Speciation

a new species is created when a group of organisms within a species separates and develops unique characteristics. The new species is generally distinct from the original species and can no longer interbreed with it.

‘The process of transformation of species into new one with the accumulation of variations in time is known as speciation.’

• speciation helps in the organisms diversification.
• speciation leads to the evolutionary progress.
• multiplication of species causes increase in the existing number of species.

Type of speciation

1. Allopatric Speciation – It is also known as geographic speciation. It is a process that occurs when a biological population becomes isolated from the rest of its species and develops into a new one.
   • This isolation can be caused by geographical changes like the formation of mountain range or river capture, social changes like emigration etc.
2. Peripatric Speciation – Peripatric speciation is a type where a new species forms from a small, isolated population that breaks off from a larger group.
   • Peripatric speciation is similar to allopatric speciation, but the new species forms from a much smaller group. In both cases physical barriers prevent the groups from interbreeding with each other.
3. Parapatric speciation – It is the process where the population is large and some of the population cannot interact with the other margin creating an environmental gradient. . Here subpopulation of a species evolve reproductive isolation while still sharing genes.
   • In the parapatric speciation hybrid zones may form at the boundary between the two populations.
4. Sympatric speciation – It is a process in evolutionary biology where a new species evolve from an ancestral species while both continue to live in the same geographical area.
   • The new species are not geographically isolated.
   • This speciation begins with complete genetic mixing between the diverging groups.

Other realted terms –

• Phyletic speciation – It is a speciation in a line or lineage. It involves a gradual change in the average character of a species to achieve better adaptations to the existing environment either due to adaptations to a changing environment or due to increasing specialization for a particular environment.
  • EX- Mesohippus evolving into Miohippus in which one has transformed into other species with the passage of time with the change in environment.
• Gratual speciation – It is slow transformation of an isolated population or population into new species due to gradual accumulation of variations. In a small population, genetic drift operates whereby even non-adaptive trails remains in the population
  • EX- a fish produces ecotypes – races – varities – subspecies – species. ‘This is example of adaptive radiation.’
• Abrupt/ Instant or Rapid speciation – The speciation due to sudden changes can be subdivided into three –
  • Macro-mutation – These are rare but produce widely different individuals – a new variety, subspecies or a species. The mutation causing genetic isolation from sibling species.
  • Autopolyploidy – It is an increase in same chromosome set of genomes. It is a common mechanism of formation of new species with in a plant genus.
  • Hybridisation or Allopolyploidy – It is crossing between different species followed by doubling of chromosomes or allopolyploidy immediately forms new species.
• Quantum speciation – It is a sudden changes in the organisation of a population to a new equilibrium, distinctly different. Quantum speciation can be explained by conceiving predaptation.
  • The organism is modified in such a way that it is also by chance adapted to some other conditions. The organism then move into new adaptive zone which is not occupied by other strong competitors. In this new adaptive zone, the organism evolves rapidly and as this new zone is devoid of competitors, the entire transition occurs in a relatively short period.
  • EX- the ‘CROSSOPTERYGIAN’ fishes were preadapted for life on land.