* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Common Gardens
Survey
Document related concepts
Genome (book) wikipedia , lookup
Pharmacogenomics wikipedia , lookup
Genetic testing wikipedia , lookup
Genetic engineering wikipedia , lookup
Hybrid (biology) wikipedia , lookup
Genetics and archaeogenetics of South Asia wikipedia , lookup
Behavioural genetics wikipedia , lookup
History of genetic engineering wikipedia , lookup
Group selection wikipedia , lookup
Quantitative trait locus wikipedia , lookup
Koinophilia wikipedia , lookup
Genetic drift wikipedia , lookup
Polymorphism (biology) wikipedia , lookup
Human genetic variation wikipedia , lookup
Population genetics wikipedia , lookup
Transcript
Components of Natural Selection • Phenotypic variation • Fitness differences – phenotypic differences must influence fitness to some extent for there to be natural selection on the trait • Heritability – phenotypic differences must have a genetic basis if there is to be evolution through natural selection Components of Fitness in Plants: A Few Examples • Fecundity – number of gametes produced • Fertilizing ability – male reproductive success • Fertility – number of offspring produced • Survivorship – chance of surviving Phenotypic selection • The effect of fitness differences related to differences in phenotype Directional selection in Danthonia spicata Total number of spikelets Phenotypic selection • The effect of fitness differences related to differences in phenotype Directional selection in Danthonia spicata Increasing fitness Phenotypic selection Number of seeds produced Stabalizing selection in Ipomoea purpurea Increasing fitness Phenotypic Selection in Multiple Traits Number of fruits produced Sea rocket: Cakile edentula Stabilizing Directional Components of Natural Selection • Phenotypic variation • Fitness differences – phenotypic differences must influence fitness to some extent for there to be natural selection on the trait • Heritability – phenotypic differences must have a genetic basis if there is to be evolution through natural selection Heritability (h2) defined “The amount of resemblence among relatives that is due to shared genes” Heritability of Height in Field Mustard Experimental design • Choose pairs of plants • Pollinate one plant with pollen from the other in the pair • Cover flowers to prevent other pollen from fertilizing • Collect seeds • Measure height of parents Field mustard Brassica campestris • Raise offspring from seed • Measure height of offspring Heritability of Height in Field Mustard Field mustard Brassica campestris Partitioning Phenotypic Variability: A Second View of Heritability (h2) VP = VG + Ve VP – Phenotypic variation VG – Genetic variation Ve – Unexplained variation Partitioning Phenotypic Variability: A Second View of Heritability (h2) h 2 = VG / V P Partitioning Phenotypic Variability: A More Complete View Vp = VG + VE + VGxE + Cov(G,E) + Ve VE – Variation due to environmental factors: plastic response VGxE – Variation due to an interaction between genotype and the environment that influences phenotype Genotype by Environment Interactions Response by a single genotype Genotype by Environment Interactions Vg in high light Vg in low light Genotype by Environment Interactions VE Genotype by Environment Interactions VGxE – Degree to which lines are not parallel Partitioning Phenotypic Variability: A More Complete View Vp = VG + VE + VGxE + Cov(G,E) + Ve Cov(G,E) – non-random association between genetic makeup and local environmental conditions Sources of Genetic Variation Factors increasing variation •Mutation 10-8 to 10-10 mutations per base pair per generation 10-5 to 10-7 mutations per gene per generation One individual out of 10 per generation Sources of Genetic Variation Factors increasing variation •Mutation •Migration Population #1 Population #2 Sources of Genetic Variation Factors decreasing variation •Natural selection •Genetic drift in small populations (<1000) Small population Loss of a allele Large population p+q=1 p = frequency (allele A) q = frequency (allele a) Loss of A allele Evidence of Selection in Natural Plant Populations Selection Among Populations The Common Garden Experiments of Clauson, Keck and Heiesy (1948) Differences in phenotype across a gradient: Yarrow (Achiella spp) as an example What is the source of variation? • Different species – genetic variation? • Same species – phenotypic plasticity? Common Garden Experiment Step #1: Obtain Plants from Source Populations Stanford – 100’ Mather – 4600’ Timberline – 10,000’ Common Garden Experiment Step #2: Produce Clones Source Plant Clones (e.g., piece of root) Location #1 Location #2 Common Garden Experiment Step #3: Plant clones in common gardens Source Plant Clones (e.g., piece of root) Common Gardens Location #1 Location #1 Location #2 Location #2 Stanford Common Garden Mather Common Garden Timberline Common Garden Interpretation of Results: Pure Plastic Response Source Plant Clones Common Gardens ? Location #1 Location #1 ? Location #2 Location #2 Interpretation of Results: Pure Genetic Response Source Plant Clones Common Gardens ? Location #1 Location #1 ? Location #2 Location #2 Plastic response Genetic response Experimental Outcome: Growth of Mather Achiella Clones A Second Example Potentilla glandulosa Copyright © 1997-2001 by Jane Strong and Tom Chester http://tchester.org/sgm/conditions/blooms/idyellow.html Lowland Plant Lowland Ecotype ©Brother Alfred Brousseau, St. Mary's College Montane Plant ©Brother Alfred Brousseau, St. Mary's College Experimental Outcome: Growth of Potentilla Clones Interpretation Part I • Not a pure plastic response • Not a pure genetic response What is the relationship between these organisms? Separate experiments show that crosses between different source populations produce viable offspring Interpretation Part II • These are not different species What then are they? Ecotypes the middle ground • Genetically distinct organisms • Phenotypically distinct in terms of • Morphology • Physiology • Phenology • Occur in distinct habitats • Differences can be traced to ecological differences in home habitat • Plants are potentially interfertile (i.e., same biologicial species)