Self-adjusting the intensity of assortative mating in genetic algorithms

Mate selection plays a crucial role in both natural and artificial systems. While traditional Evolutionary Algorithms (EA) usually engage in random mating strategies, that is, mating chance is independent of genotypic or phenotypic distance between individuals, in natural systems non-random mating is common, which means that somehow this mechanism has been favored during the evolutionary process. In non-random mating, the individuals mate according to their parenthood or likeness. Previous studies indicate that negative assortative mating (AM)—also known as dissortative mating—, which is a specific type of non-random mating, may improve EAs performance by maintaining the genetic diversity of the population at a higher level during the search process. In this paper we present the Variable Dissortative Mating Genetic Algorithm (VDMGA). The algorithm holds a mechanism that varies the GA’s mating restrictions during the run by means of simple rule based on the number of chromosomes created in each generation and indirectly influenced by the genetic diversity of the population. We compare VDMGA not only with traditional Genetic Algorithms (GA) but also with two preceding non-random mating EAs: the CHC algorithm and the negative Assortative Mating Genetic Algorithm (nAMGA). We intend to study the effects of the different methods in the performance of GAs and verify the reliability of the proposed algorithm when facing an heterogeneous set of landscapes. In addition, we include the positive Assortative Mating Genetic Algorithm (pAMGA) in the experiments in order test both negative and positive AM mechanisms, and try to understand if and when negative AM (or DM) speeds up the search process or enables the GAs to escape local optima traps. For these purposes, an extensive set of optimization test problems was chosen to cover a variety of search landscapes with different characteristics. Our results confirm that negative AM is effective in leading EAs out of local optima traps, and show that the proposed VDMGA is at least as efficient as nAMGA when applied to the range of our problems, being more efficient in very hard functions were traditional GAs usually fail to escape local optima. Also, scalability tests have been made that show VDMGA ability to decrease optimal population size, thus reducing the amount of evaluations needed to attain global optima. We like to stress that only two parameters need to be hand-tuned in VDMGA, thus reducing the tuning effort present in traditional GAs and nAMGA.     

A comparative study on the performance of dissortative mating and immigrants-based strategies for evolutionary dynamic optimization

Traditional Genetic Algorithms (GAs) mating schemes select individuals for crossover independently of their genotypic or phenotypic similarities. In Nature, this behavior is known as random mating. However, non-random protocols, in which individuals mate according to their kinship or likeness, are more common in natural species. Previous studies indicate that when applied to GAs, dissortative mating - a type of non-random mating in which individuals are chosen according to their similarities - may improve their performance (on both speed and reliability). Dissortative mating maintains genetic diversity at a higher level during the run, a fact that is frequently observed as a possible cause of dissortative GAs’ ability to escape local optima. Dynamic optimization demands a special attention when designing and tuning a GA, since diversity plays an even more crucial role than it does when tackling static ones. This paper investigates the behavior of the Adaptive Dissortative Mating GA (ADMGA) in dynamic problems and compares it to GAs based on random immigrants. ADMGA selects parents according to their Hamming distance, via a self-adjustable threshold value. The method, by keeping population diversity during the run, provides an effective means to deal with dynamic problems. Tests conducted with dynamic trap functions and dynamic versions of Road Royal and knapsack problems indicate that ADMGA is able to outperform other GAs on a wide range of tests, being particularly effective when the frequency of changes is low. Specifically, ADMGA outperforms two state-of-the-art algorithms on many dynamic scenarios. In addition, and unlike preceding dissortative mating GAs and other evolutionary techniques for dynamic optimization, ADMGA self-regulates the intensity of the mating restrictions and does not increase the set of parameters in GAs, thus being easier to tune.     

Male response to natural sex pheromone ofMigdolus fryanus westwood (Coleoptera: Cerambycidae) females as affected by daily climatic factors

Males of the sugarcane borer,Migdolus fryanus (Coleoptera: Cerambycidae), are attracted to females by means of a sex pheromone. Mating usually occurs during a few days from October to March under field conditions in São Paulo State, Brazil. This work reports on mating of this species as affected by daily climatic factors, during a single nuptial flight. Maximum male capture by the natural sex pheromone occurred from 1000 to 1100 AM at air and soil temperatures of 30.0°C and relative humidity of 57.0%. As these temperatures increased, females burrowed into the soil, as they are more sensitive to heat than males. Thus, it was concluded that sex pheromone-mediated mating in this cerambycid is directly affected by temperatures of air and soil.     

Snake Mating Systems, Behavior, and Evolution: The Revisionary Implications of Recent Findings.

Sexual selection and mating systems profoundly influence the behavior and psychology of animals. Using their own studies of green anacondas (Eunectes murinus) and reviewing other recent studies, the authors conclude that incomplete data derived from a few well-studied snake species have led to general acceptance of polygyny as the dominant mating system in snakes. New data on behavior, paternity, and life history in a diverse taxonomic array of snakes support the view that polyandry is not only common in snakes but may have been the ancestral mating system. This interpretation helps to explain many seemingly paradoxical behavioral differences between lizards and snakes, such as the lack of territorial systems in most snakes and their frequent female-biased sexual size dimorphism. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generation of assembly models from kinematic constraints

In this paper, we propose a new joint-based assembly modeling method. In joint-based assembly modeling, the assembly constraints are specified on the components, but not on the geometric elements of the components. The proposed method generates assembly models from kinematic joint constraints by applying three procedures (1) to extract all feasible JMFs (Joint Mating Feature) for each mating component using information on joint constraints, (2) to derive mating alternatives for each pair of mating components after reducing the number of JMFs using the pruning criteria, and (3) to generate an assembly model by choosing the intended one from the mating alternatives for each pair of mating components and solving the JMF constraints. Since the joint constraints are expressed in terms of the relations between components rather than relations between geometric elements, the proposed method is more intuitive and natural for assembly modeling and supports modeling activities effectively by minimizing user interactions. By using joint mating constraints for assembly modeling, moreover, the kinematic behaviors of assemblies determined in the conceptual design stage can be directly applied and consistently maintained up to the detailed design stage. In the proposed method, it is also not necessary to re-input the mating constraints even when the component topology is changed.     

Pheromone responsiveness is regulated by components of the Gpr1p‐mediated glucose sensing pathway in Saccharomyces cerevisiae

Many fungi have evolved mechanisms to assess environmental nutrient availability prior to the energy‐intensive process of mating. In this study, we examined one such system in Saccharomyces cerevisiae, involving a glucose‐sensing pathway mediated by Gpr1p and the pheromone‐induced mating pathway. Initially we observed that the mating pathway in MATa cells is sensitive to environmental glucose depletion. This phenomenon can be partially reversed with a high glucose spike, but not with the addition of low levels of glucose. Deletion of the low‐affinity glucose receptor, Gpr1p, eliminated this glucose‐induced recovery of pheromone responsiveness. We then determined the impact of GPR1 deletion on the mating pathway and observed that, in all end points studied, the mating pathway response to pheromone is reduced in the absence of Gpr1p. Similarly, elimination of the Gα for Gpr1p, Gpa2p, resulted in reduction in pheromone sensitivity in all assays studied. The negative effect of removing Gpr1p on mating pathway activation could be recovered by overexpressing the mating receptor, Ste2p. Furthermore, Ste2p levels are reduced in the absence of glucose and GPR1. These data suggest that activity of the GPCR‐mediated mating pathway in S. cerevisiae is modulated by extracellular glucose concentrations through the only other GPCR in MATa cells, Gpr1p. Copyright © 2014 John Wiley & Sons, Ltd.     

HST1, a new member of the SIR2 family of genes

A novel Saccharomyces cerevisiae gene, HST1, was identified from among anonymous cDNAs and the complete corresponding genomic clone was isolated and sequenced. HST1 is very closely related to SIR2, showing 71% sequence identity over 84% of its length. Polymerase chain reaction with degenerate primers on S. cerevisiae DNA identified three additional SIR2-related genes designated HST2, HST3 and HST4. The sequences of HST2, HST3 and HST4 correspond to sequences previously released by the S. cerevisiae genome sequencing project as U33335, NCBI gi:965078; X87331, NCBI gi:829135; and Z48784, YD9346.03, respectively. Disruption of HST1 has shown no phenotype with respect to mechanisms in which SIR2 has a role, namely, regional silencing of HMLα, or in rDNA recombination. The sequence of HST1 has been deposited in the DDBJ, EMBL and GenBank at NCBI database under Accession Number L47120.     

Sex pheromone of caddisflyHesperophylax occidentalis (Banks) (Trichoptera: Limnephilidae)

The main component of the sex pheromone of the caddisflyHesperophylax occidentalis (Banks) (Trichoptera: Limnephilidae) was identified as 6-methylnonan-3-one (enantiomeric composition has not yet been determined). Extracts of adult females elicited strong electroantennogram (EAG) responses from adult male antennae, but elicited significantly smaller EAG responses from adult female antennae. Extracts of adult males did not elicit appreciable EAG responses from antennae of either sex. Racemic 6-methylnonan-3-one was synthesized and elicited EAG responses from male antennae as strong as those obtained with female extracts. In field tests with baited sticky traps near lakes and streams, traps baited with synthetic racemic 6-methylnonan-3-one caught significantly more males than control traps. Female adults contained approximately 1 µg of 6-methylnonan-3-one per individual. Related ketones and alcohols of other chain lengths were also tentatively identified, being present in tiny amounts in female extracts. Extraction of different body parts showed that 6-methylnonan-3-one occurs only in a region near the intersegmental membrane between the fourth and fifth abdominal sternites of the female (no discrete glands were observed). Extracts of males did not contain 6-methylnonan-3-one, nor did pupae of either sex.     

六妹羊肚菌原生质体再生菌株交配型的分离鉴定

该研究对六妹羊肚菌（Morchella sextelata）的原生质体进行制备及再生,且对分离后的原生质体再生菌株的交配型进行分子生物学鉴定,并对其交配型稳定性进行验证。结果表明,CYM液态培养制备原生质体效果较好,再生率及回收率分别为0.15%～9.00%、60%～80%;共获得182株再生菌株,其中,MAT1-1-1交配型菌株占34.62%,MAT1-2-1交配型菌株占24.73%,双交配型（MAT1-2-1/MAT1-2-1）菌株占36.26%。稳定性试验结果表明,经过原生质体化过程及诱变处理,六妹羊肚菌的单交配型原生质体“同核体”的“二代”再生菌株交配型没有改变,与亲本菌株交配型一致,而双交配型原生质体的再生菌株中又发生了两种交配型分离的现象。