A new Neotropical species of spot-thoraxed Drosophila (Diptera, Drosophilidae)

Drosophila pauliceia sp. nov., a spot-thoraxed species closely related to Drosophila boraceia Vilela & Val, 2004, is described from flies collected in an urban remnant of the montane Atlantic Forest located at the Cidade Universitária "Armando de Salles Oliveira", São Paulo city, state of São Paulo, Brazil. The two forest-dwelling species can be externally distinguished mainly by having a different pattern of thoracic spots. A new group of spotted flies (peruensis group) is proposed to include them, in addition to Drosophila peruensis Wheeler, 1959, from Urubamba River, Peru, and Drosophila atalaia Vilela & Sene, 1982, from Brazil and Argentina. To facilitate comparisons, illustrations of the male and female terminalia of the new species and of some unpublished views of those of D. atalaia are included. Additionally, a new group of unspotted species (named caponei group) is proposed to include Drosophila caponei Pavan & Cunha, 1947 and D. neochracea Wheeler, 1959, both previously considered to be related to D. atalaia.

Drosophila pauliceia sp. nov., espécie com tórax pintado e muito semelhante à Drosophila boraceia Vilela & Val, 2004, é descrita a partir de exemplares procedentes de um fragmento urbano da Mata Atlântica de planalto, localizado na reserva da Cidade Universitßria "Armando de Salles Oliveira", cidade de São Paulo, estado de São Paulo, Brasil. As duas espécies podem ser separadas principalmente com base no padrão das pintas do tórax e, juntamente com Drosophila peruensis Wheeler, 1959 e Drosophila atalaia Vilela & Sene, 1982, são incluídas em um novo grupo proposto no presente artigo sob o nome peruensis. Além das ilustrações detalhadas das terminálias masculina e feminina da nova espécie, desenhos inéditos dessas estruturas foram preparados também para Drosophila atalaia. Adicionalmente é proposto o grupo caponei que inclui D. caponei Pavan & Cunha, 1947 e D. neochracea Wheeler, 1959, duas espécies com tórax não pintado embora previamente consideradas próximas à D. atalaia.

The costae presenting in high-temperature-induced vestigial wings of Drosophila: implications for anterior wing margin formation.

It has long been noted that high temperature produces great variation in wing forms of the vestigial mutant of Drosophila. Most of the wings have defects in the wing blade and partially formed wing margin, which are the result of autonomous cell death in the presumptive wing blade or costal region of the wing disc. The vestigial gene (vg) and the interaction of Vg protein with other gene products are well understood. With this biochemical knowledge, reinvestigations of the high-temperature-induced vestigial wings and the elucidation of the molecular mechanism underlying the large-scale variation of the wing forms may provide insight into further understanding of development of the wing of Drosophila. As a first step of such explorations, I examined high-temperature-induced (29 degrees C) vestigial wings. In the first part of this paper, I provide evidences to show that the proximal and distal costae in these wings exhibit regular and continuous variation, which suggests different developmental processes for the proximal and distal costal sections. Judging by the costae presenting in the anterior wing margin, I propose that the proximal and distal costal sections are independent growth units. The genes that regulate formation of the distal costal section also strongly affect proliferation of cells nearby; however, the same phenomenon has not been found in the proximal costal section. The distal costal section seems to be an extension of the radius vein. vestigial, one of the most intensely researched temperature-sensitive mutations, is a good candidate for the study of marginal vein formation. In the second part of the paper, I regroup the wing forms of these wings, chiefly by comparison of venation among these wings, and try to elucidate the variation of the wing forms according to the results of previous work and the conclusions reached in the first part of this paper, and provide clues for further researches.

Curvature measurement as a tool for the analysis of morphometric variation using Drosophila wings as a model

This article describes the use of geometric measurements of continuous, discrete parameters to studymorphometric variation in the wing cells of two sibling species, Drosophila mercatorum and Drosophilaparanaensis. To validate the results, the same wing samples were also analyzed using truss networks andpartial warps, in addition to a comparison with the ellipse method. The use of discriminative measurementsin conjunction with a Bayesian-based classification method yielded a relatively high number of correctclassifications for new individuals. These results compared favorably with those obtained using trussnetworks, partial warps and the ellipse method. These findings indicate that continuous curvature and arclength measurements may be useful parameters for the morphometric analysis of insect wings and possiblyother biological structures and shapes.

Aedeagus morphology as a discriminant marker in two closely related Cactophilic species of Drosophila (Diptera; Drosophilidae) in South America

Drosophila serido e D. antonietae são espécies crípticas pertencentes ao ''cluster'' Drosophila buzzatii. Morfologicamente, elas podem ser discriminadas apenas por diferenças quantitativas. Neste trabalho, nós analisamos o comprimento e a média da curvatura equalizada de quatro regiões do edeago de indivíduos de D. antonietae e D. serido. Os espécimes de D. serido e D. antonietae foram discriminados com 96,74% de eficiência. Apenas com base na variável que mais contribuiu para discriminação dos grupos (média da curvatura equalizada do arco IV do edeago), nós observamos significativa divergência morfológica intraespecífica em D. serido em relação a D. antonietae, o que está em concordância com outros marcadores. A alta divergência morfológica apenas na média da curvatura equalizada do arco IV do edeago mostra que essa região do edeago evoluiu mais rápido que as demais desde a divergência entre as duas espécies. A importância do presente estudo para o entendimento das bases genética que controlam a formação do edeago, nas espécies do ''cluster'' Drosophila buzzatii, é discutida.

Drosophila angustibucca Duda sensu Frota-Pessoa is an undescribed species (Diptera, Drosophilidae)

Drosophila angustibucca Duda sensu Frota-Pessoa é uma espécie ainda não descrita (Diptera, Drosophilidae). Uma nova espécie sul-americana de Drosophila, incluída no subgrupo I do grupo tripunctata e identificada incorretamente nos últimos 50 anos como sendo a espécie costarriquenha Drosophila angustibucca (sensu Frota-Pessoa, 1954; non Duda, 1925), é descrita no presente artigo sob o binômio Drosophila nappae sp. nov. Os espécimens-tipo foram retirados de uma linhagem obtida a partir de várias fêmeas coletadas entre julho de 1994 e abril de 1995 no Morro Santana, Porto Alegre (RS), Brasil. A descrição é acompanhada de ilustrações detalhadas das terminálias masculina e feminina.

Quantitative-genetic analysis of wing form and bilateral asymmetry in isochromosomal lines of Drosophila subobscura using Procrustes methods.

Fluctuating asymmetry (FA) is often used as a measure of underlying developmental instability (DI), motivated by the idea that morphological variance is maladaptive. Whether or not DI has evolutionary potential is a highly disputed topic, marred by methodological problems and fuzzy prejudices. We report here some results from an ongoing study of the effects of karyotype, homozygosity and temperature on wing form and bilateral asymmetry using isochromosomal lines of Drosophila subobscura. Our approach uses the recently developed methodologies in geometric morphometrics to analyse shape configurations of landmarks within the standard statistical framework employed in studies of bilateral asymmetries, and we have extended these methods to partition the individual variation and the variation in asymmetries into genetic and environmental causal components. The analyses revealed temperature-dependent expression of genetic variation for wing size and wing shape, directional asymmetry (DA) of wing size, increased asymmetries at suboptimal temperature, and a transition from FA to DA in males as a result of increase in the rearing temperature. No genetic variation was generally detected for FA in our samples, but these are preliminary results because no crosses between lines were carried out and, therefore, the contribution of dominance was not taken into account. In addition, only a subset of the standing genetic variation was represented in the experiments.

Body size and mating success in Drosophila willistoni are uncorrelated under laboratory conditions.

Mating activity and wing length were investigated in the F1; progeny of Drosophila willistoni females collected in the field to examine any possible relationship between body size and mating success. The flies were observed in a mating chamber under laboratory conditions. No significant differences in wing length were observed between copulating and noncopulating flies, and there was no significant correlation between wing length and copulation latency for both males and females. These results therefore suggest that the commonly accepted view that large body size is positively correlated with mating success in Drosophila does not always hold true. The results support the view that the extent of environmentally induced variation in body size may be an important factor in determining whether an association between body size and mating success is observed in Drosophila species.

Racial divergence in abdominal bristles among parental races and newly evolved cytoraces of nasuta-albomicans complex of Drosophila.

Cytoraces are the products of interracial hybridization between Drosophila nasuta nasuta and D. nasuta albomicans. These races differ from their parents in the chromosome composition, mating preference, certain fitness phenotypes and also a few morphophenotypic traits. Now, these cytoraces are passing through 330 generations. Racial divergence in the 4th and 5th abdominal bristles among the parental races and the newly evolved cytorace 1 and 2 is reported. The results revealed that the parental races have more number of bristles than newly evolved cytoraces. Thus, these cytoraces are evolved/evolving with reduced abdominal bristle number and better fitness.

Variability of morphological traits in Drosophila bipectinata complex.

Phenotypic or morphological differences among different populations and sexual dimorphism in certain metric traits were analysed in D. bipectinata complex. It was noticed that different populations of D. bipectinata species group harbour large amount of variation for these characters. In all the populations, morphometric characters such as lengths of femur, tibia and wing length, wing width, number of sternopleural bristles and bristles on epandrium varied significantly among populations. The study indicates that the morphological variations are due to the interplay of genetic and environmental endowments. Further, females had significantly larger values, for lengths of femur, tibia and wing length, wing width and sternopleural bristles.

Body size, mating success and advantage of large flies in Drosophila bipectinata species complex.

Mating success of large and small flies of Drosophila malerkotliana and D. bipectinata was studied using multiple, male and female choice methods. In multiple choice method the large male mated with large female and small male paired with small female. In female choice method, large male was successful in mating with female irrespective of its size while in male choice method, preferential mating occurred between large male and large female as well as small male and small female. The consequence of such non-random mating in the presence of male rivarly and preferential mating has been discussed.

Selection for high and low number of sternopleural bristles in Drosophila ananassae: correlated response in the frequency of chromosome inversions

Directional selection for high and low number of sternopleural bristles in Drosophila ananassae was applied for 13 generations. The selection produced a rapid divergence in the mean number of sternopleural bristles in the replicates high and low lines: i-high (H1 -25.75, H2 -25.69); ii-low (L1 -14.16 L2 -13.55); iii-control (17.21) lines in G13. Regression coefficients for the high and low lines were significantly different from zero. The realized heritability over thirteen generations was 21-23 for the high lines and 14-18 for the low lines. The results suggest that the number of sternopleural bristles in D. ananassae is under polygenic control, with a substantial amount of additive genetic variation. Flies of the base population had three chromosome inversions: AL (2L), ZE (2R) and DE (3L). The comparisons of chromosome arrangement between high and low lines (the G13 generation of selection) indicates significant changes in the inversion frequency during the course of selection, providing evidence for correlation between the bristle number and particular chromosome arrangements