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Université de Fribourg

Genomic admixture analysis in european Populus spp. reveals unexpected patterns of reproductive isolation and mating

Lexer, Christian ; Joseph, Jeffrey A. ; Loo, Marcela van ; Barbará, Thelma ; Heinze, Berthold ; Bartha, Denes ; Castiglione, Stefano ; Fay, Michael F. ; Buerkle, C. Alex

In: Genetics, 2010, vol. 186, p. 699–712

Admixture between genetically divergent populations facilitates genomic studies of the mechanisms involved in adaptation, reproductive isolation and speciation, including mapping of the loci involved in these phenomena. Little is known about how pre- and postzygotic barriers will affect the prospects of 'admixture mapping' in wild species. We have studied 93 mapped genetic markers...

Université de Fribourg

Comparative analysis of pistil transcriptomes reveals conserved and novel genes expressed in dry, wet and semi-dry stigmas

Hiscock, Simon J. ; Allen, Alexandra M. ; Lexer, Christian

In: Plant Physiology, 2010, p. -

Fertilization in angiosperms depends on a complex cellular "courtship" between haploid pollen and diploid pistil. These pollen-pistil interactions are regulated by a diversity of molecules, many of which remain to be identified and characterized. Thus it is unclear to what extent these processes are conserved among angiosperms, a fact confounded by limited sampling across taxa. Here we report...

Université de Fribourg

Phylogeography of Populus alba (L.) and Populus tremula (L.) in Central Europe: secondary contact and hybridisation during recolonisation from disconnected refugia

Fussi, Barbara ; Lexer, Christian ; Heinze, Berthold

In: Tree Genetics & Genomes, 2010, vol. 6, no. 3, p. 439-450

The central aim of this paper is to clarify the picture of postglacial recolonisation and the reconstruction of refugia of Populus alba (L.) and Populus tremula (L.) in the light of hybridisation of the two species. We focussed our study on Central and Southeastern Europe including reference samples from Spain, Sweden and Northern Africa.We investigated 414 individuals of 26 populations using...

Université de Fribourg

Range-wide patterns of nuclear and chloroplast DNA diversity in Vriesea gigantea (Bromeliaceae), a neotropical forest species

Palma-Silva, Clarisse ; Lexer, Christian ; Paggi, G. M. ; Barbará, Thelma ; Bered, F. ; Bodanese-Zanettini, M. H.

In: Heredity, 2009, vol. 103, p. 503–512

The processes that have shaped the extraordinary species diversity in neotropical rainforests are poorly understood, and knowledge about the patterns of genetic diversity across species' ranges is scarce, in contrast to other regions of the globe. We have conducted a range-wide study of genetic diversity in a plant endemic to the Brazilian Atlantic Rainforest, Vriesea gigantea (Bromeliaceae),...

Université de Fribourg

Genetic diversity in Cypripedium calceolus (Orchidaceae) with a focus on north-western Europe, as revealed by plastid DNA length polymorphisms

Fay, Michael F. ; Bone, Ruth ; Cook, Peter ; Kahandawala, Imalka ; Greensmith, Jennifer ; Harris, Stacey ; Pedersen, Henrik Æ. ; Ingrouille, Martin J. ; Lexer, Christian

In: Annals of Botany, 2009, vol. 104, no. 3, p. 517-525

Background and Aims: Cypripedium calceolus, although widespread in Eurasia, is rare in many countries in which it occurs. Population genetics studies with nuclear DNA markers on this species have been hampered by its large nuclear genome size. Plastid DNA markers are used here to gain an understanding of variation within and between populations and of biogeographical patterns. Methods:...

Université de Fribourg

The use of digital image-based morphometrics to study the phenotypic mosaic in taxa with porous genomes

Lexer, Christian ; Jeffrey, Joseph ; Loo, Marcela van ; Prenner, Gerhard ; Heinze, Berthold ; Chase, Mark W. ; Kirkup, Don

In: Taxon, 2009, vol. 58, no. 2, p. 349-364

Rapid recent developments in DNA sequencing and genetic marker technologies call for the establishment of cost-effective, automated phenotyping assays for evolutionary biology and systematics, so that the effects of DNA polymorphisms and epigenetic changes on the phenotype can be evaluated. We discuss the use of digital image-based morphometrics in evolutionary biology and systematics with...

Université de Fribourg

How sympatric is speciation in the Howea palms of Lord Howe Island?

Babik, Wiesław ; Butlin, Roger K. ; Baker, William J. ; Papadopulos, Alexander S. T. ; Boulesteix, Matthieu ; Anstett, Marie-Charlotte ; Lexer, Christian ; Hutton, Ian ; Savolainen, Vincent

In: Molecular Ecology, 2009, vol. 18, no. 7, p. 3629 - 3638

The two species of the palm genus Howea (Arecaceae) from Lord Howe Island, a minute volcanic island in the Tasman Sea, are now regarded as one of the most compelling examples of sympatric speciation, although this view is still disputed by some authors. Population genetic and ecological data are necessary to provide a more coherent and comprehensive understanding of this emerging model system....

Université de Fribourg

Genetic relationships and variation in reproductive strategies in four closely related bromeliads adapted to neotropical ‘inselbergs’: Alcantarea glaziouana, A. regina, A. geniculata and A. imperialis (Bromeliaceae)

Barbará, Thelma ; Martinelli, Gustavo ; Palma-Silva, Clarisse ; Fay, Michael F. ; Mayo, Simon ; Lexer, Christian

In: Annals of Botany, 2009, vol. 103, no. 1, p. 65-77

Background and Aims: Bromeliads (Bromeliaceae) adapted to rock outcrops or ‘inselbergs’ in neotropical rain forests have been identified as suitable plant models for studying population divergence and speciation during continental plant radiations. Little is known about genetic relationships and variation in reproductive strategies within and among inselberg-adapted species, yet knowledge...

Université de Fribourg

Admixture as the basis for genetic mapping

Buerkle, C. Alex ; Lexer, Christian

In: Trends in Ecology & Evolution, 2008, vol. 23, no. 12, p. 686-694

Genetic mapping in natural populations is increasing rapidly in feasibility and accessibility. As with many areas in genetics, advances in molecular techniques and statistics are drastically altering how we can investigate inheritance in wild organisms. For ecology and evolution, this is particularly significant and promising, because many of the organisms of interest are not amenable to...