The Stabilizing Effect Of Intraspecific Genetic Variation On Population Dynamics In Novel And Ancestral Habitats

Recent studies show that intraspecific genetic variation in asexual species may have large effects on community and ecosystem functions, increasing their stability, productivity, and species richness. However, major questions regarding its population-level impact remain empirically unanswered: (a) How does intraspecific genetic diversity affect the ecological characteristics of sexual species, in which recombination can alter the outcome of causal mechanisms such as selection and niche diversification? (b) Does genetic diversity increase population dynamic stability? (c) Is the impact of genetic diversity dependent on the selective environment? To answer these questions, I founded replicate flour beetle (Tribolium castaneum) populations with different degrees of ecologically relevant, heritable trait variation and monitored their dynamics for approximately eight generations. I show that population stability and persistence increased with greater genetic variation but that the stabilizing effect was independent of the selective habitat (different proportions of ancestral and novel resources). Alleles from a single founding strain underwent a selective sweep in the homogeneous ancestral habitat but not in a novel heterogeneous habitat. These results expand current understanding of the ecological impacts of genetic diversity by showing that genetically more diverse sexual populations persist longer and are more stable but that the selective environment determines the mechanistic basis of increased stability.Integrative Biolog

Stability of Nations and Genetic Diversity

This paper presents a model of nations where culturally heterogeneous agents vote on the optimal level of public spending. Larger nations benefit from increasing returns in the provision of public goods, but bear the costs of greater cultural heterogeneity. This tradeoff induces agents' preferences over different geographical configurations, thus determining the likelihood of secession or unification. We provide empirical support for choosing genetic distances as a proxy of cultural heterogeneity and by using data on genetic distances, we examine the stability of the current map of Europe. We then identify the regions prone to secession and the countries that are more likely to merge. Furthermore, we estimate the welfare gains from European Union membership.nation formation, genetic diversity, cultural heterogeneity, secession, uniï¬cation, European Union

In vivo evidence for quasispecies distributions in the bovine respiratory syncytial virus genome

We analyzed the genetic evolution of bovine respiratory syncytial virus (BRSV) isolate W2-00131, from its isolation in bovine turbinate (BT) cells to its inoculation in calves. Results showed that the BRSV genomic region encoding the highly variable glycoprotein G remains genetically stable after virus isolation and over 10 serial infections in BT cells, as well as following experimental inoculation in calves. This remarkable genetic stability led us to examine the mutant spectrum of several populations derived from this field isolate. Sequence analysis of molecular clones revealed an important genetic heterogeneity in G coding region of each population, with mutation frequencies ranging from 6.8 to 10.1 10-4 substitutions/nucleotide. The non-synonymous mutations of the mutant spectrum mapped preferentially within the two variable antigenic regions of the ectodomain or close to the highly conserved domain. These results suggest that RSV populations may evolve as complex and dynamic mutant swarms, despite apparent genetic stability

Why not "do simple things in a simple way": Use of the Pap test as the first step in screening genetic stability for human cultured stem cell therapy?

The aim of this study was to analyze adipose tissue-derived mesenchymal stem cells (AT-MSCs) using the Pap test as a first screening step to evaluate genetic stability. Human adipose tissue from six healthy female donors was obtained from elective liposuction procedures. The cells were isolated, cultivated at P2/P3, characterized by flow cytometric analysis, and differentiation induced. The AT-MSCs were stained by Papanicolaou staining and analyzed according to the Bethesda classification, and viability-apoptosis relationships were evaluated. The results of the Pap test for Sample I indicated high-grade alterations consistent with genetic instability; for Samples II-V, atypical cells of undetermined significance; and for Sample VI, normal cells. These results demonstrate the potential of using the Pap test as an initial screening step to evaluate the genetic stability of cultured AT-MSCs and also suggest its use for other adherent cells such as embryonic stem cells or induced pluripotent stem cells

Genetic networks with canalyzing Boolean rules are always stable

We determine stability and attractor properties of random Boolean genetic network models with canalyzing rules for a variety of architectures. For all power law, exponential, and flat in-degree distributions, we find that the networks are dynamically stable. Furthermore, for architectures with few inputs per node, the dynamics of the networks is close to critical. In addition, the fraction of genes that are active decreases with the number of inputs per node. These results are based upon investigating ensembles of networks using analytical methods. Also, for different in-degree distributions, the numbers of fixed points and cycles are calculated, with results intuitively consistent with stability analysis; fewer inputs per node implies more cycles, and vice versa. There are hints that genetic networks acquire broader degree distributions with evolution, and hence our results indicate that for single cells, the dynamics should become more stable with evolution. However, such an effect is very likely compensated for by multicellular dynamics, because one expects less stability when interactions among cells are included. We verify this by simulations of a simple model for interactions among cells.Comment: Final version available through PNAS open access at http://www.pnas.org/cgi/content/abstract/0407783101v

Genetic stability of Campylobacter coli in patients with primary antibody deficiencies

In the Clinical Communication, Dion et al 1 reported that in patients with severe primary antibody deficiency (PAD), Campylobacter infection is a major cause (6.5%) of chronic or recurrent diarrhea. Moreover, by a molecular study performed in a subset of 18 strains from 5 patients with recurrent infections, they demonstrated that all strains were different, even when the episodes occurred closely over time. Thus, the authors hypothesized that reinfection would be more likely than persistent colonization, although colonization with multiple strains cannot be excluded. In a previous study, 2 our group showed that Campylobacter coli (C. coli) (6.7%) was the first cause of diarrhea in patients with symptomatic PAD with a positive stool culture, followed by Campylobacter jejuni (C. jejuni) (3.9%). Moreover, C. coli was also the most frequent isolate (5%) in patients with asymptomatic PAD, followed by C. jejuni (1.2%), whereas in immunocompetent individuals, C. jejuni is one of the most prevalent etiologic agents of gastroenteritis and C. coli has a low prevalence in diarrheal disease