Facultative Symbiont Infections Affect Aphid Reproduction

Some bacterial symbionts alter their hosts reproduction through various mechanisms that enhance their transmission in the host population. In addition to its obligatory symbiont Buchnera aphidicola, the pea aphid Acyrthosiphon pisum harbors several facultative symbionts influencing several aspects of host ecology. Aphids reproduce by cyclical parthenogenesis whereby clonal and sexual reproduction alternate within the annual life cycle. Many species, including the pea aphid, also show variation in their reproductive mode at the population level, with some lineages reproducing by cyclical parthenogenesis and others by permanent parthenogenesis. While the role of facultative symbionts has been well studied during the parthenogenetic phase of their aphid hosts, very little is known on their possible influence during the sexual phase. Here we investigated whether facultative symbionts modulate the capacity to produce sexual forms in various genetic backgrounds of the pea aphid with controlled symbiont composition and also in different aphid genotypes from natural populations with previously characterized infection status and reproductive mode. We found that most facultative symbionts exhibited detrimental effects on their hosts fitness under sex-inducing conditions in comparison with the reference lines. We also showed that the loss of sexual phase in permanently parthenogenetic lineages of A. pisum was not explained by facultative symbionts. Finally, we demonstrated that Spiroplasma infection annihilated the production of males in the host progeny by inducing a male-killing phenotype, an unexpected result for organisms such as aphids that reproduce primarily through clonal reproduction

Where do fishmeal and fish oil products come from? An analysis of the conversion ratios in the global fishmeal industry

International audienceAs a result of the stagnation of commercial fishery landings, aquaculture activities are expected to increase over the next decades to match the growing demand for marine protein Overall, it is expected that the aquaculture sector could reduce sonic of the fishing pressure applied to wild stocks However, this development is likely to be limited by the availability of key aquaculture inputs, specifically fishmeal and fish oil products (FMFOP) Aquaculture provided 60% (fish meal) and 80% (fish oil) of the world total consumption of these products in 2007 FMFOP are generally derived from small pelagic fish species, but can also be derived from other sources Identifying the origin of FMFOP is crucial to understanding the effects of this new pressure on marine social-ecological systems Two factors are of particular importance in the reduction sector transforming wild fish into fishmeal or fish oil the two "conversion ratios" (le the ratio between the quantity of wild fish harvested and the resulting quantity of FMFOP), and the ratio between the quantity of FMFOP and aquaculture production), and the type of raw material used by the reduction sector Based on trade and production databases from FAO and the International Fishmeal and Fish oil Organisation (IFFO), this paper proposes an approach to identify the origin of FMFOP It shows that whereas different countries use different pelagic resources to produce FMFOP, other countries use non-pelagic sources, and some countries use pelagic resources for human consumption (C) 2010 Elsevier Ltd All rights reserve

Where do fishmeal and fish oil products come from? An analysis of the conversion ratios in the global fishmeal industry

As a result of the stagnation of commercial fishery landings, aquaculture activities are expected to increase over the next decades to match the growing demand for marine protein. Overall, it is expected that the aquaculture sector could reduce some of the fishing pressure applied to wild stocks. However, this development is likely to be limited by the availability of key aquaculture inputs, specifically fishmeal and fish oil products (FMFOP). Aquaculture provided 60 % (fish meal) and 80 % (fish oil) of the world total consumption of these products in 2007. FMFOP are generally derived from small pelagic fish species, but can also be derived from other sources. Identifying the origin of FMFOP is crucial to understanding the effects of this new pressure on marine social-ecological systems. Two factors are of particular importance in the reduction sector transforming wild fish into fishmeal or fish oil: the two "conversion ratios" (i.e. the ratio between the quantity of wild fish harvested and the resulting quantity of FMFOP, and the ratio between the quantity of FMFOP and aquaculture production), and the type of raw material used by the reduction sector. Based on trade and production databases from FAO and the International Fishmeal and Fish oil Organisation (IFFO), this paper proposes an approach to identify the origin of FMFOP. It shows that whereas different countries use different pelagic resources to produce FMFOP, other countries use non-pelagic sources, and some countries use pelagic resources for human consumption.Fishmeal Fish oil Pelagic fish Aquaculture Sustainable growth Conversion ratios

Data from: Conditional reduction of predation risk associated with a facultative symbiont in an insect

Symbionts are widespread among eukaryotes and their impacts on the ecology and evolution of their hosts are meaningful. Most insects harbour obligate and facultative symbiotic bacteria that can influence their phenotype. In the pea aphid Acyrthosiphon pisum, an astounding symbiotic-mediated phenotype has been recently observed: when infected with the symbiotic bacteria Rickettsiella viridis, young red aphid larvae become greener at adulthood and even darker green when co-infected with Rickettsiella viridis and Hamiltonella defensa. As body colour affects the susceptibility towards natural enemies in aphids, the influence of the colour change due to these facultative symbionts on the host survival in presence of predators was tested. Our results suggested that the Rickettsiella viridis infection may impact positively host survival by reducing predation risk. Due to results from uninfected aphids (i.e., more green ones attacked), the main assumption is that this symbiotic infection would deter the predatory ladybird feeding by reducing the profitability of their hosts rather than decreasing host detection through body colour change. Aphids co-infected with Rickettsiella viridis and Hamiltonella defensa were, however, more exposed to predation suggesting an ecological cost associated with multiple infections. The underlying mechanisms and ecological consequences of these symbiotic effects are discussed

Economic structural change in global greenhouse gas emissions scenarios

International audienc

Global socio-economic and climate change mitigation scenarios through the lens of structural change

International audienceThis paper analyses structural change in the economy as a key but largely unexplored aspect of global socioeconomic and climate change mitigation scenarios. Structural change can actually drive energy and land use as much as economic growth and influence mitigation opportunities and barriers. Conversely, stringent climate policy is bound to induce specific structural and socioeconomic transformations that are still insufficiently understood. We introduce Multi-Sectoral Integrated Assessment Models as main tools to capture the key drivers of structural change and we conduct a multi-model study to assess main structural effectschanges of the sectoral composition and intensity of trade of global and regional economiesin a baseline and 2°C policy scenario by 2050. First, the range of baseline projections across models, for which we identify the main drivers, illustrates the uncertainty on future economic pathways-in emerging economies especially-and inform on plausible alternative futures with implications for energy use and emissions. Second, in all models, climate policy in the 2°C scenario imposes only a second-order impact on the economic structure at the macrosectoral level-agriculture, manufacturing and services-compared to changes modelled in the baseline. However, this hides more radical changes for individual industries-within the energy sector especially. The study, which adopts a top-down framing of global structural change, represents a starting point to kick-start a conversation and propose a new research agenda seeking to improve understanding of the structural change effects in socioeconomic and mitigation scenarios, and better inform policy assessments

Polin et al PlosOne 2015 Symbiosis Predation datafile

This Excel file contains all the results obtained in the study detailed in the present manuscrip

The experimental treatments.

<p>The six experimental treatments combining pairs of aphid types in order to test the effects of colour and symbiotic complement on aphid survival under predation pressure. Aphid type was defined as a combination of aphid colour and symbiotype. The aphid survival rate was tested (A) between red and green aphid types with different symbiotic complement and (B) among green types differing by their symbiotic complements. Letters reported in the aphids stand for the symbiotic complement including the obligate symbiont <i>Buchnera</i> (B) and the two facultative symbionts, <i>Rickettsiella</i> (R) and <i>Hamiltonella</i> (H). The name code of each treatment is indicated on the link between considered aphid types (Capital letter: the aphid colour; Subscript letters: symbiotic complement).</p

The survival rate of aphids depending on their type.

<p>Proportion of surviving <i>Acyrthosiphon pisum</i> aphids among fifteen of each type exposed to predation by an adult <i>Coccinella septempunctata</i> during 24 hours. Each treatment is the combination of two aphid types exposed to predation. Twenty replicates have been conducted per treatment (except for treatment G_BR-G_BRH where N = 16). (A)–(F): results for each experiment treatment. Error bars represent the standard error of the proportion. Different letters presents significant difference (p < 0.05; GLMM).</p

Protective symbiosis: distribution of Hamiltonella defensa in natural populations of pea aphid

Symbiotic associations between microorganisms and eukaryotes are common in nature. These microorganisms can play important role of the evolution and ecology of their hosts by modifying their phenotype like conferring protection against parasitic wasps. This symbiotic protection is encountered in the pea aphid, Acyrthosiphon pisum, where the bacterial symbiont Hamiltonella defensa confers protection against parasitoid wasp, Aphidius ervi. Despite this protective benefit, this symbiont occurs only at intermediate frequencies in natural populations. To identify factors influencing the frequency of H. defensa in natural population, we measured pea aphid life history traits and the protective effect of this symbiont. We found that protective symbiont doesn’t influence the host life history traits and the protection conferred by this symbiont varies according the biotype of pea aphid and the bacterial strain. However, the multiple infections with facultative symbionts reduce the fitness of the host while increasing protection against parasitoids. We also observed the positive correlation between aphid reproduction in the absence of parasitoid and the level of resistance: higher the symbiotic protection higher the aphid fecundity. This finding has important implications for the evolution of defensive symbiosis and allows evidence the need for better understanding of how these protective symbionts is maintained in the population