Evolution of male genitalia: environmental and genetic factors affect genital morphology in two Drosophila sibling species and their hybrids

<p>Abstract</p> <p>Background</p> <p>The rapid evolution of genital morphology is a fascinating feature that accompanies many speciation events. However, the underlying patterns and explanatory processes remain to be settled. In this work we investigate the patterns of intraspecific variation and interspecific divergence in male genitalic morphology (size and shape) in the cactophilic sibling species <it>Drosophila buzzatii </it>and <it>D. koepferae</it>. Genital morphology in interspecific hybrids was examined and compared to the corresponding parental lines.</p> <p>Results</p> <p>Despite of being siblings, <it>D. buzzatii </it>and <it>D. koepferae </it>showed contrasting patterns of genital morphological variation. Though genitalic size and shape variation have a significant genetic component in both species, shape varied across host cacti only in <it>D. buzzatii</it>. Such plastic expression of genital shape is the first evidence of the effect of rearing substrate on genitalic morphology in <it>Drosophila</it>. Hybrid genital morphology was not intermediate between parental species and the morphological resemblance to parental strains was cross-dependent.</p> <p>Conclusion</p> <p>Our results suggest the evolution of different developmental networks after interspecific divergence and the existence of a complex genetic architecture, involving genetic factors with major effects affecting genital morphology.</p

Geographic Patterns of Inversion Polymorphism in the Second Chromosome of the Cactophilic Drosophila buzzatii from Northeastern Argentina

The inversion polymorphisms of the cactophilic Drosophila buzzatti Patterson and Wheeler (Diptera: Drosophilidae) were studied in new areas of its distribution in Argentina. A total of thirty-eight natural populations, including 29 from previous studies, were analyzed using multiple regression analyses. The results showed that about 23% of total variation was accounted for by a multiple regression model in which only altitude contributed significantly to population variation, despite the fact that latitude and longitude were also included in the model. Also, inversion frequencies exhibited significant associations with mean annual temperature, precipitation, and atmospheric pressure. In addition, expected heterozygosity exhibited a negative association with temperature and precipitation and a positive association with atmospheric pressure. The close similarity of the patterns detected in this larger dataset to previous reports is an indication of the stability of the clines. Also, the concurrence of the clines detected in Argentina with those reported for colonizing populations of Australia suggests the involvement of natural selection as the main mechanism shaping inversion frequencies in D. buzzatii

Stage-Specific Effects of Candidate Heterochronic Genes on Variation in Developmental Time along an Altitudinal Cline of Drosophila melanogaster

Background: Previously, we have shown there is clinal variation for egg-to-adult developmental time along geographic gradients in Drosophila melanogaster. Further, we also have identified mutations in genes involved in metabolic and neurogenic pathways that affect development time (heterochronic genes). However, we do not know whether these loci affect variation in developmental time in natural populations. Methodology/Principal Findings: Here, we constructed second chromosome substitution lines from natural populations of Drosophila melanogaster from an altitudinal cline, and measured egg-adult development time for each line. We found not only a large amount of genetic variation for developmental time, but also positive associations of the development time with thermal amplitude and altitude. We performed genetic complementation tests using substitution lines with the longest and shortest developmental times and heterochronic mutations. We identified segregating variation for neurogenic and metabolic genes that largely affected the duration of the larval stages but had no impact on the timing of metamorphosis. Conclusions/Significance: Altitudinal clinal variation in developmental time for natural chromosome substitution lines provides a unique opportunity to dissect the response of heterochronic genes to environmental gradients. Ontogenetic stage-specific variation in invected, mastermind, cricklet and CG14591 may affect natural variation in development time an

Identifying candidate genes affecting developmental time in Drosophila melanogaster: pervasive pleiotropy and gene-by-environment interaction

<p>Abstract</p> <p>Background</p> <p>Understanding the genetic architecture of ecologically relevant adaptive traits requires the contribution of developmental and evolutionary biology. The time to reach the age of reproduction is a complex life history trait commonly known as developmental time. In particular, in holometabolous insects that occupy ephemeral habitats, like fruit flies, the impact of developmental time on fitness is further exaggerated. The present work is one of the first systematic studies of the genetic basis of developmental time, in which we also evaluate the impact of environmental variation on the expression of the trait.</p> <p>Results</p> <p>We analyzed 179 co-isogenic single <it>P[GT1]-</it>element insertion lines of <it>Drosophila melanogaster </it>to identify novel genes affecting developmental time in flies reared at 25°C. Sixty percent of the lines showed a heterochronic phenotype, suggesting that a large number of genes affect this trait. Mutant lines for the genes <it>Merlin </it>and <it>Karl </it>showed the most extreme phenotypes exhibiting a developmental time reduction and increase, respectively, of over 2 days and 4 days relative to the control (a co-isogenic <it>P</it>-element insertion free line). In addition, a subset of 42 lines selected at random from the initial set of 179 lines was screened at 17°C. Interestingly, the gene-by-environment interaction accounted for 52% of total phenotypic variance. Plastic reaction norms were found for a large number of developmental time candidate genes.</p> <p>Conclusion</p> <p>We identified components of several integrated time-dependent pathways affecting egg-to-adult developmental time in <it>Drosophila</it>. At the same time, we also show that many heterochronic phenotypes may arise from changes in genes involved in several developmental mechanisms that do not explicitly control the timing of specific events. We also demonstrate that many developmental time genes have pleiotropic effects on several adult traits and that the action of most of them is sensitive to temperature during development. Taken together, our results stress the need to take into account the effect of environmental variation and the dynamics of gene interactions on the genetic architecture of this complex life-history trait.</p

Phenotypic plasticity for Drosophila melanogaster (Diptera: Drosophilidae) larval olfactory behaviour in response to whole fruit olfactory stimuli Plasticidad fenotípica para el comportamiento olfativo larval de Drosophila melanogaster (Diptera: Drosophilidae) como respuesta a estímulos olfativos de frutos enteros

Drosophila melanogaster Meigen 1830 (Diptera: Drosophilidae) is the quintessential insect model organism. However, with a few exceptions, ecological features of this species have been poorly investigated. In the present work we describe a behavioural assay to quantify olfactory behaviour of D. melanogaster larvae in response to complex olfactory stimuli that are present in the natural environments, i. e.: rotten fruits that act as hosts in nature. Results obtained using this assay reveal that there is intra-population genetic variation and phenotypic plasticity for the character in a natural population from west-central Argentina.Drosophila melanogaster Meigen 1830 (Diptera: Drosophilidae) es el organismo modelo por excelencia en insectos. Sin embargo, salvo algunas excepciones, los aspectos ecológicos de esta especie han sido poco estudiados. En el presente trabajo, se describe un ensayo comportamental para cuantificar la conducta olfativa de larvas de D. melanogaster en respuesta a estímulos olfativos complejos que se encuentran en los ambientes naturales, i. e.: frutos en descomposición que son hospedadores en la naturaleza. Los resultados obtenidos, utilizando este ensayo, revelaron que existe variabilidad genética intra-poblacional y plasticidad fenotípica para el carácter en una población natural del centro oeste de Argentina

Phenotypic plasticity for Drosophila melanogaster (Diptera: Drosophilidae) larval olfactory behaviour in response to whole fruit olfactory stimuli

Drosophila melanogaster Meigen 1830 (Diptera: Drosophilidae) es el organismo modelo por excelencia en insectos. Sin embargo, salvo algunas excepciones, los aspectos ecológicos de esta especie han sido poco estudiados. En el presente trabajo, se describe un ensayo comportamental para cuantificar la conducta olfativa de larvas de D. melanogaster en respuesta a estímulos olfativos complejos que se encuentran en los ambientes naturales, i. e.: frutos en descomposición que son hospedadores en la naturaleza. Los resultados obtenidos, utilizando este ensayo, revelaron que existe variabilidad genética intra-poblacional y plasticidad fenotípica para el carácter en una población natural del centro oeste de Argentina

Genetic variation in heat-stress tolerance among South American Drosophila populations

Spatial or temporal differences in environmental variables, such as temperature, are ubiquitous in nature and impose stress on organisms. This is especially true for organisms that are isothermal with the environment, such as insects. Understanding the means by which insects respond to temperature and how they will react to novel changes in environmental temperature is important for understanding the adaptive capacity of populations and to predict future trajectories of evolutionary change. The organismal response to heat has been identified as an important environmental variable for insects that can dramatically influence life history characters and geographic range. In the current study we surveyed the amount of variation in heat tolerance among Drosophila melanogaster populations collected at diverse sites along a latitudinal gradient in Argentina (24°-38°S). This is the first study to quantify heat tolerance in South American populations and our work demonstrates that most of the populations surveyed have abundant within-population phenotypic variation, while still exhibiting significant variation among populations. The one exception was the most heat tolerant population that comes from a climate exhibiting the warmest annual mean temperature. All together our results suggest there is abundant genetic variation for heat-tolerance phenotypes within and among natural populations of Drosophila and this variation has likely been shaped by environmental temperature.Fil: Fallis, Lindsey C.. Kansas State University; Estados UnidosFil: Fanara, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ecología, Genética y Evolución; ArgentinaFil: Morgan, Theodore J.. Kansas State University; Estados Unido

Developmental thermal plasticity among Drosophila melanogaster populations

Many biotic and abiotic variables influence the dispersal and distribution of organisms. Temperature has a major role in determining these patterns because it changes daily, seasonally and spatially, and these fluctuations have a significant impact on an organism's behaviour and fitness. Most ecologically relevant phenotypes that are adaptive are also complex and thus they are influenced by many underlying loci that interact with the environment. In this study, we quantified the degree of thermal phenotypic plasticity within and among populations by measuring chill-coma recovery times of lines reared from egg to adult at two different environmental temperatures. We used sixty genotypes from six natural populations of Drosophila melanogaster sampled along a latitudinal gradient in South America. We found significant variation in thermal plasticity both within and among populations. All populations exhibit a cold acclimation response, with flies reared at lower temperatures having increased resistance to cold. We tested a series of environmental parameters against the variation in population mean thermal plasticity and discovered the mean thermal plasticity was significantly correlated with altitude of origin of the population. Pairing our data with previous experiments on viability fitness assays in the same populations in fixed and variable environments suggests an adaptive role of this thermal plasticity in variable laboratory environments. Altogether, these data demonstrate abundant variation in adaptive thermal plasticity within and among populations.Fil: Fallis, L. C.. Kansas State University; Estados UnidosFil: Fanara, Juan Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Ecología, Genética y Evolución de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Ecología, Genética y Evolución de Buenos Aires; ArgentinaFil: Morgan, T. J.. Kansas State University; Estados Unido

Geographic distribution and hosts of Zaprionus indianus (Diptera: Drosophilidae) in North-Eastern Argentina Distribución geográfica y hospedadores de Zaprionus indianus (Diptera: Drosophilidae) en el noreste de Argentina

The first published record of the African drosophilid Zaprionus indianus Gupta 1970 in the Americas refers to individuals observed on fallen persimmon (Diospyros kaki Linnaei, «caqui») fruits in São Paulo city (Brazil) in March 1999. Since that date, this species colonized altered and natural environments across the continent. In the present work we report new records for Z. indianus in north eastern Argentina. Moreover, our results showed that this species represents a fairly high proportion among collected drosophilids in some sampling sites. Our survey also revealed that this invading species has the ability to breed and feed in a wide range of native and cultivated host-plants.El primer registro publicado de la especie africana Zaprionus indianus Gupta 1970 en el continente Americano se refiere a individuos observados en frutos caídos de «caqui» (Diospyros kaki Linnaei) en la ciudad de São Paulo, (Brasil) en Marzo de 1999. Desde esa fecha, esta especie ha colonizado ambientes naturales y perturbados en todo el continente. En el presente trabajo, confirmamos la presencia de Z. indianus en el noreste de Argentina y mostramos que, en algunas localidades, representa una alta proporción entre las especies de drosofílidos colectados. Nuestra investigación reveló que esta especie invasora es capaz de criarse y alimentarse en un amplio rango de plantas hospedadoras tanto nativas como cultivadas