BIOL 4120: Principles of Ecology Lecture 2: Adaptation and Evolution

1. BIOL 4120: Principles of Ecology Lecture 2: Adaptation and Evolution Dafeng Hui Office: Harned Hall 320 Phone: 963-5777 Email: dhui@tnstate.edu

2. Evolutionary Ecology 2.1 Nature selection as a force of evolution 2.2 Heritability is the feature of Natural Selection 2.3 Genes are the units of inheritance 2.4 Genetic variation is the ingredient of NS 2.5 Evolution is the outcome of NS resulted from gene frequency change 2.6 Speciation and mechanisms

3. Introduction to evolutionary ecology Major question in Ecology: What determines distribution & abundance of species? Two classes of answers Contemporary, local factors (domain of traditional Ecology, biomes and PPT and T) Historical factors (= evolutionary ones) Why different species live in different environments? (Adaptation) E.g., long necked giraffe in savannas of Africa (widely dispersed, umbrella-shaped trees); white coated polar bear in Arctic (invisible to prey)

4. 2.1 Nature selection as a force of evolution What is Darwin�s natural selection? The differential success (survival and reproduction) of individuals within the population that results from their interaction with their environment. �Survival of fitness, elimination of �inferior� individual� Fitness of an individual is measured by the proportionate contribution it makes to future generations. Fitness is �reproduction� Selection works on population, not individual.Fitness of an individual is measured by the proportionate contribution it makes to future generations. Fitness is �reproduction� Selection works on population, not individual.

5. Two conditions (assumptions): 1. There is variation in populations. Variation is heritable. 2. In every generation some organisms are more successful at surviving and reproducing than others. Survival and reproduction are not random, but are related to variation among individuals. Organisms with best characteristics are �naturally selected.� If 2 conditions are met then the population will change from one generation to the next. Evolution will occur.

6. Evidence of natural selection Evolution of beak shape in Finches. Peter and Rosemary Grant�s (and colleagues) work on Medium Ground Finches Geospiza fortis. Do we have any evidence of NS? (Domestic animal, crops Natural+articifical selection?) webbed foot of a duck enables it to swim better than a foot that is not webbed. There are two forms of the peppered moth (Biston betularia) in England- a dark-colored form (carbonaria) and a light form (typica). Do we have any evidence of NS? (Domestic animal, crops Natural+articifical selection?) webbed foot of a duck enables it to swim better than a foot that is not webbed. There are two forms of the peppered moth (Biston betularia) in England- a dark-colored form (carbonaria) and a light form (typica).

7. Natural selection Darwin�s Finches Genetic studies show all arise from a single ancestral species.

9. Is there a phenotypic variation in beak size?

10. Is variation in beak size correlated with variation in fitness?

11. Beak size evolves

12. Stabilizing selection: human birth weight. Black bellied seedcraker: feed on seeds of two species of sedge. Seeds are same in size, but differ in hardness. Large beak on hard seed, small on soft seeds. Stabilizing selection: human birth weight. Black bellied seedcraker: feed on seeds of two species of sedge. Seeds are same in size, but differ in hardness. Large beak on hard seed, small on soft seeds.

13. 2.2 Heritability is an essential feature of NS Heritability: individual�s characteristics are passed from one generation to the next. Measured as proportion of the variation in a trait in a population that is due to variation in genes. Mendel�s genetics and inheritance For NS to occurs, the first thing is inheritable variation. �Blending inheritance� before Mendel.For NS to occurs, the first thing is inheritable variation. �Blending inheritance� before Mendel.

15. 2.3 Genes are the units of inheritance

16. What are genes? At any locus, diploid individuals have two copies of genes (alleles). At any locus, diploid individuals have two copies of genes (alleles).

17. Flower color is controlled by one gene, two alleles. P and W. (Picture was cut somehow, differ from textbook) Gametes: egg or sperm Flower color is controlled by one gene, two alleles. P and W. (Picture was cut somehow, differ from textbook) Gametes: egg or sperm

18. Phenotypic plasticity

19. Norm of reaction

20. 2.4 Genetic variation is the ingredient for Natural Selection Genetic variation within a population is absolutely necessary for natural selection to occur If all individuals are identical within a population then their fitness will all be the same

21. Sources of genetic variation Mutation: inheritable changes in a gene or a chromosome Gene mutation: (point mutation) Chromosome mutation deletion, duplication, inversion, translocation Genetic recombination Sexual reproduction two individuals produce haploid gametes (egg or sperm) � that combine to form a diploid cell or zygote. Reassortment of genes provided by two parents in the offspring Increases dramatically the variation within a population by creating new combinations of existing genes. Asexual reproduction: less variation (only mutation)

22. What do we mean by genetic variation? Range (variance) of phenotypes, as in Darwin�s Finch example Different chromosomal arrangements (cytogenetics) DNA sequence differences among individuals Electrophoresis--> electromorphs = allozymes Molecular marks: RFLP, RAPD, etc.

23. 2.5 Evolution is a change in gene frequency Evolution is a change of gene frequencies within a population (or species) over time Individuals do not evolve, populations evolve Focus on gene pool, collective But why do we see populations are still the �same� over many generations?

24. The Hardy-Weinberg Principle The Hardy-Weinberg Principle: Gene frequencies will remain the same in successive generations of a sexually reproducing population if the following five conditions hold: Random mating There is no mutation The population is very large There is no selection There is no migrations (isolated from other populations)

25. The Hardy-Weinberg Principle

26. Five Causes of evolution Mutations Gene flow - Emigration and immigration of individuals (Flow of alleles) Genetic Drift � Changes in the gene pool of a small population due to chance Nonrandom mating: (AA mates AA, Aa) Natural selection Gene frequency: any thing influencing gene f willGene frequency: any thing influencing gene f will

28. Flooding Flooding

29. 2.6 Speciation and mechanisms Speciation: splitting of one species into 2 different species. Concept of species: Biological Species: a species is a group of organisms whose individual have the potential to interbreed and produce fertile offspring. Reproductively isolated: don�t produce fertile hybrids Natural conditions: artificial breeding doesn�t count. For example, artificial insemination, keeping 2 species locked up together. Morphological species: members of the same species look similar to each other. Many examples of organisms that look similar but can�t produce fertile offspring. No one species concept applies to all organisms

30. Genetic isolation mechanisms (reproductive barriers) Premating mechanisms Habitat selection; temporal isolation; behavior or mechanical or structure incompatibility Postmating mechanisms Genetic barrier such as hybrids are sterile; seed abortion; hybrid inviability.

31. Mechanisms of speciation Several are well documented: Allopatric speciation (probably most vertebrates) allopatric species occupy areas separated by time or space. Sympatric speciation (especially plants and insects) Sympatric species occupy the same place at the same time

32. Allopatric Speciation Geographic isolation, Easy to understand. The following concepts mentioned in the textbook. Cline: measurable, gradual change over a geographic region in the average of some phenotypic charter, such as size, coloration or a gradient genotypic frequency. Example, weight change of White-tailed deer, 136 kg in Canada, 93 kg in Kansa, 46 in Louisiana. Ecotype: a population adapted to local environmental conditions (step clines). Examples, Yarrows from high elevation to low elevation. Short Stature from high elevation retained no matter where planted. Geographic isolates (subspecies): distinguishable by certain characters, but there is gene flow between them. First stage of speciation.The following concepts mentioned in the textbook. Cline: measurable, gradual change over a geographic region in the average of some phenotypic charter, such as size, coloration or a gradient genotypic frequency. Example, weight change of White-tailed deer, 136 kg in Canada, 93 kg in Kansa, 46 in Louisiana. Ecotype: a population adapted to local environmental conditions (step clines). Examples, Yarrows from high elevation to low elevation. Short Stature from high elevation retained no matter where planted. Geographic isolates (subspecies): distinguishable by certain characters, but there is gene flow between them. First stage of speciation.

33. Ring species: population of a single species encircle an area of unsuitable habitat. As a result, the species becomes geographically distributed in a circular, or ring, pattern over a large geographic area. Ring species: population of a single species encircle an area of unsuitable habitat. As a result, the species becomes geographically distributed in a circular, or ring, pattern over a large geographic area.

35. Sympatric speciation (e.g: Speciation by Polyploidy) About half of all flowering plants are polyploid: more than 2 copies of each gene. Polyploids are the result of failure of cell division (mitosis or meiosis) to separate the chromosomes into 2 cells.

36. 2.4 Adaptations reflect trade-offs and constraints Adaptation: Individuals of a species have certain characteristics that enable an organism to thrive in a given environment. Adaptations maintain or increase fitness of an organism in a given environmental conditions.

37. Tradeoff Evolution is reflected in changes in gene frequencies and phenotypes However, changes in gene frequencies involve tradeoffs Giraffes do not graze well on grass due to their long necks Snow leopards can hide in snowy mountains, ordinary leopards can hide well in green trees.

38. Constraint There are many other factors that can influence species adaptation. For example, response of an organism to an environmental gradient such as temperature. All these factors influence species adaptation.

39. The End

40. Brief history of integration of Genetics into Ecological studies Natural Selection�Darwin (1859) The Origin of Species Particulate genetics & inheritance�Gregor Mendel (1856-1864) Mutations & chromosomes�Hugo Devries & others (1901)--sources of variation in populations; rediscovery of Mendel�s work �The Modern Synthesis� (Dobzhansky, Wright, Fisher, Haldane, Mayr, Simpson--1930s & 1940s) Integration Natural Selection & mutation; genetic drift; migration Appreciation of genetic variation within populations in nature DNA structure/importance elucidated by Watson & Crick (1953) double helix structure of DNA Molecular variation in natural populations (Harris; Lewontin & Hubby 1966)--using starch gel electrophoresis ? molecular biology. Synthesis of Ecology with Genetics --> Evolutionary Ecology (starting in 1970s)!

41. The major factors affecting the organisms� survival in the system is Fitness Darwinian fitness: ability of an organism to survive and reproduce in its environment. Adaptation is a characteristic or trait of an organism that increases its fitness relative to individuals that do not possess it. It is an inherited characteristic that increases the ability of an organism to survive and reproduce. Evolution by Natural Selection

42. The traits selected for by natural selection need to be inheritable so that the next generation after selection retains the change Three types of selection Directional See finches Stabilizing Long necks in giraffes Disruptive Sexual dimorphism

44. Summary What is natural selection? Different types of NS Gene and genetic variation Evolution Hardy-Weinberg principle Concept of species. Speciation and mechanisms Adaptation and trade-offs

45. What is a species Ecology is based on the idea that we can identify different groups of organisms within an ecosystem These groups are generally called species There are three specific means of defining a species Morphological species concept A species is defined as a morphologically consistent group of organisms than can be distinguished from all other species Can fail. So called cryptic species Biological species concept A group of populations whose individuals can interbreed and produce fertile offspring and cannot interbreed with other species Reproductive isolation Still fails. If you cannot tell the individuals apart morphologically, how can you tell if they are interbreeding or not Also, some species can interbreed and produce viable offspring Bontebok and Blesbok in South Africa Genetic species concept A group of populations whose individuals have a distinct genetic makeup and who do not interbreed with others groups of populations for some reason Bontebok and Blesbok are genetically distinct as well as being morphologically different. Do not naturally overlap in range

46. Geographical isolates

48. Recap What�s Nature selection? 2 assumptions? Three types of natural selection Concept in genetics: gene, chromosome, DNA, allele, locus, genotype, phenotype, dominance, incomplete dominance etc