The Experts below are selected from a list of 149541 Experts worldwide ranked by ideXlab platform
Jon Ågren - One of the best experts on this subject based on the ideXlab platform.
-
No evidence for adaptive Population Differentiation during seed germination between woodland and grassland Populations of the orchid Platanthera bifolia
2018Co-Authors: Judith Trunschke, Nina Sletvold, Jon ÅgrenAbstract:No evidence for adaptive Population Differentiation during seed germination between woodland and grassland Populations of the orchid Platanthera bifolia
-
Population Differentiation and phenotypic selection in natural Populations of Arabidopsis lyrata
2007Co-Authors: Saskia Sandring, Jon ÅgrenAbstract:In this thesis, I combined comparative and experimental approaches to examine selection on reproductive traits, and Population Differentiation in the insect-pollinated, outcrossing, perennial herb Arabidopsis lyrata. More specifically, I (1) determined whether selection on flowering phenology and floral display can be attributed to interactions with pollinators and herbivores, (2) examined whether Population Differentiation in flowering phenology and floral display is correlated with current selection on these traits, and (3) tested for local adaptation from contrasting environments in Europe.A field experiment conducted in a Swedish Population demonstrated, that interactions with pollinators may markedly affect selection on both floral display and phenology of flowering. In an alpine Population in Norway, grazing damage to inflorescences strongly influenced selection on floral display. The results suggest that variation in the abundance of pollinators and herbivores should contribute to spatio-temporal variation in selection on flowering phenology and floral display in A. lyrata. A common-garden experiment showed that flowering phenology and floral display vary among Scandinavian Populations of A. lyrata. For some traits patterns of Population Differentiation were consistent with differences in the direction and strength of phenotypic selection determined in comparisons (a) between an alpine Population in Norway and a coastal Population in Sweden, and (b) among coastal Populations in Sweden. This suggests that current selection contributes to the maintenance of genetic Differentiation in these traits.Adaptive Differentiation among Populations was examined in a reciprocal transplant experiment that included Populations from three contrasting environments, alpine Norway, coastal Sweden and lowland, continental Germany. The experiment provided evidence for local adaptation, and indicated that Populations have diverged in traits affecting plant establishment and early growth.
-
Site quality and among-Population Differentiation in flowering phenology and reproductive allocation in the perennial herb Primula farinosa
2007Co-Authors: Per Toräng, Johan Ehrlén, Jon ÅgrenAbstract:Site quality and among-Population Differentiation in flowering phenology and reproductive allocation in the perennial herb Primula farinosa
-
Adaptive Population Differentiation across Europe in the perennial herb Lythrum salicaria.
2004Co-Authors: Katarina Olsson, Jon ÅgrenAbstract:In this thesis, quantitative genetic approaches, common-garden experiments, and field studies were combined to examine patterns of Population Differentiation and the genetic architecture of characters of putative adaptive significance in the widely distributed perennial herb Lythrum salicaria. In this work, I (1) documented patterns of Population Differentiation in phenology, life-history, and morphology along latitudinal gradients at different geographical scales, (2) investigated the genetic architecture of phenology, flower morphology, and inflorescence size, and (3) combined estimates of phenotypic selection in the field with information on the genetic variance-covariance matrix (G) to examine potential constraints to adaptive evolution. A common-garden experiment demonstrated latitudinal variation in life-history, and phenology of growth and reproduction among L. salicaria Populations sampled across Sweden. Flower morphology varied significantly among Populations, but was, with the exception of calyx length, not related to latitude of origin. A second experiment, which included two Swedish, two Dutch, and two Spanish Populations, indicated that the latitudinal gradient in reproductive and vegetative phenology might extend throughout Europe.A quantitative-genetic study of two Swedish Populations revealed significant additive genetic variation for all phenological and morphological traits investigated. The G matrices of the Populations differed significantly according to common principal component analysis, and genetic correlations within the study Populations did not strictly correspond to trait correlations observed among Populations.In a field study, I detected directional selection through female function for larger inflorescences in two consecutive years. Relative fitness increased disproportionately with inflorescence size in the year when supplemental hand-pollination indicated that pollen limitation was severe. Genetic correlations with inflorescence size considerably influenced predicted response to selection in other characters.Taken together, the results suggest that among-Population differences in phenology and life-history in L. salicaria have evolved in response to latitudinal variation in length of the growing season. They demonstrate that the evolutionary potential of local Populations may be considerable. The genetic covariance structure substantially influences predicted short-term evolutionary trajectories. However, the weak correspondence between genetic correlations documented within Populations and trait correlations among Populations, suggest that the G matrix has not imposed strict constraints on patterns of among-Population Differentiation.
-
Latitudinal Population Differentiation in phenology, life history and flower morphology in the perennial herb Lythrum salicaria
Journal of Evolutionary Biology, 2002Co-Authors: Katarina Olsson, Jon ÅgrenAbstract:In plants with a wide distribution, phenological characters can be expected to vary clinally along climatic gradients, whereas other characters important for adaptation to local biotic and abiotic factors may vary in a more mosaic fashion. We used common-garden experiments and controlled crosses to examine Population Differentiation in phenology, life history and morphology in the perennial herb Lythrum salicaria along a latitudinal transect through Sweden (57°N to 66°N). Northern Populations initiated growth and flowering earlier, flowered for a shorter period, were shorter, produced more and larger winter buds, and were older at first reproduction than southern Populations. Flower morphology varied significantly among Populations, but was, with the exception of calyx length, not significantly related to latitude of origin. Survival in the common garden (at 63°49′N) was positively correlated with latitude of origin and the size and number of winter buds produced in the preceding year. The results suggest that the among-Population differences in phenology and life history have evolved in response to latitudinal variation in length of the growing season. Further studies are required to determine whether Population Differentiation in flower morphology is maintained by selection.
Katarina Olsson - One of the best experts on this subject based on the ideXlab platform.
-
Population Differentiation in Lythrum salicaria along a latitudinal gradient
2004Co-Authors: Katarina OlssonAbstract:In this thesis, quantitative genetic approaches, common-garden experiments, and field studies were combined to examine patterns of Population Differentiation and the genetic architecture of charact ...
-
Adaptive Population Differentiation across Europe in the perennial herb Lythrum salicaria.
2004Co-Authors: Katarina Olsson, Jon ÅgrenAbstract:In this thesis, quantitative genetic approaches, common-garden experiments, and field studies were combined to examine patterns of Population Differentiation and the genetic architecture of characters of putative adaptive significance in the widely distributed perennial herb Lythrum salicaria. In this work, I (1) documented patterns of Population Differentiation in phenology, life-history, and morphology along latitudinal gradients at different geographical scales, (2) investigated the genetic architecture of phenology, flower morphology, and inflorescence size, and (3) combined estimates of phenotypic selection in the field with information on the genetic variance-covariance matrix (G) to examine potential constraints to adaptive evolution. A common-garden experiment demonstrated latitudinal variation in life-history, and phenology of growth and reproduction among L. salicaria Populations sampled across Sweden. Flower morphology varied significantly among Populations, but was, with the exception of calyx length, not related to latitude of origin. A second experiment, which included two Swedish, two Dutch, and two Spanish Populations, indicated that the latitudinal gradient in reproductive and vegetative phenology might extend throughout Europe.A quantitative-genetic study of two Swedish Populations revealed significant additive genetic variation for all phenological and morphological traits investigated. The G matrices of the Populations differed significantly according to common principal component analysis, and genetic correlations within the study Populations did not strictly correspond to trait correlations observed among Populations.In a field study, I detected directional selection through female function for larger inflorescences in two consecutive years. Relative fitness increased disproportionately with inflorescence size in the year when supplemental hand-pollination indicated that pollen limitation was severe. Genetic correlations with inflorescence size considerably influenced predicted response to selection in other characters.Taken together, the results suggest that among-Population differences in phenology and life-history in L. salicaria have evolved in response to latitudinal variation in length of the growing season. They demonstrate that the evolutionary potential of local Populations may be considerable. The genetic covariance structure substantially influences predicted short-term evolutionary trajectories. However, the weak correspondence between genetic correlations documented within Populations and trait correlations among Populations, suggest that the G matrix has not imposed strict constraints on patterns of among-Population Differentiation.
-
Latitudinal Population Differentiation in phenology, life history and flower morphology in the perennial herb Lythrum salicaria
Journal of Evolutionary Biology, 2002Co-Authors: Katarina Olsson, Jon ÅgrenAbstract:In plants with a wide distribution, phenological characters can be expected to vary clinally along climatic gradients, whereas other characters important for adaptation to local biotic and abiotic factors may vary in a more mosaic fashion. We used common-garden experiments and controlled crosses to examine Population Differentiation in phenology, life history and morphology in the perennial herb Lythrum salicaria along a latitudinal transect through Sweden (57°N to 66°N). Northern Populations initiated growth and flowering earlier, flowered for a shorter period, were shorter, produced more and larger winter buds, and were older at first reproduction than southern Populations. Flower morphology varied significantly among Populations, but was, with the exception of calyx length, not significantly related to latitude of origin. Survival in the common garden (at 63°49′N) was positively correlated with latitude of origin and the size and number of winter buds produced in the preceding year. The results suggest that the among-Population differences in phenology and life history have evolved in response to latitudinal variation in length of the growing season. Further studies are required to determine whether Population Differentiation in flower morphology is maintained by selection.
F Guillaume - One of the best experts on this subject based on the ideXlab platform.
-
The role of phenotypic plasticity on Population Differentiation
Heredity, 2017Co-Authors: M Schmid, F GuillaumeAbstract:Several evolutionary processes shape the genetic and phenotypic Differentiation of Populations. Among them, the joint effects of gene flow, selection and phenotypic plasticity are poorly known, especially when trying to understand how maladaptive plasticity affects Population divergence. We extended a quantitative genetic model of Hendry et al. (2001) to describe these joint effects on phenotypic and additive genetic divergence between two Populations, and their phenotypic and genetic Differentiation ( P _ST and Q _ST). With individual-based simulations, we tested our model predictions and further modeled allelic Differentiation at neutral ( F _ST) and adaptive ( F _STQ) loci. While adaptive phenotypic plasticity allows for large phenotypic divergence and Differentiation despite high gene flow, maladaptive plasticity promotes genetic divergence and generates countergradient variation, under extensive migration with phenotypic differences sometimes opposed to genetic differences. Maladaptive plasticity can also promote adaptive phenotypic divergence by reducing the effective gene flow. Overall, plasticity decouples genetic from phenotypic differences between Populations, and blurs the correlation between phenotypic divergence and local adaptation. By deriving models of Population Differentiation for three different life cycles, we further describe the effect of a species’ ecology on evolution in structured Populations.
Ben C. Sheldon - One of the best experts on this subject based on the ideXlab platform.
-
Adaptive maternal effects and rapid Population Differentiation
Trends in Ecology & Evolution, 2002Co-Authors: Ben C. SheldonAbstract:Abstract How rapidly can two Populations diverge when exposed to different selection pressures? And what mechanisms contribute to rapid Population divergence? A remarkable new study by Badyaev et al. of house finches Carpodacus mexicanus suggests that simultaneous maternal adjustment of offspring sex ratio and growth rates has played an important role in rapid Population Differentiation associated with an explosive range expansion.
Katherine L Tucker - One of the best experts on this subject based on the ideXlab platform.
-
disparities in allele frequencies and Population Differentiation for 101 disease associated single nucleotide polymorphisms between puerto ricans and non hispanic whites
BMC Genetics, 2009Co-Authors: Josiemer Mattei, Bibiana Garciabailo, Serkalem Demissie, Xian Adiconis, Katherine L Tucker, Donna K Arnett, Laurence D Parnell, Jian ShenAbstract:Background: Variations in gene allele frequencies can contribute to differences in the prevalence of some common complex diseases among Populations. Natural selection modulates the balance in allele frequencies across Populations. Population Differentiation (F ST ) can evidence environmental selection pressures. Such genetic information is limited in Puerto Ricans, the second largest Hispanic ethnic group in the US, and a group with high prevalence of chronic disease. We determined allele frequencies and Population Differentiation for 101 single nucleotide polymorphisms (SNPs) in 30 genes involved in major metabolic and disease-relevant pathways in Puerto Ricans (n = 969, ages 45–75 years) and compared them to similarly aged non-Hispanic whites (NHW) (n = 597). Results: Minor allele frequency (MAF) distributions for 45.5% of the SNPs assessed in Puerto Ricans were significantly different from those of NHW. Puerto Ricans carried risk alleles in higher frequency and protective alleles in lower frequency than NHW. Patterns of Population Differentiation showed that Puerto Ricans had SNPs with exceptional FST values in intronic, nonsynonymous and promoter regions. NHW had exceptional FST values in intronic and promoter region SNPs only. Conclusion: These observations may serve to explain and broaden studies on the impact of gene polymorphisms on chronic diseases affecting Puerto Ricans.