Types of evolutionary stability and the problem of cooperation.

The evolutionary stability of cooperation is a problem of fundamental importance for the biological and social sciences. Different claims have been made about this issue: whereas Axelrod and Hamilton's [Axelrod, R. & Hamilton, W. (1981) Science 211, 1390-1398] widely recognized conclusion is that cooperative rules such as "tit for tat" are evolutionarily stable strategies in the iterated prisoner's dilemma (IPD), Boyd and Lorberbaum [Boyd, R. & Lorberbaum, J. (1987) Nature (London) 327, 58-59] have claimed that no pure strategy is evolutionarily stable in this game. Here we explain why these claims are not contradictory by showing in what sense strategies in the IPD can and cannot be stable and by creating a conceptual framework that yields the type of evolutionary stability attainable in the IPD and in repeated games in general. Having established the relevant concept of stability, we report theorems on some basic properties of strategies that are stable in this sense. We first show that the IPD has "too many" such strategies, so that being stable does not discriminate among behavioral rules. Stable strategies differ, however, on a property that is crucial for their evolutionary survival--the size of the invasion they can resist. This property can be interpreted as a strategy's evolutionary robustness. Conditionally cooperative strategies such as tit for tat are the most robust. Cooperative behavior supported by these strategies is the most robust evolutionary equilibrium: the easiest to attain, and the hardest to disrupt.

Large-scale clustering measurements with photometric redshifts: comparing the dark matter haloes of X-ray AGN, star-forming and passive galaxies at z ≈ 1

We combine multi-wavelength data in the AEGIS-XD and C-COSMOS surveys to measure the typical dark matter halo mass of X-ray selected active galactic nuclei (AGN) [L_X(2–10 keV) > 10^42 erg s^− 1] in comparison with far-infrared selected star-forming galaxies detected in the Herschel/PEP survey (PACS Evolutionary Probe; L_IR > 10^11 L_⊙) and quiescent systems at z ≈ 1. We develop a novel method to measure the clustering of extragalactic populations that uses photometric redshift probability distribution functions in addition to any spectroscopy. This is advantageous in that all sources in the sample are used in the clustering analysis, not just the subset with secure spectroscopy. The method works best for large samples. The loss of accuracy because of the lack of spectroscopy is balanced by increasing the number of sources used to measure the clustering. We find that X-ray AGN, far-infrared selected star-forming galaxies and passive systems in the redshift interval 0.6 < z < 1.4 are found in haloes of similar mass, log M_DMH/(M_⊙ h^−1) ≈ 13.0. We argue that this is because the galaxies in all three samples (AGN, star-forming, passive) have similar stellar mass distributions, approximated by the J-band luminosity. Therefore, all galaxies that can potentially host X-ray AGN, because they have stellar masses in the appropriate range, live in dark matter haloes of log M_DMH/(M_⊙ h^−1) ≈ 13.0 independent of their star formation rates. This suggests that the stellar mass of X-ray AGN hosts is driving the observed clustering properties of this population. We also speculate that trends between AGN properties (e.g. luminosity, level of obscuration) and large-scale environment may be related to differences in the stellar mass of the host galaxies.

The evolutionary paths among galaxy types on the red sequence at 0.3 < Z < 1.5

We have studied the main evolutionary paths among the galaxy types residing on the massive end of the Red Sequence and nearby locations on the Green Valley during the last ∼9 Gyr. The morphological and star formation properties of a sample of these galaxies at 0 . 3 < z < 1 .5 with stellar masses M_∗ > 5 × 10^10 M_⊙ have been analysed. We present direct observational evidence for the first time of the existence of two main evolutionary paths among the different red galaxy types since z ∼ 1 .5, which provide some clues on the nature of the processes that have governed the assembly of present-day massive quiescent galaxies. The results are in excellent agreement with the hierarchical evolutionary framework proposed in the Eliche-Moral et al. (2010) model. Data from SHARDS (one of the ESO/GTC Large Programmes approved in 2009A) will complement and improve the present findings, shedding some light into many of the still unsettled questions concerning the migration of galaxies from the Blue Cloud to the Red Sequence at z < 1 .5.

The high-bias stability of monatomic chains

For the metals Au, Pt and Ir it is possible to form freely suspended monatomic chains between bulk electrodes. The atomic chains sustain very large current densities, but finally fail at high bias. We investigate the breaking mechanism, that involves current-induced heating of the atomic wires and electromigration forces. We find good agreement of the observations for Au based on models due to Todorov and co-workers. The high-bias breaking of atomic chains for Pt can also be described by the models, although here the parameters have not been obtained independently. In the limit of long chains the breaking voltage decreases inversely proportional to the length.

Emergence of half-metallicity in suspended NiO chains: Ab initio electronic structure and quantum transport calculations

Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors that displays very large magnetoresistance and a spin-valve behavior controlled by a single atom.

Europe's LNG Strategy in the Wider EU Gas Market. CEPS Policy Brief No. 333, October 2015

In its Communication on an Energy Union published in February 2015, the European Commission committed itself to “explore the full potential of liquefied natural gas (LNG), including as a back-up in crisis situations when insufficient gas is coming into Europe through the existing pipeline system” and to address the potential of gas storage in Europe by developing a comprehensive LNG and storage strategy by the end of 2015 or early in 2016. This is a comprehensible move in the current context. Geopolitical tensions between the EU and Russia explain the EU’s willingness to further diversify its supply sources of natural gas to reinforce its long-term energy security on the one hand, and to strengthen its ability to solve future crises on the other hand. Moreover, the current market dynamics could support diversification towards LNG. Increasing the flexibility of LNG trade, decreasing LNG prices and LNG charter rates and an apparent price convergence between the European and the Asia-Pacific LNG imports would all reinforce the economic viability of such a strategy. This Policy Brief makes three main points: • For the LNG and gas storage strategy to work, it needs to be embedded in the realities of the natural gas market. • The key to a successful LNG strategy is to develop sufficient infrastructure. • The LNG strategy needs an innovation component.

What strategy for a genuine Single Market? CEPS Special Report No. 126/January 2016

This strategy paper focuses on making the most of the EU single market. The EU should pursue a genuine single market, and treat it as a common asset of all its citizens, economic operators and member states. The economic case to be made on behalf of the genuine single market is powerful and even more so due to the findings of recent empirical economic research. However, only the genuine single market can realise the expectations of such large gains. Weak, ‘feasible’ action plans cannot! The strategy is based, first of all, on a clear design of the genuine single market and subsequently concentrates on ‘what it takes’. Ten types of actions sum up ‘what it takes’: five at the EU level, four at the EU-member state interface, and finally, the realisation of legitimacy and acceptance.

China’s foreign direct investments within the ‘16+1’ cooperation formula: strategy, institutions, results. OSW Commentary Number 191|27.11.2015

The ‘16+1’ formula of cooperation between the countries of Central and Eastern Europe (CEE) and China was launched in 2012. One of its priorities involved increasing the inflow of China’s foreign direct investments (FDI) to the region. China has been interested in carrying out investments which are likely to help Chinese companies gain competitive advantage in areas such as advanced technologies, recognizable brands and distribution channels. The following sectors were identified as areas of priority importance in CEE: construction and modernisation of transport infrastructure, including motorways; development of the network of railways, airports and sea ports; energy, in particular renewable sources of energy and nuclear energy; companies trading in commodities; the food production sector. China’s strategy mainly involves purchasing existing companies, preceded by cherry picking the most favourable candidates for investment, rather than making large greenfield investments.

Crystal structures of fusion proteins with large-affinity tags

The fusion of a protein of interest to a large-affinity tag, such as the maltose-binding protein (MBP), thioredoxin (TRX), or glutathione-S-transferase (GST), can be advantageous in terms of increased expression, enhanced solubility, protection from proteolysis, improved folding, and protein purification via affinity chromatography. Unfortunately, crystal growth is hindered by the conformational heterogeneity induced by the fusion tag, requiring that the tag is removed by a potentially problematic cleavage step. The first three crystal structures of fusion proteins with large-affinity tags have been reported recently. All three structures used a novel strategy to rigidly fuse the protein of interest to MBP via a short three- to five-amino acid spacer. This strategy has the potential to aid structure determination of proteins that present particular experimental challenges and are not conducive to more conventional crystallization strategies (e.g., membrane proteins). Structural genomics initiatives may also benefit from this approach as a way to crystallize problematic proteins of significant interest.

Large size in an island-dwelling bird: intraspecific competition and the Dominance Hypothesis

Differences between island- and mainland-dwelling forms provide several classic ecological puzzles. Why, for instance, are island-dwelling passerine birds consistently larger than their mainland counterparts? We examine the 'Dominance hypothesis', based on intraspecific competition, which states that large size in island passerines evolves through selection for success in agonistic encounters. We use the Heron Island population of Capricorn silvereyes (Zosterops lateralis chlorocephalus), a large-bodied island-dwelling race of white-eye (Zosteropidae), to test three assumptions of this hypothesis; that (i) large size is positively associated with high fitness, (ii) large size is associated with dominance, and (iii) the relationship between size and dominance is particularly pronounced under extreme intraspecific competition. Our results supported the first two of these assumptions, but provided mixed evidence on the third. On balance, we suggest that the Dominance Hypothesis is a plausible mechanism for the evolution of large size of island passerines, but urge further empirical tests on the role of intraspecific competition on oceanic islands versus that on mainlands.

Initiation of fungal epizootics in diamondback moth populations within a large field cage: proof of concept for auto-dissemination

Adult diamondback moths (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae), inoculated with the fungus Zoophthora radicans, were released within a large field cage containing DBM-infested potted broccoli plants. Larvae and pupae on exposed and caged control plants were examined on five occasions over the next 48 days for evidence of Z. radicans infection. Infected larvae were first detected on exposed plants 4 days after the initial release of adults, and after 48 days the infection level reached 79%. Aerially borne conidia were a factor in transmission of the fungus. Infection had no effect on possible losses of larval and adult cadavers due to scavengers in field crops. In a trial to measure the influence of infection on dispersal, twice as many non-infected as infected males were recaptured in pheromone traps, although the difference in cumulative catch only became significant 3 days after release of the males. In a separate experiment, when adult moths were inoculated with Beauveria bassiana conidia and released into the field cage, DBM larvae collected from 37 of 96 plants sampled 4 days later subsequently died from B. bassiana infection. The distribution of plants from which the infected larvae were collected was random, but the distribution of infected larvae was clustered within the cage. These findings suggest that the auto-dissemination of fungal pathogens may be a feasible strategy for DBM control, provided that epizootics can be established and maintained when DBM population densities are low.

An evolutionary radiation of beeflies in semi-arid Australia: systematics of the Exoprosopini (Diptera : Bombyliidae)

Almost half of the 4822 described beeflies in the world belong to the subfamily Anthracinae, with most of the diversity found in three cosmopolitan tribes: Villini, Anthracini, and Exoprosopini. The Australian Exoprosopini previously contained three genera, Ligyra Newman, Pseudopenthes Roberts and Exoprosopa Macquart. Pseudopenthes is an Australian endemic, with two species including Ps. hesperis, sp. nov. from Western Australia. Two new species of the exoprosopine Atrichochira Hesse, Atr. commoni, sp. nov. and Atr. paramonovi, sp. nov., are also described from Australia, extending the generic distribution from Africa. Cladistic analysis clarified the phylogenetic relationships between the recognised groups of the Exoprosopini and determined generic limits on a world scale. Inclusion of 18 Australian exoprosopines placed the Australian species in the context of the world fauna. The Exoprosopini contains six large groups. The basal group I contains species previously included in Exoprosopa to which the name Defilippia Lioy is applied. Group II contains Heteralonia Rondani, Atrichochira, Micomitra Bowden, Pseudopenthes, and Diatropomma Bowden. Colossoptera Hull is newly synonymised with Heteralonia. Group III is a paraphyletic assemblage of Pterobates Bezzi and Exoprosopa including the Australian Ex. sylvana ( Fabricius). Ligyra is paraphyletic, forming two well-separated clades. The African clade is described as Euligyra Lambkin, gen. nov., which, together with Litorhina Bezzi and Hyperalonia Rondani, form group IV. The Australian group V is true Ligyra. The remaining monophyletic lineage of exoprosopines, group VI, the Balaana-group of genera, shows evidence of an evolutionary radiation of beeflies in semi-arid Australia. Phylogenetic analysis of all 42 species of the Balaana-group of genera formed a basis for delimiting genera. Seven new genera are described by Lambkin & Yeates: Balaana, Kapua, Larrpana, Munjua, Muwarna, Palirika and Wurda. Four non-Australian species belong to Balaana. Thirty two new Australian species are described: Bal. abscondita, Bal. bicuspis, Bal. centrosa, Bal. gigantea, Bal. kingcascadensis, K. corusca, K. irwini, K. westralica, Lar. collessi, Lar. zwicki, Mun. erugata, Mun. lepidokingi, Mun. paralutea, Mun. trigona, Muw. vitreilinearis, Pa. anaxios, Pa. basilikos, Pa. blackdownensis, Pa. bouchardi, Pa. cyanea, Pa. danielsi, Pa. decora, Pa. viridula, Pa. whyalla, W. emu, W. impatientis, W. montebelloensis, W. norrisi, W. patrellia, W. skevingtoni, W. windorah, and W. wyperfeldensis. The following new combinations are proposed: from Colossoptera: Heteralonia latipennis (Brunetti); from Exoprosopa: Bal. grandis (Pallas), Bal. efflatounbeyi (Paramonov), Bal. latelimbata ( Bigot), Bal. obliquebifasciata ( Macquart), Bal. tamerlan (Portschinsky), Bal. onusta ( Walker), Def. busiris (Jaennicke), Def. efflatouni ( Bezzi), Def. eritreae (Greathead), Def. gentilis ( Bezzi), Def. luteicosta ( Bezzi), Def. minos (Meigen), Def. nigrifimbriata ( Hesse), Def. rubescens ( Bezzi), K. adelaidica ( Macquart), Lar. dimidiatipennis ( Bowden), Muw. stellifera ( Walker), and Pa. marginicollis ( Gray); from Ligyra: Eu. enderleini ( Paramonov), Eu. mars ( Bezzi), Eu. monacha (Klug), Eu. paris ( Bezzi), Eu. sisyphus ( Fabricius), and Eu. venus (Karsch).

Simulating the effects of dominance and epistasis on selection response in the CIMMYT wheat breeding program using QuCim

Plant breeders use many different breeding methods to develop superior cultivars. However, it is difficult, cumbersome, and expensive to evaluate the performance of a breeding method or to compare the efficiencies of different breeding methods within an ongoing breeding program. To facilitate comparisons, we developed a QU-GENE module called QuCim that can simulate a large number of breeding strategies for self-pollinated species. The wheat breeding strategy Selected Bulk used by CIMMYT's wheat breeding program was defined in QuCim as an example of how this is done. This selection method was simulated in QuCim to investigate the effects of deviations from the additive genetic model, in the form of dominance and epistasis, on selection outcomes. The simulation results indicate that the partial dominance model does not greatly influence genetic advance compared with the pure additive model. Genetic advance in genetic systems with overdominance and epistasis are slower than when gene effects are purely additive or partially dominant. The additive gene effect is an appropriate indicator of the change in gene frequency following selection when epistasis is absent. In the absence of epistasis, the additive variance decreases rapidly with selection. However, after several cycles of selection it remains relatively fixed when epistasis is present. The variance from partial dominance is relatively small and therefore hard to detect by the covariance among half sibs and the covariance among full sibs. The dominance variance from the overdominance model can be identified successfully, but it does not change significantly, which confirms that overdominance cannot be utilized by an inbred breeding program. QuCim is an effective tool to compare selection strategies and to validate some theories in quantitative genetics.

Searching oligo sets of human chromosome 12 using evolutionary strategies

DNA Microarray is a powerful tool to measure the level of a mixed population of nucleic acids at one time, which has great impact in many aspects of life sciences research. In order to distinguish nucleic acids with very similar composition by hybridization, it is necessary to design microarray probes with high specificities and sensitivities. Highly specific probes correspond to probes having unique DNA sequences; whereas highly sensitive probes correspond to those with melting temperature within a desired range and having no secondary structure. The selection of these probes from a set of functional DNA sequences (exons) constitutes a computationally expensive discrete non-linear search problem. We delegate the search task to a simple yet effective Evolution Strategy algorithm. The computational efficiency is also greatly improved by making use of an available bioinformatics tool.

Cloning and expression of the large zebrafish protocadherin gene, Fat

The cadherin superfamily members play an important role in mediating cell-cell contact and adhesion (Takeichi, M., 1991. Cadherin cell adhesion receptors as a morphogenetic regulator. Science 251, 1451-1455). A distinct subfamily, neither belonging to the classical or protocadherins includes Fat, the largest member of the cadherin super-family. Fat was originally identified in Drosophila. Subsequently, orthologues of Fat have been described in man (Dunne, J., Hanby, A. M., Poulsom, R., Jones, T. A., Sheer, D., Chin, W. G., Da, S. M., Zhao, Q., Beverley, P. C., Owen, M. J., 1995. Molecular cloning and tissue expression of FAT, the human homologue of the Drosophila fat gene that is located on chromosome 4q34-q35 and encodes a putative adhesion molecule. Genomics 30, 207-223), rat (Ponassi, M., Jacques, T. S., Ciani, L., ffrench, C. C., 1999. Expression of the rat homologue of the Drosophila fat tumour suppressor gene. Mech. Dev. 80, 207-212) and mouse (Cox, B., Hadjantonakis, A. K., Collins, J. E., Magee, A. I., 2000. Cloning and expression throughout mouse development of mfat 1, a homologue of the Drosophila tumour suppressor gene fat [In Process Citation]. Dev. Dyn. 217, 233-240). In Drosophila, Fat has been shown to play an important role in both planar cell polarity and cell boundary formation during development. In this study we describe the characterization of zebrafish Fat, the first non-mammalian, vertebrate Fat homologue to be identified. The Fat protein has 64% amino acid identity and 80% similarity to human FAT and an identical domain structure to other vertebrate Fat proteins. During embryogenesis fat mRNA is expressed in the developing brain, specialised epithelial surfaces the notochord, ears, eyes and digestive tract, a pattern similar but distinct to that found in mammals. (c) 2005 Elsevier B.V. All rights reserved.