Speciations

Species / generalized :

  • Reproduce within sp.

  • Have similar traits

There is no true definition of species that fits to all organisms

Tan and white striped sparrows!

Biological species concept:

“A population whose members are ble to interbreed freely undeer natural conditions and are reproductively isolated”

  • If two individuals from two different species reproduce sexually the offspring will have a mix of the two traits

  • Gene flow — associated with losing biodiversity

    • Unique traits lost

    • e.g. mallard; preference for male not of their own species (NA male which is very colorful)

Reproductively isolated:

  • Barriers can be biological

    • Incompatibility of primary sex characteristics, different mating calls

  • Barriers can be physical

    • Mountain range, river, ocean separating individuals

Speciation

  • Creation of new species

  • Population naturally experiences changes in phenotypes/genotypes over time

    • Mutation

    • Evolution, genetic drift

  • If the changes in phenotypes/genotypes can be sustained through reproductive/geographic boundaries, speciationoccurs

Allopatric speciation

  • Most common

  • physical barrier deparates population

  • gene flow must be low

Depening on how large the isolated populations are

  • Vicariant: equally large land masses

  • Peripatric: one land mass larger than other (e.g. island colonization)

Changes are predictable

Island rule: expected phenotypic changes— each new mutation takes much less time in a small pop such as that on an island to demonstrate phenotypically

  • Larger animals evolve to become smaller (insular dwarfism) — e.g. homo floriensis

  • Smaller animals evolve to become larger (insular gigantism) — e.g. house mouse that feeds on albatross

Island ecosystems differ from mainland ecosystems

  • less food for large animals (especially herbivores)

  • Reduced species diversity (less competition, entire trophic levels may be missing)

Herbivores:

  • Large size deters predators; large size no longer selected for on predator-limited islands

Carnivores: prey tends to be smaller on islands; less food to support large body; large size no longer needed to catch large prey

Parapatric: partial range overlap between original and new species

  1. Abiotic conditions vary over the range of a species

  2. individuals in one part of range begin to differ phenotypically from main source

  3. Individuals in teh evolving pop mainly isolated in local envr conditions

  4. Speciation occurs over time

Sympatric: complete range overlap between og and new species

  1. sudden change (behavior or physical)

Shift in niche (food sources)

Chain in host for a parasiye

switch in reproductive strategy

Sudden genetic mutation

  1. Changed indivudals are able to access and reproduce (with) each other

Hypothesis: envr vs genetics

Hybrid Speciation: creation of species thru hybridization of different species

  • Must be fertile

  • Must be fit enough to compete in the same envr as their two parent species

Hard for hybrid to become species:

  • many are sterile

  • rare

  • hard to guarantee access to another hybrid

Questions to ask yourself:

  • Are the pops of = size

  • Do the ranges overlap

  • Is the entire range found within the range of the other

Speciation can only occur when there is minimal or no gene flow

Rates of speciation

  • Gradual speciation

    • small and gradual over time, many intermediates (“evolution creeping forward” — fossil recorded needed) e.g. horses

  • punctuated equilibrium

    • species diverge very rapidly

    • after quick divergence, remain unchanged for a long period of time

    • single or few mutations must occur in short period of time

    • mutations must be severe enough

    • e.g. tiger salamander and mexican axolotl

  • mexican axolotl endured one gene mutation causing massive change that allow land dwelling

Rates of evolution varies between taxonomic groups

exception = Adaptive radiation

  • Many species evolve in short period of time

  • frequently correlates with sudden abundance of open niches

Creation of new niches thru

  • mass extinction

  • development of new traits which create new, unexploited niches

    • e.g. first animals to come onto lands, frist plants to produce seeds, flowers, diversification of birds

coevolution indicates that both species are benefitting