Much of our knowledge of speciation genetics stems from quantitative trait locus (QTL) studies. H... more Much of our knowledge of speciation genetics stems from quantitative trait locus (QTL) studies. However, interpretations,of the size and,distribution of QTL underlying,species differences,are complicated,by differences in the way QTL magnitudes are estimated. Also, many studies fail to exploit information about QTL directions or to compare inter- and intraspecific QTL variation. Here, we comprehensively analyze an extensive QTL data set
Pollen-pistil interactions are an essential prelude to fertilization in angiosperms and determine... more Pollen-pistil interactions are an essential prelude to fertilization in angiosperms and determine compatibility/incompatibility. Pollen-pistil interactions have been studied at a molecular and cellular level in relatively few families. Self-incompatibility (SI) is the best understood pollen-pistil interaction at a molecular level where three different molecular mechanisms have been identified in just five families. Here we review studies of pollen-pistil interactions and SI in the Asteraceae, an important family that has been relatively understudied in these areas of reproductive biology. We begin by describing the historical literature which first identified sporophytic SI (SSI) in species of Asteraceae, the SI system later identified and characterized at a molecular level in the Brassicaceae. Early structural and cytological studies in these two families suggested that pollen-pistil interactions and SSI were similar, if not the same. Recent cellular and molecular studies in Seneci...
We have studied the origin of salt adaptation in wild sunflower hybrids (Helianthus annuus x H. p... more We have studied the origin of salt adaptation in wild sunflower hybrids (Helianthus annuus x H. petiolaris), the precursors of the diploid hybrid species H. paradoxus, at the level of phenotypic traits and quantitative trait loci (QTLs). Here, we review this work and present new results on candidate gene polymorphisms.Salt tolerance candidate genes were identified in expressed sequence tag (EST) libraries of sunflower, based on homology to genes with known function, and on previous QTL results. EST polymorphisms were assayed by denaturing HPLC and for which fitness estimates in the wild genetically mapped in an interspecific BC(2) were available.Out of 11 genes studied, one mapped to a salt tolerance QTL. This EST codes for a Ca-dependent protein kinase (CDPK) and stems from stress-induced root tissue of Helianthus annuus. Two additional stress-induced genes exhibited a significant fitness effect in the wild: an ER-type calcium ATPase, and a transcriptional regulator.Our results sug...
Pollen dispersal inferred from paternity analysis in a mixed oak stand of Quercus robur L. and Q.... more Pollen dispersal inferred from paternity analysis in a mixed oak stand of Quercus robur L. and Q. petraea(Matt.) Liebl. ... By pooling the data over all families, the average pollen dispersal curve within the stand was inferred and fitted to a negative exponential distribution. ...
Selection experiments in the wild have greatly aided our understanding of how selection shapes ph... more Selection experiments in the wild have greatly aided our understanding of how selection shapes phenotypic diversity in natural populations. However, these experi- ments have been hindered by the fact that the traits most important to adaptation and speciation may be fixed within populations. Experimental hybridization offers a means to circumvent this problem since crosses can be made between populations or
A genetic linkage map of an intraspecific cross between 2 Silene vulgaris s.l. ecotypes is presen... more A genetic linkage map of an intraspecific cross between 2 Silene vulgaris s.l. ecotypes is presented. Three-hundred AFLP markers from 2 different restriction enzyme combinations were used to genotype an F2 mapping population. Maternal and paternal pure-coupling phase maps with 114 and 186 markers on 12 and 13 linkage groups, respectively, were constructed. Total map length of the paternal and maternal maps are 547 and 446 Kosambi cM, respectively. Nearly half of the markers (49%) exhibited significant transmission ratio distortion. Genome coverage and potential causes of the observed segregation ratio distortions are discussed. The maps represent a first step towards the identification of quantitative trait loci associated with habitat adaptation in the non-model species Silene vulgaris.
Spatial genetic structure (SGS) holds the key to understanding the role of clonality in hybrid pe... more Spatial genetic structure (SGS) holds the key to understanding the role of clonality in hybrid persistence, but multilocus SGS in hybrid zones has rarely been quantified. Here, the aim was to fill this gap for natural hybrids between two diploid, ecologically divergent European tree species with mixed sexual/asexual reproduction, Populus alba and P. tremula. Nuclear microsatellites were used to quantify clonality, SGS, and historical gene dispersal distances in up to 407 trees from an extensive Central European hybrid zone including three subpopulation replicates. The focus was on P. x canescens and its backcross parent P. alba, as these two genotypic classes co-occur and interact directly. Sexual recombination in both taxa was more prominent than previously thought, but P. x canescens hybrids tended to build larger clones extending over larger areas than P. alba. The 3.4 times stronger SGS in the P. x canescens genet population was best explained by a combination of interspecific gene flow, assortative mating, and increased clonality in hybrids. Clonality potentially contributes to the maintenance of hybrid zones of P. alba and P. tremula in time and space. Both clonality and SGS need to be taken into account explicitly when designing population genomics studies of locus-specific effects in hybrid zones.
Much of our knowledge of speciation genetics stems from quantitative trait locus (QTL) studies. H... more Much of our knowledge of speciation genetics stems from quantitative trait locus (QTL) studies. However, interpretations,of the size and,distribution of QTL underlying,species differences,are complicated,by differences in the way QTL magnitudes are estimated. Also, many studies fail to exploit information about QTL directions or to compare inter- and intraspecific QTL variation. Here, we comprehensively analyze an extensive QTL data set
Pollen-pistil interactions are an essential prelude to fertilization in angiosperms and determine... more Pollen-pistil interactions are an essential prelude to fertilization in angiosperms and determine compatibility/incompatibility. Pollen-pistil interactions have been studied at a molecular and cellular level in relatively few families. Self-incompatibility (SI) is the best understood pollen-pistil interaction at a molecular level where three different molecular mechanisms have been identified in just five families. Here we review studies of pollen-pistil interactions and SI in the Asteraceae, an important family that has been relatively understudied in these areas of reproductive biology. We begin by describing the historical literature which first identified sporophytic SI (SSI) in species of Asteraceae, the SI system later identified and characterized at a molecular level in the Brassicaceae. Early structural and cytological studies in these two families suggested that pollen-pistil interactions and SSI were similar, if not the same. Recent cellular and molecular studies in Seneci...
We have studied the origin of salt adaptation in wild sunflower hybrids (Helianthus annuus x H. p... more We have studied the origin of salt adaptation in wild sunflower hybrids (Helianthus annuus x H. petiolaris), the precursors of the diploid hybrid species H. paradoxus, at the level of phenotypic traits and quantitative trait loci (QTLs). Here, we review this work and present new results on candidate gene polymorphisms.Salt tolerance candidate genes were identified in expressed sequence tag (EST) libraries of sunflower, based on homology to genes with known function, and on previous QTL results. EST polymorphisms were assayed by denaturing HPLC and for which fitness estimates in the wild genetically mapped in an interspecific BC(2) were available.Out of 11 genes studied, one mapped to a salt tolerance QTL. This EST codes for a Ca-dependent protein kinase (CDPK) and stems from stress-induced root tissue of Helianthus annuus. Two additional stress-induced genes exhibited a significant fitness effect in the wild: an ER-type calcium ATPase, and a transcriptional regulator.Our results sug...
Pollen dispersal inferred from paternity analysis in a mixed oak stand of Quercus robur L. and Q.... more Pollen dispersal inferred from paternity analysis in a mixed oak stand of Quercus robur L. and Q. petraea(Matt.) Liebl. ... By pooling the data over all families, the average pollen dispersal curve within the stand was inferred and fitted to a negative exponential distribution. ...
Selection experiments in the wild have greatly aided our understanding of how selection shapes ph... more Selection experiments in the wild have greatly aided our understanding of how selection shapes phenotypic diversity in natural populations. However, these experi- ments have been hindered by the fact that the traits most important to adaptation and speciation may be fixed within populations. Experimental hybridization offers a means to circumvent this problem since crosses can be made between populations or
A genetic linkage map of an intraspecific cross between 2 Silene vulgaris s.l. ecotypes is presen... more A genetic linkage map of an intraspecific cross between 2 Silene vulgaris s.l. ecotypes is presented. Three-hundred AFLP markers from 2 different restriction enzyme combinations were used to genotype an F2 mapping population. Maternal and paternal pure-coupling phase maps with 114 and 186 markers on 12 and 13 linkage groups, respectively, were constructed. Total map length of the paternal and maternal maps are 547 and 446 Kosambi cM, respectively. Nearly half of the markers (49%) exhibited significant transmission ratio distortion. Genome coverage and potential causes of the observed segregation ratio distortions are discussed. The maps represent a first step towards the identification of quantitative trait loci associated with habitat adaptation in the non-model species Silene vulgaris.
Spatial genetic structure (SGS) holds the key to understanding the role of clonality in hybrid pe... more Spatial genetic structure (SGS) holds the key to understanding the role of clonality in hybrid persistence, but multilocus SGS in hybrid zones has rarely been quantified. Here, the aim was to fill this gap for natural hybrids between two diploid, ecologically divergent European tree species with mixed sexual/asexual reproduction, Populus alba and P. tremula. Nuclear microsatellites were used to quantify clonality, SGS, and historical gene dispersal distances in up to 407 trees from an extensive Central European hybrid zone including three subpopulation replicates. The focus was on P. x canescens and its backcross parent P. alba, as these two genotypic classes co-occur and interact directly. Sexual recombination in both taxa was more prominent than previously thought, but P. x canescens hybrids tended to build larger clones extending over larger areas than P. alba. The 3.4 times stronger SGS in the P. x canescens genet population was best explained by a combination of interspecific gene flow, assortative mating, and increased clonality in hybrids. Clonality potentially contributes to the maintenance of hybrid zones of P. alba and P. tremula in time and space. Both clonality and SGS need to be taken into account explicitly when designing population genomics studies of locus-specific effects in hybrid zones.
Uploads