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Aubree, F., David, P., Jarne, P., Loreau, M., Mouquet, N., & Calcagno, V. (2020). How community adaptation affects biodiversity-ecosystem functioning relationships. Ecol. Lett., 23(8), 1263–1275.
Résumé: Evidence is growing that evolutionary dynamics can impact biodiversity-ecosystem functioning (BEF) relationships. However the nature of such impacts remains poorly understood. Here we use a modelling approach to compare random communities, with no trait evolutionary fine-tuning, and co-adapted communities, where traits have co-evolved, in terms of emerging biodiversity-productivity, biodiversity-stability and biodiversity-invasion relationships. Community adaptation impacted most BEF relationships, sometimes inverting the slope of the relationship compared to random communities. Biodiversity-productivity relationships were generally less positive among co-adapted communities, with reduced contribution of sampling effects. The effect of community-adaptation, though modest regarding invasion resistance, was striking regarding invasion tolerance: co-adapted communities could remain very tolerant to invasions even at high diversity. BEF relationships are thus contingent on the history of ecosystems and their degree of community adaptation. Short-term experiments and observations following recent changes may not be safely extrapolated into the future, once eco-evolutionary feedbacks have taken place.
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Besson, M., Allal, F., Chatain, B., Vergnet, A., Clota, F., & Vandeputte, M. (2019). Combining Individual Phenotypes of Feed Intake With Genomic Data to Improve Feed Efficiency in Sea Bass. Front. Genet., 10.
Résumé: Measuring individual feed intake of fish in farms is complex and precludes direct selective breeding for feed conversion ratio (FCR). Here, we estimated the individual FCR of 588 sea bass using individual rearing under restricted feeding. These fish were also phenotyped for their weight loss at fasting and muscle fat content as possible indirect indicators of FCR. The 588 fish were from a full factorial mating between parental lines divergently selected for high (F+) or low (F-) weight loss at fasting. The pedigree was known back to the great grandparents. A subset of 400 offspring and their ancestors were genotyped for 1,110 SNPs, which allowed estimating the genomic heritability of traits. Individual FCR and growth rate in aquarium were both heritable (genomic h² = 0.47 and 0.76, respectively) and strongly genetically correlated (-0.98), meaning that under restricted feeding, faster growing fish were more efficient. FCR in aquariums was significantly better for fish with two F- parents (1.38), worse for fish with two F+ parents (1.51) and intermediate (1.46) for crossbred fish (F+/F- or F-/F+). Muscle fat content was positively genetically correlated to growth rate in aquarium and during fasting. Thus, higher growth rate in aquariums, lower weight loss at fasting and fat content are all traits that could improve FCR in aquarium. Improving these traits would also improve FCR of fish in normal group rearing conditions, as we showed that groups composed of fish with good individual FCR were significantly more efficient in groups. The FCR of groups was also better when the fish composing the groups had, on average, lower estimated breeding values for growth rate during fasting (losing less weight). Thus, FCR in aquarium and weight loss at fasting are both promising to improve FCR of fish in groups. Finally, we showed that the reliability of estimated breeding values was higher (from +10% to +125%) with single-step genomic BLUP than with pedigree-based BLUP, showing that genomic data would enhance the accuracy of EBV prediction o in selection candidates from a limited number of sibs individually phenotyped for FCR in aquariums.
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Boyd, C., Grunbaum, D., Hunt, G. L., Punt, A. E., Weimerskirch, H., & Bertrand, S. (2016). Effectiveness of social information used by seabirds searching for unpredictable and ephemeral prey. Behav. Ecol., 27(4), 1223–1234.
Résumé: Understanding how seabirds and other central place foragers locate food resources represents a key step in predicting responses to changes in resource abundance and distribution. Where prey distributions are unpredictable and ephemeral, seabirds may gain up-to-date information by monitoring the direction of birds returning to the colony or by monitoring the foraging behavior of other birds through local enhancement. However, search strategies based on social information may require high population densities, raising concerns about the potential loss of information in declining populations. Our objectives were to explore the mechanisms that underpin effective search strategies based on social information under a range of population densities and different foraging conditions. Testing relevant hypotheses through field observation is challenging because of limitations in the ability to manipulate population densities and foraging conditions. We therefore developed a spatially explicit individual-based foraging model, informed by data on the movement and foraging patterns of seabirds foraging on pelagic prey, and used model simulations to investigate the mechanisms underpinning search strategies. Orientation of outbound headings in line with returning birds enables departing birds to avoid areas without prey even at relatively low population densities. The mechanisms underpinning local enhancement are more effective as population densities increase and may be facilitated by other mechanisms that concentrate individuals in profitable areas. For seabirds and other central place foragers foraging on unpredictable and ephemeral food resources, information is especially valuable when resources are spatially concentrated and may play an important role in mitigating poor foraging conditions.
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Courbin, N., Besnard, A., Peron, C., Saraux, C., Fort, J., Perret, S., et al. (2018). Short-term prey field lability constrains individual specialisation in resource selection and foraging site fidelity in a marine predator. Ecol. Lett., 21(7), 1043–1054.
Résumé: Spatio-temporally stable prey distributions coupled with individual foraging site fidelity are predicted to favour individual resource specialisation. Conversely, predators coping with dynamic prey distributions should diversify their individual diet and/or shift foraging areas to increase net intake. We studied individual specialisation in Scopoli's shearwaters (Calonectris diomedea) from the highly dynamic Western Mediterranean, using daily prey distributions together with resource selection, site fidelity and trophic-level analyses. As hypothesised, we found dietary diversification, low foraging site fidelity and almost no individual specialisation in resource selection. Crucially, shearwaters switched daily foraging tactics, selecting areas with contrasting prey of varying trophic levels. Overall, information use and plastic resource selection of individuals with reduced short-term foraging site fidelity allow predators to overcome prey field lability. Our study is an essential step towards a better understanding of individual responses to enhanced environmental stochasticity driven by global changes, and of pathways favouring population persistence.
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Cox, S. L., Authier, M., Orgeret, F., Weimerskirch, H., & Guinet, C. (2020). High mortality rates in a juvenile free-ranging marine predator and links to dive and forage ability. Ecol. Evol., 10(1), 410–430.
Résumé: High juvenile mortality rates are typical of many long-lived marine vertebrate predators. Insufficient development in dive and forage ability is considered a key driver of this. However, direct links to survival outcome are sparse, particularly in free-ranging marine animals that may not return to land. In this study, we conduct exploratory investigations toward early mortality in juvenile southern elephant seals Mirounga leonina. Twenty postweaning pups were equipped with (a) a new-generation satellite relay data tag, capable of remotely transmitting fine-scale behavioral movements from accelerometers, and (b) a location transmitting only tag (so that mortality events could be distinguished from device failures). Individuals were followed during their first trip at sea (until mortality or return to land). Two analyses were conducted. First, the behavioral movements and encountered environmental conditions of nonsurviving pups were individually compared to temporally concurrent observations from grouped survivors. Second, common causes of mortality were investigated using Cox's proportional hazard regression and penalized shrinkage techniques. Nine individuals died (two females and seven males) and 11 survived (eight females and three males). All but one individual died before the return phase of their first trip at sea, and all but one were negatively buoyant. Causes of death were variable, although common factors included increased horizontal travel speeds and distances, decreased development in dive and forage ability, and habitat type visited (lower sea surface temperatures and decreased total [eddy] kinetic energy). For long-lived marine vertebrate predators, such as the southern elephant seal, the first few months of life following independence represent a critical period, when small deviations in behavior from the norm appear sufficient to increase mortality risk. Survival rates may subsequently be particularly vulnerable to changes in climate and environment, which will have concomitant consequences on the demography and dynamics of populations.
Mots-Clés: antarctic fur seals; behavior; bio-logging; body condition; early life; foraging ecology; juvenile mortality; Mirounga leonina; mirounga-leonina; population; regularization paths; southern elephant seal; southern elephant seals; survival; survival analyses; variable selection; weaning mass
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