Exploring the relationship between tychoparthenogenesis and inbreeding depression in the Desert Locust, Schistocerca gregaria

Tychoparthenogenesis, a form of asexual reproduction in which a small proportion of unfertilized eggs can hatch spontaneously, could be an intermediate evolutionary link in the transition from sexual to parthenogenetic reproduction. The lower fitness of tychoparthenogenetic offspring could be due to either developmental constraints or to inbreeding depression in more homozygous individuals. We tested the hypothesis that in populations where inbreeding depression has been purged, tychoparthenogenesis may be less costly. To assess this hypothesis, we compared the impact of inbreeding and parthenogenetic treatments on eight life-history traits (five measuring inbreeding depression and three measuring inbreeding avoidance) in four laboratory populations of the desert locust, Schistocerca gregaria, with contrasted demographic histories. Overall, we found no clear relationship between the population history (illustrated by the levels of genetic diversity or inbreeding) and inbreeding depression, or between inbreeding depression and parthenogenetic capacity. First, there was a general lack of inbreeding depression in every population, except in two populations for two traits. This pattern could not be explained by the purging of inbreeding load in the studied populations. Second, we observed large differences between populations in their capacity to reproduce through tychoparthenogenesis. Only the oldest laboratory population successfully produced parthenogenetic offspring. However, the level of inbreeding depression did not explain the differences in parthenogenetic success between all studied populations. Differences in development constraints may arise driven by random and selective processes between populations. (Résumé d'auteur

Quantitative genetics of the Desert Locust's larval growth: Rate and life-history strategy : PS3M358 Ecology

Schistocerca gregaria, the desert locust, which is distributed from north-west Africa to south-east Asia, is one of the most known and studied locust species. In order to prevent local human populations from the threat of pullulations, we need to know more about population dynamics of the desert locust, especially for the solitarious populations which are less studied than gregarious ones. Predicting the evolution of population dynamics needs a good knowledge of life-history traits that influence population demography. Growth is one of these traits, since it is directly linked to the onset of sexual maturity, then reproduction. Moreover, in order to investigate the potential of selection on individual growth, one needs to evaluate its heritability by disentangling genetic and additive variation in traits phenotype from non-genetic variance due to other (environmental) factors. Here we present a work done on a first generation lab population of S. gregaria sampled in the field. We recorded individual larval growth of 15 full-sib families, based on body weight and morphology in controlled conditions. We describe larval growth by analyzing growth rate as well as several key variables involved in life-history strategy (body weight and size at emergence, growth rate until adult emergence, maximum body weight, age at adult emergence, larval strategy). Thanks to the known relatedness structure of our sample, we also calculate the heritability of those traits and make predictions about the ability of S. gregaria populations to respond to selection on larval growth

Correlation between parasite prevalence and adult size in a trematode-mollusc system: evidence for evolutionary gigantism in the freshwater snail Galba truncatula?

The snail-trematode host-parasite system has been widely studied, as trematodes are known to greatly influence the fitness of their hosts. Indeed, during their development, the trematodes castrate the snail and one possible consequence of infection is gigantism of the snail. Snail gigantism is usually investigated experimentally by comparing the size of healthy and artificially infected snails. Here, I focused on naturally infected populations in order to investigate if snails submitted to trematode pressure have evolved specific life-history traits to respond to the parasite prevalence in their natural population. To this end, I estimated the correlations between measures of size (obtained from healthy laboratory individuals originating from populations) and the parasite prevalence at the population level. I found that the adult size of populations was positively correlated with population prevalence, an indication that gigantism might be operating. Moreover, I found a positive relation between growth and fecundity in healthy populations, while no such trade off was found in highly parasitized populations, suggesting that there may be a cost in fecundity to this gigantis

Landsharing for climat smart lanscapes in dry and humid tropical livestock areas

Livestock activities present large GHG emissions, especially in the Southern countries, but in the same time high potentialities for mitigation and adaptation. Promoting a transition to explore theses potentialities is a key challenge for CSA. The communication propose a strategy based on landscape structure designing in Amazon and Sahel, we discuss the contributions of landscape sharing or sparing debate. In the Amazon, research references about the mitigation capacities of managed pasture and forest can improve practices. New landscapes are appearing, with land use matrixes highly efficient to produce ecosystemic services, for production and conservation objectives. Forage diversification and forest connectivity are key to increase the adaptability to CC. In West Africa, research conducted at landscape level underlined the capacity of extensive pastoral systems to mitigate the GHG emissions with carbon sequestration in soil and vegetation. Village terroirs were traditionally built around a complementary between rangelands and cultivated areas. The challenge is to keep this equilibrium to ensure nutrient spatial transfers, C soil sequestration, and food productivity. An adapted governance to promote these landscape structure appears therefore as a key factor determining the land sharing level and the performances of these livestock agro-ecosystems face to CC (mitigation, resilience and productivity)

Basics of Dynamic Programming for Revenue Management

International audienceThe Revenue Management (RM), namely the pricing and the inventory control of a perishable product, is usually used to improve services marketing efficiency. While booking a flight, the manager has to allocate seats to various fare classes. Then, he has to assess the consequence of a current decision on the future stream of revenue, i.e. accept an certain incoming reservation or wait for a possible higher fare demand, but later. Since its practice becomes omnipresent this last decade, this paper presents some basics of Dynamic Programming (DP) through the most common model, the dynamic discrete allocation of a resource to n fare classes. The properties of the opportunity cost of using a unit of a given capacity, the key of any RM optimizations, are studied in details

Price Fairness versus Pricing Fairness

International audienceThis research note discusses the distinction between these two concepts of perceptions of fairness, based on the theory of distributive justice and procedural justice, in order to helps understand consumer behavior. With a sample of 250 tourists in French Polynesia and a structural equation model, tourists do not confuse price fairness and pricing fairness. The theoretical implications are that future research should use two distinct scales. For managers, the study suggests that the attention devoted to explaining the fairness of the pricing has more impact on consumer satisfaction than some attempts to explain the price