The Calibrated Phylogeny of the Drosophila fasciola Subgroup (D. repleta Group Wasserman) Indicates Neogene Diversification of Its Internal Branches.

The species of the Drosophila fasciola subgroup Wasserman represent the dominant section of the Drosophila repleta group Wasserman in the American rainforests and have a broad geographical distribution in the New World. However, despite of its wide range, the D. fasciola subgroup is one of the most overlooked D. repleta subgroups. Here, we report a molecular phylogenetic analysis focused on the D. fasciola subgroup using two mitochondrial [cytochrome oxidase subunit I (COI), cytochrome oxidase subunit II (COII)] and two nuclear [elongation factor-1alpha F1 (EF-alphaF1) and transformer (tra)] genes. Overall, we found that this subgroup is a monophyletic taxon, subdivided into two main internal branches: named Fas1 and Fas2 clades. The diversification of these clades is estimated to have begun in the middle Miocene, around 12 Ma [95% high posterior density (HPD) 9.0-15 Ma], and might be associated with the colonization of South America by Central America populations after the closure of Isthmus of Panama due to the temporal congruence between these events. The terminal branches had their origins estimated to be in the Pliocene or the Plio-Pleistocene transition. For the later estimates, both the geomorphological influences and the climatic oscillations of the Pleistocene may have played a role in shaping the diversification of the D. fasciola group.

Contrasting patterns of within-species morphological variation in two cactophilic Drosophila species (Diptera: Drosophilidae).

In this work, we investigated the morphological variation of the intromittent male copulatory organ (aedeagus) of specimens from natural populations of two cactophilic Drosophila species distributed in the southeast region of Brazil, Drosophila gouveai Tidon-Sklorz & Sene and Drosophila antonietae Tidon-Sklorz & Sene. It was explored how the within-species variability is arranged for both species, considering their historical and ecological features. Our results showed two distinct aedeagal morphologies for these species, and differences within species were observed only in D. gouveai as specimens could be distinguished by their population origin. In contrast, after size discrepancies correction, this feature was not detected in D. antonietae. The contrasting patterns of intraspecific variation, together with the other features exhibited by these two species, are most likely to be explained by differences in the historical host plant association and distribution and in demographic events, which determined the evolutionary history of these two South American cactophilic Drosophila species.

The Drosophila community in xerophytic vegetations of the upper Parana-Paraguay river basin.

The genus Drosophila is the most abundant in the Drosophilidae family. Some species are endemic to certain regions and others are cosmopolitans. In Brazil, there are several ecosystems to explore regarding the composition and ecological aspects of Drosophila. Xerophytic areas are an example. They can be found in the South and Southeast of Brazil as islands, a result of paleoclimatic cycle changes. The aim of the present work is to provide information about the composition of the Drosophila community in eight xerophytic areas (where the cactus Cereus hildmaniannus occurs) in the South and Southeast of Brazil. This work is an important step in the study of quantitative ecological aspects of the Drosophila community in xerophytic areas that form continental islands in the Neotropical region. The composition of the Drosophila community which was found is compatible with previous work in several aspects. The ecological indexes showed a possible positive association between diversity and the degree of preservation of the studied areas. São Paulo state communities presented the highest similarity among the sites tested, although no statistical significant correlation between the Jaccard index and geographical distance was found using the Mantel test.

The Drosophila community in xerophytic vegetations of the upper Parana-Paraguay river basin

O gênero Drosophila é o mais abundante da família Drosophilidae. Algumas espécies são endêmicas em certas regiões e outras são cosmopolitas. No Brasil existem diversos ecossistemas a serem explorados a respeito da composição e aspectos ecológicos de Drosophila. Áreas xerofíticas são um exemplo, podendo ser consideradas como ilhas continentais no sul e sudeste do Brasil, resultado de mudanças paleoclimáticas cíclicas. O presente trabalho teve o objetivo de fornecer informação sobre a composição da comunidade de Drosophila em oito áreas xerofíticas (onde o cacto Cereus hildmaniannus ocorre) no sul e sudeste do Brasil. Este trabalho é um passo importante no estudo de aspectos ecológicos quantitativos das comunidades de Drosophila em ilhas de vegetação xerofítica na região Neotropical. De modo geral, a composição das comunidades de Drosophila está de acordo com trabalhos anteriores em diversos aspectos. Os índices ecológicos mostraram uma possível associação positiva da diversidade e o grau de preservação das áreas. As comunidades do estado de São Paulo apresentaram as maiores similaridades entre elas, apesar de não ter sido encontrada correlação estatisticamente significativa entre o índice de Jaccard e distâncias geográficas entre as comunidades, através do teste de Mantel.

Preliminary notes on yeasts associated with necrotic cactus stems from different localities in Brazil.

The yeast species found in necrotic stems of three columnar cacti (Pilosocereus machrisii, Pilosocereus vilaboensis, and Praecereus euchlorus) at eight localities in Brazil were described and a similarity analysis using Sorensen distances was used to compare the composition of yeast species at these localities. Of 56 necrotic cactus stems sampled, 32 produced yeast colonies. Ten species of yeast or yeast-like microorganisms were identified from 53 isolates, with Pichia cactophila, Candida sonorensis, Geotrichum sp., and Sporopachydermia cereana being the most common. The remaining species occurred in low proportions in the cacti surveyed. The similarity analysis provided a dendogram (UPGMA) that clustered the yeast communities from different cactus species and indicated that host cactus species was unimportant in this clustering.

Preliminary notes on yeasts associated with necrotic cactus stems from different localities in Brazil

As leveduras encontradas em cladódios necrosados de três cactos colunares (Pilosocereus machrisii, Pilosocereus vilaboensis and Praecereus euchlorus) em oito localidades no Brasil foram identificadas e uma análise de similaridade baseada na distância Sorensen foi usada para comparar as comunidades nas diferentes localidades. Dos 56 cladódios necrosados amostrados, 32 produziram colônias de leveduras. Dez espécies de leveduras foram identificadas a partir de 53 isolados, com as espécies Pichia cactophila, Candida sonorensis, Geotrichum sp. e Sporopachydermia cereana sendo as mais comuns. As espécies restantes ocorreram em baixas freqüências. O dendograma (UPGMA) construído a partir da análise de similaridade agrupou comunidades de leveduras obtidas em diferentes espécies de cactos e indicou que as espécies de cactos hospedeiros não foram determinantes nesse agrupamento.

Wing shape heritability and morphological divergence of the sibling species Drosophila mercatorum and Drosophila paranaensis.

The fruit-flies Drosophila paranaensis and Drosophila mercatorum pararepleta are sibling species belonging to the repleta group. Females of these two species are normally considered to be morphologically indistinguishable while males only differ consistently in the morphology of their genitalia. These species are sympatric throughout a large area of their geographic distribution. In this study, we investigated the degree of morphological divergence between D. paranaensis and D. mercatorum pararepleta based on morphometric analysis of their wings. The ellipse method was used to describe the placement of the longitudinal and transversal wing veins as well as the size of the wing and the shape of its outline. The heritability under laboratory and field conditions was also estimated from the parameters generated. Multivariate analysis showed that wing morphology possessed sufficient differences to discriminate between the two species with a successful classification rate of 95-98% for females and 82-87% for males. The results of the autoclassification were confirmed by a cross-validation test for females (92-96%). Most measurements possessed significant natural heritability (a mean of 0.48 for D. mercatorum and 0.88 for D. paranaensis), indicating that the variation observed was related to differences in genes acting additively. The principal difference between the two species was in the placement of the posterior transverse wing vein. However, the pattern of morphological variation in the wings of both species was similar, possibly because of shared restrictions in wing development pathways.

Temporal and spatial allozyme variation in the South American cactophilic Drosophila antonietae (Diptera; Drosophilidae).

Drosophila antonietae is an endemic South American cactophilic species that uses Cereus hildmaniannus rotting cladodes as breeding sites. We assessed temporal and spatial intrapopulational allozyme variation of two natural populations. Our results suggest that environmental variation (rain precipitation) is probably influencing allozyme temporal variation. Moreover, it seems that D. antonietae does not have intrapopulation structure and has N(ev) (variance effective size) approximately equal to 83 and N(ec) (number of adult flies that colonize each rotting cladode) = 21. The deficiency of heterozygotes found must be due to null alleles, a temporal Wahlund effect, or selection against heterozygotes. Assortative mating and inbreeding are discarded. This is the first report on allozyme variation in D. antonietae. It gives some insight on intrapopulational genetics through space and time for this species. This is important to understand its general genetic variability and will be essential to future works on the natural history and evolution of this species.

Relationships between necrotic cactus availability and population size in a cactophilic Drosophila (Diptera, Drosophilidae) located on a sandstone table hill in Brazil

Drosophila gouveai is a cactophilic species endemic to South America. In southeast Brazil it is found on summits of isolated hills, which apparently are current refugia resulting from climatic changes during the Quaternary Period. It breeds only in necrotic cactus cladodes of Pilosocereus machrisii. Temporal differences in necrotic cactus availability could have a great impact upon D. gouveai population size, and could thus influence its evolutionary history. We analyzed the relationship between necrotic cactus availability and population size of D. gouveai. The fluctuation in the population size, variation in necrotic cactus availability and exploitation of this resource by larvae were surveyed bimonthly for one year on a sandstone table hill in central-south Brazil. Temporal necrotic cactus availability did not vary significantly, though in June there was a moderate decrease Larval populations were highest in October and December. The D. gouveai population size was highest in February and remained relatively stable the rest of the year. The observed fluctuation in population size was not a function of temporal necrotic cactus availability in quantitative terms.

Relationships between necrotic cactus availability and population size in a cactophilic Drosophila (Diptera, Drosophilidae) located on a sandstone table hill in Brazil.

Drosophila gouveai is a cactophilic species endemic to South America. In southeast Brazil it is found on summits of isolated hills, which apparently are current refugia resulting from climatic changes during the Quaternary Period. It breeds only in necrotic cactus cladodes of Pilosocereus machrisii. Temporal differences in necrotic cactus availability could have a great impact upon D. gouveai population size, and could thus influence its evolutionary history. We analyzed the relationship between necrotic cactus availability and population size of D. gouveai. The fluctuation in the population size, variation in necrotic cactus availability and exploitation of this resource by larvae were surveyed bimonthly for one year on a sandstone table hill in central-south Brazil. Temporal necrotic cactus availability did not vary significantly, though in June there was a moderate decrease Larval populations were highest in October and December. The D. gouveai population size was highest in February and remained relatively stable the rest of the year. The observed fluctuation in population size was not a function of temporal necrotic cactus availability in quantitative terms.

Characterization of courtship sounds of species of the subgroup fasciola (Diptera, Drosophilidae, Drosophila repleta group): interspecific and interpopulational analyses

The aim of this work was to characterize the male courtship song pattern of various species of the fasciola subgroup and to determine the level of variation both within and among species. The parameters analyzed were intrapulse interval (PI), interpulse interval (IPI), and intrapulse frequency (IF). Six different species were analyzed: D. coroica (three populations), D. ellisoni, D. fascioloides, D. moju, D. onca, and D. rosinae (one population each). There were significant differences among the six species for these three courtship song parameters. The IPI was the most variable parameter among these species, suggesting that this parameter is important for female discrimination. Four different hypotheses could explain this variation: 1. different selection pressures with absence of flow gene; 2. intraspecific sexual selection; 3. sympatric effects on song evolution; and 4. genetic drift. The PI was the only parameter that was significantly different among the three population of D. coroica. Low variability among populations within the same species was already observed for other subgroups and could be explained by the following hypotheses: strong selection acting on the song parameters, gene flow, or recent colonization from a common source. Additional studies of the courtship song of other species of the fasciola subgroup, as well as for other subgroups of the repleta group, and studies, using molecular makers, that focus on the genetic basis of the differences among these species in courtship song would allow us to evaluate the association of courtship song and sexual isolation in these species, and would also help us to understand the evolution of these behavioural differences

Characterization of courtship sounds of species of the subgroup fasciola (Diptera, Drosophilidae, Drosophila repleta group): interspecific and interpopulational analyses.

The aim of this work was to characterize the male courtship song pattern of various species of the fasciola subgroup and to determine the level of variation both within and among species. The parameters analyzed were intrapulse interval (PI), interpulse interval (IPI), and intrapulse frequency (IF). Six different species were analyzed: D. coroica (three populations), D. ellisoni, D. fascioloides, D. moju, D. onca, and D. rosinae (one population each). There were significant differences among the six species for these three courtship song parameters. The IPI was the most variable parameter among these species, suggesting that this parameter is important for female discrimination. Four different hypotheses could explain this variation: 1. different selection pressures with absence of flow gene; 2. intraspecific sexual selection; 3. sympatric effects on song evolution; and 4. genetic drift. The PI was the only parameter that was significantly different among the three population of D. coroica. Low variability among populations within the same species was already observed for other subgroups and could be explained by the following hypotheses: strong selection acting on the song parameters, gene flow, or recent colonization from a common source. Additional studies of the courtship song of other species of the fasciola subgroup, as well as for other subgroups of the repleta group, and studies, using molecular makers, that focus on the genetic basis of the differences among these species in courtship song would allow us to evaluate the association of courtship song and sexual isolation in these species, and would also help us to understand the evolution of these behavioural differences.

Low courtship song variation in south and southeastern Brazilian populations of Drosophila meridionalis (Diptera, Drosophilidae).

Drosophila meridionalis is a cactus-breeding species with a wide distribution in South America. Most populations of this species are geographically isolated, what provides a promising scenario for studying evolution. Former studies of this species revealed a remarkable karyotypic variation among its populations. Up to six distinct metaphase chromosomes were described, showing that this species is polymorphic at least at the chromosomal level. In order to elucidate the taxonomic status of populations showing different metaphase chromosomes, we analyzed the courtship song of five populations of D. meridionalis in South and Southeastern Brazil. In addition, we analyzed the metaphase chromosomes of each population. Our results show that, despite the two karyotype observed, most courtship song parameters did not vary among the populations. Altogether, our results suggest that D. meridionalis from South and Southeastern Brazil represents one species with an inter-population chromosomal variability.

The Drosophila serido speciation puzzle: putting new pieces together.

The D. serido superspecies is a complex mosaic of populations distributed over a vast part of South America and showing various degrees of genetical divergence. We have analyzed its chromosomal constitution in 16 new localities of southeastern and southern Brazil. Both the metaphase and salivary gland chromosomes show a sharp split of these populations in two groups. Four populations, fixed for inversion 2e8 and showing the type I karyotype, represent the southwestern limit of D. serido type B, which inhabits the Cerrado in central-western Brazil. The remaining populations are homozygous for 2x7, an inversion also fixed in the Caatinga populations of northeastern Brazil. However, their karyotype, in those populations analyzed, belong to a different type (V) from that of the Caatinga populations. Populations in this second group are polymorphic for five inversions on chromosome 2 plus another on chromosome 5 and show considerable interpopulation differentiation. The breakpoints of chromosome 2 inversions are described and the inversion loops of several heterokaryotypes are presented. Biogeographical information suggests that there are clear ecological differences between the two groups of populations as well as among the populations within the second group. Thepossible role of host plants in promoting the genetic divergence among the D. serido populations is discussed.

Genetic variation in Hawaiian Drosophila. IV. Allozymic similarity between D. silvestris and D. heteroneura from the island of Hawaii.

The species are endemic to the newest island in the archipelago and are broadly sympatric. They are easily distinguished morphologically in both sexes. Using standard electrophoretic procedures, we have examined 25 loci encoding for structural proteins from 539 silvestris and 325 heteroneura collected at three widely-separated localities where the two species are sympatric. Pairwise comparisons within and between the species show the following coefficients of genetic identity (NEI'S I): within silvestris, 0.961 +/- 0.01; within heteroneura, 0.949 +/- 0.02; between silvestris and heteroneura, 0.939 +/- 0.01. Neither the differences within nor between the species are significant. There are no fixed allelic diffrences either within or between the species. At the three areas of sympatry, the species show gene frequency differences (P less than 0.05) at 9,11 and 13 loci respectively. This is not much different from the variation within either one of the species across the three localities. The two species have similar heterozygosity (H) levels (silvestris, 0.083; heteroneura, 0.089) and percent of polymorphic loci (both 0.37). It is suggested that despite their morphological divergence, these species are much more newly formed than classical sibling species. Significant allozymic differences may not have had time to accumulate.

Allozymic and chromosomal similarity in two Drosophila species.

D. setosimentum and ochrobasis are a pair of very close, partly sympatric species endemic to Hawaii island. Males of the two species differ strikingly in wing-pattern and there are altitudinal and breeding-site differences. Similarity indices have been calculated for both chromosomal (C) ald allozymic (A) variants. Within the main populations of each species both kinds of data give coefficients above 0.98. Interspecific comparison of the main populations shows 0.66 (C) and 0.79 (A). An isolated population of ochrobasis from Kohala Volcano (Ohu), when compared with setosimentum, shows 0.68 (C) and 0.98 (A). Chromosomes are thus much more sensitive than allozymes in distinguishing these species; the same is true in the case of D. silvestris and heteroneura from the same forests. These morphologically distinct species, when compared, show 0.96 (A). All four species appear to be very new in the historical sense. In one area, about 2% of wild-caught D. setosimentum/ochrobasis are interspecific hybrids although adequate samples indicate that the separate gene pools have not broken down. The specific names should be retained but the two entities are perhaps best described as quite advanced semispecies in which reproductive isolation in nature is now nearly complete.

Drosophila hybrids in nature: proof of gene exchange between sympatric species.

Genetic studies of two closely related endemic Hawaiian species show that in one area of sympatry about 2 percent of the naturally occurring individuals are hybrids. More than 20 times this many would be expected if the population consisted of a single panmictic unit. Despite hybridization, natural selection appears to maintain the essential integrity of each separate gene pool.