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The island of Madagascar and surrounding volcanic and coralline islands are considered to form a biodiversity hotspot with large numbers of unique taxa. The origin of this endemic fauna can be explained by two different factors: vicariance or over-water-dispersal. Deciphering which factor explains the current distributional pattern of a given taxonomic group requires robust phylogenies as well as estimates of divergence times. The lineage of Indian Ocean scops-owls (Otus: Strigidae) includes six or seven species that are endemic to Madagascar and portions of the Comoros and Seychelles archipelagos; little is known about the species limits, biogeographic affinities and relationships to each other. In the present study, using DNA sequence data gathered from six loci, we examine the biogeographic history of the Indian Ocean scops-owls. We also compare the pattern and timing of colonization of the Indian Ocean islands by scops-owls with divergence times already proposed for other bird taxa.Results:Our analyses revealed that Indian Ocean islands scops-owls do not form a monophyletic assemblage: the Seychelles Otus insularis is genetically closer to the South-East Asian endemic O. sunia than to species from the Comoros and Madagascar. The Pemba Scops-owls O. pembaensis, often considered closely related to, if not conspecific with O. rutilus of Madagascar, is instead closely related to the African mainland O. senegalensis. Relationships among the Indian Ocean taxa from the Comoros and Madagascar are unresolved, despite the analysis of over 4000 bp, suggesting a diversification burst after the initial colonization event. We also highlight one case of putative back-colonization to the Asian mainland from an island ancestor (O. sunia). Our divergence date estimates, using a Bayesian relaxed clock method, suggest that all these events occurred during the last 3.6 myr; albeit colonization of the Indian Ocean islands were not synchronous, O. pembaensis diverged from O. senegalensis about 1.7 mya while species from Madagascar and the Comoro diverged from their continental sister-group about 3.6 mya. We highlight that our estimates coincide with estimates of diversification from other bird lineages.Conclusion:Our analyses revealed the occurrence of multiple synchronous colonization events of the Indian Ocean islands by scops-owls, at a time when faunistic exchanges involving Madagascar was common as a result of lowered sea-level that would have allowed the formation of stepping-stone islands. Patterns of diversification that emerged from the scops-owls data are: 1) a star-like pattern concerning the order of colonization of the Indian Ocean islands and 2) the high genetic distinctiveness among all Indian Ocean taxa, reinforcing their recognition as distinct species.

The Eurasian Treecreeper is a forest bird distributed from South-Western Europe up to Northern Asia. Two phylogenetic groups have been recently identified within this species, one restricted to Corsica Island (Mediterranean) and the Caucasus region, the other distributed over most of Eurasia and in Northern Asia. Little is known on the natural history of the Corsican population. We present here new comprehensive data on its distribution and habitat. The Eurasian Treecreeper is found from sea level to the upper limit of the forest but absent from the treeless macchia, a dominant vegetation in Corsica. Breeding occurs in a variety of tree species with a strong preference for mature stands and large trees. Its preferred habitat consists of old stands of Corsican Pines and of Sweet Chestnuts, although they are not the commonest tree species in Corsica. The current decline of Sweet Chestnut orchards confers a particular importance to the future preservation of mature stands of Corsican Pine, a patrimonial habitat of great value hosting several endemic bird taxa. [ABSTRACT FROM AUTHOR]

A recent taxonomic revision of the Malagasy Scops-Owl (Otus rutilus) recognized two distinct endemic species on the island based on plumage, vocal, and morphological characters: O. rutilus (sensu stricto) from eastern humid forest formations and O. madagascariensis from western dry forest areas. An evaluation of these characters calls into question their validity for taxonomic studies, as they may be ecologically linked. To independently assess the two-species hypothesis, we used sequence data from 1449 base pairs (bp) of mitochondrial DNA (mtDNA) from 34 scops-owls obtained across the range of these two putative species. Nineteen haplotypes were detected, four of which were shared by more than one individual. Maximum sequence divergence was 0.6% (mean = 0.24%). While the most common haplotype was shared by 10 individuals originating from different eastern and western localities, 12 haplotypes were exclusive to O. rutilus and five to O. madagascariensis. An analvsis of molecular variance showed significant partitioning of the genetic variability between O. rutilus and O. madagascariensis. The estimate of the divergence time between populations associated with the names O. rutilus and O. madagascariensis was 8070 years BP. Based on haplotype frequencies and sequence divergence, we conclude that there are two populations of Otus on Madagascar that started to diverge in recent geological time following an ecological parapatric model, perhaps associated with Quaternary climatic shifts. Using these results, it is inappropriate to recognize two species of Otus on Madagascar. Key words: coalescent analyses, Madagascar, mitochondrial DNA, Otus, phylogeography, two-species hypothesis. Con base en caracteres del plumaje, vocales y morfologicos, una revision taxonomica reciente del buho Otus rutilus reconoce dos especies distintas endemicas de Madagascar: O. rutilus (sensu stricto), de las formaciones de bosque humedo del este, y O. madagascariensis, de las areas de bosque seco del oeste. Una evaluacion de estos caracteres conduce a cuestionar su validez para estudios taxonomicos debido a que estos pueden estar ecologicamente relacionados. Para comprobar de forma independiente la hipotesis de la existencia de dos especies, usamos datos de secuencias de 1449 pares de bases de ADN mitocondrial obtenidas para 34 individuos de Otus rutilus colectados a traves del rango de distribucion de las dos especies hipoteticas. Se detectaron 19 haplotipos, de los cuales cuatro fueron compartidos entre individuos. La divergencia maxima entre secuencias fue del 0.6% (promedio = 0.24%). El haplotipo mas comun fue compartido por diez individuos originarios de localidades del este y del oeste, mientras que doce haplotipos se observaron exclusivamente en O. rutilus y cinco en O. madagascariensis. Un analisis de varianza molecular mostro una particion significativa de la variabilidad genetica entre O. rutilus y O. madagascariensis. La estimacion del tiempo de divergencia entre las poblaciones asociadas con el nombre de O. rutilus y O. madagaseariensis fue de 8070 anos antes del presente. Con base en las frecuencias haplotipicas y la divergencia entre secuencias, concluimos que hay dos poblaciones de Otus en Madagascar que comenzaron a divergir en un tiempo geologico reciente siguiendo un modelo parapatrico, quizas asociado con los cambios climaticos del Cuaternario. Utilizando estos resultados, reconocer dos especies de Otus en Madagascar es inapropiado.

The production of beta-lactone through Lewis acid-promoted (2+2+ cycloaddition was investigated utilizing semiempirical (AM1/RHF and AM1/CI) and ab initio (HF/6-3)G* and MP2/6-31G*) computations. Ab initio and/or semiempirical studies on solvent and Lewis acid (BH3 and BF3) effects focused on the mechanism involving the prior formation of the C-C bond. At the HF/6-31G* level of theory the introduction of BF3 induced a reduction of the activation energy from 40.8 to 11.9 kcal/mol and computations performed with AM1/COSMO revealed that that the introduction of a solvent causes the formation of an earlier transition state.

A synthesis scheme for the strong pancreatic lipase inhibitor (-)-lipstatin from dimethyl (S)-s(-)-malate and dienal is presented. The synthesis involves the diastereoselective Lewis-acid (2+2) cycloaddition reaction between n-hexyl(trimethylsilyl)ketene and (R)-(-)-(Z,Z)-3-(tert-butyldimethylsilyl)oxy-5,8-tetradecadienal. The study shows the importance of silyl-stabilized ketenes as synthetic reagents, their reactivity with aldehydes in the presence of sensitive 1,4-diene moiety and the efficiency of (Z)-selective Wittig chain elongation for the synthesis of (Z,Z)-1,4-dienes.

Abstract Background The island of Madagascar and surrounding volcanic and coralline islands are considered to form a biodiversity hotspot with large numbers of unique taxa. The origin of this endemic fauna can be explained by two different factors: vicariance or over-water-dispersal. Deciphering which factor explains the current distributional pattern of a given taxonomic group requires robust phylogenies as well as estimates of divergence times. The lineage of Indian Ocean scops-owls (Otus: Strigidae) includes six or seven species that are endemic to Madagascar and portions of the Comoros and Seychelles archipelagos; little is known about the species limits, biogeographic affinities and relationships to each other. In the present study, using DNA sequence data gathered from six loci, we examine the biogeographic history of the Indian Ocean scops-owls. We also compare the pattern and timing of colonization of the Indian Ocean islands by scops-owls with divergence times already proposed for other bird taxa. Results Our analyses revealed that Indian Ocean islands scops-owls do not form a monophyletic assemblage: the Seychelles Otus insularis is genetically closer to the South-East Asian endemic O. sunia than to species from the Comoros and Madagascar. The Pemba Scops-owls O. pembaensis, often considered closely related to, if not conspecific with O. rutilus of Madagascar, is instead closely related to the African mainland O. senegalensis. Relationships among the Indian Ocean taxa from the Comoros and Madagascar are unresolved, despite the analysis of over 4000 bp, suggesting a diversification burst after the initial colonization event. We also highlight one case of putative back-colonization to the Asian mainland from an island ancestor (O. sunia). Our divergence date estimates, using a Bayesian relaxed clock method, suggest that all these events occurred during the last 3.6 myr; albeit colonization of the Indian Ocean islands were not synchronous, O. pembaensis diverged from O. senegalensis about 1.7 mya while species from Madagascar and the Comoro diverged from their continental sister-group about 3.6 mya. We highlight that our estimates coincide with estimates of diversification from other bird lineages. Conclusion Our analyses revealed the occurrence of multiple synchronous colonization events of the Indian Ocean islands by scops-owls, at a time when faunistic exchanges involving Madagascar was common as a result of lowered sea-level that would have allowed the formation of stepping-stone islands. Patterns of diversification that emerged from the scops-owls data are: 1) a star-like pattern concerning the order of colonization of the Indian Ocean islands and 2) the high genetic distinctiveness among all Indian Ocean taxa, reinforcing their recognition as distinct species.

Abstract Background The major impact of Plio-Pleistocene climatic oscillations on the current genetic structure of many species is widely recognised but their importance in driving speciation remains a matter of controversies. In addition, since most studies focused on Europe and North America, the influence of many other biogeographic barriers such as the Sahara remains poorly understood. In this paper, climate-driven diversification was investigated by using a comparative phylogeographic approach in combination with phenotypic data in two avian species groups distributed on both sides of the deserts belt of Africa and Asia. In particular, we tested whether: 1) vicariance diversification events are concomitant with past climatic events; and 2) current ecological factors (using climate and competition as proxies) contribute to phenotypic divergence between allopatric populations. Results Mitochondrial and nuclear sequence data indicated that the crested and Thekla lark species groups diverged in the early Pliocene and that subsequent speciation events were congruent with major late Pliocene and Pleistocene climatic events. In particular, steep increase in aridity in Africa near 2.8 and 1.7 million years ago were coincident with two north-south vicariance speciation events mediated by the Sahara. Subsequent glacial cycles of the last million years seem to have shaped patterns of genetic variation within the two widespread species (G. cristata and G. theklae). The Sahara appears to have allowed dispersal from the tropical areas during climatic optima but to have isolated populations north and south of it during more arid phases. Phenotypic variation did not correlate with the history of populations, but was strongly influenced by current ecological conditions. In particular, our results suggested that (i) desert-adapted plumage evolved at least three times and (ii) variation in body size was mainly driven by interspecific competition, but the response to competition was stronger in more arid areas. Conclusion Climatic fluctuations of the Plio-Pleistocene strongly impacted diversification patterns in the Galerida larks. Firstly, we found that cladogenesis coincides with major climatic changes, and the Sahara appears to have played a key role in driving speciation events. Secondly, we found that morphology and plumage were strongly determined by ecological factors (interspecific competition, climate) following vicariance.