Evolutionary Biology

• Innah Marie O. Lao, RN, MD 2022
• Interactions Among Species


  • Coevolution and Interactions among Species
  • The Evolution of Enemies and Victims
  • Mutualisms
  • The Evolution of Competitive Interactions
  • Evolution and Community Structure
• Coevolution


  Reciprocal genetic change in interacting species, owing to natural selection imposed by each on the other
• Coevolution


  • The nature and strength of an interaction between two species may vary depending on the genotype, environmental conditions, and other species which those species interact
  • Selection that species exert on each other differ among populations
• Specific coevolution


  Two species evolve in response to each other
• Diffuse coevolution


  Several species are involved and their effects are not independent

  
• Escape-and-radiate coevolution


  Species evolves a defense against enemies, hence are enabled to radiate into diverse descendant species to which different enemies may later adapt
• The Red Queen Hypothesis

  Species (or populations) must continually evolve new adaptations in response to evolutionary changes in other organisms to avoid extinction
• The Red Queen Hypothesis

  • Escalation (evolutionary arms race)
  • Oscillation
• Aposematism


  Biological means by which an organism advertises its dangerous nature to a potential predator
• Mimicry


  Form of convergent evolution where resemblance between different species has evolved because it is advantageous for members of one species to resemble another
• Types of mimicry


  • Defensive mimicry
  • Batesian mimicry
  • Müllerian mimicry
• Secondary compounds


  Plant products that play little or no role in primary metabolism, many are toxic or repellent to animals
• Parasite-host interactions and infectious disease

  • Overcoming the host's defenses
  • Movement from one host to another by vertical or horizontal transmission

  
• Virulent parasites


  Parasites that reduce survival or reproduction of hosts
• Evolution of virulence


  • In a host with multiple, unrelated genotypes of parasites, selection will favor the one with highest reproductive rate (may be highly virulent)
  • Virulent genotypes in horizontally transmitted parasites > vertically transmitted
  • If host can only support parasite reproduction for a short time, selection favors rapid parasite reproduction (greater virulence)

  
• Mutualisms


  Interactions between species that benefit individuals of both species
• Mutualisms


  • Important basis for adaptation and evolution of biochemical complexity
  • Some provide one or both partners with new capabilities
  • Some have arisen from parasitic or other exploitative relationships
  • Several factors can reduce fitness of the cheater genotypes to maintain a mutualistic relationship
• Intraspecific competition


  Competition for resources between members of the same species
• Interspecific competition


  Competition for resources between members of different species
• Effects of interspecific competition

  • Extinction - occur when >2 competing species for the same resources cannot coexist indefinitely
  • Specialization - occur when competing species evolve to different adaptations
• Ecological Character Displacement


  Divergence in response to competition between species
• Ecological Release


  Species (or population) exhibits greater variation in resource use, and in associated phenotypic characters, if it occurs alone
• Interference Competition


  Competition wherein individuals suppress competitors by behavioral dominance or other means, such as poisoning the competitor
• Community


  Assemblage of species in a local habitat
• Evolution and Community Structure

  • Phylogenetically conservative traits can affect which clade could (and could not) persist in a new ecological setting
  • Diversity of species results from evolutionary divergence that reduces competition among different species
  • In two regions of similar environments, convergent evolution may be expected
  • Convergence may be seen in parallel adaptive radiations as well
• Phylogeny: The Unity and Diversity of Life
• Challenges in Inferring Phylogenies

  • Homoplasty
  • Convergent evolution
  • Parallel evolution
  • Evolutionary Reversal
  • Rapid Diversification
  • Radiation
  • Incomplete Lineage Sorting
  • Introgression
• Analytical Methods of Developing Phylogenies from DNA Sequence Data

  • Parsimony or Occam's Razor
  • Maximum Likelihood
  • Bayesian Inference
• Derived Character


  Trait that arose independently in two or more lineages
• Coevolution


  Interactions among species
• Lecture Outline


  • Coevolution and Interactions among Species
  • The Evolution of Enemies and Victims
  • Mutualisms
  • The Evolution of Competitive Interactions
  • Evolution and Community Structure
• Phylogeny


  The study of evolutionary relationships among organisms
• The Unity and Diversity of Life

  • Challenges in Inferring Phylogenies
  • Homoplasty
  • Convergent evolution
  • Parallel evolution
  • Evolutionary Reversal
  • Rapid Diversification
  • Radiation
  • Incomplete Lineage Sorting
  • Introgression
• Analytical Methods of Developing Phylogenies from DNA Sequence Data

  1. Parsimony or Occam's Razor

  2. Maximum Likelihood

  3. Bayesian Inference
• Derived Character


  Trait that arose in the ancestor of a particular lineage and was passed along to its descendants
• Synapomorphy


  Derived character that is shared by a group of species
• Primitive (ancestral) Character


  Trait of a lineage that is inherited from the common ancestor of a clade and has undergone little change since
• Monophyletic group (clade)


  Set of species that descended from a common ancestor
• Outgroup


  Species more distantly related to the members of the clade of interest, used to determine the direction of evolutionary change