Evolutionary games and quasispecies

We discuss a population of sequences subject to mutations and frequency-dependent selection, where the fitness of a sequence depends on the composition of the entire population. This type of dynamics is crucial to understand the evolution of genomic regulation. Mathematically, it takes the form of a reaction-diffusion problem that is nonlinear in the population state. In our model system, the fitness is determined by a simple mathematical game, the hawk-dove game. The stationary population distribution is found to be a quasispecies with properties different from those which hold in fixed fitness landscapes.Comment: 7 pages, 2 figures. Typos corrected, references updated. An exact solution for the hawks-dove game is provide

On the Neutrality of Flowshop Scheduling Fitness Landscapes

Solving efficiently complex problems using metaheuristics, and in particular local searches, requires incorporating knowledge about the problem to solve. In this paper, the permutation flowshop problem is studied. It is well known that in such problems, several solutions may have the same fitness value. As this neutrality property is an important one, it should be taken into account during the design of optimization methods. Then in the context of the permutation flowshop, a deep landscape analysis focused on the neutrality property is driven and propositions on the way to use this neutrality to guide efficiently the search are given.Comment: Learning and Intelligent OptimizatioN Conference (LION 5), Rome : Italy (2011

Clinical determinants of vaginal dryness in patients with primary Sjögren's syndrome

Objective. The majority of women with primary Sjogren's syndrome (pSS) suffer from vaginal dryness, which negatively impacts daily and sexual activities. As little is known about the aetiology and clinical context of this complaint, this study investigated the relationship between vaginal dryness and other clinical parameters associated with pSS. Methods. Female participants of the REgistry of Sjogren syndrome at UMCG - LongiTudinal (RESULT) cohort who fulfilled ACR-EULAR and/or AECG classification criteria for pSS were included, using baseline data for analyses. Patient-reported vaginal dryness (range 0-10) was correlated with demographic characteristics, systemic disease activity (i.e. ESSDAI), Sjogren's Syndrome Disease Damage Index, salivary and lacrimal gland function, patient-reported outcomes (ESSPRI, MFI), serology and quality of life (SF-36, EQ-5D). Significantly associated parameters (p Results. This cross-sectional study included 199 women with pSS; mean age was 52 +/- 14 years, 53% were postmenopausal, and median vaginal dryness score was 5 (IQR 2-7). Vaginal dryness was significantly associated with older age, postmenopausal status, peripheral neuropathy, oral and ocular dryness, ESSPRI and SF-36 mental and general health. After correction for age, menopausal status and medication use, peripheral neuropathy (B=1.632), oral dryness (B=0.302), and ocular dryness (B=0.230) were independently associated with vaginal dryness. Conclusion. The independent association of vaginal dryness with oral and ocular dryness might imply that the aetiology of these symptoms is partly shared. Of all extraglandular features, only peripheral neuropathy was independently associated with vaginal dryness, suggesting that peripheral neuropathy plays a significant role in the pathology of vaginal dryness in pSS

Does the Red Queen reign in the kingdom of digital organisms?

In competition experiments between two RNA viruses of equal or almost equal fitness, often both strains gain in fitness before one eventually excludes the other. This observation has been linked to the Red Queen effect, which describes a situation in which organisms have to constantly adapt just to keep their status quo. I carried out experiments with digital organisms (self-replicating computer programs) in order to clarify how the competing strains' location in fitness space influences the Red-Queen effect. I found that gains in fitness during competition were prevalent for organisms that were taken from the base of a fitness peak, but absent or rare for organisms that were taken from the top of a peak or from a considerable distance away from the nearest peak. In the latter two cases, either neutral drift and loss of the fittest mutants or the waiting time to the first beneficial mutation were more important factors. Moreover, I found that the Red-Queen dynamic in general led to faster exclusion than the other two mechanisms.Comment: 10 pages, 5 eps figure