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• Coevolution


  Two or more species driving each others evolution through natural selection
• Types of coevolution


  • Gene-for-gene/matching gene coevolution
  • Pairwise/ Specific coevolution – between two species
  • Guild/ diffuse/ Multi-species coevolution – between multiple species or guilds

  
• Complex organisms require coevolved interactions to survive and reproduce
• Complex coevolved interactions


  • Mitochondria, chloroplast, and eukaryotic cells
  • Plant and pollinators
  • Plant and mycorrhizal fungi
  • Animals and gut symbionts
• Species-rich ecosystems are built based on coevolved interactions
• Ecosystems built on coevolved interactions

  • Forest: interactions between plants, fungi, and bacteria
  • Marine ecosystem: Coral reefs and dinoflagellates
  • Hydrothermal vents: Specialized bacteria and animals
• Forms of coevolution


  • Mutualistic
  • Antagonistic
  • Competitive
• Coevolution takes multiple forms and generates a diversity of ecological outcomes
• Interactions coevolve as constantly changing geographic mosaics
• Assumptions about coevolution


  • Species are often collections of genetically distinct populations
  • Interacting species often differ in their geographic ranges
  • Interactions among species differ among environments in their ecological outcomes
• Geographic selection mosaic


  • Natural selection differ among environments
  • Genes are expressed differently in different environment
• Coevolutionary hotspots


  • Areas with strong reciprocal selection (change in one partner put pressure on the other partner to change)
  • Often surrounded by coevolutionary coldspots (little to none reciprocal selection)
• Trait remixing


  • Genetic structure of coevolving species or populations continually changes
  • Mutations, genomic alterations, gene flow, differential genetic drift, and local extinction provides new genetic material for natural selection to act on
  • Alters spatial distribution distributions of coevolving genes and traits
• Coevolution of pine cones and predators

  • Habitat with both predators: Evolution of squirrel-proof cones (small, wide cones, with small distal scales, heavier cones with fewer seeds)
  • Habitat with squirrels only: Evolution of squirrel-proof cones (small, wide cones, with small distal scales, heavier cones with fewer seeds)
  • Habitat with crossbills only: Evolution of crossbill-proof cones (large, narrow cones, with large distal scales), Crossbills in turn evolve deeper, less curved beaks
• Mutualistic coevolution


  • Results from mutual exploitation
  • Both species benefit from the interaction
  • Species increases the fitness of each other
  • In extreme cases, the two species may not survive without each other
• Mutualistic coevolution between different free-living species

  • Plants and pollinators
  • Plants and seed-dispersers
• Mutualistic coevolution between plants and pollinators


  • Creates complex web of interactions
  • Mutual benefits: flower gets pollinated and the insects/ birds/ bats got fed
• Evolutionary perspective of plant-pollinator coevolution

  1. Early angiosperms with nectar evolved

  2. Pollinators take advantage of this available food source

  3. Plants with more scent and vibrant colors (blue or red-orange) get visited more often

  4. More pollination = more seeds = population with the selected phenotype increased

  5. Microevolution happened = new phenotypes emerged (e.g. longer tubes, more complex structure = longer chance of contact between pollen and pollinator)

  6. Pollinators which can access nectar from these structures are selected (e.g. individuals which cannot access nectar died out or moved to other more accessible flowers)

  7. Pollinators associate certain plant characters to availability of nectar

  8. Certain plant features make them more attractive to specific pollinators

  9. Pollinators develop adaptations allowing them to access this nectar (co-adaptation)
• Plant-pollinator and plant-seed disperser coevolution is product coevolution vortex
• Different flowers can be pollinated by different insect or bird species (but not both)
• Figs (Ficus sp.) can only be pollinated by fig wasps (Chalcidoidea) which rely on the figs for a safe location to lay their eggs
• Coevolution of myrmecophytism (ant symbiosis) and spininess


  • Acacia ant (Pseudomyrmex ferruguinea) provides protection for Valcheilla spp.
  • Valcheilla spp. provide home and food for the ants.
  • P. ferruguinea developed adaptations to exploit the tree, Valcheilla spp. developed adaptation to attract the ants
• Antagonistic coevolution


  Struggle between competing genes, traits, and species resulting in adaptations and counter-adaptations
• Antagonistic coevolution


  • Predator-prey interaction
  • Plant – herbivory
  • Predator avoidance
  • Active defense mechanisms (e.g. spines, scales, shells, being faster or bigger)
  • Camouflage
  • Mimicry
  • Toxicity
  • Host-parasite interaction (co-speciation)
• The evolution of offensive and corresponding defensive adaptations does not go on forever
• Costs of adaptations


  • Longer legs = greater speed = greater chance of breaking
  • Better camouflage = better predator avoidance but may also lead to non-detection by a mate
  • Thicker shells = better protection = greater weight
  • Bigger size = greater chance of being avoided by a predator but will require larger food source
• Plant defense mechanisms against herbivores

  • Physical defense – thorns, spines
  • Mechanical defense – thigmotrophism
  • Chemical defense – allelochemicals/ secondary metabolites (tannins, caffeine, capsaicin)
• Herbivore adaptations


  • Mechanical adaptations (molars, beak)
  • Better digestive systems (symbiosis with gut bacteria)
  • Ability to detect plants with lesser noxious compounds
  • Ability to detoxify secondary metabolites
• Secondary metabolites in ripe fruit function to deter fruit consumption by vertebrates that do not disperse seeds, while not impacting consumption by those that do
• Evolutionary arms race between Brassicales and Pierinae: Brassicales evolved glucosinolates against herbivores. Pierinae evolved nitrile-specifier proteins allowing them to neutralize glucosinolates and colonize the Brassicales
• Predator adaptations


  • Evolved senses (sight, smell, hearing) for prey detection
  • Claws, jaws, and teeth suited for seizing and killing prey
• Prey adaptations


  • Evolved senses (sight, smell, hearing) for predator detection
  • Aposematism (spines, shells, chemicals, warning colors or display)
  • Behavioral adaptations (forming groups/ colonies; startle display)
• Camouflage adaptations


  • Resemblance to surrounding
  • Disruptive coloration
  • Shadow elimination
  • Distractive coloration
  • Self-decoration
  • Changing color and texture
  • Ultrablackness
  • Counter-illumination
  • Transparency
  • Silvering
• Mimicry


  Resemblance to a harmful species or inanimate object to gain a selective advantage by being avoided by the predator
• Types of mimicry


  • Deception hypothesis
  • Coincidence hypothesis
  • Defensive mimicry
  • Aggressive mimicry
  • Reproductive mimicry
  • Automimicry
  • Mimesis
  • Batesian mimicry
  • Mullerian mimicry
  • Mertensian mimicry
  • Wasmannian mimicry
  • Vavilovian mimicry
  • Gilbertian mimicry
• Mimicry examples


  • Prosoplecta sp., a cockroach mimics the noxious lady bug
  • Heliconius sp. are co-mimics
  • Non-venomous Milksnake (Lampropeltis triangulum) mimics Highly venomous coral snake (Micrurus sp.) and Mildly venomous false coral snake (Erythrolamprus sp.)
  • Myrmerachne plataleiodes is an aggressive mimic of the weaver ants (Oecophylla smaragdina)
  • Echinochloa orizoides became an unintentional mimic of rice
  • Members of genus Passiflora produces nectaries which resembles eggs of Heliconius butterflies
  • Members of genus Argiope adds special web with reflects ultraviolet light imitating those found in flowers
  • The spider-tailed horned viper (Pseudocerastes urarachnoides) uses a spider-like structure at the tips of its tail to attract prey
  • The nematode Myrmeconema neotropicum parasitize ants. It turns the abdomen of the ant red to mimic a fruit, making the ant more attractive to birds
  • Cuckoos mimic sparrowhawks to scare small birds to leave their nest
  • Certain orchids mimic female bees to attract males (Pseudocopulation)
  • Smaller male Paracerceis sculpta mimics females and juveniles to sneak on the alpha males (Intersexual mimicry)
• The rough skinned newt (Taricha granulosa) produces tetradotoxin for defense. The common garter snake (Thamnophis sirtalis) developed the ability to counter the poison. Through selective pressure, the newt evolved more potent poison while the snake evolved greater immunity to the poison.
• Fahrenholz Rule


  Phylogeny of host and parasites mirror each other
• Ecological Fitting


  Parasites have a certain physiological range to certain conditions and environment which allow them to survive on a particular host
• Chase-Away Selection


  The mating frequency and secondary sexual traits of males are in step with the female's level of resistance