological role of each frugivore species by integrating their degree of generalization in interactions with plants with their contributions to network nestedness and modularity. We estimated the potential contribution of each frugivore species to community-wide seed dispersal, on the basis of a set of frugivore ecological, morphological and behavioral characteristics important for seed dispersal, together with frugivore abundance and frugivory degree. 4. The various frugivore species showed strong differences in their network structural roles, with generalist species contributing the most to network modularity and nestedness. Frugivores also showed strong variability in terms of potential contribution to seed dispersal, depending on the specific combinations of frugivore abundance, frugivory degree and the different traits and behaviors. 5. For both localities, the seed dispersal potential of a frugivore species responded positively to its contribution to network structure, evidencing that the most important frugivore species in the network topology were also those making the strongest contribution as seed dispersers. Contribution to network structure was correlated with frugivore abundance, diet, and behavioral characteristics. This suggests that the species-level link between structure and function is due to the fact that the occurrence of frugivore-plant interactions depends largely on the characteristics of the frugivore involved, which also condition its ultimate role in seed dispersal. 22-May-2020
Net benefits of a mutualism: influence of the quality of extrafloral nectar on the colony fitness of a mutualistic ant
<p><span><span><span><span><span><span><span><span><span><span><span><strong>Aim</strong>: Extrafloral nectar, a carbohydrate-rich liquid, is the main plant-based resource offered in exchange for ant protection. The positive results of this protection provided by ants are widely studied and supported; however, studies showing the benefits that ants and their colonies have from the resources offered by plants such as extrafloral nectar are scarce. Here, we evaluated how extrafloral nectar and artificial food resources with different nutrient concentration benefit short- and long-term <i>Camponotus crassus</i> colony fitness (number and weight of individuals) and survival. </span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><strong>Methods</strong>: We conducted two sets of experiments: (1) in the field we attached artificial ant nests to plants with clogged and unclogged extrafloral nectaries; and (2) in the laboratory we offered artificial food resources with different carbohydrate-protein ratios to ant colonies. With these experiments we evaluated the number and weight of queens, adult workers, pupae, larvae, and eggs, as well as the survival probability of the colonies.</span></span></span></span></span></span></span></span></span></span></span></p> <p><span><span><span><span><span><span><span><span><span><span><span><strong>Results</strong>: In the first experiment, the short-term provision of extrafloral nectar resulted in a larger number and weight of individuals with access to this resource. In the second experiment, regardless of time, the supply of more concentrated carbohydrate and nitrogen food increased ant colony fitness and survival. Conclusion: We provided new evidence that extrafloral nectar significantly benefits ant colonies. Our results corroborate the assertion that these relationships are reciprocally beneficial. </span></span></span></span></span></span></span></span></span></span></span></p>
Data from: Effect of plant chemical variation and mutualistic ants on the local population genetic structure of an aphid herbivore
1.Plants exhibit impressive genetic and chemical diversity, not just between species but also within species, and the importance of plant intraspecific variation for structuring ecological communities is well known. When there is variation at the local population level, this can create a spatially‐heterogeneous habitat for specialized herbivores potentially leading to non‐random distribution of individuals across host‐plants. 2.Plant variation can affect herbivores directly and indirectly via a third species, resulting in variable herbivore growth rates across different host plants. Herbivores also exhibit within‐species variation, with some genotypes better adapted to some plant variants than others. 3.We genotyped aphids collected across two years from a field site containing ~200 patchily‐distributed host plants that exhibit high chemical diversity. The distribution of aphid genotypes, their ant mutualists, and other predators was assessed across the plants. 4.We present evidence that the local distribution of aphid (Metopeurum fuscoviride) genotypes across host‐plant individuals is associated with variation in the plant volatiles (chemotypes) and non‐volatile metabolites (metabotypes) of their host plant tansy (Tanacetum vulgare). Furthermore, these interactions in the field were influenced by plant‐host preferences of aphid‐mutualist ants. 5.Our results emphasize that plant intraspecific variation can structure ecological communities not only at the species level but also at the genetic level within species, and that this effect can be enhanced through indirect interactions with a third species.
Data from: Acquisition of obligate mutualist symbionts during the larval stage is not beneficial for a coral host
Theory suggests that the direct transmission of endosymbionts from parents to offspring (vertical transmission) in animal hosts is advantageous and evolutionarily stable, yet many host species instead acquire their symbionts from the environment (horizontal acquisition). An outstanding question in marine biology is why some scleractinian corals do not provision their eggs and larvae with the endosymbiotic dinoflagellates that are necessary for a juvenile's ultimate survival. We tested whether the acquisition of photosynthetic endosymbionts (family Symbiodiniaceae) during the planktonic larval stage was advantageous, as is widely assumed, in the ecologically important and threatened Caribbean reef-building coral Orbicella faveolata. Following acquisition, similar changes occurred in larval energetic lipid use and gene expression regardless of whether their symbionts were photosynthesizing, suggesting the algae did not provide the energetic benefits characteristic of the mutualism in adults. Larvae that acquired photosymbionts isolated from conspecific adults on their natal reef exhibited a reduction in swimming, which may interfere with their ability to find suitable settlement substrate, and also a decrease in survival. Larvae exposed to two cultured algal species did not exhibit differences in survival, but decreased their swimming activity in response to one species. We conclude that acquiring photosymbionts during the larval stage confers no advantages and can in fact be disadvantageous to this coral host. The timing of symbiont acquisition appears to be a critical component of a host's life history strategy and overall reproductive fitness, and this timing itself appears to be under selective pressure.
Data from: Functional outcomes of mutualistic network interactions: a community-scale study of frugivore gut passage on germination
1. Current understanding of mutualistic networks is grounded largely in data on interaction frequency, yet mutualistic network dynamics are also shaped by interaction quality—the functional outcomes of individual interactions on reproduction and survival. The difficulty of obtaining data on functional outcomes has resulted in limited understanding of functional variation among a network's pairwise species interactions, of the study designs that are necessary to capture major sources of functional variation, and of predictors of functional variation that may allow generalization across networks. 2. In this community-scale study, we targeted a key functional outcome in plant-frugivore networks: the impact of frugivore gut passage on seed germination. We used captive frugivore feeding trials and germination experiments in an island ecosystem, attaining species-level coverage across all extant native frugivores and the plants they consume to 1) assess sources of functional variation, 2) separate effects of pulp removal from those of scarification via gut passage, and 3) test trait-based correlates of gut passage effect sizes. 3. We found antagonistic seed predation effects of a frugivore previously assumed to be a seed disperser, highlighting the need to consider functional outcomes rather than interaction frequency alone. The other frugivores each exhibited similar impacts for individual plant species, with benefits primarily caused by pulp removal rather than scarification, supporting the use of animal functional groups in this context. In contrast, plant species varied widely in impacts of gut passage on germination. Species with smaller seeds and more frugivore partners had larger benefits of gut passage, showing promise for network metrics and functional traits to predict functional variation among plants. 4. Synthesis. Combining network and demographic approaches, we assessed the degree and sources of variation in a key functional outcome of plant-frugivore interactions across an entire network. Using a detailed study design, our work shows how simpler study designs can capture primary sources of functional variation and that functional traits and network metrics may allow generalization across networks. Efficiently measuring and generalizing sources of functional variation within mutualistic networks will strengthen our ability to model network dynamics and predict mutualist responses to global change.
Data from: Social transmission of information about a mutualist via trophallaxis in ant colonies
Partner discrimination is crucial in mutualistic interactions between organisms to counteract cheating by the partner. Trophobiosis between ants and aphids is a model system of such mutualistic interaction. To establish and maintain the mutualistic association, ants need to correctly discriminate mutualistic aphids. However, the mechanism by which ants recognize aphids as their partners is poorly understood, despite its ecological and evolutionary importance. Here, we show for the first time the evidence that interaction with nest-mates that have tended aphids (Aphis craccivora) allows ants (Tetramorium tsushimae) to learn to recognize the aphid species as their partner. When ants had previously tended aphids, they moderated their aggressiveness towards aphids. More importantly, ants that had interacted with aphid-experienced nest-mates also reduced their aggressiveness towards aphids, even though they had never directly experienced them, indicating that aphid information was transmitted from aphid-experienced ants to inexperienced ants. Furthermore, inhibition of mouth-to-mouth contact (trophallaxis) from aphid-experienced ants to inexperienced ants by providing the inexperienced ants with artificial honeydew solution caused the inexperienced ants to become aggressive towards aphids. These results, with further supporting data, strongly suggest that ants transfer information on their mutualists during trophallactic interactions.
Data from: Effect of mutualist partner identity on plant demography
Mutualisms play a central role in the origin and maintenance of biodiversity. Because many mutualisms have strong demographic effects, interspecific variation in partner quality could have important consequences for population dynamics. Nevertheless, few studies have quantified how a mutualist partner influences population growth rates, and still fewer have compared the demographic impacts of multiple partner species. We used integral projection models parameterized with three years of census data to compare the demographic effects of two ant species - Crematogaster laevis and Pheidole minutula - on populations of the Amazonian ant-plant Maieta guianensis. Estimated population growth rates were positive (i.e., λ>1) for all ant-plant combinations. However, populations with only Pheidole minutula had the highest asymptotic growth rate (λ=1.23), followed by those colonized by Crematogaster laevis (λ=1.16), and in which the partner ant alternated between C. laevis and P. minutula at least once during our study (λ=1.15). Our results indicate that the short-term superiority of a mutualist partner - in this system P. minutula is a better defender of plants against herbivores than C. laevis - can have long-term demographic consequences. Furthermore, the demographic effects of switching among alternative partners appear to be context-dependent, with no benefits to plants hosting C. laevis but a major cost of switching to plants hosting P. minutula. Our results underscore the importance of expanding the study of mutualisms beyond the study of pair-wise interactions to consider the demographic costs and benefits of interacting with different, and multiple, potential partners.
Data from: Attracting mutualists and antagonists: plant trait variation explains the distribution of specialist floral herbivores and pollinators on crops and wild gourds
PREMISE OF THE STUDY: Floral traits play important roles in pollinator attraction and defense against floral herbivory. However, plants may experience trade-offs between conspicuousness to pollinators and herbivore attraction. Comparative studies provide an excellent framework to examine the role of multiple traits shaping mutualist and antagonist interactions. METHODS: To assess whether putative defensive and attractive traits predict species interactions, we grew 20 different Cucurbitaceae species and varieties in the field to measure interactions with pollinators and herbivores and in the greenhouse to assess trait variation. Cucurbits are characterized by the production of cucurbitacins, bitter nonvolatile terpenoids that are effective against generalist herbivores but can attract specialist beetles. We determined whether plant traits such as cucurbitacins predict herbivore resistance and pollinator attraction using an information-theoretic approach. KEY RESULTS: Mutualists and floral antagonists were attracted to the same cucurbit varieties once they flowered. However, rather than cucurbitacin concentration, we found that the size of the flower and volatile emissions of floral sesquiterpenoids explained both pollinator and floral herbivore visitation preference across cucurbit taxa. This pattern held across cucurbit taxa and within the Cucurbita genus. CONCLUSIONS: Surprisingly, floral sesquiterpenoid volatiles, which are associated with direct defense, indirect defense, and attraction, rather than defense traits such as cucurbitacins, appeared to drive interactions with both pollinators and floral herbivores across cucurbit taxa. Identifying the relevant plant traits for attraction and deterrence is important in this economically valuable crop, particularly if pollinators and floral herbivores use the same plant traits as cues.
Data from: Resilient networks of ant-plant mutualists in Amazonian forest fragments
BACKGROUND: The organization of networks of interacting species, such as plants and animals engaged in mutualisms, strongly influences the ecology and evolution of partner communities. Habitat fragmentation is a globally pervasive form of spatial heterogeneity that could profoundly impact the structure of mutualist networks. This is particularly true for biodiversity-rich tropical ecosystems, where the majority of plant species depend on mutualisms with animals and it is thought that changes in the structure of mutualist networks could lead to cascades of extinctions. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated effects of fragmentation on mutualistic networks by calculating metrics of network structure for ant-plant networks in continuous Amazonian forests with those in forest fragments. We hypothesized that networks in fragments would have fewer species and higher connectance, but equal nestedness and resilience compared to forest networks. Only one of the nine metrics we compared differed between continuous forest and forest fragments, indicating that networks were resistant to the biotic and abiotic changes that accompany fragmentation. This is partially the result of the loss of only specialist species with one connection that were lost in forest fragments. CONCLUSIONS/SIGNIFICANCE: We found that the networks of ant-plant mutualists in twenty-five year old fragments are similar to those in continuous forest, suggesting these interactions are resistant to the detrimental changes associated with habitat fragmentation, at least in landscapes that are a mosaic of fragments, regenerating forests, and pastures. However, ant-plant mutualistic networks may have several properties that may promote their persistence in fragmented landscapes. Proactive identification of key mutualist partners may be necessary to focus conservation efforts on the interactions that insure the integrity of network structure and the ecosystems services networks provide.
Data from: Geographical variation in mutualistic networks: similarity, turnover and partner fidelity
Although species and their interactions in unison represent biodiversity and all the ecological and evolutionary processes associated with life, biotic interactions have, contrary to species, rarely been integrated into the concepts of spatial β-diversity. Here, we examine β-diversity of ecological networks by using pollination networks sampled across the Canary Islands. We show that adjacent and distant communities are more and less similar, respectively, in their composition of plants, pollinators and interactions than expected from random distributions. We further show that replacement of species is the major driver of interaction turnover and that this contribution increases with distance. Finally, we quantify that species-specific partner compositions (here called partner fidelity) deviate from random partner use, but vary as a result of ecological and geographical variables. In particular, breakdown of partner fidelity was facilitated by increasing geographical distance, changing abundances and changing linkage levels, but was not related to the geographical distribution of the species. This highlights the importance of space when comparing communities of interacting species and may stimulate a rethinking of the spatial interpretation of interaction networks. Moreover, geographical interaction dynamics and its causes are important in our efforts to anticipate effects of large-scale changes, such as anthropogenic disturbances.
Data from: Can social partnerships influence the microbiome? insights from ant farmers and their trophobiont mutualists.
Mutualistic interactions with microbes have played a crucial role in the evolution and ecology of animal hosts. However, it is unclear what factors are most important in influencing particular host-microbe associations. While closely related animal species may have more similar microbiota than distantly related ones due to phylogenetic contingencies, social partnerships with other organisms, such as those in which one animal farms another, may also influence an organism's symbiotic microbiome. We studied a mutualistic network of Brachymyrmex and Lasius ants farming several honeydew-producing Prociphilus aphids and Rhizoecus mealybugs to test whether the mutualistic microbiomes of these interacting insects are primarily correlated with their phylogeny or with their shared social partnerships. Our results confirm a phylogenetic signal in the microbiomes of aphid and mealybug trophobionts, with each species harboring species-specific endosymbiont strains of Buchnera (aphids), Tremblaya and Sodalis (mealybugs), and Serratia (both mealybugs and aphids) despite being farmed by the same ants. This is likely explained by strict vertical transmission of trophobiont endosymbionts between generations. In contrast, the ants' microbiome is potentially shaped by their social partnerships, with ants that farm the same trophobionts also sharing strains of sugar-processing Acetobacteraceae bacteria, known from other honeydew-feeding ants and which likely reside extracellularly in the ants' guts. These ant-microbe associations are arguably more 'open' and subject to horizontal transmission or social transmission within ant colonies. These findings suggest that the role of social partnerships in shaping a host's symbiotic microbiome can be variable, and is likely dependent on how the microbes are transmitted across generations.
Data from: Intra-population genomics in a model mutualist: population structure and candidate symbiosis genes under selection in Medicago truncatula
Bottom-up evolutionary approaches, including geographically-explicit population genomic analyses, have the power to reveal the mechanistic basis of adaptation. Here we conduct a population genomic analysis in the model legume, Medicago truncatula, in order to characterize population genetic structure and identify symbiosis-related genes showing evidence of spatially-variable selection. Using RAD-seq, we generated over 26,000 SNPs from 191 accessions from within three regions of the native range in Europe. Results from STRUCTURE analysis identify 5 distinct genetic clusters with divisions that separate east and west regions in the Mediterranean basin. Much of the genetic variation is maintained within sampling sites, and there is evidence for isolation by distance. Extensive linkage disequilibrium was identified, particularly within populations. We conducted genetic outlier analysis with FST-based genome scans and a bayesian modeling approach (PCAdapt). There were 70 core outlier loci shared between these distinct methods with one clear candidate symbiosis related gene, DMI1. This work sets that stage for functional experiments to determine the important phenotypes that selection has acted upon and complementary efforts in rhizobium populations.
Importance of intraspecific variation in the pollination and seed dispersal functions of a double mutualist animal species
Although most plants depend on different animals for pollination and seed dispersal, sometimes the same animal species provides both functions, being thus involved in what has been termed a 'double mutualism'. Very little is known on the effectiveness of such species as both pollinators and seed dispersers, and even less on the intraspecific level differences at the contribution of an animal mutualist to plant fitness. In this study, we focused on the interaction between a Mediterranean shrub <i>Cneorum tricoccon</i> L. (Rutaceae) and the Balearic lizard <i>Podarcis lilfordi</i> L. (Lacertidae) in order to assess: (1) the role of this lizard as a legitimate pollinator of the plant (previously thought to be exclusively insect-pollinated), and (2) the intraspecific variation in the use of flowers and fruits by lizard individuals, comparing males, females and juveniles. We further evaluated whether lizards show different fruit size selection depending on sex and age, with potential consequences for seed germination. Lizards visited more flowers and selected more hermaphrodite flowers than insects did, leading to relative increases in both fruit and seed set. Interestingly, female and juvenile lizards were the main flower visitors, whereas males were the main fruit consumers. Males selected the largest fruits (bearing the largest seeds) though this did not increase seed germination, which was only ca. 15%. We concluded that <i>P. lilfordi</i> acts as a legitimate pollinator of <i>C. tricoccon</i> and, thus, confirm that this system constitutes a new case of double mutualism, especially common in island compared to mainland systems. Moreover, our findings show a large variation among conspecific individuals in their role as either pollinators or seed dispersers, with potential implications for plant reproductive success. Our study, therefore, highlights the importance of evaluating plant-animal interactions at the intraspecific level, and calls for more in-depth studies on the consequences of such intraspecific variation.
Data from: Ecological outsourcing: a pitcher plant benefits from transferring pre-digestion of prey to a bat mutualist
Mutualisms are interspecific interactions where each of the species involved gains net benefits from the other(s). The exchange of resources and/or services between mutualistic partners often involves tasks that species originally accomplished themselves but which have been taken over by or transferred to the more efficient partner during the evolution of the mutualism. Such 'ecological outsourcing' can be seen, for example, in several carnivorous plants that have transferred prey capture and digestion to animal partners. However, the outcome of this transfer and its fitness relevance has rarely been quantified. Using a digestive mutualism between a carnivorous pitcher plant (Nepenthes hemsleyana) and a bat (Kerivoula hardwickii) as a model, we tested the hypothesis that ecological outsourcing is a profitable strategy for the outsourcing partner. To evaluate the value of this mutualism, we conducted a series of field and glasshouse experiments. We measured the benefits of ecological outsourcing by comparing survival, growth, photosynthesis and nutrient content of N. hemsleyana plants fed with bat faeces to those fed with arthropods. To investigate the costs of such outsourcing processes, we repeated the experiment with the closest relative (Nepenthes rafflesiana) that is not adapted to digest bat faeces. We found that N. hemsleyana plants fed with faeces had increased survival, growth and photosynthesis compared to plants fed with arthropods only. On average, plants covered 95% of their nitrogen demand from faeces under strong nutrient deprivation. Despite N. rafflesiana's higher arthropod capture rate, faeces covered a large part of this species' nutrient demand as well, suggesting low costs for outsourcing. Synthesis. Outsourcing prey capture and digestion to the mutualism partner seems to be a beneficial strategy for N. hemsleyana. It may explain the evolutionary trend of several carnivorous plants to lose their carnivorous traits while increasing their attractiveness to mutualistic partners. On a much broader scale, we propose that ecological outsourcing could be one of the major drivers for the evolution and maintenance of mutualisms.
Data from: Integrating plant species contribution to mycorrhizal and seed dispersal mutualistic networks
Mutualistic interactions like those established between plants and mycorrhizal fungi or seed dispersers are key drivers of plant population dynamics and ecosystem functioning, however, these interactions have rarely been explored together. We assembled a tripartite fungi-plant-disperser network in the Gorongosa National Park - Mozambique, to test 1) if the diversity and importance of plant mutualists above- and belowground are correlated, and 2) whether biotically and abiotically dispersed plants are associated with similar or distinct arbuscular mycorrhizal fungi (AMF) communities. We quantified seed dispersal by animals during one year and characterized the community of 26 common plant species. Sixteen plant species were dispersed by 15 animals and colonized by 48 AMF virtual taxa (VT), while the remaining ten plant species were not dispersed by animals and associated with 34 AMF VT. We found no evidence for a correlation between the number of plant partners above- and belowground or on plant specialization on both types of partners. We also found no evidence for differentiation of AMF communities between biotically and abiotically dispersed plants. Altogether, these results suggest that the establishment of plant interactions with seed dispersers and mycorrhizal fungi are largely independent and that both biotically and abiotically dispersed plants seem to associate with similar communities of AM fungi.
Data from: Camponotus floridanus ants incur a trade-off between phenotypic development and pathogen susceptibility from their mutualistic Endosymbiont Blochmannia
Various insects engage in microbial mutualisms in which the reciprocal benefits exceed the costs. Ants of the genus Camponotus benefit from nutrient supplementation by their mutualistic endosymbiotic bacteria, Blochmannia, but suffer a cost in tolerating and regulating the symbiont. This cost suggests that the ants face secondary consequences such as susceptibility to pathogenic infection and transmission. In order to elucidate the symbiont's effects on development and disease defence, Blochmannia floridanus was reduced in colonies of Camponotus floridanus using antibiotics. Colonies with reduced symbiont levels exhibited workers of smaller body size, smaller colony size, and a lower major-to-minor worker caste ratio, indicating the symbiont's crucial role in development. Moreover, these ants had decreased cuticular melanisation, yet higher resistance to the entomopathogen Metarhizium brunneum, suggesting that the symbiont reduces the ants' ability to fight infection, despite the availability of melanin to aid in mounting an immune response. While the benefits of improved growth and development likely drive the mutualism, the symbiont imposes a critical trade-off. The ants' increased susceptibility to infection exacerbates the danger of pathogen transmission, a significant risk given ants' social lifestyle. Thus, the results warrant research into potential adaptations of the ants and pathogens that remedy and exploit the described disease vulnerability.
Data from: Standing genetic variation in host preference for mutualist microbial symbionts
Many models of mutualisms show that mutualisms are unstable if hosts lack mechanisms enabling preferential associations with mutualistic symbiotic partners over exploitative partners. Despite the theoretical importance of mutualism-stabilizing mechanisms, we have little empirical evidence to infer their evolutionary dynamics in response to exploitation by non-beneficial partners. Using a model mutualism—the interaction between legumes and nitrogen-fixing soil symbionts—we tested for quantitative genetic variation in plant responses to mutualistic and exploitative symbiotic rhizobia in controlled greenhouse conditions. We found significant broad-sense heritability in a legume host's preferential association with mutualistic over exploitative symbionts and selection to reduce frequency of associations with exploitative partners. We failed to detect evidence that selection will favour the loss of mutualism-stabilizing mechanisms in the absence of exploitation, as we found no evidence for a fitness cost to the host trait or indirect selection on genetically correlated traits. Our results show that genetic variation in the ability to preferentially reduce associations with an exploitative partner exists within mutualisms and is under selection, indicating that micro-evolutionary responses in mutualism-stabilizing traits in the face of rapidly evolving mutualistic and exploitative symbiotic bacteria can occur in natural host populations.
Data from: Additive effects of plant chemotype, mutualistic ants and predators on aphid performance and survival
1. Cascading effects in ecological systems acting across three or more trophic levels can be either of a resource-based (bottom-up) or natural enemy-based (top-down) nature. But, due to their complexity these effects are often considered separately and their relative strength, acting simultaneously, remains unknown. 2. In a semi-natural field experiment using tansy (Tanacetum vulgare L.) and the specialised tansy aphid Metopeurum fuscoviride Stroyan as a model system, we compared the effects of four distinct plant chemotypes (i.e. bottom-up), defined by the bouquet of their volatile terpenoids, on aphid population dynamics by manipulating the presence/absence of mutualistic ants and presence/absence of naturally-occurring predators (i.e. top-down). 3. Predators reduced aphid abundance and colony survival but did not reduce initial growth rate due to a time lag until predators arrived on the plants. Ants directly benefited initial aphid growth rates and abundance, even in the absence of predators, but not the number of days an aphid colony persisted on the plant. 4. Plant chemotype directly affected aphid growth rate and final abundances across the different plants and indirectly affected the abundances of tending ants and predators through effects on aphids. We found that tending ants were more abundant on one plant chemotype. Although ant abundance did not affect aphid population development, it became clear that ants had a preference towards aphids on certain chemotypes. However, a higher number of predators led to a lower number of aphids. 5. The results confirm the importance of plant chemical variation, acting through multiple effects on many species in arthropod communities, and support results from field studies. In a natural population, with a diverse selection of host-plant variants, aphid populations and their interacting species can therefore be structured at the level of an individual plant. Specialist aphids on patchily-distributed host plants can exhibit metacommunity dynamics at very local scales. Plant within-species variation within a local population is often ignored in metacommunity ecology, yet our work shows that this can have strong effects on insect-ant-natural enemy dynamics and therefore future research should incorporate this into current theory and experimental studies.
Data from: Chemical tradeoffs in seed dispersal: Defensive metabolites in fruits deter consumption by mutualist bats
Although fleshy fruits function primarily to attract seed dispersers, many animal-dispersed fruits contain potentially toxic secondary metabolites. These metabolites can provide defense against seed predators and pathogens, but their effects on dispersers are still poorly understood. In some cases plants may experience a tradeoff, where the metabolites that provide fruit defense also reduce seed disperser preferences. In other cases the bioactivity of fruit secondary metabolites may be directed primarily at pests with no negative effects on seed-dispersing vertebrates. We tested the effects of amides, a group of nitrogen-based defensive compounds common in the plant genus Piper (Piperaceae), in interactions with the primary seed dispersers of Piper in the neotropics – fruit-feeding bats in the genus Carollia (Phyllostomidae). In a series of flight cage experiments, pure amides and amide-rich fruit extracts reduced the preferences of bats for Piper fruit, affecting both the bats' initial choices to remove Piper infructescences and the proportion of fruit consumed from individual infructescences once they were removed. However, the effects of amides varied considerably among three species of Carollia and among the specific individual amides and extracts tested. Overall, our results support the hypothesis that plants experience a tradeoff between seed dispersal and fruit defense, but the strength of this tradeoff and the overall fitness consequences may depend strongly on ecological context.
Data from: Quantifying the climatic niche of symbiont partners in a lichen symbiosis indicates mutualist-mediated niche expansions
The large distributional areas and ecological niches of many lichenized fungi may in part be due to the plasticity in interactions between the fungus (mycobiont) and its algal or cyanobacterial partners (photobionts). On the one hand, broad-scale phylogenetic analyses show that partner compatibility in lichens is rather constrained and shaped by reciprocal selection pressures and codiversification independent of ecological drivers. On the other hand, sub-species-level associations among lichen symbionts appear to be environmentally structured rather than phylogenetically constrained. In particular, switching between photobiont ecotypes with distinct environmental preferences has been hypothesized as an adaptive strategy for lichen-forming fungi to broaden their ecological niche. The extent and direction of photobiont-mediated range expansions in lichens, however, have not been examined comprehensively at a broad geographic scale. Here we investigate the population genetic structure of Lasallia pustulata symbionts at sub-species-level resolution across the mycobiont's Europe-wide range, using fungal MCM7 and algal ITS rDNA sequence markers. We show that variance in occurrence probabilities in the geographic distribution of genetic diversity in mycobiont-photobiont interactions is closely related to changes in climatic niches. Quantification of niche extent and overlap based on species distribution modeling and construction of Hutchinsonian climatic hypervolumes revealed that combinations of fungal-algal interactions change at the sub-species level along latitudinal temperature gradients and in Mediterranean climate zones. Our study provides evidence for symbiont-mediated niche expansion in lichens. We discuss our results in the light of symbiont polymorphism and partner switching as potential mechanisms of environmental adaptation and niche evolution in mutualisms.
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Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
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