The phylogeny of closely related species as revealed by the genealogy of a speciation gene, Odysseus

Molecular differentiation between races or closely related species is often incongruent with the reproductive divergence of the taxa of interest. Shared ancient polymorphism and/or introgression during secondary contact may be responsible for the incongruence. At loci contributing to speciation, these two complications should be minimized (1, 2); hence, their variation may more faithfully reflect the history of the species' reproductive differentiation. In this study, we analyzed DNA polymorphism at the Odysseus (OdsH) locus of hybrid sterility between Drosophila mauritiana and Drosophila simulans and were able to verify such a prediction. Interestingly, DNA variation only a short distance away (1.8 kb) appears not to be influenced by the forces that shape the recent evolution of the OdsH coding region. This locus thus may represent a test case of inferring phylogeny of very closely related species.

Naturally occurring variation in copia expression is due to both element (cis) and host (trans) regulatory variation.

Significant differences in levels of copia [Drosophila long terminal repeat (LTR) retrotransposon] expression exist among six species representing the Drosophila melanogaster species complex (D. melanogaster, Drosophila mauritiana, Drosophila simulans, Drosophila sechellia, Drosophila yakuba, and Drosophila erecta) and a more distantly related species (Drosophila willistoni). These differences in expression are correlated with major size variation mapping to putative regulatory regions of the copia 5' LTR and adjacent untranslated leader region (ULR). Sequence analysis indicates that these size variants were derived from a series of regional duplication events. The ability of the copia LTR-ULR size variants to drive expression of a bacterial chloramphenicol acetyltransferase reporter gene was tested in each of the seven species. The results indicate that both element-encoded (cis) and host-genome-encoded (trans) genetic differences are responsible for the variability in copia expression within and between Drosophila species. This finding indicates that models purporting to explain the dynamics and distribution of retrotransposons in natural populations must consider the potential impact of both element-encoded and host-genome-encoded regulatory variation to be valid. We propose that interelement selection among retrotransposons may provide a molecular drive mechanism for the evolution of eukaryotic enhancers which can be subsequently distributed throughout the genome by retrotransposition.

Evolution of single and double Wolbachia symbioses during speciation in the Drosophila simulans complex.

Maternally inherited bacteria of the genus Wolbachia are responsible for the early death of embryos in crosses between uninfected females and infected males in several insect species. This phenomenon, known as cytoplasmic incompatibility, also occurs between strains infected by different symbionts in some species, including Drosophila simulans. Wolbachia was found in two species closely related to D. simulans, Drosophila mauritiana, and Drosophila sechellia, and shown to cause incompatibility in the latter species but not in D. mauritiana. Comparison of bacterial and mtDNA history clarifies the origins of bacterial and incompatibility polymorphisms in D. simulans. Infection in D. mauritiana is probably the result of introgression of an infected D. simulans cytoplasm. Some D. simulans and D. sechellia cytoplasmic lineages harbor two bacteria as a consequence of a double infection which probably occurred in a common ancestor. The descendant symbionts in each species are associated with similar incompatibility relationships, which suggests that little variation of incompatibility types has occurred within maternal lineages beyond that related to the density of symbionts in their hosts.

Paleoclimate reconstruction from Miocene macroflora in Kazakhstan compiled from various publications

25 datasets (13 fossil leaf and pollen assemblages, 12 quantitative palaeoclimatic datasets) are provided in order to analyse Early Miocene palaeoclimate in Kazakhstan. The rich fossil record in Kazakhstan documents that during the Oligocene and Early Miocene this area in Central Eurasia was densely forested with warm-temperate deciduous trees and shrubs of the so-called "Turgayan flora". 29 fossil floras from 13 localities have been selected for a quantitative analysis of the Aquitanian (early Early Miocene) climate situation in Kazakhstan. The assessed mean annual temperatures generally place around 15 °C, while values of mean annual precipitation are of about 1000 mm. In combination with several other climate parameters estimated (temperatures of warmest and coldest months, precipitation rates of wettest, driest and warmest months), these data reflect uniform climatic conditions over several thousands of square kilometres. Data of temperature parameters show slight spatial differentiations, with generally cooler mean annual temperatures and higher seasonality (i.e. warmer summers and colder winters) in the north-eastern part of the study area compared with the south-western area around Lake Aral. As compared with palaeoclimate estimates for the European and East Asian Aquitanian, the central part of the Eurasian continent reveals evident signals of higher seasonality and slightly increased continentality.

Pollen distribution of sediment core MD96-2048 from the Western Indian Ocean

Glacial-interglacial fluctuations in the vegetation of South Africa might elucidate the climate system at the edge of the tropics between the Indian and Atlantic Oceans. However, vegetation records covering a full glacial cycle have only been published from the eastern South Atlantic. We present a pollen record of the marine core MD96-2048 retrieved by the Marion Dufresne from the Indian Ocean ~120 km south of the Limpopo River mouth. The sedimentation at the site is slow and continuous. The upper 6 m (spanning the past 342 Ka) have been analysed for pollen and spores at millennial resolution. The terrestrial pollen assemblages indicate that during interglacials, the vegetation of eastern South Africa and southern Mozambique largely consisted of evergreen and deciduous forests. During glacials open mountainous scrubland dominated. Montane forest with Podocarpus extended during humid periods was favoured by strong local insolation. Correlation with the sea surface temperature record of the same core indicates that the extension of mountainous scrubland primarily depends on sea surface temperatures of the Agulhas Current. Our record corroborates terrestrial evidence of the extension of open mountainous scrubland (including fynbos-like species of the high-altitude Grassland biome) for the last glacial as well as for other glacial periods of the past 300 Ka.

Pollen and spore counts of sediment core GeoB12624

In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ~ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

Plantas forrageiras das caatingas: usos e potencialidades.

Coleta de analises; descricao e usos das especies: camaratuba, carqueija, catingueira-verdadeira, espinheiro/jacurutu/jiquiri, facheiro, favela/faveleira, feijao-brabo, imbuzeiro/umbuzeiro, juazeiro, jurema-preta, jurema-vermelha, macambira, mandacaru/mandacaru-de-boi, manicoba, marmeleiro/marmeleiro-preto, moleque-duro, mororo/unha-de-vaca, quebra-faca, sabia, sete-cascas/cascudo/pau-de-casca. Comentarios gerais e recomendacoes.