Detection of Orientia sp. DNA in rodents from Asia, West Africa and Europe

Article Open AccessInternational audienceOrientia bacterium is the agent of the scrub typhus, a seriously neglected life-threatening disease in Asia. Here, we report the detection of DNA of Orientia in rodents from Europe and Africa. These findings have important implications for public health. Surveillance outside Asia, where the disease is not expected by sanitary services, needs to be improved

Large mammals on small islands : short term effects of forest fragmentation on the large mammal fauna in french Guiana

In this study, we present data on species richness of large marnrnals (mostly with body mass > 1 kg) in two contiguous areas at Saint-Eugène, French Guiana, before and after forest fragmentation by flooding. Assessment realized in 1993-94, i.e. before and during flooding, showed similar species richness and composition in the two studied areas. Before fragmentation, the large mammal community at Saint-Eugène was comparable to that recorded from a site of pristine forest in French Guiana. After forest fragmentation, one of these zones became isolated (medium-sized island) while the second one remained as a continuous forest. As a consequence, the number of species present on that newly isolated patch decreased of 30 % while it seemed non-affected in the continuous forest. This Joss in species richness on the fragmented area was confirmed by a survey conducted in 1995-99 at three additional medium-sized islands (> 20 ha), 22 small-sized islands (1-10 ha) and 11 islets (< 1 ha). Occurrence status of the 32 large mammal species observed at Saint-Eugène is drawn up for ail studied sites, and preliminary results on their overall abundance are presented for nine sites. The number of species present in a site was positively correlated to its area, but seemed not to be correlated to its isolation distance from the nearest larger landmass. Islands of less than 10 hectares had a mammal community that was rapidly impoverished and imbalanced in comparison to the one observed on medium-sized islands. The latter presented a marnrnal community that was richer and more complex, including all trophic guilds, despite it appeared affected in comparison to the continuous forest. Large mammal community on small and medium islands typically included species with small home ranges, and mostly generalist or herbivorous 1 granivorous feeding habits: armadillos (Dasypus spp.), acouchi (Myoprocta acouchy), agouti (Dasyprocta leporina), kinkajou (Potos flavus), sloths (Choelopus didactylus and Bradypus tridactylus), and squirrels (Sciurus aestuans and Sciurillus pusillus). However, species with larger home range, as felids, tapir (Tapirus terrestris), peccaries (Pecari tajacu and Tayassu pecari) and brocket deers (Mazama spp.) still frequented islands, at least temporarily. We thus discuss the role that fragments may potentially have in connecting larger landmassesLa richesse spécifique en gros mammifères (pour la plupart, de masse corporelle > 1 kg) a été étudiée à Saint-Eugène, Guyane française, dans deux zones adjacentes d'une forêt humide avant et après isolement de l'une d'elles par la mise en eau d'un barrage hydroélectrique. L'état des lieux en 1993-94, avant et pendant la montée des eaux, montre une richesse et une composition spécifiques de gros mammifères similaires entre les deux zones. Avant fragmentation, le peuplement de gros mammifères de Saint-Eugène était relativement complet et comparable à celui d'un site de forêt peu perturbée en Guyane française. Après fragmentation et isolement de l' une des deux zones, devenue une île de taille moyenne, le nombre d' espèces y a diminué d'un tiers tandis qu' il semble inchangé sur la terre ferme. Le suivi après fragmentation (1995-99) de trois îles moyennes supplémentaires (> 20 ha), 22 petites îles (1-10 ha), et 11 îlots ( < 1 ha) confirme la perte de richesse spécifique en situation insulaire. Un bilan de l'occurrence des 32 espèces de gros mammifères détectés à Saint-Eugène est dressé pour chaque site, et des résultats préliminaires sur leur abondance globale présentés pour neuf d'entre eux. Le nombre d'espèces présentes sur les îles augmente avec la surface, mais ne semble pas corrélé à la distance d'isolement par rapport à une terre émergée de superficie supérieure. Les îles de moins de 10 ha montrent un peuplement de gros mammifères rapidement appauvri et déséquilibré par rapport à celui des îles de taille moyenne, qui possèdent un peuplement plus riche et plus complexe, comprenant l'ensemble des guildes trophiques, bien que nettement altéré par rapport à la forêt continue. Le peuplement de gros mammifères présents sur les petites et moyennes îles est typiquement composé d'espèces ayant un petit domaine vital et pour la plupart un régime alimentaire généraliste ou herbivore 1 granivore : les tatous (Dasypus spp.), l'Acouchi (Myoprocta acouchy), l' Agouti (Dasyprocta leporina), le Kinkajou (Potos jlavus), ainsi que les paresseux (Choelopus didactylus et Bradypus tridactylus) et les écureuils (Sciurus aestuans et Sciurillus pusillus) . Cependant, les espèces à grand domaine vital, telles que les félins, le Tapir (Tapirus terrestris), les pécaris (Pecari tajacu et Tayassu pecari) et les mazamas (Mazama ame ricana et M. gouazoubira), exploitent encore les îles, au moins de façon transitoire. Ceci nous amène à discuter du rôle potentiel que pourraient jouer les fragments dans la connectivité entre de plus grands blocs forestier

Parasites and invasions: changes in gastrointestinal helminth assemblages in invasive and native rodents in Senegal

Understanding why some exotic species become widespread and abundant in their colonised range is a fundamental issue that still needs to be addressed. Among many hypotheses, newly established host populations may benefit from a parasite loss ("enemy release" hypothesis) through impoverishment of their original parasite communities or reduced infection levels. Moreover, the fitness of competing native hosts may be negatively affected by the acquisition of exotic taxa from invaders ("parasite spillover") and/or by an increased transmission risk of native parasites due to their amplification by invaders ("parasite spillback"). We focused on gastrointestinal helminth communities to determine whether these predictions could explain the ongoing invasion success of the commensal house mouse (Mus musculus domesticus) and black rat (Rattus rattus), as well as the associated decrease in native Mastomys spp., in Senegal. For both invasive species, our results were consistent with the predictions of the enemy release hypothesis. A decrease in overall gastrointestinal helminth prevalence and infracommunity species richness was observed along the invasion gradients as well as lower specific prevalence/abundance (Aspiculuris tetraptera in Mus musculus domesticus, Hymenolepis diminuta in Rattus rattus) on the invasion fronts. Conversely, we did not find strong evidence of GIH spillover or spillback in invasion fronts, where native and invasive rodents co-occurred. Further experimental research is needed to determine whether and how the loss of gastrointestinal helminths and reduced infection levels along invasion routes may result in any advantageous effects on invader fitness and competitive advantage

Resistance Evolution to Bt Crops: Predispersal Mating of European Corn Borers

Over the past decade, the high-dose refuge (HDR) strategy, aimed at delaying the evolution of pest resistance to Bacillus thuringiensis (Bt) toxins produced by transgenic crops, became mandatory in the United States and is being discussed for Europe. However, precopulatory dispersal and the mating rate between resident and immigrant individuals, two features influencing the efficiency of this strategy, have seldom been quantified in pests targeted by these toxins. We combined mark-recapture and biogeochemical marking over three breeding seasons to quantify these features directly in natural populations of Ostrinia nubilalis, a major lepidopteran corn pest. At the local scale, resident females mated regardless of males having dispersed beforehand or not, as assumed in the HDR strategy. Accordingly, 0–67% of resident females mating before dispersal did so with resident males, this percentage depending on the local proportion of resident males (0% to 67.2%). However, resident males rarely mated with immigrant females (which mostly arrived mated), the fraction of females mating before dispersal was variable and sometimes substantial (4.8% to 56.8%), and there was no evidence for male premating dispersal being higher. Hence, O. nubilalis probably mates at a more restricted spatial scale than previously assumed, a feature that may decrease the efficiency of the HDR strategy under certain circumstances, depending for example on crop rotation practices

Range Expansion Drives Dispersal Evolution In An Equatorial Three-Species Symbiosis

A-09-14International audienceBackground Recurrent climatic oscillations have produced dramatic changes in species distributions. This process has been proposed to be a major evolutionary force, shaping many life history traits of species, and to govern global patterns of biodiversity at different scales. During range expansions selection may favor the evolution of higher dispersal, and symbiotic interactions may be affected. It has been argued that a weakness of climate fluctuation-driven range dynamics at equatorial latitudes has facilitated the persistence there of more specialized species and interactions. However, how much the biology and ecology of species is changed by range dynamics has seldom been investigated, particularly in equatorial regions. Methodology/Principal Findings We studied a three-species symbiosis endemic to coastal equatorial rainforests in Cameroon, where the impact of range dynamics is supposed to be limited, comprised of two species-specific obligate mutualists –an ant-plant and its protective ant– and a species-specific ant parasite of this mutualism. We combined analyses of within-species genetic diversity and of phenotypic variation in a transect at the southern range limit of this ant-plant system. All three species present congruent genetic signatures of recent gradual southward expansion, a result compatible with available regional paleoclimatic data. As predicted, this expansion has been accompanied by the evolution of more dispersive traits in the two ant species. In contrast, we detected no evidence of change in lifetime reproductive strategy in the tree, nor in its investment in food resources provided to its symbiotic ants. Conclusions/Significance Despite the decreasing investment in protective workers and the increasing investment in dispersing females by both the mutualistic and the parasitic ant species, there was no evidence of destabilization of the symbiosis at the colonization front. To our knowledge, we provide here the first evidence at equatorial latitudes that biological traits associated with dispersal are affected by the range expansion dynamics of a set of interacting species

Contemporary evolution of immunity during range expansion of two invasive rodents in Senegal

International audienceBiological invasions provide unique opportunities for studying life history trait changes over contemporary time scales. As spatial spread may be related to changes in parasite communities, several hypotheses (such as the evolution of increased competitive ability (EICA) or EICA-refined hypotheses) suggest immune changes in invasive species along invasion gradients. Although native hosts may be subject to similar changes in parasite selection pressures, their immune responses have been rarely investigated in invasion contexts. In this study, we evaluated immune variations for invasive house mice Mus musculus domesticus, invasive black rats Rattus rattus and native rodents Mastomys erythroleucus and Mastomys natalensis along well-characterised invasion gradients in Senegal. We focused on antibody-mediated (natural antibodies and complement) and inflammatory (haptoglobin) responses. One invasion route was considered for each invasive species, and environmental conditions were recorded. Natural-antibody mediated responses increased between sites of long-established invasion and recently invaded sites only in house mice. Both invasive species exhibited higher inflammatory responses at the invasion front than in sites of long-established invasion. The immune responses of native species did not change with the presence of invasive species. These patterns of immune variations do not support the EICA and EICA refined hypotheses, and they rather suggest a higher risk of exposure to parasites on the invasion front. Altogether, these results provide a first basis to further assess the role of immune changes in invasion success

La prévision des abondances de rongeurs et l’estimation de leurs dégâts dans les rizières et les stocks dans la Vallée du fleuve Sénégal

International audienc

Contemporary evolution of immunity during range expansion of two invasive rodents in Senegal

International audienceBiological invasions provide unique opportunities for studying life history trait changes over contemporary time scales. As spatial spread may be related to changes in parasite communities, several hypotheses (such as the evolution of increased competitive ability (EICA) or EICA-refined hypotheses) suggest immune changes in invasive species along invasion gradients. Although native hosts may be subject to similar changes in parasite selection pressures, their immune responses have been rarely investigated in invasion contexts. In this study, we evaluated immune variations for invasive house mice Mus musculus domesticus, invasive black rats Rattus rattus and native rodents Mastomys erythroleucus and Mastomys natalensis along well-characterised invasion gradients in Senegal. We focused on antibody-mediated (natural antibodies and complement) and inflammatory (haptoglobin) responses. One invasion route was considered for each invasive species, and environmental conditions were recorded. Natural-antibody mediated responses increased between sites of long-established invasion and recently invaded sites only in house mice. Both invasive species exhibited higher inflammatory responses at the invasion front than in sites of long-established invasion. The immune responses of native species did not change with the presence of invasive species. These patterns of immune variations do not support the EICA and EICA refined hypotheses, and they rather suggest a higher risk of exposure to parasites on the invasion front. Altogether, these results provide a first basis to further assess the role of immune changes in invasion success

Stratégies de dispersion, structuration entre populations et évolution de la variation morphologique (le cas de "Petalomyrmex phylax" à polygynie facultative symbiotique de "Leonardoxa africana africana")

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Age and relatedness have an interactive effect on the feeding behaviour of helpers in cooperatively breeding sociable weavers

International audienceIn cooperative species, helpers often assist close relatives and kin selection is thought to be a major selective force underlying the evolution and maintenance of helping. However, in some cases helpers may be unrelated individuals, which require other types of explanation. Here, we used genetic analyses and observations of feeding behaviour to investigate the relationships between helping at the nest and relatedness in a species where helpers vary in their relatedness to the breeders, the sociable weaver, Philetairus socius. We also investigated the effect of age and breeding group size on feeding behaviour. We found no overall increase of feeding rate with relatedness. Instead, the relationship between helpers' feeding rate and relatedness changed with age. Yearling helpers, which were typically the offspring of one or both parents, did not feed significantly more often when more related to the nestlings or the breeding male or female but did bring larger prey when more related to the nestlings or breeding female. For adult helpers, contrary to the expectations of the kin selection hypothesis, the feeding rate and the size of the prey brought was negatively linked to their relatedness to the nestlings and the breeding female. These results suggest that the reasons for helping in this population change with age. Indirect benefits seem important for yearling helpers while direct benefits may influence the evolution and maintenance of helping behaviour in adult helpers