Simulating the effects of long‐distance dispersal and landscape heterogeneity on the eco‐evolutionary outcomes of range expansion in an invasive riverine fish, Tench (Tinca tinca)

Predicting how quickly populations expand their range and whether they will retain genetic diversity when they are introduced to new regions or track environmental conditions suited to their survival is an important applied and theoretical challenge. The literature suggests that long-distance dispersal, landscape heterogeneity and the evolution of dispersal influence populations' expansion rates and genetic diversity. We used individual-based spatially explicit simulations to examine these relationships for Tench (Tinca tinca), an invasive fish expanding its geographical range in eastern North America since the 1990s. Simulated populations varied greatly in expansion rates (1.1–28.6 patches year−1) and genetic diversity metrics, including changes in observed heterozygosity (−19 to +0.8%) and effective number of alleles (−0.32 to −0.01). Populations with greater dispersal distances expanded faster than those with smaller dispersal distances but exhibited considerable variation in expansion rate among local populations, implying less predictable expansions. However, they tended to retain genetic diversity as they expanded, suggesting more predictable evolutionary trajectories. In contrast, populations with smaller dispersal distances spread predictably more slowly but exhibited more variability among local populations in genetic diversity losses. Consistent with empirical data, populations spreading in a longer, narrower dispersal corridor lost more neutral genetic variation to the stochastic fixation of alleles. Given the unprecedented pace of anthropogenic environmental change and the increasing need to manage range-expanding populations, our results have conservation ramifications as they imply that the evolutionary trajectories of populations characterised by shorter dispersal distances spreading in narrower landscapes are more variable and, therefore, less predictable

Genetic diversity and structure of a recent fish invasion: Tench (Tinca tinca) in eastern North America

Introduced and geographically expanding populations experience similar eco-evolutionary challenges, including founder events, genetic bottlenecks, and novel environments. Theory predicts that reduced genetic diversity resulting from such phenomena limits the success of introduced populations. Using 1900 SNPs obtained from restriction-site-associated DNA sequencing, we evaluated hypotheses related to the invasion history and connectivity of an invasive population of Tench (Tinca tinca), a Eurasian freshwater fish that has been expanding geographically in eastern North America for three decades. Consistent with the reported history of a single introduction event, our findings suggest that multiple introductions from distinct genetic sources are unlikely as Tench had a small effective population size (~114 [95% CI = 106–123] individuals), no strong population subdivision across time and space, and evidence of a recent genetic bottleneck. The large genetic neighbourhood size (220 km) and weak within-population genetic substructure suggested high connectivity across the invaded range, despite the relatively large area occupied. There was some evidence for a small decay in genetic diversity as the species expanded northward, but not southward, into new habitats. As eradicating the species within a ~112 km radius would be necessary to prevent recolonization, eradicating Tench is likely not feasible at watershed—and possibly local—scales. Management should instead focus on reducing abundance in priority conservation areas to mitigate adverse impacts. Our study indicates that introduced populations can thrive and exhibit relatively high levels of genetic diversity despite severe bottlenecks (<1.5% of the ancestral effective population size) and suggests that landscape heterogeneity and population demographics can generate variability in spatial patterns of genetic diversity within a single range expansion

A classification system for assessing the ecosystem services provided by permanent grasslands and farms in Bearn and the Northern Basque Country

We developed a system for classifying permanent grasslands in Beam and the Northern Basque Country that serves several specific purposes. It emerged from a significant collective investment that aimed to offer users a tool that accounts for the multifunctionality of grasslands in this area. The system also highlights the relationship between cultural heritage and product quality. Using an up-to-date database, we were able to identify 21 types of grasslands. By analysing grassland vegetation, species functional ecology, and farming practices, we could calculate indices reflecting forage production levels, environmental conditions, and cheese quality. The Geroko application calculates farm-level indices based on parcel-level data and allows users to simulate changes in forage systems. An index providing plant names in Basque is a helpful addition to this comprehensive description of our classification system, which comes complete with illustrations

Impact of electron-electron interactions induced by disorder at interfaces on spin-dependent tunneling in Co-Fe-B/MgO/Co-Fe-B magnetic tunnel junctions

International audienceIn this study, we demonstrate that, beyond the standard magnon excitations, the electron-electron interactions in presence of disorder in CoFeB electrodes play a significant role on the zero-bias anomaly measured in CoFeB/MgO/CoFeB junctions. The low-temperature dependence of the tunneling conductance presents cusp-like dip at low voltage varying as the square root of the bias voltage. The amplitude of this zero-bias anomaly decreases with the annealing temperature, indicating interface crystallization and related increase in the tunnel magnetoresistance

Le « monstre » humain

Les « monstres » humains nous fascinent par la tension entre les sentiments de proximité et d'altérité radicale que fait naître leur aspect déroutant. Etudiés dans le contexte mental de leur époque, lorsqu'ils procèdent de l'imaginaire, ou à travers la succession des explications scientifiques ou religieuses de leur genèse, ils l'ont été plus rarement dans la perspective de leur insertion sociale. Où commence la monstruosité ? Comment se donne-t-elle à voir ? Comment se laisse-t-elle appréhender par la raison ? Ces études se proposent d'aborder les problèmes de définition et de visibilité du monstre dans la société de son temps ; de repérer quelques tentatives de réintégration du monstre dans l'ordre du monde, qu'il semble ébranler ; d'illustrer enfin des façons d'utiliser le monstre comme métaphore en politique, en art ou en littérature