From Biol301

Contents 1 Species 1.1 Biological Species Concept 1.1.1 Problems with the BSC 1.1.2 Strength of the BSC 1.2 Morphological Species Concept 1.2.1 Problems with the MSC 1.2.2 Strength of the MSC 1.3 Phylogenic Species Concept 1.3.1 Problems with the PSC 1.3.2 Strengths of the PSC 1.4 Unified Species Concept

Species

• Earnst Mayr solved question of how species originate in 1942.
• Darwin was just talking about adaptations.
• There are many concepts about how to define a species.

Biological Species Concept

Problems with the BSC

• BSC does not answer questions about many organisms we know to be different species can interbreed.
  • Examples:
    • Mallards can hybridize with lots of other species
    • Baltimore orioles
    • Red and white oaks
    • Wolves and coyotes, wolves and most dogs
    • German Shephards and Chihuahuas cannot interbreed
• BSC does not work for asexual organisms
  • If you're asexual you're considered to be female.
  • Whiptail lizards are an example of an asexual vertebrate.
• BSC does not work with extinct animals
  • Homo florences: small people in Indonesia, can't know if they could interbreed with Homo sapiens
• BSC does not work when species are allopatric (being in separate areas)
  • Reindeer of the old world (Norway, etc.) and Caribou of Canada and Alaska

Strength of the BSC

• Interbreeding causes similar morphology and DNA

Morphological Species Concept

• Defines species based strictly on their looks, behaviors, habits, etc.

Problems with the MSC

• Differences in morphology of females and males of the same sex (indeed, male and female mallards were first classified as separate species!)
• mutations: we may not know if it is a mutation or a different species
• The question remains: how much difference is enough to justify a new species.

Strength of the MSC

• All you have to do is measure morphology which makes using fossils, pictures, drawings, video, etc. useful.

Phylogenic Species Concept

• defines as a species any group of organims that have DNA that shows they all came from a single ancestor
  • This is termed being monophyletic

Problems with the PSC

• Many species that we know are distinct are not monophyletic.
  • Example: as far as DNA analysis goes, wolves from Eastern Canada look more like coyotes than like Alaskan wolves.

Strengths of the PSC

• Less subjective than other concepts; strictly a matter of ATC&G
• Can possibly be used for some extinct species (only back about 100,000 years though as DNA degrades)

Unified Species Concept

• Defines species using DNA, morphology and interbreeding information as well as observations about ecological niche, habit, etc.
• Example: Orioles
  • Baltimore Orioles: found in the northeast and midwest
  • Bullocks Orioles: found in the midwest and west
  • Hybrids between these two birds are viable and fertile.