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opencc-zeroDec 2014View details →

Data from: Concurrent co-evolution of intra-organismal cheaters and resisters

The evolution of multicellularity is a major transition that is not yet fully understood. Specifically, we do not know if there are any mechanisms by which multicellularity can be maintained without a single cell bottleneck or other relatedness enhancing mechanisms. Under low relatedness, cheaters can evolve that benefit from the altruistic behaviour of others without themselves sacrificing. If these are obligate cheaters, incapable of co-operating, their spread can lead to the demise of multicellularity. One possibility, however, is that co-operators can evolve resistance to cheaters. We tested this idea in a facultatively multicellular social amoeba, Dictyostelium discoideum. This amoeba usually exists as a single cell but, when stressed, thousands of cells aggregate to form a multicellular organism in which some of the cells sacrifice for the good of others. We used lineages that had undergone experimental evolution at very low relatedness, during which time obligate cheaters evolved. Unlike earlier experiments, which found resistance to cheaters that were prevented from evolving, we competed cheaters and non-cheaters that evolved together, and cheaters with their ancestors. We found that non-cheaters can evolve resistance to cheating before cheating sweeps through the population and multicellularity is lost. Our results provide insight into cheater-resister co-evolutionary dynamics, in turn providing experimental evidence for the maintenance of at least a simple form of multicellularity by means other than high relatedness.

opencc-zeroDec 2014View details →

Data from: Co-expression of two subtypes of melatonin receptor on rat M1-type intrinsically photosensitive retinal ganglion cells

Intrinsically photosensitive retinal ganglion cells (ipRGCs) are involved in circadian and other non-image forming visual responses. An open question is whether the activity of these neurons may also be under the regulation mediated by the neurohormone melatonin. In the present work, by double-staining immunohistochemical technique, we studied the expression of MT1 and MT2, two known subtypes of mammalian melatonin receptors, in rat ipRGCs. A single subset of retinal ganglion cells labeled by the specific antibody against melanopsin exhibited the morphology typical of M1-type ipRGCs. Immunoreactivity for both MT1 and MT2 receptors was clearly seen in the cytoplasm of all labeled ipRGCs, indicating that these two receptors were co-expressed in each of these neurons. Furthermore, labeling for both the receptors were found in neonatal M1 cells as early as the day of birth. It is therefore highly plausible that retinal melatonin may directly modulate the activity of ipRGCs, thus regulating non-image forming visual functions.

Data from: No evidence for social immunity in co-founding queen associations

Ant queens often associate to found new colonies, yet the benefits of this behaviour remain unclear. A major hypothesis is that queens founding in groups are protected by social immunity and can better resist disease than solitary queens, due to mutual grooming, sharing of antimicrobials, or higher genetic diversity among their workers. We tested this hypothesis by manipulating the number of queens in incipient colonies of Lasius niger and measuring their resistance to the fungal entomopathogen Metarhizium brunneum. We found no evidence for social immunity in associations of founding queens. First, co-founding queens engaged in self-grooming, but performed very little allo-grooming or trophallaxis. Second, co-founding queens did not exhibit higher pathogen resistance than solitary queens, and their respective workers did not differ in disease resistance. Finally, queens founding in groups increased their investment in a component of individual immunity, as expected if they do not benefit from social immunity but respond to a higher risk of disease. Overall, our results provide no evidence that joint colony founding by L. niger queens increases their ability to resist fungal pathogens.

Data from: An active-radio-frequency-identification system capable of identifying co-locations and social-structure: validation with a wild free-ranging animal

Behavioural events that are important for understanding sociobiology and movement ecology are often rare, transient and localised, but can occur at spatially distant sites e.g. territorial incursions and co-locating individuals. Existing animal tracking technologies, capable of detecting such events, are limited by one or more of: battery life; data resolution; location accuracy; data security; ability to co-locate individuals both spatially and temporally. Technology that at least partly resolves these limitations would be advantageous. European badgers (Meles meles L.), present a challenging test-bed, with extra-group paternity (apparent from genotyping) contradicting established views on rigid group territoriality with little social-group mixing. In a proof of concept study we assess the utility of a fully automated active-radio-frequency-identification (aRFID) system combining badger-borne aRFID-tags with static, wirelessly-networked, aRFID-detector base-stations to record badger co-locations at setts (burrows) and near notional border latrines. We summarise the time badgers spent co-locating within and between social-groups, applying network analysis to provide evidence of co-location based community structure, at both these scales. The aRFID system co-located animals within 31.5 m (adjustable) of base-stations. Efficient radio transmission between aRFIDs and base-stations enables a 20 g tag to last for 2–5 years (depending on transmission interval). Data security was high (data stored off tag), with remote access capability. Badgers spent most co-location time with members of their own social-groups at setts; remaining co-location time was divided evenly between intra- and inter-social-group co-locations near latrines and inter-social-group co-locations at setts. Network analysis showed that 20–100% of tracked badgers engaged in inter-social-group mixing per week, with evidence of trans-border super-groups, that is, badgers frequently transgressed notional territorial borders. aRFID occupies a distinct niche amongst established tracking technologies. We validated the utility of aRFID to identify co-locations, social-structure and inter-group mixing within a wild badger population, leading us to refute the conventional view that badgers (social-groups) are territorial and to question management strategies, for controlling bovine TB, based on this model. Ultimately aRFID proved a versatile system capable of identifying social-structure at the landscape scale, operating for years and suitable for use with a range of species.

Data from: Disentangling demographic co-effects of predation and pollution on population dynamics

In nature species react to a variety of endogenous and exogenous ecological factors. Understanding the mechanisms by which these factors interact and drive population dynamics is a need for understanding and managing ecosystems. In this study we assess, using laboratory experiments, the effects that the combinations of two exogenous factors exert on the endogenous structure of the population dynamics of a size-structured population of Daphnia. One exogenous factor was size-selective predation, which was applied on experimental populations through simulating: (a) selective predation on small prey, (b) selective predation on large prey and (c) non-selective predation. The second exogenous factor was pesticide exposure, applied experimentally in a quasi-continuous regime. Our analysis combined theoretical models and statistical testing of experimental data for analyzing how the density dependence structure of the population dynamics was shifted by the different exogenous factors. Our results showed that pesticide exposure interacted with the mode of predation in determining the endogenous dynamics. Populations exposed to the pesticide and to either selective predation on newborns or selective predation on adults exhibited marked nonlinear effects of pesticide exposure. However, the specific mechanisms behind such nonlinear effects were dependent on the mode of size-selectivity. In populations under non-selective predation the pesticide exposure exerted a weak lateral effect. The ways in which endogenous process and exogenous factors may interact determine population dynamics. Increases in equilibrium density results in higher variance of population fluctuations but do not modify the stability properties of the system, while changes in the maximum growth rate induce changes in the dynamic regimes and stability properties of the population. Future consideration for research includes the consequences of the seasonal variation in the composition and activity of the predator assembly in interaction with the seasonal variation in exposure to agrochemicals on freshwater population dynamics.

Data from: Cyclic population dynamics and density-dependent intransitivity as pathways to coexistence between co-occurring annual plants

1. Recent studies have brought renewed attention to the importance of complex species interactions - notably intransitive interactions - to patterns of plant community diversity. One underappreciated avenue through which intransitivity can occur is through cyclic population dynamics. Though such cyclic intransitive relationships have been extensively studied in predator-prey systems, evidence of their importance in competitive communities, notably plant communities, is more limited. Most studies of coexistence in plant communities assume fixed-point coexistence even while utilizing models that allow for cyclic population dynamics. 2. In this paper, we explore the potential for density-dependent, cyclic population dynamics and intransitivity in a model for annual plants. We then examine how these density-dependent cycles impact mutual invasibility and ultimately stable coexistence between plant species pairs. We do this using data collected from four co-occurring annual plant species living in natural wildflower communities in SW Western Australia. To maximize the number of biologically plausible pathways by which coexistence mediated by density-dependent cyclic intransitivity can occur, we use an annual plant model that allows for competitive direct interactions, facilitative direct interactions, and higher-order interactions between species. 3. Results from our empirically-parameterized model suggest that monocultures of all four focal species can have cyclic solutions with periodicity greater than 1 under sunny ("open") or shaded field conditions. Cyclic patterns drive variation in annual abundance patterns, with stable solutions for persistent monocultures and invasibility potential (the capacity of one population to invade another) common. Mutual invasibility in the face of cyclic population dynamics was found for just one of six species pairs, only under open environmental conditions. Our results illustrate the potential for cyclic intransitivity to both drive and prevent stable coexistence in environmentally heterogeneous biological communities. 4. Synthesis. We provide analytical and empirical evidence that coexistence in competitive communities (annual plants) can be achieved under non-equilibrium circumstances, through density-dependent cyclic intransitivity. Our results suggest that cyclic population dynamics may be common and important for coexistence dynamics in some types of communities. In such communities, the exploration of stable coexistence should therefore include consideration of cyclic as well as fixed-point equilibria for maximal accuracy.

opencc-zeroJun 2019View details →

Data from: Respiratory syncytial virus co-opts host mitochondrial function to favour infectious virus production

Although respiratory syncytial virus (RSV) is responsible for more human deaths each year than influenza, its pathogenic mechanisms are poorly understood. Here high-resolution quantitative imaging, bioenergetics measurements and mitochondrial membrane potential- and redox-sensitive dyes are used to define RSV's impact on host mitochondria for the first time, delineating RSV-induced microtubule/dynein-dependent mitochondrial perinuclear clustering, and translocation towards the microtubule-organizing centre. These changes are concomitant with impaired mitochondrial respiration, loss of mitochondrial membrane potential and increased production of mitochondrial reactive oxygen species (ROS). Strikingly, agents that target microtubule integrity the dynein motor protein, or inhibit mitochondrial ROS production strongly suppresses RSV virus production, including in a mouse model with concomitantly reduced virus-induced lung inflammation. The results establish RSV's unique ability to co-opt host cell mitochondria to facilitate viral infection, revealing the RSV-mitochondrial interface for the first time as a viable target for therapeutic intervention.

opencc-zeroDec 2015View details →

Data from: Competitor relatedness, indirect soil effects and plant co-existence

How species co-exist is a central question in ecology. Niche differentiation can prevent two species from excluding each other by competition. However, this interaction can vary in space because of internal factors such as intraspecific genetic variation, or external ones such as the presence of a third species. While these effects have been repeatedly observed, their joint effect on the outcome of competition has rarely been considered. We experimentally investigated how a dominant ecosystem engineer (the shrub Thymus vulgaris) affects interactions between two co-occurring and closely related annuals (Medicago minima and M. rigidula). We ask first if the outcome of their interaction depends on the genetic identity of the competitors, and in particular if intraspecific interaction differs between genetically related versus unrelated conspecifics. Second, we ask if co-existence of the two species is modified by the presence of thyme plants altering local soil conditions. We grew genotypes collected in nature of both annual species in inter- and intraspecific competition experiments using soil collected directly underneath thyme plant (thyme soil), and soil collected away from thyme plants (no-thyme soil). We found that thyme soil affected interactions in a way that shifted the species' rank. Crucial for this result was the division of intraspecific competition between genetically related and unrelated individuals. Intraspecific competition was significantly less detrimental to kin than to unrelated conspecifics. In highly structured plant populations, such effects could favor local dominance of a patch by one species. However this kin effect occurred for each species only in its preferred soil (thyme versus no-thyme), promoting a stabilizing co-existence mechanism at the landscape level. Synthesis: This study shows that the importance of intraspecific competition relative to interspecific competition can be highly dependent on the genotype identity of intraspecific competitors and of the local environment in which the interaction occurs. The local environment can itself be modified by the presence of a third species in the community. These results emphasize how, in order to understand the overall problem of species co-existence, it can be insightful to divide this into smaller local scale problems of co-existence.

Data from: Taxon abundance, diversity, co-occurrence and network analysis of the ruminal microbiota in response to dietary changes in dairy cows

The effects of sunflower oil (SO) (0 or 50 g/kg diet dry matter), supplemented to diets contrasting in the proportion of forage and concentrate (FC) (65:35 vs 35:65), were evaluated for their influence on rumen microbiome. Four multiparous Nordic Red dairy cows fitted with rumen cannulae were used in a 4 × 4 Latin square with a 2 × 2 factorial arrangement of treatments and four 35-d periods. Ruminal digesta samples were collected on d 22 and d 24 of each experimental period and DNA was extracted from a combined sample. Diet effect on rumen microbial community was explored by qPCR, T-RFLP and metabarcoding sequencing. QPCR analysis showed that the total amounts of bacteria, archaea or ciliate protozoa were not significantly altered either by FC ratio or addition of SO. Only fungi were reduced by half in high concentrate (H) compared to high forage (L) diets (P=0.03). Further significant reduction of fungi was observed due to SO in both HSO and LSO diets but the effect was stronger in HSO (H vs HSO by 10.5x, P=0.03; L vs LSO by 1.9x, P=0.04). Metabarcoding sequencing analysis showed that SO affected bacterial, archaeal, ciliate protozoa and fungal community structure and diversity and the effect was FC ratio dependent. As expected, Simpson's index of diversity was higher in diets containing higher proportion of forage. These diets were dominated by Firmicutes, while Bacteroidetes and Proteobacteria were more abundant in H diets. Methanobrevibacter ruminantium and Methanobrevibacter gottschalkii dominated archaea community but they were in negative relation to each other. Methanobrevibacter gottschalkii was more abundant in L, while Methanobrevibacter ruminantium in H diet. The strongest diet effect was observed on fungal community, represented by both well classified and novel fungal groups. Both, increase in concentrate and supplementation of SO significantly reduced fungal diversity. We explored microbial interactions by building taxa co-occurrence networks. Our results suggest that studying entire rumen microbiome simultaneously is needed aiming to better understand how diet induced changes within microbial community are associated with microbial function, subsequently leading to better understanding of rumen fermentation and methanogenesis.

Data from: Divergence in strategies for coping with winter embolism among co-occurring temperate tree species: the role of positive xylem pressure, wood type and tree stature

1. In temperate ecosystems, freeze-thaw events are an important environmental stress that can induce severe xylem embolism (i.e. clogging of conduits by air bubbles) in overwintering organs of trees. However, no comparative studies of different adaptive strategies among sympatric tree species for coping with winter embolism have examined the potential role of the presence or absence of embolism refilling by positive xylem pressure. 2. We evaluated the degree of winter embolism and hydraulic architecture traits in 22 deciduous angiosperm tree species typical of temperate forest sites in NE China. Co-occurring trees growing in a local botanical garden were used to minimize variation caused by differences in proximal environmental conditions and to ensure that interspecific variation reflected genetic differences between species. 3. Four functional groups with potentially different strategies for coping with winter embolism were compared: positive xylem pressure generating species (PXP) that are all diffuse-porous, except a semi-ring-porous species, large (LDP) and small (SDP) statured diffuse-porous tree species that are unable to generate positive xylem pressure, and ring-porous species (RP). 4. The PXP group exhibited nearly full recovery from winter embolism in contrast to the other three groups, which showed persistent and relatively high degrees of hydraulic dysfunction during the subsequent growing season. The absence of a functional trade-off between hydraulic efficiency and safety against freeze-thaw induced embolism in the PXP group and the presence of a trade-off in the other three groups, suggests that the ability to generate root or stem pressure for embolism refilling may partially free some temperate tree species from adaptive constraints imposed by winter embolism formation. 5. Efficient winter embolism reversal by positive pressure in PXP species did not distinguish them from their non-xylem pressure-generating LDP counterparts in terms of various measures of xylem hydraulic efficiency during the growing season. Divergence in the ability to refill winter embolism through generation of positive xylem pressure implies a series of functional trade-offs that may partially explain the co-existence of these two types of temperate tree species.

Data from: Nitrogen and chlorine co-doped carbon dots as probe for sensing and imaging in biological samples

A facile one step hydrothermal synthesis approach was proposed to prepare nitrogen and chlorine co-doped carbon dots using l-ornithine hydrochloride as the sole precursor. The configuration and component of carbon dots were characterized by TEM, XPS, and FTIR. The obtained CDs (Orn-CDs) with a mean diameter of 2.1 nm were well monodispersed in aqueous solutions. The as-prepared CDs exhibited a bright blue fluorescence with a high yield of 60%, good photostability and low cytotoxicity. The emission of Orn-CDs could be selectively and effectively suppressed by Fe3+. Thus, a quantitative assay of Fe3+ was realized by this nanoprobe with a detection limit of 95.6 nmol L-1 in the range of 0.3-50 µmol L-1. Furthermore, ascorbic acid could recover the fluorescence of Orn-CDs suppressed by Fe3+, owing to the transformation of Fe3+ to Fe2+ by ascorbic acid. The limit of detection for ascorbic acid was 137 nmol L-1 in the range of 0.5-10 µmol L-1. In addition, the established method was successfully applied for Fe3+ and ascorbic acid sensing in human serum and urine specimans and for imaging of Fe3+ in living cells. With merits of low economic cost, easy to scale up, without additional functionalized and sample pretreatment, Orn-CDs based sensing platform showed its potential to be used for biomedical related study.

opencc-zeroDec 2012View details →

Data from: Genetic regulatory network motifs constrain adaptation through curvature in the landscape of mutational (co)variance

Systems biology is accumulating a wealth of understanding about the structure of genetic regulatory networks, leading to a more complete picture of the complex genotype-phenotype relationship. However, models of multivariate phenotypic evolution based on quantitative genetics have largely not incorporated a network-based view of genetic variation. Here we model a set of two-node, two-phenotype genetic network motifs, covering a full range of regulatory interactions. We find that network interactions result in different patterns of mutational (co)variance at the phenotypic level (the M-matrix), not only across network motifs but also across phenotypic space within single motifs. This effect is due almost entirely to mutational input of additive genetic (co)variance. Variation in M has the effect of stretching and bending phenotypic space with respect to evolvability, analogous to the curvature of space-time under general relativity, and similar mathematical tools may apply in each case. We explored the consequences of curvature in mutational variation by simulating adaptation under divergent selection with gene flow. Both standing genetic variation (the G-matrix) and rate of adaptation are constrained by M, so that G and adaptive trajectories are curved across phenotypic space. Under weak selection the phenotypic mean at migration-selection balance also depends on M.

opencc-zeroOct 2019View details →

Populations of a widespread invader and co-occurring native species vary in phenotypic plasticity

Phenotypic plasticity can promote plant invasions and enhance impacts on native species but little is known about variation in plasticity among invader populations compared to native species. Variation in plasticity among invader populations could inform more precise predictions of invader spread and impacts across heterogeneous resource environments. We used a common garden experiment with sun and shade treatments to test for variation in plasticity among 12 populations of an invasive grass, and to determine if the invader exhibited greater plasticity than six native species that co-occur in the Southeast US. Principal component analysis revealed that invader populations from different native ranges consistently varied from each other and native species in traits linked to more favorable phenotypes under resource limitation. Overall, the invader exhibited greater plasticity than native species, as demonstrated by higher plasticity index values for traits such as plant height, leaf mass ratio, and root shoot ratio. Variation in phenotypic plasticity among invader populations suggests the potential for evolution of plasticity, and greater plasticity of invader populations than native species may underlie invader dominance. Differences in plasticity among populations appears to play an important role in predictions of the spread and potentially the impacts of invasive species.

Data from: Porous poly-l-lactide-co-ε-caprolactone scaffold: a novel biomaterial for vaginal tissue engineering

The surgical reconstruction of functional neovagina is challenging and susceptible to complications. Therefore, developing tissue engineering based treatment methods for vaginal defects is important. Our aim was to develop and test a novel supercritical carbon dioxide foamed poly-l-lactide-co-ε-caprolactone (scPLCL) scaffold for vaginal reconstruction. The scaffolds were manufactured and characterized for porosity (65±4%), pore size (350±150µm) and elastic modulus (2.8±0.4MPa). Vaginal epithelial (EC) and stromal cells (SC) were isolated, expanded, and characterized with flow cytometry. Finally, cells were cultured with scPLCL scaffolds in separate and/or co-cultures. Their attachment, viability, proliferation and phenotype were analyzed. Both cell types strongly expressed cell surface markers CD44, CD73, and CD166. Strong expression of CD326 was detected with ECs and CD90 and CD105 with SCs. Both ECs and SCs attached and maintained viability on scPLCL. Further, scPLCL supported the proliferation of especially ECs, which also maintained epithelial phenotype (cytokeratin expression) during 14d assessment period. Interestingly, ECs expressed uroplakin (UP) Ia, UPIb, and UPIII markers, further, UPIa and UPIII expression was significantly higher on ECs cultured on scPLCL than on cell culture plastic. In conclusion, the scPLCL is potential scaffold for vaginal tissue engineering and the results of this study further illustrates the excellent biocompatibility of PLCL.

Data from: Fluctuating seawater pH/ p CO 2 regimes are more energetically expensive than static pH/ p CO 2 levels in the mussel Mytilus edulis

Ocean acidification (OA) studies typically use stable open-ocean pH or CO2 values. However, species living within dynamic coastal environments can naturally experience wide fluctuations in abiotic factors, suggesting their responses to stable pH conditions may not be reflective of either present or near-future conditions. Here we investigate the physiological responses of the mussel Mytilus edulis to variable seawater pH conditions over short- (6 h) and medium-term (2 weeks) exposures under both current and near-future OA scenarios. Mussel haemolymph pH closely mirrored that of seawater pH over short-term changes of 1 pH unit with acidosis or recovery accordingly, highlighting a limited capacity for acid–base regulation. After 2 weeks, mussels under variable pH conditions had significantly higher metabolic rates, antioxidant enzyme activities and lipid peroxidation than those exposed to static pH under both current and near-future OA scenarios. Static near-future pH conditions induced significant acid–base disturbances and lipid peroxidation compared with the static present-day conditions but did not affect the metabolic rate. These results clearly demonstrate that living in naturally variable environments is energetically more expensive than living in static seawater conditions, which has consequences for how we extrapolate future OA responses in coastal species.

Data from: Minor environmental concentrations of antibiotics can modify bacterial virulence in co-infection with a non-targeted parasite

Leakage of medical residues into the environment can significantly impact natural communities. For example, antibiotic contamination from agriculture and aquaculture can directly influence targeted pathogens, but also other non-targeted taxa of commensals and parasites that regularly co-occur and co-infect the same host. Consequently, antibiotics could significantly alter interspecific interactions and epidemiology of the co-infecting parasite community. We studied how minor environmental concentration of antibiotic affects the coinfection of two parasites, the bacterium Flavobacterium columnare and the fluke Diplostomum pseudospathaceum, in their fish host. We found that antibiotic in feed, and particularly the minute concentration in water, significantly decreased bacterial virulence and changed the infection success of the flukes. These effects depended on the level of antibiotic resistance of the bacterial strains. Antibiotic, however, did not compensate for the higher virulence of co-infections. Our results demonstrate that even very low environmental concentration of antibiotic can influence ecology and epidemiology of diseases in co-infection with non-targeted parasites. Leakage of antibiotics into the environment may thus have more complex effects on disease ecology than previously anticipated.

opencc-zeroDec 2014View details →

Data from: Co-evolutionary dynamics between public good producers and cheats in the bacterium Pseudomonas aeruginosa

The production of beneficial public goods is common in the microbial world, and so is cheating – the exploitation of public goods by non-producing mutants. Here, we examine co-evolutionary dynamics between cooperators and cheats and ask whether cooperators can evolve strategies to reduce the burden of exploitation, and whether cheats in turn can improve their exploitation abilities. We evolved cooperators of the bacterium Pseudomonas aeruginosa, producing the shareable iron-scavenging siderophore pyoverdine, together with cheats, defective in pyoverdine production but proficient in uptake. We found that cooperators managed to co-exist with cheats in 56% of all replicates over approximately 150 generations of experimental evolution. Growth and competition assays revealed that co-existence was fostered by a combination of general adaptions to the media and specific adaptions to the co-evolving opponent. Phenotypic screening and whole-genome re-sequencing of evolved clones confirmed this pattern, and suggest that cooperators became less exploitable by cheats because they significantly reduced their pyoverdine investment. Cheats, meanwhile, improved exploitation efficiency through mutations blocking the costly pyoverdine-signalling pathway. Moreover, cooperators and cheats evolved reduced motility, a pattern that likely represents adaptation to laboratory conditions, but at the same time also affects social interactions by reducing strain mixing and pyoverdine sharing. Overall, we observed parallel evolution, where co-existence of cooperators and cheats was enabled by a combination of adaptations to the abiotic and social environment and their interactions.

Data from: Predicting the effects of parasite co-infection across species boundaries

It is normal for hosts to be coinfected by parasites. Interactions among coinfecting species can have profound consequences, including changing parasite transmission dynamics, altering disease severity, and confounding attempts at parasite control. Despite the importance of coinfection, there is currently no way to predict how different parasite species may interact with one another, nor the consequences of those interactions. Here we demonstrate a method that enables such prediction by identifying two nematode parasite groups based on taxonomy and characteristics of parasitological niche. From an understanding of the interactions between the two defined groups in one host system (wild rabbits), we predict how two different nematode species, from the same defined groups, will interact in coinfections in a different host system (sheep), and then we test this experimentally. We show that as predicted, in coinfections, the blood-feeding nematode Haemonchus contortus suppresses aspects of the sheep immune response, thereby facilitating the establishment and / or survival of the nematode Trichostrongylus colubriformis; and that the T. colubriformis-induced immune response negatively affects H. contortus. This work is the first to use empirical data from one host system to successfully predict the specific outcome of a different coinfection in a second host species. The study therefore takes the first step in defining a practical framework for predicting interspecific parasite interactions in other animal systems.

opencc-zeroDec 2013View details →

Data from: Multidimensional (co)evolutionary stability

The complexity of biotic and abiotic environmental conditions is such that the fitness of individuals is likely to depend on multiple traits. Using a synthetic framework of phenotypic evolution that draws from adaptive dynamics and quantitative genetics approaches, we explore how the number of traits under selection influences convergence stability and evolutionary stability in models for coevolution in multidimensional phenotype spaces. Our results allow us to identify three different effects of trait dimensionality on stability. First are (i) a "combinatorial effect": without epistasis and genetic correlations, a higher number of trait dimensions offers more opportunities for equilibria to be unstable; and (ii) epistatic interactions, that is, fitness interactions between traits, which tend to destabilize evolutionary equilibria; this effect increases with the dimension of phenotype space. These first two effects influence both convergence stability and evolutionary stability, while (iii) genetic correlations (due, e.g., to pleiotropy or linkage disequilibrium) can affect only convergence stability. We illustrate the general prediction that increased dimensionality destabilizes evolutionary equilibria using examples drawn from well-studied classical models of frequency-dependent competition for resources, adaptation to a spatially heterogeneous environment, and antagonistic coevolution. In addition, our analyses show that increased dimensionality can favor diversification, for example, in the form of local adaptation, as well as evolutionary escape.