Microtaxonomy pt 2

• Speciation - formation of new and distinct species in the course of evolution
• Anagenesis

  • linear change
  • one species changes another
• Cladogenesis

  • divergence
  • branching evolution
  • branches off new taxa from common ancestral lineages
• Characterstasis - no change in the characteristic of the species
• Anacladogenesis - a species exhibiting both anagenesis and cladogenesis
• Anagenesis

  • slow transition
  • no geographical barrier
  • the parent species is gradually transformed into a new species and does not exist
• Cladogenesis

  • rapid splitting
  • a geographical barrier is responsible
  • the parent species and the new species might exist together
• Allopatric Speciation

  • geographic barrier
  • genetic divergence
• Sympatric Speciation

  • speciation happens geographically overlapping populations when biological factors (e.g. chromosomal changes, nonrandom mating) reduce gene flow
• Balanced polymorphism - two or more variant forms of a specific DNA sequence that can occur among different individuals

  • crypsis - avoid detection by blending in with the background
• Polyploidy - three or more complete set of chromosomes

  • more applicable to plants
• Parapatric Speciation - two separate regions occur with a zone of hybridization where two sub-populations overlap; there is a small contact zone
• An infraspecies is the categories below the species level
• 1870s-1900

  • splitters vs lumpers
  • Darwin: species doesn't differ from variety
  • Elliot Coues: Catalog of American Birds, subspecies prefix was "var."
  • Robert Ridgeway: dropped the "var."
  • Karl Jordan: recognized subspecies
• 1930s

  • Otto Kleinschmidt's Formenkreis Theory - subspecies and trinomial nomenclature
  • Bernhard Rensch: Rassenkreis (circle of races) and Artenkreis (circle of species)
• 1940s

  • Mayr: subspecies, semispecies, superspecies
• 1950s

  • Brown & Wilson: attack on subspecies or the trinomial concept
• A subspecies is a population that a taxonomist considers to differ from previously named population of a species
• You can tell that it is a subspecies through...

  • Morphological or fossil evidence
  • genetic or genomic evidence
  • Ecological, behavioral, or physiological characters
• Polytypic species

  • contains two or more subspecies
  • only applicable for subspecies
  • simplification to classification
• Monotypic species has no subspecies
• Section 5 Article 24

  Names of Taxa Below the Rank of Species

  • the name of an infraspecific taxon is a combination of the name of a species and an infraspecific epithet. A connecting term is used to denote the rank
• International Code of Zoological Nomenclature replaced variety
• International Code of Nomenclature of Bacteria
• Temporal Variation

  • age variation: seasonal polyphenism
• Social Variation

  • caste polymorphism - different roles in a colony
• Ecological Variation

  • mainly due to environmental factors: density dependent
• Ecological Variation

  • host dependent
• Ecological Variation

  • allometric
• Ecological Variation

  • Ecotypic variation: phenotypic plasticity
• Traumatic Variation

  • endosymbiont-induced
• Foundation for Evolution

  • mutation and recombination - gives rise to genetic differences among many members of a population
• Ring species - interconnected because of a contact zone
• A semispecies is considered as an incipient or is transitional towards superspecies
• Artenkries consists of superspecies and semispecies
• • Shenzhen code - algae, fungi, plant
  • International code of zoological nomenclature
  • International code of nomenclature for bacteria
  • uses variety
  • bacteria = strain
• Temporal Variation - differ in morphological phases
• Phenotypic plasticity - difference in phenotype
• Caste polymorphism - 2 or more differentiated forms among colonies
• Seasonal polyphenism - change in form, color of a pupa because of change in season