Multiple paternity and its consequences in the white campion " Silene latifolia "

Summary Several studies have demonstrated that the number of pollen donors siring seeds of individual fruits is frequently greater than one and, consequently, that plants have multiple mates. Multiple paternity can have important consequences at the population level. It influences the genetic variability of a population, the reproductive success of males and the fitness of females and future generations. It also influences male-male interactions for fertilization and it is fundamental in providing opportunity of female choice. I investigated the occurrence and the importance of multiple paternity within fruits in natural populations of the dioecious Silene latifolia using microsatellite DNA markers, especially developed for this study. I found that multiple paternity occurs in all populations investigated in the European range of the species, varying from one to nine sires per fruit with a mean of three, suggesting that multiple paternity is highly prevalent in natural populations. In the presence of multiple paternity I investigated if there was a female genotype influence on siring success of the males. I used the same pollen mixture from two males and applied it to three replicate females of different relatedness (two full sisters and one unrelated). I found female genotype influence in one of the two populations investigated, which might reflect different population history. Since these results suggested some degree of female choice, we investigated whether the occurrence of multiple paternity and post-pollination selection could provide opportunity for inbreeding avoidance. First, I measured inbreeding depression at different life-cycle stages for offspring obtained by single-donor crosses with brothers or unrelated males replicated on distinct flowers on the same female plant. To address inbreeding avoidance, I determined paternity in crosses using mixed pollen loads of the two males. I found significant inbreeding depression in the studied population, even under benign experimental conditions, and although the unrelated male did not sire significantly more offspring, there was an effect of genetic dissimilarity on paternity. This suggests that paternity is affected by relatedness among mates, but maybe additionally affected by other factors such as pollen competitive ability or male-female interactions. Using inbred and outbred crosses, I further investigated sex ratio bias inheritance in this species, and found that sex ratio bias of the parental generation was significantly correlated to pollen germination success of the F2 generation, which suggests that sex ratio bias in this species results from the specific X/Y combination and not only on Y performance. An effect of X and Y is consistent with sex chromosome meiotic drive. In conclusion, I found multiple paternity to be widespread in the study species and that females of similar genotype produce similar paternity shares. I found that inbreeding depression is substantial, therefore receiving pollen from several donors might lead to fewer inbred offspring, I also found an effect of genetic dissimilarity on paternity shares, which indicates that there is some ability to discriminate against related pollen, although this seems not to be the only determinant of paternity outcome. Finally I found sex ratio bias to be dependent on both X and Y chromosomes as predicted by sex chromosome meiotic drive. Résumé Plusieurs études ont démontré qu'il n'était pas rare que les graines contenues dans un même fruit soient issues de la fécondation par plusieurs pollens provenant de mâles différents, ce qui sous-entend que les plantes peuvent avoir plusieurs partenaires sexuels. La paternité multiple peut avoir d'importantes conséquences au niveau populationnel dans la mesure où elle peut influencer le degré de variabilité génétique de la population, le succès reproducteur des mâles, la fitness des femelles et des futures générations. La paternité multiple peut également avoir un impact sur les interactions mâle-mâle lors de la fertilisation et peut être considérée comme fondamentale vis-à-vis de la femelle, qui y trouve alors une opportunité de choisir son ou ses partenaires. Dans le cadre de ce travail de thèse j'ai cherché à déterminer si la paternité multiple était un phénomène observable et important dans les populations naturelles de l'espèce dioïque, Silene latifolia. Pour ce faire, j'ai utilisé des marqueurs microsatellites, spécialement développés pour cette étude. J'ai observé des phénomènes de paternité multiple dans toutes les populations de l'étude, réparties dans l'aire de distribution européenne de l'espèce. Le nombre de pères par fruit varie de un à neuf, avec un nombre moyen de trois, ce qui signifie que la paternité multiple est très répandue dans les populations naturelles. En raison de ces résultats, je me suis demandée si le génotype de la femelle influence le succès de paternité des mâles. J'ai alors réalisé des pollinisations manuelles sur la base d'un mélange de pollens issus de deux mâles, que j'ai appliqué sur trois femelles (réplicats) présentant différents degrés d'apparentement (deux soeurs. et une femelle étrangère). Il ressort de cette expérience que le génotype de la femelle peut influencer la paternité dans l'une des deux populations étudiées, ce qui pourrait refléter des différences en terme d'histoire des populations. Dans la mesure où ces résultats suggèrent un certain degré de choix chez la femelle, j'ai cherché à savoir si la paternité multiple et la sélection post-pollinisation pouvaient être des moyens d'éviter les croisements consanguins. Dans un premier temps, j'ai évalué la dépression de consanguinité à différentes étapes du cycle de vie chez des descendants issus de croisements à un seul donneur, celui-ci étant alternativement un frère ou un étranger, répliqués sur plusieurs fleurs d'une même plante femelle. Afin d'estimer l'évitement de croisements consanguins, j'ai effectué des croisements dont le pollen était un mélange des deux mâles (frère et étranger), puis j'ai déterminé la paternité dans les fruits obtenus. J'ai pu mettre en évidence un effet de dépression de consanguinité- significatif dans les populations étudiées, même dans des conditions expérimentales moins rudes qu'à l'extérieur. Bien que le mâle étranger n'ait pas engendré un nombre significativement plus important de graines, il y avait un effet de dissimilarité génétique sur la paternité. Ceci suggère que la paternité est affectée par le degré d'apparentement entre les partenaires, mais qu'elle peut aussi être affectée par d'autres facteurs tels que la compétitivité du pollen ou encore par les interactions mâles-femelles. L'utilisation de croisements consanguins et hybrides m'a également permis d'étudier l'héritabilité du biais de sex ratio chez cette espèce. Il s'est avéré que le biais de sex ratio de la génération parentale était significativement corrélé au succès de germination du pollen de la génération F2, ce qui signifie que, chez cette espèce, le biais de sex ratio résulte d'une combinaison spécifique de X/Y et non uniquement de la performance de Y. Un effet de X et Y est compatible avec l'hypothèse de distorsion de ségrégation méiotique des chromosomes sexuels. En conclusion, il ressort de mes résultats que la paternité multiple est un phénomène largement répandu chez S. latifolia et la paternité accomplie par un mâle est plus similaire entre soeurs qu'avec une femelle étrangère J'ai également mis en évidence que la dépression de consanguinité a un impact considérable; aussi, recevoir du pollen de plusieurs donneurs différents pourrait permettre à la femelle de produire moins de descendants consanguins. J'ai aussi trouvé un effet de la dissimilarité génétique sur le partage de paternité, ce qui indique que la discrimination contre le pollen d'apparentés est possible, bien que cela ne semble pas être le seul facteur déterminant dans le résultat de la paternité. Enfin, j'ai trouvé que le biais de sex ratio est dépendant des deux chromosomes X et Y, conformément à la théorie de distorsion de ségrégation méiotique des chromosomes sexuels.

Phylogeographical footprints of the Strait of Gibraltar and Quaternary climatic fluctuations in the western Mediterranean: a case study with the greater white-toothed shrew, Crocidura russula (Mammalia: Soricidae).

We used mitochondrial cyt b sequences to investigate the phylogenetic relationships of Crocidura russula (sensu lato) populations across the Strait of Gibraltar, western Europe, Maghreb, and the Mediterranean and Atlantic islands. This revealed very low genetic divergence between European and Moroccan populations. The application of a molecular clock previously calibrated for shrews suggested that the separation of European from Moroccan lineages occurred less than 60 000 bp, which is at least 5 million years (Myr) after the reopening of the Strait of Gibraltar. This means that an overwater dispersal event was responsible for the observed phylogeographical structure. In contrast, genetic analyses revealed that Moroccan populations were highly distinct from Tunisian ones. According to the molecular clock, these populations separated about 2.2 million years ago (Ma), a time marked by sharp alternations of dry and humid climates in the Maghreb. The populations of the Mediterranean islands Ibiza, Pantelleria, and Sardinia were founded from Tunisian populations by overwater dispersal. In conclusion, overwater dispersal across the Strait of Gibraltar, probably assisted by humans, is possible for small terrestrial vertebrates. Moreover, as in Europe, Quaternary climatic fluctuations had a major effect on the phylogeographical structure of the Maghreb biota.

Revisiting the Dollar-Euro Permanent Equilibrium Exchange Rate: Evidence from Multivariate Unobserved Components Models

We propose an alternative approach to obtaining a permanent equilibrium exchange rate (PEER), based on an unobserved components (UC) model. This approach offers a number of advantages over the conventional cointegration-based PEER. Firstly, we do not rely on the prerequisite that cointegration has to be found between the real exchange rate and macroeconomic fundamentals to obtain non-spurious long-run relationships and the PEER. Secondly, the impact that the permanent and transitory components of the macroeconomic fundamentals have on the real exchange rate can be modelled separately in the UC model. This is important for variables where the long and short-run effects may drive the real exchange rate in opposite directions, such as the relative government expenditure ratio. We also demonstrate that our proposed exchange rate models have good out-of sample forecasting properties. Our approach would be a useful technique for central banks to estimate the equilibrium exchange rate and to forecast the long-run movements of the exchange rate.

Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.

Secondary contact zones and hybridizations: the case of the lesser white-toothed shrew (Crocidura suaveolens group, Soricidae)

In the present study, we analyzed 58 samples of the lesser white-toothed shrew group (Crocidura suaveolens) from eastern Europe and Turkey, where, according to previous publications, three different mitochondrial and nuclear lineages are present. We sequenced 799 bp of the nuclear BRCA1 gene and 400 bp of the mitochondrial cytochrome b gene to: (1) determine a potential contact zone between the lineages; (2) detect hybridizations and introgressions between them; and (3) comment on the level of reproductive isolation of the different lineages. We revealed two zones of hybridization in Turkey, of which the first occurred west of the Bosphorus Straits (three hybrids) and the second in Anatolia (twelve hybrids). In the latter, the nuclear markers revealed a large zone of hybridization, of approximately 600 km. It also revealed that hybrids of first, second, and later generations are present within the populations, and therefore that the reproductive isolation between the different lineages is weak.

Service offshoring and white-collar employment

This paper empirically studies the effects of service offshoring on white-collar employment, using data for more than one hundred U.S. occupations. A model of firm behavior based on separability allows to derive the labor demand elasticity with respect to service offshoring for each occupation. Estimation is performed with Quasi-Maximum Likelihood, to account for high degrees of censoring in the employment variable. The estimated elasticities are then related to proxies for the skill level and the degree of tradability of the occupations. Results show that service offshoring increases high skilled employment and decreases medium and low skilled employment. Within each skill group, however, service offshoring penalizes tradable occupations and benefits non-tradable occupations.

Experimental heteroxenous cycle of Lagochilascaris minor Leiper, 1909 (Nematoda: Ascarididae) in white mice and in cats

Reports of natural infections of sylvatic carnivores by adult worms of species similar to Lagochilascaris minor in the Neotropical region led to attempts to estabilish experimental cycles in laboratory mice and in cats. Also, larval development was seen in the skeletal muscle of an agouti (Dasyprocta leporina) infected per os with incubated eggs of the parasite obtained from a human case. In cats, adult worms develop and fertile eggs are expelled in the feces: in mice, larval stages of the parasite develop, and are encapsulate in the skeletal muscle, and in the adipose and subcutaneous connective tissue. From our observations, we conclude that the larva infective for the mouse is the early 3rd stage, while for the final host the infective form is the later 3rd stage. A single moult was seen in the mouse, giving rise to a small population of 4th stage larvae, long after the initial infection.

Binding under Conflict Conditions: State-Space Analysis of Multivariate EEG Synchronization.

Real-world objects are often endowed with features that violate Gestalt principles. In our experiment, we examined the neural correlates of binding under conflict conditions in terms of the binding-by-synchronization hypothesis. We presented an ambiguous stimulus ("diamond illusion") to 12 observers. The display consisted of four oblique gratings drifting within circular apertures. Its interpretation fluctuates between bound ("diamond") and unbound (component gratings) percepts. To model a situation in which Gestalt-driven analysis contradicts the perceptually explicit bound interpretation, we modified the original diamond (OD) stimulus by speeding up one grating. Using OD and modified diamond (MD) stimuli, we managed to dissociate the neural correlates of Gestalt-related (OD vs. MD) and perception-related (bound vs. unbound) factors. Their interaction was expected to reveal the neural networks synchronized specifically in the conflict situation. The synchronization topography of EEG was analyzed with the multivariate S-estimator technique. We found that good Gestalt (OD vs. MD) was associated with a higher posterior synchronization in the beta-gamma band. The effect of perception manifested itself as reciprocal modulations over the posterior and anterior regions (theta/beta-gamma bands). Specifically, higher posterior and lower anterior synchronization supported the bound percept, and the opposite was true for the unbound percept. The interaction showed that binding under challenging perceptual conditions is sustained by enhanced parietal synchronization. We argue that this distributed pattern of synchronization relates to the processes of multistage integration ranging from early grouping operations in the visual areas to maintaining representations in the frontal networks of sensory memory.

Modelling dependence in a ratemaking procedure with multivariate Poisson regression models

When actuaries face with the problem of pricing an insurance contract that contains different types of coverage, such as a motor insurance or homeowner's insurance policy, they usually assume that types of claim are independent. However, this assumption may not be realistic: several studies have shown that there is a positive correlation between types of claim. Here we introduce different regression models in order to relax the independence assumption, including zero-inflated models to account for excess of zeros and overdispersion. These models have been largely ignored to multivariate Poisson date, mainly because of their computational di±culties. Bayesian inference based on MCMC helps to solve this problem (and also lets us derive, for several quantities of interest, posterior summaries to account for uncertainty). Finally, these models are applied to an automobile insurance claims database with three different types of claims. We analyse the consequences for pure and loaded premiums when the independence assumption is relaxed by using different multivariate Poisson regression models and their zero-inflated versions.

Improved virological outcome in White patients infected with HIV-1 non-B subtypes compared to subtype B.

BACKGROUND: Antiretroviral compounds have been predominantly studied in human immunodeficiency virus type 1 (HIV-1) subtype B, but only ~10% of infections worldwide are caused by this subtype. The analysis of the impact of different HIV subtypes on treatment outcome is important. METHODS: The effect of HIV-1 subtype B and non-B on the time to virological failure while taking combination antiretroviral therapy (cART) was analyzed. Other studies that have addressed this question were limited by the strong correlation between subtype and ethnicity. Our analysis was restricted to white patients from the Swiss HIV Cohort Study who started cART between 1996 and 2009. Cox regression models were performed; adjusted for age, sex, transmission category, first cART, baseline CD4 cell counts, and HIV RNA levels; and stratified for previous mono/dual nucleoside reverse-transcriptase inhibitor treatment. RESULTS: Included in our study were 4729 patients infected with subtype B and 539 with non-B subtypes. The most prevalent non-B subtypes were CRF02_AG (23.8%), A (23.4%), C (12.8%), and CRF01_AE (12.6%). The incidence of virological failure was higher in patients with subtype B (4.3 failures/100 person-years; 95% confidence interval [CI], 4.0-4.5]) compared with non-B (1.8 failures/100 person-years; 95% CI, 1.4-2.4). Cox regression models confirmed that patients infected with non-B subtypes had a lower risk of virological failure than those infected with subtype B (univariable hazard ratio [HR], 0.39 [95% CI, .30-.52; P < .001]; multivariable HR, 0.68 [95% CI, .51-.91; P = .009]). In particular, subtypes A and CRF02_AG revealed improved outcomes (multivariable HR, 0.54 [95% CI, .29-.98] and 0.39 [95% CI, .19-.79], respectively). CONCLUSIONS: Improved virological outcomes among patients infected with non-B subtypes invalidate concerns that these individuals are at a disadvantage because drugs have been designed primarily for subtype B infections.