Question

Define allopatric speciation and explain how it occurs. Use at least one specific example (real or hypothetical) to aid your explanation. Be sure to include the role of geographic separation, evolutionary mechanism(s), reproductive isolation, and reinforcement. Is allopatric speciation a common mode of speciation? What evidence is there of allopatric speciation in nature? Briefly contrast allopatric speciation with sympatric speciation.

Answer 1

Allopatric speciation is speciation that results when a population is separated by a physical barrier like mountain, river or oceans where two populations are unable to meet for breeding. It is also called as geographical speciation. The two isolated population evolve in course of evolution over a period developing into a different species form one another. For example some population picture winged drosophila cross geographical barrier ocean form an island Kauai to Oahu, at Oahu one population started emerging which was different form parental species. The new species of population at Oahu Island was genetically different form their parental species and due to interbreeding among themselves at the Oahu island found a new species. Over course of time due to natural selection and natural pressure by reinforcement the two populations at different islands have evolved into two different species developing new genetic traits such that the two population species are no longer able to interbreed. Due to reproduction isolation cased by the barrier they have developed into two different species, to become into isolated species they must isolated through reproductive isolation.

Accodring to research speciation was seen in two species of Midas cichlid fish (Amphilophus species) living in lake Apoyo a volcanic crater lake in Nicaragua researchers were able to analyze the DNA, the ecology of separation and appearance of the fishes. These fishes showed slight variation in their appearance and were unable to interbred indicating theta these fishes have under gone a series of evolution after their separation due the natural barrier volcanic crater

Sympatric speciation: It is the speciation of new species in population living on the same geographical location. Gene glow in interrupted by non physical barriers like sexual selection

Allopatric speciation: Gene flow is interrupted by physical barriers