Signals of demographic expansion in Drosophila virilis

BACKGROUND: The pattern of genetic variation within and among populations of a species is strongly affected by its phylogeographic history. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonizations, can be inferred. Drosophila virilis is a cosmopolitan species belonging to the virilis group, where divergence times between different phylads go back to the early Miocene. We analysed mitochondrial DNA sequence variation among 35 Drosophila virilis strains covering the species' range in order to detect demographic events that could be used to understand the present characteristics of the species, as well as its differences from other members of the group. RESULTS: Drosophila virilis showed very low nucleotide diversity with haplotypes distributed in a star-like network, consistent with a recent world-wide exponential expansion possibly associated either with domestication or post-glacial colonization. All analyses point towards a rapid population expansion. Coalescence models support this interpretation. The central haplotype in the network, which could be interpreted as ancestral, is widely distributed and gives no information about the geographical origin of the population expansion. The species showed no geographic structure in the distribution of mitochondrial haplotypes, in contrast to results of a recent microsatellite-based analysis. CONCLUSION: The lack of geographic structure and the star-like topology depicted by the D. virilis haplotypes indicate a pattern of global demographic expansion, probably related to human movements, although this interpretation cannot be distinguished from a selective sweep in the mitochondrial DNA until nuclear sequence data become available. The particular behavioural traits of this species, including weak species-discrimination and intraspecific mate choice exercised by the females, can be understood from this perspective

Teräsbetonisten siltakansien vedeneristeen kuplimisongelma

Tiivistelmä. Tässä diplomityössä tarkastellaan teräsbetonisten siltakansien vedeneristeen kuplimisongelmaa. Yleisen suomalaisen käsityksen mukaan kupliminen johtuu betonirakenteen suurista kosteuspitoisuuksista, betonin huokoisuudesta ja työvirheistä. Kuitenkaan kuplimisongelma ei ole ratkennut ja kupliminen aiheuttaa edelleen yhteiskunnalle liikenteellisiä haittoja ja ylimääräisiä korjauskustannuksia. Diplomityön tavoitteena oli perehtyä siltakansien vedeneristeen kuplimisongelmaan sekä kotimaisten että kansainvälisten tutkimusten kautta, ja pyrkiä löytämään uusia näkökulmia ja havaintoja kuplimisongelman ymmärtämiseksi. Työn tavoitteena oli myös kartoittaa mahdollisia jatkotutkimustarpeita uusien näkökulmien ja havaintojen tueksi. Työvirheet olivat edelleenkin suurin kuplimisen selittävä tekijä valtaosassa tutkimuksista. Uusien tutkimusten mukaan myös kuumuudella oli suuri myötävaikutus kuplien muodostumiseen siltakannelle. Kansainvälisten tutkimusten mukaan vesihöyrynpaineen lisäksi kuumuus aiheuttaa siltakannella kemiallisia reaktioita, jotka ovat nimetty kylmä- ja kuumaprosesseiksi. Myös osmoosin vaikutus kuplimiseen on tiedostettu kosteilla betonialustoilla. Tutkimuksen perusteella kuplimista voitaisiin vähentää rajoittamalla muodostuvan kaasun painetta kermin alle. Eristysalustan kuivattaminen kosteusvaatimuksiin on oleellinen asia tartuntalujuuksien kannalta. Ehyt tiivistyskäsittely tai laadukas suojabetonikerros estävät kuplan muodostumisen pintarakenteeseen. Työvirheiden välttäminen ja tarkat laadunmittaukset ovat loppujen lopuksi avain onnistumiseen.Problem with blistering of waterproofing of reinforced concrete bridge decks. Abstract. This thesis examines the blistering problem of the waterproofing of reinforced concrete bridge decks. The common consensus within Finland, is that blistering is caused due to the high moisture content of the concrete structure, the porosity of the concrete and work defects. Despite the identification of these issues, blistering has not been solved and blistering continues to cause roadway inconveniences and incurs additional repair costs for the taxpayer. The aim of this thesis was to become acquainted with the blistering problem that can occur during the bridge deck waterproofing process. Information was gathered using both domestic and international studies so as to discover new perspectives and to better understand the blistering problem and its causes. The aim of this work is also to map the possible needs for further research of this topic. This research identified work defects as being the most prominent explanatory factor for blistering in the majority of studies. According to more recent studies, temperature contributed greatly to the formation of blisters on bridge decks. According to international studies, in addition to water vapor pressure, variances in temperature cause chemical reactions within the bridge deck, termed cold and hot processes. These chemical processes should be studied in greater detail in Finland, so as to gain a better understanding of this problem and to allow for the development of new methods and quality guidelines pertaining to materials and/or practices to limit the possibilities of chemical reactions. According to this study, blistering could be reduced by limiting the pressure of the gas formed below the waterproofing. Ensuring that the insulation substrate is dry and meets the moisture requirements is essential for adhesion strength during the waterproofing process. Proper sealing treatment or a protective concrete layer aides in the prevention of blister formation in the surface structure. Avoiding work defects and ensuring accurate measurements are crucial to the success of, as well

Cooperation between Different CRISPR-Cas Types Enables Adaptation in an RNA-Targeting System

CRISPR-Cas immune systems adapt to new threats by acquiring new spacers from invading nucleic acids such as phage genomes. However, some CRISPR-Cas loci lack genes necessary for spacer acquisition despite variation in spacer content between microbial strains. It has been suggested that such loci may use acquisition machinery from cooccurring CRISPR-Cas systems within the same strain. Here, following infection by a virulent phage with a double-stranded DNA (dsDNA) genome, we observed spacer acquisition in the native host Flavobacterium columnare that carries an acquisition-deficient CRISPR-Cas subtype VI-B system and a complete subtype II-C system. We show that the VI-B locus acquires spacers from both the bacterial and phage genomes, while the newly acquired II-C spacers mainly target the viral genome. Both loci preferably target the terminal end of the phage genome, with priming-like patterns around a preexisting II-C protospacer. Through gene deletion, we show that the RNA-cleaving VI-B system acquires spacers in trans using acquisition machinery from the DNA-cleaving II-C system. Our observations support the concept of cross talk between CRISPR-Cas systems and raise further questions regarding the plasticity of adaptation modules. IMPORTANCE CRISPR-Cas systems are immune systems that protect bacteria and archaea against their viruses, bacteriophages. Immunity is achieved through the acquisition of short DNA fragments from the viral invader's genome. These fragments, called spacers, are integrated into a memory bank on the bacterial genome called the CRISPR array. The spacers allow for the recognition of the same invader upon subsequent infection. Most CRISPR-Cas systems target DNA, but recently, systems that exclusively target RNA have been discovered. RNA-targeting CRISPR-Cas systems often lack genes necessary for spacer acquisition, and it is thus unknown how new spacers are acquired and if they can be acquired from DNA phages. Here, we show that an RNA-targeting system "borrows" acquisition machinery from another CRISPR-Cas locus in the genome. Most new spacers in this locus are unable to target phage mRNA and are therefore likely redundant. Our results reveal collaboration between distinct CRISPR-Cas types and raise further questions on how other CRISPR-Cas loci may cooperate.Peer reviewe

Meaningful learning with mobile devices: pre-service class teachers’ experiences of mobile learning in the outdoors

The authors consider the use of mobile learning environment ActionTrack in teacher education. Pre-service class teachers’ (N = 277) experiences of the mobile learning environment were measured with a 7-point Likert-scale questionnaire based on seven attributes of meaningful learning. Students’ ratings for different attributes were analysed quantitatively. The authors conclude that, based on this analysis, it is possible to create meaningful learning experiences using ActionTrack. All the measured attributes of meaningful learning obtained positive values. In the mobile learning events of this study, three attributes arose as the essential features: mobile learning in the outdoors was primarily considered collaborative, active and contextual.</p

How consistent are the transcriptome changes associated with cold acclimation in two species of the Drosophila virilis group?

This work was financially support by a Marie Curie Initial Training Network grant, “Understanding the evolutionary origin of biological diversity” (ITN-2008–213780 SPECIATION), grants from the Academy of Finland to A.H. (project 132619) and M.K. (projects 268214 and 272927), a grant from NERC, UK to M.G.R. (grant NE/J020818/1), and NERC, UK PhD studentship to D.J.P. (NE/I528634/1).For many organisms the ability to cold acclimate with the onset of seasonal cold has major implications for their fitness. In insects, where this ability is widespread, the physiological changes associated with increased cold tolerance have been well studied. Despite this, little work has been done to trace changes in gene expression during cold acclimation that lead to an increase in cold tolerance. We used an RNA-Seq approach to investigate this in two species of the Drosophila virilis group. We found that the majority of genes that are differentially expressed during cold acclimation differ between the two species. Despite this, the biological processes associated with the differentially expressed genes were broadly similar in the two species. These included: metabolism, cell membrane composition, and circadian rhythms, which are largely consistent with previous work on cold acclimation/cold tolerance. In addition, we also found evidence of the involvement of the rhodopsin pathway in cold acclimation, a pathway that has been recently linked to thermotaxis. Interestingly, we found no evidence of differential expression of stress genes implying that long-term cold acclimation and short-term stress response may have a different physiological basis.PostprintPeer reviewe

Acoustic signals in the sand fly Lutzomyia (Nyssomyia) intermedia (Diptera: Psychodidae)

<p>Abstract</p> <p>Background</p> <p>Acoustic signals are part of the courtship of many insects and they often act as species-specific signals that are important in the reproductive isolation of closely related species. Here we report the courtship songs of the sand fly <it>Lutzomyia (Nyssomyia) intermedia</it>, one of the main vectors of cutaneous leishmaniasis in Brazil.</p> <p>Findings</p> <p>Recordings were performed using insects from three localities from Eastern Brazil: Posse and Jacarepaguá in Rio de Janeiro State and Corte de Pedra in Bahia State. The three areas have remnants of the Brazilian Atlantic forest, they are endemic for cutaneous leishmaniasis and <it>L. intermedia </it>is the predominant sand fly species. We observed that during courtship <it>L. intermedia </it>males from all populations produced pulse songs consisting of short trains. No significant differences in song parameters were observed between the males of the three localities.</p> <p>Conclusions</p> <p><it>L. intermedia </it>males produce acoustic signals as reported for some other sand flies such as the sibling species of the <it>Lutzomyia longipalpis </it>complex. The lack of differences between the males from the three localities is consistent with previous molecular studies of the <it>period </it>gene carried out in the same populations, reinforcing the idea that <it>L. intermedia </it>is not a species complex in the studied areas and that the three populations are likely to have similar vectorial capacities.</p

Variation in the Male Pheromones and Mating Success of Wild Caught Drosophila melanogaster

Drosophila melanogaster males express two primary cuticular hydrocarbons (male-predominant hydrocarbons). These act as sex pheromones by influencing female receptivity to mating. The relative quantities of these hydrocarbons vary widely among natural populations and can contribute to variation in mating success. We tested four isofemale lines collected from a wild population to assess the effect of intrapopulation variation in male-predominant hydrocarbons on mating success. The receptivity of laboratory females to males of the four wild-caught lines varied significantly, but not consistently in the direction predicted by variation in male-predominant hydrocarbons. Receptivity of the wild-caught females to laboratory males also varied significantly, but females from lines with male-predominant hydrocarbon profiles closer to a more cosmopolitan one did not show a correspondingly strong mating bias toward a cosmopolitan male. Among wild-caught lines, the male-specific ejaculatory bulb lipid, cis-vaccenyl acetate, varied more than two-fold, but was not associated with variation in male mating success. We observed a strong inverse relationship between the receptivity of wild-caught females and the mating success of males from their own lines, when tested with laboratory flies of the opposite sex

Both male and female identity influence variation in male signalling effort

<p>Abstract</p> <p>Background</p> <p>Male sexual displays play an important role in sexual selection by affecting reproductive success. However, for such displays to be useful for female mate choice, courtship should vary more among than within individual males. In this regard, a potentially important source of within male variation is adjustment of male courtship effort in response to female traits. Accordingly, we set out to dissect sources of variation in male courtship effort in a fish, the desert goby (<it>Chlamydogobius eremius</it>). We did so by designing an experiment that allowed simultaneous estimation of within and between male variation in courtship, while also assessing the importance of the males and females as sources of courtship variation.</p> <p>Results</p> <p>Although males adjusted their courtship depending on the identity of the female (a potentially important source of within-male variation), among-male differences were considerably greater. In addition, male courtship effort towards a pair of females was highly repeatable over a short time frame.</p> <p>Conclusion</p> <p>Despite the plasticity in male courtship effort, courtship displays had the potential to reliably convey information about the male to mate-searching females. Our experiment therefore underscores the importance of addressing the different sources contributing to variation in the expression of sexually-selected traits.</p

Molecular and Behavioral Differentiation among Brazilian Populations of Lutzomyia longipalpis (Diptera: Psychodidae: Phlebotominae)

Lutzomyia longipalpis is the main vector of visceral leishmaniasis in the Americas. There is strong evidence that L. longipalpis is a species complex, but there is still no consensus regarding the number of species occurring in Brazil. We combined molecular and behavioral analyses of a number of L. longipalpis populations in order to help clarify this question. This approach has allowed us to identify two main groups of populations in Brazil. One group probably represents a single species distributed mainly throughout the coastal regions of North and Northeast Brazil and whose males produce the same type of copulation song and pheromone. The second group is more heterogeneous, probably represented by a number of incipient species with different levels of genetic divergence among the siblings that produce different combinations of copulation songs and pheromones. The high level of complexity observed raises important questions concerning the epidemiological consequences of this incipient speciation process