Great Britain and Ireland still contain some of the best stocks of Austropotamobius pallipes in Europe despite the fact that since the early 1980s many populations have been devastated by the effects of crayfish plague and compétitive exclusion by non-native crayfish. Austropotamobiuspallipes is the only crayfish native to Great Britain and Ireland but in récent years a number of introductions of foreign crayfish have been made into Great Britain, for aquacultural, culinary and aquarist purposes. This has resulted in four non-native crayfish species becoming established in thewild, wheretwo, Pacifastacus leniusculus and Astacusleptodactylus, have formed large, harvestable populations, particularly in southern England.Although A. pallipes in Great Britain and Ireland is protected by national and European législation, this has not been enough to protect it from crayfish plague and, in Great Britain, from non-native crayfish. In an attempt to protect A. pallipes even further, législation has been implemented in England, Scotland and Wales which bans the keeping of ail non-native crayfish, except wherethey are being prepared for human consumption. P. leniusculus is, however, exempt from this ban in certain parts of southern Great Britain dueto its high prépondérance on crayfish farms and in the wild. Ireland already bans the introduction of non-native crayfish.It is hoped that the new législation, plus the heightened profile which A. pallipes has recently been given in Great Britain, will ensure its future survival. Key-words :Austropotamobius pallipes, Pacifastacus leniusculus, Astacus leptodactylus, crayfish piague, conservation, législation. Bien que A pallipes soit protégée en Grande-Bretagne et en Irlande par une législation nationale et européenne, ce n'est pas suffisant pour la protéger de la peste et, en Grande-Bretagne, des écrevisses exotiques. Dans le but de protéger encore mieux A. pallipes, une législation a été appliquée en Angleterre, en Ecosse et au Pays de Galles en interdisant de garder les écrevisses exotiques, sauf si elles ont été préparées pour la consommation. Cependant, P. leniusculus échappe à cette interdiction dans certaines parties du sud de la Grande-Bretagne à cause de sa grande prépondérance dans les astacicultures et dans la nature. « L'Irlande vient juste d'interdire l'introduction d'écrevisses exotiques. L'ÉCREVISSE À PATTES BLANCHES, AUSTROPOTAMOBIUS PALLIPES, EN GRANDE-BRETAGNE ET EN IRLANDE ET LES PROBLÈMESNous pouvons espérer que la nouvelle législation en vigueur ainsi que les efforts de sensibilisation pour A pallipes favoriseront sa survie dans le futur.

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Predators may create healthier prey populations by selectively removing diseased individuals. Predators typically prefer some ages of prey over others, which may, or may not, align with those prey ages that are most likely to be diseased. The interaction of age‐specific infection and predation has not been previously explored and likely has sizable effects on disease dynamics. We hypothesize that predator cleansing effects will be greater when the disease and predation occur in the same prey age groups. We examine the predator cleansing effect using a model where both vulnerability to predators and pathogen prevalence vary with age. We tailor this model to chronic wasting disease (CWD) in mule deer and elk populations in the Greater Yellowstone Ecosystem, with empirical data from Yellowstone grey wolves and cougars. Model results suggest that under moderate, yet realistic, predation pressure from cougars and wolves independently, predators may decrease CWD outbreak size substantially and delay the accumulation of symptomatic deer and elk. The magnitude of this effect is driven by the ability of predators to selectively remove late‐stage CWD infections that are likely the most responsible for transmission, but this may not be the age class they typically select. Thus, predators that select for infected young adults over uninfected juveniles have a stronger cleansing effect, and these effects are strengthened when transmission rates increase with increasing prey morbidity. There are also trade‐offs from a management perspective—that is, increasing predator kill rates can result in opposing forces on prey abundance and CWD prevalence. Our modelling exploration shows that predators have the potential to reduce prevalence in prey populations when prey age and disease severity are considered, yet the strength of this effect is influenced by predators' selection for demography or body condition. Current CWD management focuses on increasing cervid hunting as the primary management tool, and our results suggest predators may also be a useful tool under certain conditions, but not necessarily without additional impacts on host abundance and demography. Protected areas with predator populations will play a large role in informing the debate over predator impacts on disease.

Environmental change, accelerated by anthropogenic activities, threatens many species and can be especially challenging for rare species given their potentially limited capacity for migration and adaptation relative to more common species. The ability to acclimate via phenotypic plasticity could provide an important path to species persistence in the face of such change. We investigated the responses of an endangered plant species endemic to a highly dynamic riparian habitat in southeastern Tennessee, USA, and its most widespread congener to environmental change to elucidate their current statuses and future vulnerability. Specifically, we compared the population-and species-level plasticity of rare Pityopsis ruthii and common P. graminifolia to contrasting light, temperature, and water conditions in a growth chamber experiment to evaluate their potential to acclimate to environmental change. Contrary to our expectations, P. ruthii had greater phenotypic plasticity than its common congener in response to both altered light and water availability. But this plasticity was not associated with increased fitness, suggesting that it was not adaptive. Concurrently, we genotyped these individuals at nine putatively neutral microsatellite loci to contrast genetic diversity across the range of each species. As expected, P. ruthii exhibited reduced genetic diversity relative to its more common congener. Overall, our findings accord with the narrow range and current habitat specificity of P. ruthii, especially its tolerance of highly variable water, and highlight its potential vulnerability to future environmental change.