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Sailing with Holger Thesleff in the open sea of the post-classical Pythagorica (1961–2024)
No full textInternational audienc
Behavioural Diversity: Conditional Movement Tactics in the Ruff (Calidris pugnax)
No full textInternational audienceUnderstanding the movement behaviour of male ruffs (Calidris pugnax) during the breeding season requires integrating recent telemetry data with long-standing theory on conditional reproductive strategies, lek dynamics, and behavioural polymorphism. A large-scale tracking study revealed extensive within-season movements among many males, with individuals visiting 1 to 23 sites, but also documented prolonged residency, with site tenures exceeding 40 days. Such variation is not contradictory but expected in a species whose reproductive system combines genetically fixed alternative strategies, governed by a supergene, with flexible conditional tactics expressed in response to ecological and social cues. Here, I synthesize movement ecology, state-dependent decision models, lekking theory, and previous empirical work to show that spatial behaviour in ruffs reflects a continuum of tactics rather than a homogeneous nomadic mode. Telemetry data thereby enrich our understanding of how individuals navigate fluctuating environments, competitive pressures, and mating opportunities. Embracing behavioural heterogeneity is essential for interpreting movement patterns and for understanding how reproductive diversity evolves and is maintained in lekking systems
Presentación del monográfico "José Bergamín y las artes mágicas del vuelo"
No full textInternational audienc
Integrative taxonomy of northeastern Atlantic top-shells of the genus Jujubinus Monterosato, 1884 (Gastropo-da, Trochidae, Cantharidinae)
No full textInternational audienceThe northeastern Atlantic species of the gastropod genus Jujubinus Monterosato, 1884 (Trochidae, Cantharidinae) are reviewed based on an integrative taxonomic approach. Based on a comprehensive phylogenetic framework of cantharidine genera, it is suggested that the scope of the genus Jujubinus should be restricted to a radiation in the northeastern Atlantic and the Mediterranean, not including the tropical Indo-West Pacific species frequently ascribed to it. For Trochus montagui Wood, 1828, traditionally ascribed to Jujubinus, we did not find unequivocal evidence of it belonging in this clade, but rather we found some indication of a closer relationship with Clelandella miliaris (Brocchi, 1814) than with the Jujubinus clade. Thirteen morphospecies were checked against a DNA-barcoding dataset (cox1) and a molecular phylogenetic framework (cox1, 16S, single genes and combined datasets, analysed by Bayesian inference and Maximum Likelihood analyses). Twenty-two secondary species hypotheses were eventually retained. For fifteen of them an available name has been found; seven are herein described as new
Coral degradation alters community diversity and stability of fish and invertebrate assemblages following recruitment
No full textInternational audienceHabitat degradation is one of the most pervasive threats to coral reef ecosystems, and the intensification of global and local disturbances is expected to further exacerbate its impacts. While many studies have investigated the effects of coral degradation on fish and invertebrates separately, its impact on the settlement and recruitment of entire coral-associated communities remains poorly understood. To fill this gap, we experimentally quantified how coral status (live versus dead) and ecological process (settlement: after 7 d, and recruitment: after 28-30 d) shape the abundance, diversity and community composition of coral-dwelling organisms in the back reef of Mo’orea, French Polynesia. Live corals supported significantly higher abundance, species richness and Shannon diversity at the recruitment stage, whereas no differences were detected during settlement. Similarly, recruits on live coral exhibited lower compositional variability, fostering a more ecologically stable community over time. Both coral status and ecological process significantly influenced taxonomic and feeding guilds, although their effects were independent. Overall, our findings demonstrate that live corals provide structurally complex, resource-rich habitats that enhance biodiversity and promote the establishment of more stable and functionally diverse communities. Coral degradation, in contrast, disrupts these dynamics, affecting not only fish communities but the entire benthic assemblage associated with corals, altering key ecological functions and potentially reducing reef resilience. Understanding how coral degradation affects settlement and recruitment across taxa is essential for preserving healthy coral structures, which should be prioritized to sustain the ecological integrity and trophic functioning of reef ecosystems
Predation Risk Does Not Delay Breeding but Reduces Nest Survival in High‐Arctic Shorebirds
No full textInternational audienceUnderstanding predator-prey interactions is crucial for correctly answering many fundamental research questions, given their behavioural, ecological and evolutionary consequences. Such interactions can result in the direct consumption of the prey, but also in behavioural responses such as changes in breeding phenology. Space use of predators and the associated predation risk is a dynamic process, resulting in constant adjustments by the prey at different spatiotemporal scales. In the Arctic, predator-prey interactions are expected to change owing to the ongoing climate change and the associated shifts in ecosystem composition. However, most studies investigating the impact of predation on ground-nesting birds use data from artificial nests that lack the behavioural component of incubation. Consequently, studies investigating the impact of predation risk on real nests are needed, especially in arctic ecosystems of relatively low productivity. Using nest data collected over 3 years in Northeast Greenland, we investigated how spatial variations in predation risk by arctic foxes (Vulpes lagopus) impacted daily nest survival rates and start of incubation dates of two sympatric species of sandpipers: the sanderling (Calidris alba) and the dunlin (Calidris alpina arctica). Fox spatial activity was estimated by calculating their Autocorrelated kernel Utilisation Distributions based on fine-scale GPS data. We found that both sandpiper species had higher daily nest survival rates in areas of low fox activity. However, sandpipers initiated their nests earlier in areas of high fox activity. Together, these results show that predation risk does not delay the breeding phenology of high-Arctic sandpipers, and that predation risk clearly translates into lower nest survival, as often claimed by previous studies using artificial nests
Approximating the Uniform Value in Hidden Stochastic Games with Doeblin Conditions
No full textIn \emph{zero-sum two-player hidden stochastic games}, players observe partial information about the state. We address: the existence of the \emph{uniform value}, i.e., a limiting average payoff that both players can guarantee for sufficiently long durations, and the existence of an algorithm to approximate it. Previous work shows that, in the general case, the uniform value may fail to exist, and, even when it does, there need not exist an algorithm to compute or approximate it. Therefore, we consider the \emph{Doeblin condition} in hidden stochastic games, requiring that, after a sufficiently long time, the posterior beliefs have a uniformly positive probability of resetting to one of finitely many neighborhoods in the belief space. We prove the existence of the uniform value and provide an algorithm to approximate it. We identify sufficient conditions, namely \emph{ergodicity} in the blind setting (when the signal is uninformative) and \emph{primitivity} in the hidden setting (when there are multiple signals). Moreover, we show that, in the hidden setting, ergodicity does not guarantee the Doeblin condition. Our results are new even for the one-player setting, i.e., partially observable Markov decision processes
Is non-local communication really impossible?
No full textThis paper shows the possibility of non-local communication between two entangled, spacelike separated sub-systems. More specifically, it is shown that if there exist (at least) two non-commuting observables respectively defined on these two sub-systems then, for some entangled state of the global system, the probability distribution of the outcomes of measurements performed in one of its parts is changed by the actions that have been performed in the other one. This causal dependency, which includes that of the settings, makes possible a nonlocal exchange of information between the parties
Unraveling viral identity: Avoiding the trap of endogenous sequences for viral surveillance of small ruminant oncogenic retroviruses
No full textSmall ruminants (sheep and goats) are one of the few mammals in which an exogenous retrovirus (XRV) and closely related endogenous retroviral elements(ERV) coexist within the same host genome. The betaretroviruses Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) cause pulmonary and nasal adenocarcinomas, respectively, and share extensive sequence similarity with their endogenous counterparts. Consequently, molecular surveillance must rely on assays that can unequivocally distinguish true exogenous infection from ERV‐derived templates; failure to do so compromises diagnosis, phylogenetic inference, and epidemiological conclusions. We retrieved all complete JSRV, ENTV-1/2, and related ERV genomes deposited in public repositories and performed a comprehensive alignment. Only a limited number of genomic segments were capable of distinguishing exogenous from endogenous sequences. We refer to these as discriminating regions (DRs). Phylogenies built using DRs revealed that several entries annotated as XRV are, in fact, ERV-derived or chimeric artefacts generated by short-amplicon reconstruction. A systematic literature review of over 100 articles identified 286 distinct primers and probes used for the XRV amplification. In-silico mapping of each oligonucleotide onto the full alignment showed that only 28 % reliably differentiate XRV from ERV. We experimentally validated the predictive power of this approach for 17 primer/probe sets, confirming that non-discriminating assays produce false-positive signals from endogenous templates. The misannotation of ERV sequences as exogenous viruses has resulting in the population of databases with dubious entries, fostering erroneous hypotheses such as vector-borne transmission of JSRV and ENTV. To address this issue, we propose a concise set of criteria for assay design, validation, and database annotation emphasizing DR targeting, specificity testing against endogenous templates, and transparent reporting. Although this framework was developed for small ruminants, it is readily applicable to any host–virus system in which exogenous viruses coexist with endogenous viral elements. This will strengthen viral surveillance, phylogenetics, and the One-Health initiatives
