RESUMO
The mesophragmatica group of Drosophila belongs to the virilis-repleta radiation of the Drosophila subgenus. This group comprises 13 Neotropical species that are endemic to the South-American continent and seem to be fundamentally Andean in their distribution. The mesophragmatica-group phylogeny has been inferred previously by other authors based on morphological, cytological, and isozyme analyses. However, the relationships within the group have not yet been completely resolved, although its monophyletic origin has already been confirmed by molecular data. This work attempts to enhance the molecular approach to the relationships among the species of the mesophragmatica group, using both nuclear and mitochondrial markers. Phylogenetic analyses were performed using fragments of the nuclear alcohol dehydrogenase (Adh; 631 bp), alpha-methyldopa (Amd; 1211 bp), dopa-decarboxylase (Ddc; 1105 bp), and hunchback (Hb; 687 bp) genes and the mitochondrial cytochrome oxidase subunit II (COII; 672 bp) gene, and included a total of 4306 bp. The sequences obtained for eight representatives of the mesophragmatica group were analyzed both individually and in combination by distance methods, maximum parsimony, and maximum likelihood. Our results support subdivision of the mesophragmatica group into three main lineages: the first is composed of D. viracochi; the second comprises a clade grouping the sibling species D. pavani and D. gaucha; and the third encompasses D. gasici, D. brncici, and D. mesophragmatica. The best supported scenario suggests that D. viracochi is an early offshoot in the mesophragmatica group, with this and other early branchings occuring in the Pliocene/Pleistocene Epochs, possibly associated with Andean glacial refuges. Also based on the phylogenies obtained, we present a genealogical view of the evolution of previously described characters within the group.
Assuntos
Drosophila/genética , Filogenia , Altitude , Animais , Ecossistema , América do SulRESUMO
The genus Drosophila has played an essential role in many biological studies during the last 100 years but much controversy and many incompletely addressed issues still remain to be elucidated regarding the phylogeny of this genus. Because information on the Neotropical species contained in the subgenus Drosophila is particularly incomplete, with this taxonomic group being underrepresented in many studies, we designed a study to answer some evolutionary questions related to these species. We subjected at least 41 Drosophilidae taxa to a phylogenetic analysis using a 516-base pair (bp) fragment of the alpha-methyldopa (Amd) nuclear gene and a 672 bp fragment of the mitochondrial cytochrome oxidase subunit II (COII) gene both individually and in combination. We found that the subgenus Drosophila is paraphyletic and subdivided into two main clusters: the first containing species traditionally placed in the virilis-repleta radiation and the second assembling species of the immigrans-Hirtodrosophila radiation. Inside the first of these clusters we could detect the monophyly of both the flavopilosa (the sister-clade of the annulimana group) and the mesophragmatica (closely related to the repleta group) species groups. Concerning the immigrans-Hirtodrosophila lineage, Zaprionus, Liodrosophila, Samoaia, and Hirtodrosophila were the early offshoots, followed by the immigrans, quinaria, testacea, and funebris species groups. The tripunctata radiation appears to be a derived clade, composed of a paraphyletic tripunctata group, intimately interposed with members of the cardini, guarani, and guaramunu species groups. Overall, the COII gene yielded a poor phylogenetic performance when compared to the Amd gene, the evolutionary hypothesis of which agreed with the total evidence tree. This phenomenon can be explained by the fast saturation of transitional substitutions in COII, due to strong biases in both base composition and substitution patterns, as also by its great among-site rate variation heterogeneity.
Assuntos
Núcleo Celular/genética , DNA Mitocondrial/genética , Drosophila/classificação , Drosophila/genética , Evolução Molecular , Filogenia , Animais , Drosophila/enzimologia , Proteínas de Drosophila/genética , Resistência a Medicamentos/genética , Complexo IV da Cadeia de Transporte de Elétrons/genética , Metildopa/farmacologia , Mitocôndrias/enzimologia , Mitocôndrias/genética , Clima TropicalRESUMO
A viabilidade ovo-adulto e o tempo de desenvolvimento em Drosophila subobscura é bastante modificada pela acumulaçäo de resíduos bióticos de larvas de D. pavani, D. immigrans e D. melanogaster. Este efeito poderia ser um fator regulador importante para estas espécies na natureza
Assuntos
Animais , Drosophila/fisiologia , Chile , Larva/crescimento & desenvolvimento , Dinâmica PopulacionalRESUMO
The palearctic species Drosophila subobscura was detected for the first time in Chile and probably in the Americas in 1978. At present, its distribution area extends between 29°54'S and 53°40'S, where it has become abundant in both domestic and wild environments, depending on the latitude and the season of the year (appearing at maximum frequency in early spring). The seasonal fluctuations of D. subobscura are the inverse of those of D. simulans, which shares the same habitat in certain regions. Under laboratory conditions D. subobscura proved to be a poor competitor during the larval developmental period in relation to D. simulans, which on the contrary seemed to be "facilitated" by the larvae of the other species. However, the existence of D. subobscura in Chile is most probably due to its population flush at a time when D. simulans is at low density.