12. Selection, adaptation , and the rise of biological complexity

1. 12. Selection, adaptation, and the rise of biological complexity Selection needs variation Most species have great variation in reproductive success. This variation is the basis for natural selectionthat means changes in gene frequencies.

2. 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.

3. 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

4. Industrial melanism Biston betularia Biston betularia was in England represented by its light variation. 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.

5. Pesticide resistance in insects Recently more than 500 insect pest species evolved resistance against major classes of insecticides.

6. 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

7. Peckhamian mimicry Wasmannian mimicry Some tropical jumping spiders mimic ants A tropical spider mimics a prey beetle species A harmless species mimics another to live in thesame nest or structure A predator species mimics its prey species

8. 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. Their is a campaign for vaccination Virulence of myxoma virus Mortality of rabbits The virus lost virulence and the rabbit evolved resistance.

9. Coevolution: flowering plants and pollinators Lamarouxia hyssophifoliais hummingbird pollinated Emorya suaveloensis butterfly pollinated Lamarouxia xalapensisis bee pollinated Magnolia grandiflorais beetle pollinated

10. Coadaptations The 900 fig tree species produce flowers concealed within an enclosed inflorescence, the fig. A fig wasppollinates and lays eggs. Fig wasps emerge from their galls and mate. Wasps develop within the galls Pollination and egg laying After pollination galls change colours and smells and become attractive to fruit eating birds, bats, monkeys, and lizards. Figs produce flowers within inflorescences Galls are dispersed by fruit eaters The female fig wasp has to enter the gall through a tiny opening.The female body is particularly adapted to this task. Most species are tree specific and find their tree due to allochemicals produced by this fig species. 600 species of fig wasps (Agaonidae) form a mostly tropical family of chalcid wasps that are morphologically and ecologically specialized fig tree pollinators. The high degree of specializaton leads to fast diversification

11. Adaptive radiations Darwin finches 13 species evolved within a few mya • Adaptive radiations mainly occur • when new adaptive peaks have been reached • on newly colonized islands Adaptive radiation refers to a fast rate of speciation within a lineage (fast cladogenesis)

12. 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.

13. 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

14. Drosophila from Hawaii pseudoobsura/persimilissimaulans/mauritianapseudoobscura/mirandapicticornis/16 other speciesmelanogaster/simulansyakuba/teissierorena/erecta 1 5 Neogene D. pseudoobsura/subobscura 23 Paleogene Hawaiian Drosophila Drosophila with spotted wings 35

15. 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

16. 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.

17. The rise of biological complexity Data from Taft, Mattick 2004 • Preliminary genome data suggest • Differential increase of gene number with genome size • A non-linear increase in higher animals • A linear increase in genome number towards vascular plants • Differential trends in genome organization in plants and animals • 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

18. The rise of regulatory genes Data from Croft et al. 2003 In prokaryotes the number of regulatory genes rises to the quadrate of the total number of genes

19. The rise of biological complexity Number of cell types After Anbar (2008) • 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 • An initial fast increase in gene number • What factors allowed complexity to increase? • Rising oxygen level • The appearance of food chains • Sex • Effective genomic repair mechanisms The constant increase in gene number generated a step wise increase in morphological complexity.

20. Numbers of genes and cell types are not correlated Cell type estimates in higher animals highly diverge. From Vogel, Chothia (2006)

21. 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

22. „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 SymbionticBacteria Fungi Bikont plant Flagellum Nucleus Unikont Mitochondria Mitochondria Aphid nucleus Lichen: Ascomycetes+Cyanobacteria Acyrthosiphon pisum Photo: J. White, N. Moran Aerobic Proterobacterium Spiro-chaetes Cyano-bacterium Archaea

23. Coevolution of endosymbiosis Proteus vulgaris Coevolutionary studies can gives estimates about the age of lineages. It might cause evolutionary arms races. Escherichia coli Schlectendalia chinensis 50-70 mya 80-160 mya Melaphis rois Pemphigus betae Chaitophorus viminalis Origin of endosymbiontic association Mindarus victoriae 80-120 mya Rhopalosiphum padi Rhopalosiphum maidis Schizaphs graminum Uroleucon sonchi Diuraphis noxia Acyrtosiphon pisum 30-80 mya Aphid host lineages Bacterial lineages Myzus persicae

24. 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)

25. Horizontal gene transfer Eukaryotes Eocyta Proterobacteria Euryarchaea Cyanobacteria Importance of horizontal gene transfer Operational genes Informational genes Root Proterobacteria are closest relatives to mitochondria. Eocyta (Crenarchaea) are thermophilous Archaea. 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. In this model Eukaryotes emerged through a fusion of two complete genomes. Today’s Eukaryote genomes contain many original mitochondrial genes. The model implies that mitochondria are a basic constituent of Eukaryotes.

26. 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