Introduction :
Instantaneous speciation refers to the “Sudden/Abrupt development of new species”, which is reproductively and ecologically isolated from the parental species. This mechanism operates through individuals (not by population)
It may occur due to :-
- Mutations : Mutations are sudden and inheritable changes while individuals with mutations are called mutants.
Significance : Such mutations can produce sibling species which are morphologically similar but ecologically and reproductively isolated. For example, the production of two sibling species of Drosophila Pseudobscura and D. Persimilis.
- Hybridization and Polyploidy :
Fig: 1. Origin of Raphanobrassica.
- Polyploidy and Hybridizaiton :
Hybridization involves the interbreeding of two genetically different individuals of two same or different species to produce hybrids while polyploidy means presence of more II two sets of chromosomes. Occasionally, the interspecific hybrids are produced naturally or artificially. Such hybrids are, however, sterile due to incompatibility between the chromosomes of two different species and their failure to pair in meiosis. But the doubling of chromosomes may produce fertile offsprings. Doubling of chromosome number allows normal meiosis and formation of normal but diploid gametes so hybridization followed by polyploidy can lead to the formation of new species very rapidly. This results in the production of new species. Some examples are the production of Raphanobrassica [ An intergeneric hybrid with 2N = 36 produced by crossing Raphanus – radish (2N = 18) and Brassica – cabbage (2N = 18) by Karpechenko. It was produced by hybridization followed by polyploidy] , (Fig. 1) It was produced by hybridization followed by polyploidy] , (Fig. 1)Tritical [hybrid between triticum (wheat) and secale (eye). Its is a man-made cereal] and Triticum aestivum (Hexaploid bread wheat).
Fig: 2 Origin of Hexaploid Weat.