Complex Coding and Regulatory Polymorphisms in a Restriction Factor Determine the Susceptibility of Drosophila to Viral Infection.

It is common to find that major-effect genes are an important cause of variation in susceptibility to infection. Here we have characterized natural variation in a gene called pastrel that explains over half of the genetic variance in susceptibility to the Drosophila C virus (DCV) in populations of Drosophila melanogaster We found extensive allelic heterogeneity, with a sample of seven alleles of pastrel from around the world conferring four phenotypically distinct levels of resistance. By modifying candidate SNPs in transgenic flies, we show that the largest effect is caused by an amino acid polymorphism that arose when an ancestral threonine was mutated to alanine, greatly increasing resistance to DCV. Overexpression of the ancestral, susceptible allele provides strong protection against DCV; indicating that this mutation acted to improve an existing restriction factor. The pastrel locus also contains complex structural variation and cis-regulatory polymorphisms altering gene expression. We find that higher expression of pastrel is associated with increased survival after DCV infection. To understand why this variation is maintained in populations, we investigated genetic variation surrounding the amino acid variant that is causing flies to be resistant. We found no evidence of natural selection causing either recent changes in allele frequency or geographical variation in frequency, suggesting that this is an old polymorphism that has been maintained at a stable frequency. Overall, our data demonstrate how complex genetic variation at a single locus can control susceptibility to a virulent natural pathogen

Recruitment Behavior During Foraging in the Neotropical Ant Gnamptogenys moelleri (Formicidae: Ponerinae): Does the Type of Food Matter?

Gnamptogenys moelleri nests in bromeliads and feeds on an array of food items, including dead and live animals, and nectar. Field data in Brazilian forests indicate that G. moelleri hunts solitarily, while retrieving is performed both by solitary workers for small items, or by a group of recruited workers for large items. This flexible foraging strategy was investigated in the laboratory through a series of experiments to assess the context in which recruitment is elicited. Three types of food were used: 50% honey solution, large insect prey, and cluster of small insects. For all food types the first encounter by a scout resulted in increased numbers of ants leaving the nest and finding the food in the arena. After finding liquid food or large prey, the forager returns to the nest and transmits information to nestmates about food location on the substrate. The successful scout repeatedly taps the sting on the ground, and recruited ants collectively retrieve the large insect to the nest. On the other hand, there is no transmission of information to nestmates about the location of small clumped prey, although the returning scout induces nestmates to leave the nest and hunt. Because foraging in G. moelleri is restricted mostly to the nest bromeliad, and small worker size (0.5 cm) precludes capturing large prey solitarily, recruitment behavior widens the spectrum of food items consumed by this ant species. Although recruitment behavior in ponerines has already been reported to vary with the type and size of a food source, this study also shows that the transmission of information about food location depends on the type of food found (large prey or liquid food versus cluster of small prey).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44946/1/10905_2004_Article_492406.pd

Ants Nesting on Cecropia purpurascens (Cecropiaceae) in Central Amazonia: Influence of Tree Height, Domatia Volume and Food Bodies

Patterns of presence of ant colonies on Cecropia purpurascens CC Berg (Cecropiaceae) were investigated in central Amazonia. All individuals of C. purpurascens along a 14.3 km transect were searched for ants and their height, internode volume, and number of trichilia were recorded. Of the 50 C. purpurascens individuals studied, 32 (64%) were colonized by ants of four species: Azteca alfari Emery (Dolichoderinae) (N = 16), Camponotus balzani Emery (Formicinae) (N = 14), C. abdominalis (Fabricius) (Formicinae) (N = 1) and Crematogaster brasiliensis Mayr (Myrmicinae) (N = 1). Probability of C. purpurascens being colonized by ants increases with tree height, internode volume, and trichilium number. Of the three variables recorded, tree height was the most important in determining the presence of ants. Trees colonized by the two most common ant species (A. alfari and C. balzani) did not differ in height, internode volume, or number of trichilia. The patterns observed, the association between the identity of the ants and plant fitness, as well as the usefulness of this particular system for future studies are discussed

The genetic architecture of resistance to virus infection in Drosophila.

Variation in susceptibility to infection has a substantial genetic component in natural populations, and it has been argued that selection by pathogens may result in it having a simpler genetic architecture than many other quantitative traits. This is important as models of host-pathogen co-evolution typically assume resistance is controlled by a small number of genes. Using the Drosophila melanogaster multiparent advanced intercross, we investigated the genetic architecture of resistance to two naturally occurring viruses, the sigma virus and DCV (Drosophila C virus). We found extensive genetic variation in resistance to both viruses. For DCV resistance, this variation is largely caused by two major-effect loci. Sigma virus resistance involves more genes - we mapped five loci, and together these explained less than half the genetic variance. Nonetheless, several of these had a large effect on resistance. Models of co-evolution typically assume strong epistatic interactions between polymorphisms controlling resistance, but we were only able to detect one locus that altered the effect of the main effect loci we had mapped. Most of the loci we mapped were probably at an intermediate frequency in natural populations. Overall, our results are consistent with major-effect genes commonly affecting susceptibility to infectious diseases, with DCV resistance being a near-Mendelian trait.European Research Council (Grant ID: DrosophilaInfection 281668), NERC (Grant ID: NE/L004232/1), São Paulo Research Foundation (FAPESP) (Grant IDs: 2015/08307-3, 2013/ 25991-0), Cambridge Commonwealth, European & International Trust, China Scholarship CouncilThis is the final version of the article. It first appeared from Wiley via http://dx.doi.org/10.1111/mec.1376

Addicted? Reduced host resistance in populations with defensive symbionts.

Heritable symbionts that protect their hosts from pathogens have been described in a wide range of insect species. By reducing the incidence or severity of infection, these symbionts have the potential to reduce the strength of selection on genes in the insect genome that increase resistance. Therefore, the presence of such symbionts may slow down the evolution of resistance. Here we investigated this idea by exposing Drosophila melanogaster populations to infection with the pathogenic Drosophila C virus (DCV) in the presence or absence of Wolbachia, a heritable symbiont of arthropods that confers protection against viruses. After nine generations of selection, we found that resistance to DCV had increased in all populations. However, in the presence of Wolbachia the resistant allele of pastrel-a gene that has a major effect on resistance to DCV-was at a lower frequency than in the symbiont-free populations. This finding suggests that defensive symbionts have the potential to hamper the evolution of insect resistance genes, potentially leading to a state of evolutionary addiction where the genetically susceptible insect host mostly relies on its symbiont to fight pathogens.Wellcome Trust (Grant ID: WT094664MA)This is the final version of the article. It first appeared from The Royal Society via https://doi.org/10.1098/rspb.2016.077

The causes and consequences of changes in virulence following pathogen host shifts.

Emerging infectious diseases are often the result of a host shift, where the pathogen originates from a different host species. Virulence--the harm a pathogen does to its host-can be extremely high following a host shift (for example Ebola, HIV, and SARs), while other host shifts may go undetected as they cause few symptoms in the new host. Here we examine how virulence varies across host species by carrying out a large cross infection experiment using 48 species of Drosophilidae and an RNA virus. Host shifts resulted in dramatic variation in virulence, with benign infections in some species and rapid death in others. The change in virulence was highly predictable from the host phylogeny, with hosts clustering together in distinct clades displaying high or low virulence. High levels of virulence are associated with high viral loads, and this may determine the transmission rate of the virus.BL and FMJ are supported by a NERC grant (NE/L004232/1), a European Research Council grant (281668, DrosophilaInfection), a Junior Research Fellowship from Christ’s College, Cambridge (BL) and a Royal Society University Research Fellowship (FMJ). JDH is supported by a Royal Society University Research Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.This is the final published version. It first appeared at http://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1004728

Varying Herbivore Population Structure Correlates with Lack of Local Adaptation in a Geographic Variable Plant-Herbivore Interaction

Local adaptation of parasites to their hosts due to coevolution is a central prediction of many theories in evolutionary biology. However, empirical studies looking for parasite local adaptation show great variation in outcomes, and the reasons for such variation are largely unknown. In a previous study, we showed adaptive differentiation in the arctiid moth Utetheisa ornatrix to its host plant, the pyrrolizidine alkaloid-bearing legume Crotalaria pallida, at the continental scale, but found no differentiation at the regional scale. In the present study, we sampled the same sites to investigate factors that may contribute to the lack of differentiation at the regional scale. We performed field observations that show that specialist and non-specialist polyphagous herbivore incidence varies among populations at both scales. With a series of common-garden experiments we show that some plant traits that may affect herbivory (pyrrolizidine alkaloids and extrafloral nectaries) vary at the regional scale, while other traits (trichomes and nitrogen content) just vary at the continental scale. These results, combined with our previous evidence for plant population differentiation based on larval performance on fresh fruits, suggest that U. ornatrix is subjected to divergent selection even at the regional scale. Finally, with a microsatellite study we investigated population structure of U. ornatrix. We found that population structure is not stable over time: we found population differentiation at the regional scale in the first year of sampling, but not in the second year. Unstable population structure of the herbivore is the most likely cause of the lack of regional adaptation

Frequência de fatores de risco cardiovascular em voluntários participantes de evento de educação em saúde

INTRODUÇÃO: As doenças cardiovasculares (DCV) constituem a principal causa de óbito no Brasil. OBJETIVO: Avaliar a frequência dos fatores de risco para DCV em indivíduos participantes de evento de educação em saúde na comunidade. MÉTODOS: Foram analisados retrospectivamente 428 formulários contendo informações clínicas e demográficas de voluntários participantes de evento em saúde, realizado em maio de 2006. Comparações entre proporções foram realizadas pelo teste do Qui quadrado e entre grupos pelo teste t de Student. As associações entre hipertensão arterial (HAS) e diabetes mellitus (DM) e variáveis clínicas foram avaliadas pelo modelo de regressão logística multivariado. O nível de significância adotado foi p30 Kg/m², 27,3% da casuística), a pressão arterial sistólica (133±16mmHg) e diastólica (84±11,5mmHg) e a glicemia casual (124±52,5mg/dl) foram maiores que nos não obesos (pINTRODUCTION: Cardiovascular diseases (CVD) are the main cause of death in Brazil. OBJECTIVE: To evaluate the frequency of CVD risk factors in a population attending a health education community event. METHODS. Retrospective study that included 428 completed forms with clinical and demographic information of volunteers attending a public event, in May, 2006. Data were expressed by means and standard deviation or proportions and compared by Student´s t test or Chi-square test. Associations between Arterial Hypertension (AH), Diabetes Mellitus (DM) and clinical variables were analyzed by multinomial logistic regression. Significance level was p 30 Kg/m2, 27.3% of the population), systolic blood pressure (133±16mmHg), diastolic blood pressure (84±11.5mmHg) and casual glycemia (124±52.5mg/dl) were higher when compared to non-obese (p<0.05). There was a significant association between obesity and dyslipidemia (p=0.04). Age and IMC were independently associated with AH and DM. CONCLUSION: The high frequency of modifiable cardiovascular risk factors in this population suggests the need for educational programs to promote primary prevention, mainly for the elderly and overweight

Coevolution at the population level: Empirical studies in an insect -plant interaction

Coevolution, the reciprocal evolutionary change in interacting species driven by natural selection, has an enormous importance on ecological and evolutionary theory. However, there are very few empirical studies demonstrating coevolution. In particular for plant-herbivore interactions, even though there are many adaptations that seem to be the result of the interaction, just a few empirical evidences on the processes leading to these adaptations exist. I used a highly integrative approach to study coevolution in an ideal plant-herbivore system: the alkaloid bearing legume Crotalaria pallida and its seed predator, the arctiid moth Utetheisa ornatrix. To unravel coevolutionary dynamics and to demonstrate reciprocal coevolutionary selection a through story of the specific interaction is necessary. In my dissertation I started to develop a through story of the coevolution between U. ornatrix and C. pallida. First, I investigated how the history of a host introduction may affect coevolutionary dynamics by showing that the native herbivore U. ornatrix has much higher fitness on the introduced host C. pallida than on a native congeneric C. incana. Second, I used a geographic approach to investigate patterns of local adaptation. I showed local adaptation of the moth to its host plant populations at a continental scale (populations from Brazil and Florida), but not at a local scale (populations ca. 150 Km apart). Third, I investigated how genetic differentiation among plant and moth populations may affect the patterns of local adaptation. I found genetic differences among populations in plant defense traits and moth differentiation on neutral microsatellite loci even at the local scale. Finally, because a thoroughly understanding of coevolutionary dynamics depends on a careful examination of the adaptations related to the interaction for both interacting species, I studied the counteradaptation of the moth to the host-plant defensive alkaloids. I combined chemical ecology techniques with extensive laboratory experiments to show that sequestration of alkaloids has no fitness costs. I discuss how these unexpected and novel results have many important implications to our understanding of coevolution

Ecologia do forrageamento e recrutamento na fomiga Gnamptogenys moelleri (Forel) (Ponerinae:Ectatommini)

Orientador: Paulo Sergio Moreira Carvalho de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: Este estudo fornece dados de campo sobre a história natural e o comportamento de forrageamento da formiga Neotropical Gnamptogenys moelleri (Ponerinae) em uma floresta de restinga do sudeste brasileiro. Essa formiga nidifica em diferentes espécies de bromélias e seus ninhos são mais freqüentemente encontrados em bromélias grandes. Gnamptogenys moelleri não apresentou um padrão claro no ritmo de atividade ao longo do dia, com notável variação entre diferentes colônias. A espécie utiliza uma ampla gama de invertebrados em sua dieta, incluindo algumas presas vivas e principalmente carcaças de invertebrados. Os itens alimentares utilizados apresentaram uma grande variação em tamanho. A procura pelo alimento foi sempre realizada por operárias solitárias. Entretanto, o transporte do alimento para o ninho foi realizado por operárias solitárias (itens pequenos), ou por um grupo de operárias recrutadas que carregaram o item grande em conjunto. Praticamente toda atividade de forrageamento de G. moelleri foi restrita à bromélia na qual a colônia nidifica. Comparando com a estação fria e seca, na estação quente e úmida mais formigas saíram para forragear, o sucesso no forrageamento foi maior e as forrageadoras caçaram a maiores distâncias do ninho. O oportunismo na utilização de sítios de nidificação e no comportamento de forrageamento, a pequena área de caça, bem como as variações sazonais na estratégia alimentar são discutidas e comparadas com outras formigas tropicaisAbstract: This study provides quantitative field data on the natural history and foraging behaviour of the Neotropical bromeliad-nesting ant Gnamptogenys moelleri (Ponerinae) in a sandy plain forest in Southeast Brazil. This ant nested on different bromeliad species and the nests were more frequent1y found in bigger bromeliads. Gnamptogenys moelleri did not have a c1ear pattem of activity rhythm along the day, with remarkable variation among colonies. The species used a wide array of invertebrates in its diet, hunting for live prey and scavenging the majority of items from dead animaIs. The food items varied greatIy in size. Hunting was aIways performed by solitary workers. Retrieving was performed by solitary workers (smalI items), or by a group of workers recruited to the food source (large items). Almost alI G. moelleri foraging activity was restricted to the nest bromeliad. In the warm period more ants Ieft the nest to forage, the percentage of successful foragers was higher, and foraging trips achieved greater distances compared to the cold season. The opportunism in nest site use and foraging behaviour, the smalI foraging area, as welI as the seasonal differences in foraging activity are discussed and compared with other tropical antsMestradoEcologiaMestre em Ecologi