Transcript Slajd 1
12. Selection, adaptation, and the rise of biological complexity 100 Differences in reproductive success of three Orchid species 80 of fruits Cumulatve percentage x Selection needs variation Oeceoclades maculata Lepanthes wendlandii Encyclia cordigera 60 40 20 Isocline 0 0 20 40 60 80 100 Cumulative percentage of individuals Most species have great variation in reproductive success. This variation is the basis for natural selection that means changes in gene frequencies. Selection should result in higher frequencies (higher reproduction rates) of genotypes that are better adapted to selection pressures Adaptations are fits to environmental conditions (selection pressures) Echolotes of bats are adaptations to catch nocturnal insects Mimese is an adaptation to escape predators Adaptations are • Heritable: adaptations are genetically determined • Functional: adaptations have been shaped by natural selection for a particular task • Adaptive: adaptations increase fitness In the course of evolution adaptations might become maladaptive. These are termed vestigial. Adaptations and Exaptations Via natural selection species become adapted to environmental conditions. But natural selection must act on something. These preadaptational features are called exaptations Feathers appeared in the Therapoda lineages for thermoregulation. This was an exaptation for later flight. The lungs in Dipnoer are primitive. This was an exaptation for the gas bladder to control buoyancy in the Actinopterygii Industrial melanism The first melanic morph was detected in 1848. By 1950 in many regions only melanic forms occurred. Since then the light form again retained dominance. Both changes are assumed to be correlated with air pollution during the industrial revolution. Main selective agent was bird predation. z melanic form Biston betularia was in England represented by its light variation. Proportion of the z Biston betularia 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1955 1965 1975 1985 1995 2005 Year Pesticide resistance in insects 500 Pyrethroids Carbamates Organophosphates # species z 400 Cyclodienes DDT 300 Total 200 100 0 1940 1950 1960 1970 1980 1990 Year Recently more than 500 insect pest species evolved resistance against major classes of insecticides. Mimicry Batesian mimicry Müllerian mimicry A tropical fly mimics a bee Two tropical butterflies look similar A harmless species mimics an unpalatable or poisonous species Several unpalatable or poisonous species have similar warning colours Peckhamian mimicry Wasmannian mimicry A tropical spider mimics a prey beetle species Some tropical jumping spiders mimic ants A predator species mimics its prey species A harmless species mimics another to live in the same nest or structure Myxomatosis and rabbits Virulence and mortality after the introduction of the myxoma virus in Australia to control the population of European rabbits (Oryctolagus cuniculus). The myxoma virus causes skin tumours in European rabbits. In 1938 it was introduced in Australia and since 1950 it spreads throughout Europe. Virulence of myxoma virus 1953 1962-1967 1968-1970 1971-1973 1974-1976 1977-1980 I 100 3 0 0 1.3 0 II 0 15.1 0 3.3 23.3 30.4 Virulence grade III 0 71.1 100 93.4 66.8 65.3 Their is a campaign for vaccination IV 0 10.3 0 3.3 8.6 4.3 V 0 0.7 0 0 0 0 Mortality of rabbits Period Unselected rabbits 1961-1966 1967-1971 1972-1975 Mortality 100 94 90 85 The virus lost virulence and the rabbit evolved resistance. Coevolution: flowering plants and pollinators Lamarouxia hyssophifolia is hummingbird pollinated Magnolia grandiflora is beetle pollinated Emorya suaveloens is butterfly pollinated Lamarouxia xalapensis is bee pollinated Coadaptations The 900 fig tree species produce flowers concealed within an enclosed inflorescence, the fig. A fig wasp pollinates and lays eggs. Fig wasps emerge from their galls and mate. Wasps develop within the galls Pollination and egg laying Figs produce flowers within inflorescences The female fig wasp has to enter the gall through a tiny Most species are tree opening. specific and find their The female body is tree due to particularly adapted allochemicals produced to this task. by this fig species. The high degree of specializaton leads to fast diversification After pollination galls change colours and smells and become attractive to fruit eating birds, bats, monkeys, and lizards. Galls are dispersed by fruit eaters 600 species of fig wasps (Agaonidae) form a mostly tropical family of chalcid wasps that are morphologically and ecologically specialized fig tree pollinators. Adaptive radiations Darwin finches 13 species evolved within a few mya Adaptive radiations mainly occur Adaptive radiation refers to a fast rate • when new adaptive peaks have been reached of speciation within a lineage (fast • on newly colonized islands cladogenesis) Adaptive radiation Number of genera of Ammonites Adaptive radiation refers to a fast increase of species richness. This increase is related to the accquition of features that allow for the invasion into previously unoccupied ecological niches and/or habitats. Fast occupation of empty niches means initially: • low degree of competition • low selection pressure • proportionally higher fitness of aberrant individuals • wider morphological, behavioural or dispersal potential • Higher probability of speciation Drosophila from Hawaii 1 5 pseudoobsura/persimilis simaulans/mauritiana pseudoobscura/miranda picticornis/16 other species melanogaster/simulans yakuba/teissier orena/erecta Neogene D. pseudoobsura/subobscura 23 Paleogene Hawaiian Drosophila Drosophila with spotted wings Freshwater fish of the great East African lakes The Cichlidae is one of the most species-rich family of vertebrates. Most of these species occur in three East African lakes, Lake Victoria, Lake Tanganyika and Lake Malawi. At least 500 endemic species have been described in Lake Malawi. They are of monoplyletic origin. Lake Malawi is 4.5-8.6 million years old. Cichlids underwent a rapid adaptive radiation. One explanation is sexual selection. Cichlidae of Lake Malawi Sexual selection Intersexual selection Intrasexual selection (male - male competition) Sexual selection might cause maladaptive traits Northern sea elephants Peacock Fisherian positive feedback loop Female preferences Reinforcement Selection for a male trait Sexual dimorphism Maladaptations Neolamprologus callipterus has the largest sexual dimorphism in vertebrates. The rise of biological complexity Data from Taft, Mattick 2004 Preliminary genome data suggest Arabidopsis thaliana Oryza sativa Homo sapiens Mus musculus 10000 • Differential increase of gene number with genome size • A non-linear increase in higher animals 1000 • A linear increase in genome number towards vascular plants 1000 10000 100000 1000000 10000000 Genome size [mB] • A constant increase in the number of non-coding DNA within Eucaryotes • High degrees of non-coding DNA in higher Eucaryotes • A doubling of non-coding DNA at the procaryote / eucaryote boundary • Differential trends in genome organization in plants and animals z 100 100 Non-coding / total DNA Number of genes 100000 1.2 1 Eucaryotes 0.8 0.6 0.4 0.2 Procaryotes 0 100 1000 10000 100000 Genome size [mB] 1000000 10000000 genes Number of regulatory z The rise of regulatory genes 900 800 700 600 500 400 300 200 100 0 Data from Croft et al. 2003 y = 2E-05x1.96 Procaryotes 0 2000 4000 6000 8000 10000 Number of genes In prokaryotes the number of regulatory genes rises to the quadrate of the total number of genes The rise of biological complexity Y=35300e 35000 x/1000000000 30000 25000 Caenorhabditis 20000 15000 Anopheles Dictyostelium 10000 5000 100 Homo Neurospora Deinococcus Nanoarchaeum 0 -5E+09 -4E+09 Plastids First eucaryotes 10 Mitochondria Pseudomonas -3E+09 -2E+09 -1E+09 Number of cell types Number of genes First major oxidation event 40000 Number of cell types z 1000 1 0 4 3 Time before present Billion years Preliminary genome size data suggest • A 2.5 fold increase of gene number per one billion years • An approximate 100 fold increase in gene number within the last 4 billion years 2 1 0 After Anbar (2008) What factors allowed complexity to increase? • • • • Rising oxygen level The appearance of food chains Sex Effective genomic repair mechanisms • An initial fast increase in gene number The constant increase in gene number generated a step wise increase in morphological complexity. Numbers of genes and cell types are not correlated Cell type estimates in higher animals highly diverge. From Vogel, Chothia (2006) Eight major transitions in evolutionary history adapted from John Maynard Smith, Eros Szathmary (1995) Replicating molecules Populations of molecules in protocells Cell membranes provide selective barriers, increased metabolic efficacy Independent replicators Chromosomes Reduced competition among genes RNA as gene and enzyme DNA genes, protein enzymes Efficient catalysators and replicators Procaryotes Cells with nucleus and organelles (eukaryotes) Effective metabolisms, increased interior surfaces Asexual clones Sexual populations Gene repair, higher adaptive potential Single-celled organisms Multicellular organisms Efficient division of labour, competitive advantage in early food webs Solitary individuals Colonies of non-reproductive casts Efficient division of labour, maximized inclusive fitness Primate societies Human societies Effective managing of environmental changes, high dispersal ability „Life did not take over the globe by combat, but by networking” Lynn Margulis Symbiosis are species interactions where species live in close association over a longer time period In symbiosis, at least one member of association benefits from the relationship. The other members may be injured = parasitism relatively unaffected ( = commensalism) may also benefit ( = mutualism) Four genomes in one cell Animal Plastids Buchnera aphidicola Fungi Symbiontic Bacteria Flagellum Nucleus Mitochondria Mitochondria Bikont plant Unikont Aphid nucleus Lichen: Ascomycetes+Cyanobacteria Acyrthosiphon pisum Photo: J. White, N. Moran Aerobic Proterobacterium Archaea Spirochaetes Cyanobacterium Coevolution of endosymbiosis Proteus vulgaris Coevolutionary studies can gives estimates about the age of lineages. Escherichia coli Schlectendalia chinensis 50-70 mya It might cause evolutionary arms races. 80-160 mya Melaphis rois Pemphigus betae Chaitophorus viminalis Mindarus victoriae Rhopalosiphum padi 80-120 mya Origin of endosymbiontic association Rhopalosiphum maidis Schizaphs graminum Uroleucon sonchi Diuraphis noxia Bacterial lineages Acyrtosiphon pisum Myzus persicae 30-80 mya Aphid host lineages Horizontal gene transfer Horizontal gene transfer is the exchange of genes between unrelated organisms. Mechanisms are: • Viral transduction (transfer of genetic material between organisms by viruses) • Endosymbiosis • Transformation (the uptake of foreign genetic material) • Bacterial conjugation (cell to cell contact of two bacteria) From Ochman et al. (2000) Horizontal gene transfer Eukaryotes Eocyta Proterobacteria Euryarchaea Cyanobacteria Operational Informational genes genes Importance of horizontal gene transfer Root The ring of life Rivera and Lake (2004) provided evidence that the first eukaryotes resulted from the genomes of two prokaryotes, an archaean and a bacterium. The model implies that mitochondria are a basic constituent of Eukaryotes. Proterobacteria are closest relatives to mitochondria. Eocyta (Crenarchaea) are thermophilous Archaea. In this model Eukaryotes emerged through a fusion of two complete genomes. Today’s Eukaryote genomes contain many original mitochondrial genes. Today’s reading Raise and fall of industrial melanism: http://www.arn.org/docs/wells/jw_pepmoth.htm and http://www.streaming.mmu.ac.uk/cook/ Coevolution and pollination: http://biology.clc.uc.edu/courses/bio303/coevolution.htm and http://biology.clc.uc.edu/courses/bio106/pollinat.htm Symbiosis: an online textbook: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Symbiosis.html Horizontal gene transfer: http://www.pnas.org/cgi/reprint/104/11/4489 The ring of life: jnason.eeob.iastate.edu:8200/courses/EEB698/papers/rivera-lake-2004.pdf Sexual selection: http://en.wikipedia.org/wiki/Sexual_selection http://www.worlddeer.org/sexualselection/home.html