Search results for "SYMBIOSIS"
showing 10 items of 627 documents
Response of an arctic predator guild to collapsing lemming cycles
2012
6 pages; International audience; Alpine and arctic lemming populations appear to be highly sensitive to climate change, and when faced with warmer and shorter winters, their well-known high-amplitude population cycles may collapse. Being keystone species in tundra ecosystems, changed lemming dynamics may convey significant knock-on effects on trophically linked species. Here, we analyse long-term (1988-2010), community-wide monitoring data from two sites in high-arctic Greenland and document how a collapse in collared lemming cyclicity affects the population dynamics of the predator guild. Dramatic changes were observed in two highly specialized lemming predators: snowy owl and stoat. Follo…
Spatial structure and nest demography reveal the influence of competition, parasitism and habitat quality on slavemaking ants and their hosts
2010
Abstract Background Natural communities are structured by intra-guild competition, predation or parasitism and the abiotic environment. We studied the relative importance of these factors in two host-social parasite ecosystems in three ant communities in Europe (Bavaria) and North America (New York, West Virginia). We tested how these factors affect colony demography, life-history and the spatial pattern of colonies, using a large sample size of more than 1000 colonies. The strength of competition was measured by the distance to the nearest competitor. Distance to the closest social parasite colony was used as a measure of parasitism risk. Nest sites (i.e., sticks or acorns) are limited in …
Effet de l'environnement sur l'interaction entre les gammares (Crustacea : Amphipoda) et leurs parasites manipulateurs acanthocéphales
2016
Many parasites with complex life cycle have developed the ability to alter the phenotype of their hosts. It is recognized that such changes in appearance and behavior are responsible for an increase in the probability of predation of their intermediate hosts by their definitive hosts. This phenomenon of parasite manipulation can have numerous consequences at the scale of the ecosystem, modifying the interactions between host populations and altering their ecological role. However, manipulative parasites received little attention from an ecological point of view. Thus, the effect of the environment on the interaction between these parasites and their hosts, in particular in terms of manipula…
Horizontal Gene Transfer to a Defensive Symbiont with a Reduced Genome in a Multipartite Beetle Microbiome
2020
Associations between microorganisms and an animal, plant, or fungal host can result in increased dependence over time. This process is due partly to the bacterium not needing to produce nutrients that the host provides, leading to loss of genes that it would need to live independently and to a consequent reduction in genome size. It is often thought that genome reduction is aided by genetic isolation—bacteria that live in monocultures in special host organs, or inside host cells, have less access to other bacterial species from which they can obtain genes. Here, we describe exposure of a genome-reduced beetle symbiont to a community of related bacteria with nonreduced genomes. We show that …
Molecular phylogeny of parabasalids with emphasis on the order Cristamonadida and its complex morphological evolution
2009
1055-7903 doi: DOI: 10.1016/j.ympev.2009.03.011; Parabasalia represents a complex assemblage of species, which recently received extensive reorganization. The newly created order Cristamonadida unites complex hypermastigids belonging to the Lophomonadida like the joeniids, the multinucleate polymonad Calonymphidae, and well-developed trichomonads in the Devescovinidae. All these protists exclusively occur in the guts of termites and related insects. In this study, small subunit rRNA and glyceraldehyde-3-phosphate dehydrogenase genes were identified without cultivation from 14 species in Cristamonadida including previously unstudied genera such as Joenina, Joenia, Joenoides, Macrotrichomonas…
Disrupting immune regulation incurs transient costs in male reproductive function.
2014
9 pages; International audience; BACKGROUND: Immune protection against pathogenic organisms has been shown to incur costs. Previous studies investigating the cost of immunity have mostly focused on the metabolic requirements of immune maintenance and activation. In addition to these metabolic costs, the immune system can induce damage to the host if the immune response is mis-targeted or over-expressed. Given its non-specific nature, an over-expressed inflammatory response is often associated with substantial damage for the host. Here, we investigated the cost of an over-expressed inflammatory response in the reproductive function of male mice. METHODOLOGY/PRINCIPAL FINDINGS: We experimenta…
Coexistence of Wolbachia with Buchnera aphidicola and a Secondary Symbiont in the Aphid Cinara cedri
2004
ABSTRACT Intracellular symbiosis is very common in the insect world. For the aphid Cinara cedri , we have identified by electron microscopy three symbiotic bacteria that can be characterized by their different sizes, morphologies, and electrodensities. PCR amplification and sequencing of the 16S ribosomal DNA (rDNA) genes showed that, in addition to harboring Buchnera aphidicola , the primary endosymbiont of aphids, C. cedri harbors a secondary symbiont (S symbiont) that was previously found to be associated with aphids (PASS, or R type) and an α-proteobacterium that belongs to the Wolbachia genus. Using in situ hybridization with specific bacterial probes designed for symbiont 16S rDNA seq…
Evolution of small prokaryotic genomes
2015
As revealed by genome sequencing, the biology of prokaryotes with reduced genomes is strikingly diverse. These include free-living prokaryotes with ∼800 genes as well as endosymbiotic bacteria with as few as ∼140 genes. Comparative genomics is revealing the evolutionary mechanisms that led to these small genomes. In the case of free-living prokaryotes, natural selection directly favored genome reduction, while in the case of endosymbiotic prokaryotes neutral processes played a more prominent role. However, new experimental data suggest that selective processes may be at operation as well for endosymbiotic prokaryotes at least during the first stages of genome reduction. Endosymbiotic prokar…
Extreme genome reduction in Buchnera spp.: Toward the minimal genome needed for symbiotic life
2002
Buchnera is a mutualistic intracellular symbiont of aphids. Their association began about 200 million years ago, with host and symbiont lineages evolving in parallel since that time. During this coevolutionary process, Buchnera has experienced a dramatic decrease of genome size, retaining only essential genes for its specialized lifestyle. Previous studies reported that genome size in Buchnera spp. is very uniform, suggesting that genome shrinkage occurred early in evolution, and that modern lineages retain the genome size of a common ancestor. Our physical mapping of Buchnera genomes obtained from five aphid lineages shows that the genome size is not conserved among them, but has been red…