Effects of landscape features and flooding on the genetic structure of a small wetland rodent, the harvest mouse (Micromys minutus)

International audienceContext: The natural patchiness of wetlands and flooding events are likely to strongly affect the genetic structure of their terrestrial species. However, these effects are not well understood yet, especially for small mammals.Objectives: We investigated at different spatial scales the genetic structure of the harvest mouse (Micromys minutus), a threatened small mammal strongly tied to wetlands, and the effects on gene flow of flooding and of the different types of landscape elements composing a wetland.Methods: 309 harvest mice were sampled in eight sites in Western Europe. Their genetic structure and diversity at 15 microsatellite loci were analyzed at a regional spatial scale and at a local scale, where the resistance of land cover and flooding to gene flow was also assessed, with the optimization procedure implemented in ResistanceGA.Results: At a regional scale, our study revealed a strong genetic differentiation between populations from Northern Europe to the Mediterranean Sea. At the local scale, in a flooded wetland in France, the species exhibited a large genetic cluster over at least 45 km2, in spite of a large river crossing it. Winter floods explained genetic structure better than landscape features alone, with a stronger resistance to gene flow in reed beds where vegetation level above water was high: contrary to meadows, from which individuals are forced to escape, reed beds can be “golden prisons”, i.e. refuges during floods but with very low possibility of movements.Conclusions: Several parameters influencing the functioning of a flooded population of harvest mouse are here highlighted that can also be useful for the development of plans to safeguard wetland ecosystems

Improving trajectories of amphibians in wildlife passages

Linear transport infrastructure can alter the viability of populations and wildlife passages are used to mitigate their impacts. The assessment of their outcomes is often limited to recording the use of the tunnels by a focal species. For amphibians, the effectiveness of tunnels is poorly evaluated with little information about whether certain features encourage individuals that may be reluctant to pass through tunnels. One study showed that acoustic enrichment with anuran calls can increase the crossing of tunnels by newts. This study recorded the behavior of three European amphibian species in three tunnels, tracking them with PIT tags and detection with four RFID antennas installed on the floor of the tunnels. We tested (1) the effectiveness of the antennas in detecting the species, (2) the effect of the length of the tunnels, and (3) the effect of acoustic enrichment. Using a multi-state capture–recapture model, we evaluated the probability of an individual advancing between the tunnel sections. The effectiveness of the antennas varied according to species, higher for Urodela species than for Anuran species. Several types of paths were detected (constant and varying speeds, halt, and back-and-forth movements). The fire salamander and the great crested newt individuals exhibited a similar variety of movements in the tunnels (21 and 40 m length). Triturus cristatus made similar movements in the tunnels with and without acoustic enrichment. In water frogs, all the individuals ( n = 16) made a complete crossing in the tunnel with enrichment vs. 75% ( n = 71) in the tunnel without enrichment. In T. cristatus , the probability of going forward at the entrance of the tunnel was 18% higher with enrichment in one tunnel. No significant effect of acoustic enrichment was observed in two others tunnels for this species. In Pelophylax esculentus , this probability was 78% higher in the tunnel with enrichment. This multi-antenna RFID system was able to provide valuable information on the behavior of these small animals when traversing the tunnels, as well as to test the effectiveness of tunnel features. The findings indicate that acoustic enrichment to attract animals to specific locations holds promise as a new conservation tool

Acoustic enrichment in wildlife passages under railways improves their use by amphibians

International audienceLinear transport infrastructure can impact wildlife directly or indirectly, and amphibians are particularly affected. In some cases, mitigation measures e such as tunnels below the linear transport infrastructure e are implemented, but an evaluation of their effectiveness is often lacking, especially for small animals such as amphibians. Few studies have focused on crossing behaviour in underpasses, yet this information may be crucial to improve mitigation measures. In this study, we conducted experiments in three tunnels below a high-speed railway with individually marked amphibians (great crested newt Triturus cristatus, marbled newt Triturus marmoratus, alpine newt Ichthyosaura alpestris, fire sala- mander Salamandra salamandra, spined toad Bufo spinosus, agile frog Rana dalmatina and edible/pool frog Pelophylax kl. esculentus/lessonae) which were released at the entrance of tunnels varying in length. Behaviours (e.g. completed crossing, U-turn, not moving, and stay) and crossing speed were recorded. R. dalmatina, S. salamandra and T. cristatus (but not B. spinosus) exhibited crossing rate differences between tunnels 21 m and 40 m in length. More individuals performed “complete crossing” through the shorter tunnel. The crossing speed of the S. salamandra and T. cristatus did not differ between the tunnels of different lengths. In a second experiment, we evaluated the effect of acoustic enrichment on the crossing behaviour of one frog and three newt species by broadcasting a soundtrack of mating calls of syntopic anuran species in the tunnels. Pelophylax kl exhibited a large in- crease in complete crossings and in speed. T. cristatus showed an increase in tunnel complete crossings (but not speed) in one of the acoustically enhanced tunnels. These results indicate that acoustic enrichment can improve the crossing of underpasses. This low cost and easily implementable method could help to inform the design of wildlife passages as mitigation measures for impacted amphibian populations, though more ex- periments on the effect of tunnel characteristics on amphibian behaviour would be valuable

Chemical supercritical fluid infiltration of pyrocarbon with thermal gradients: deposition kinetics and multiphysics modeling

International audienceThe chemical supercritical fluid infiltration process is a recent variation of the chemical vapor infiltration (CVI) process that allows rapid and efficient manufacturing of ceramic-matrix composites (CMCs), albeit still needing optimization. This article proposes a quantitative assessment of the process dynamics through experiments and modeling. The kinetics of carbon deposition were determined through two sets of experiments: CVD on a single filament at pressures between 10 and 50 bar and infiltration at pressures ranging between 50 and 120 bar. The CVI experiments were conducted under important thermal gradients and were interpreted using a model-based reconstitution of these gradients. We found that (i) the kinetic law has to incorporate the potential effect of the reverse reaction (i.e., etching of C by H2); (ii) the activation energy and pre-exponential factor both decrease with pressure up to 50 bar, then remain roughly constant, and (iii) although the apparent activation energy is modest, a favorable situation occurs in which an infiltration front builds up and travels from the hottest to the coldest part of the preform due to the presence of sufficient heat flux. A numerical simulation of the process, based on the solution of momentum, heat, and mass balance equations, fed with appropriate laws for the effective transfer properties of the porous medium and their evolution with infiltration progress, was performed and validated by comparing the simulated and actual infiltration profiles

Author Correction: Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper

Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France

This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Amphibians are particularly sensitive to landscape fragmentation. Potential barriers between breeding sites can negatively infuence the dispersal of individuals and increase genetic structure between populations. In this study, we genotyped 10 microsatellites for 334 marbled newts (Triturus marmoratus) at 11 diferent locations in Western France. Samples were collected in diferent regions with contrasting agricultural landscapes (low and high proportion of arable land in the north and south, respectively). We found a strong genetic structure between the northern and southern sampling sites. Isolation by distance was recorded after 62km, but within the northern region, little or no genetic structure was detected over large distances (up to 114km). Genetic structure at shorter distance (43km) was found between sites situated in landscapes with larger amounts of arable lands. A signifcant positive relationship was found between the pairwise genetic distance (Fst) between sites and the amount of arable land together with the distance between sites. Our results suggest that the Loire River might act as a corridor for the marbled newt, while arable land might act as a barrier. Finally, although a large city is located between sampling sites, no efect was detected on population structure.publishedVersio

Agricultural landscapes and the Loire River influence the genetic structure of the marbled newt in Western France

Amphibians are particularly sensitive to landscape fragmentation. Potential barriers between breeding sites can negatively infuence the dispersal of individuals and increase genetic structure between populations. In this study, we genotyped 10 microsatellites for 334 marbled newts (Triturus marmoratus) at 11 diferent locations in Western France. Samples were collected in diferent regions with contrasting agricultural landscapes (low and high proportion of arable land in the north and south, respectively). We found a strong genetic structure between the northern and southern sampling sites. Isolation by distance was recorded after 62km, but within the northern region, little or no genetic structure was detected over large distances (up to 114km). Genetic structure at shorter distance (43km) was found between sites situated in landscapes with larger amounts of arable lands. A signifcant positive relationship was found between the pairwise genetic distance (Fst) between sites and the amount of arable land together with the distance between sites. Our results suggest that the Loire River might act as a corridor for the marbled newt, while arable land might act as a barrier. Finally, although a large city is located between sampling sites, no efect was detected on population structure