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Application Evolution: Part 0.1 General Introduction S. chilense S. peruvianum Summer Semester 2013 Prof Aurélien Tellier FG Populationsgenetik Evolutionary biology: study of the evolution of life Apparition of life around 4.6 billions years ago Since: history of evolution by adaptations and extinctions The history of life evolution is not over!!! Evolutionary theory explains the transformation of life forms! History of the Evolution idea Paradigm shifts in Science Thomas Kuhn A bit of history: the foundations Bases of species descriptions by naturalists: Carl von Linné Comte de Buffon Alexander von Humboldt Lamarck: first „Evolutionary theory“ (1809) Each organism has the ability to adapt to his environment Each organism tends to reach for perfection. Abilities aquired during the life time will be transmitted to the next generation Darwin and Wallace: Theory of selection and common descent (1838) Species are developing continuously and die eventually out Similar organisms descent from a common ancestor Evolution occurs at slow pace, not by jumps Evolution proceeds by means of natural selection A bit of history: the foundations Darwin‘s four postulates Individuals within a species are variable A part of this natural variation will be transmitted to the next generation The amount of offspring of individuals is (much) higher than the capacity of the environment, thus there is concurrence (Malthusian idea) At each generation the most succesful individuals reproduce and transmit their characteristics further, the unsuccesful ones do not => The survival and reproduction is not random, but driven by natural selection Example: Galapagos/Darwin-Finches (see Peter and Rosemary Grant works) A bit of history: the foundations Evolutionary Theory 1.0: Darwinism Common descent Natural selection Connection agriculture (human selection) and Natural selection Missing a theory of heredity Agriculture = accelerated and directed evolution? Diamond and Bellwood, Science, 2003 Darwin and disease Darwin, C. R. to Gray, Asa, 16 Apr [1866] My dear Gray I have been a scandalously ungrateful, & idle dog for not having thanked you very long ago for the second article on climbing plants, which pleased me greatly. But, as I have before said, now that I work a little, I seldom feel inclined to write to anyone, but this evening the spirit has moved me to do so, though I have little to say, & my dear amanuensis is poorly with influenza, which has likewise knocked me up for a week.— …. Note: According to Emma Darwin's diary (DAR 242), she came down with influenza on 9 April. CD had contracted influenza the previous day, having gone to bed with a cold on 6 April. By 14 April, CD had recovered. From Darwin Correspondence Database No mention that parasites might be life forms and evolve…. A bit of history: the modern synthesis Evolutionary Theory 2.0: birth of the modern synthesis Compatibility between Mendelism and statistical genetics Theory of selection and random drift => Birth of population genetics The „Holy Trinity“ of evolutionary biology R.A. Fisher Sewall Wright J.B.S Haldane A bit of history: the modern synthesis Evolutionary Theory 2.0: birth of the modern synthesis Statistical population genetics: Wright-Fisher model Model of evolution: geometric model of Fisher Fisher‘s fundamental theorem of selection R.A. Fisher A bit of history: the modern synthesis Evolutionary Theory 2.0: birth of the modern synthesis Statistical population genetics: Wright-Fisher model Fitness landscape: how populations adapt? Sewall Wright A bit of history: the modern synthesis Evolutionary Theory 2.0: birth of the modern synthesis Statistical population genetics Quantitative genetics First one to point out the role of parasites and coevolution The Causes of Evolution (Haldane 1932) J.B.S Haldane “A study of the causes of death in man, animals, and plants leaves no doubt that one of the principal characters possessing survival value is immunity to disease. Unfortunately, this is not a very permanent acquisition, because the agents of disease also evolve, and on the whole more rapidly than their victims.” A bit of history: the modern synthesis Evolutionary Theory 2.0: birth of the modern synthesis Disease and Evolution* J. B. S. Haldane J.B.S Haldane SUMMARY Examples quoted by biologists, in order to show hownatural selection is working, almost present structures or functions concerned either with protection against natural forces or against predators, or with purchase of food or mates. The Author suggests that the struggle against diseases, and especially infectious diseases, has been a very important evolutionary agent and that some of its results have been rather unlike those of the struggle for life in its common meaning Haldane, J. B. S. 1949 Disease and evolution. La Ricerca Scientifica 19, 68–76 A bit of history: the modern synthesis I want to suggest that the struggle against disease, and particularly infectious disease, has been a very important evolutionary agent,… J.B.S Haldane Under the heading infectious disease I shall include, when considering animals, all attacks by smaller organisms, including bacteria,viruses, fungi, protozoa, and metazoan parasites. In the case of plants it is not so clear whether we should regard aphids or caterpillars as a disease…. Within a species of plant we can generally find individuals resistant to any particular race of rust (Uredineae) or any particular bacterial disease. Quite often this resistance is determined by a single pair, or a very few pairs, of genes…. A bit of history: the modern synthesis J.B.S Haldane Probably a very small biochemical change will give a host species a substantial degree of resistance to a highly adapted microorganism. This has an important evolutionary effect. It means that it is an advantage to the individual to possess a rare biochemical phenotype. For just because of its rarity it will be resistant to diseases which attack the majority of its fellows. And it means that it is an advantage to a species to be biochemically diverse, and even to be mutable as regards genes concerned in disease resistance. For the biochemically diverse species will contain at least some members capable of resisting any particular pestiience. And the biochemically mutable species will not remain in a condition where it is resistant to all the diseases so far encountered, but an easy prey to the next one. A beautiful example of the danger of homogeneity is the case of the cuitivated banana clone « Gross Michel » which is well adapted for export and has been widely planted in the West Indies. However it is susceptible to a root infection by the fungus Fusarium cubense to which many varieties are immune, and its exclusive cultivation in many areas has therefore had serious economic effects. A bit of history: the modern synthesis Evolutionary Theory 2.1: the mature modern synthesis „neutral theory of evolution“ (Kimura) Kin selection (Hamilton) Evolution and game theory (Maynard-Smith) Red Queen hypothesis (van Valen) M. Kimura W.D. Hamilton J. Maynard-Smith L. Van Valen A bit of history: the modern synthesis “The major tenets of the evolutionary synthesis were that - populations contain genetic variation that arises by random mutation and recombination; - populations evolve by changes in gene frequency brought about by random genetic drift, gene flow, and especially natural selection; - most adaptive genetic variants have individually slight phenotypic effects so that phenotypic changes are gradual; - diversification comes about by speciation, which normally entails the gradual evolution of reproductive isolation among populations; - and these processes, continued for sufficiently long, give rise to changes of such great magnitude as to warrant the designation of higher taxonomic levels.” Douglas Futuyma Population genetics Evolution = changes between generations of frequency of characters, traits or alleles Why study the genetics of populations? the population is the main unit at which selection acts !!!!!!!!! Population genetics Populations and species show variability: what type and how much genetic variation exist within populations/species? what are the forces that influence the amount of variation within populations? Population genetics: 4 evolutionary forces random genomic processes (mutation, duplication, recombination, gene conversion) molecular diversity natural selection random spatial process (migration) random demographic process (drift) Population genetics investigates the laws governing the genetic structure of populations, and changes in allele frequencies over time Population genetics: 4 evolutionary forces random genomic processes (mutation, duplication, recombination, gene conversion) molecular diversity natural selection random spatial process (migration) phenotypic variability random demographic process (drift) Color code Color code: Red = Important result or definition Purple: exercise to do Green: some bits of maths