Search results
Results From The WOW.Com Content Network
The types of barriers that can cause this isolation include: different habitats, physical barriers, and a difference in the time of sexual maturity or flowering. [6] [7] An example of the ecological or habitat differences that impede the meeting of potential pairs occurs in two fish species of the family Gasterosteidae (sticklebacks).
Ecological speciation can occur pre-zygotically (barriers to reproduction that occur before the formation of a zygote) or post-zygotically (barriers to reproduction that occur after the formation of a zygote). Examples of pre-zygotic isolation include habitat isolation, isolation via pollinator-pollination systems, and
For example: If population has the prezygotic isolating allele and the high fitness, post-zygotic alleles and ; and population has the prezygotic allele a and the high fitness, post-zygotic alleles and , both and genotypes will experience recombination in the face of gene flow. Somehow, the populations must be maintained.
Costus plants: Costus allenii, C. laevis, and C. guanaiensis; [62] [63] C. pulverulentus and C. scaber [64] A unique case of post-zygotic instead of prezygotic isolation has been observed in both Gossypium and Gilia, suggesting that in plants, post-zygotic isolation's role in reinforcement may play a larger role. [3]: 361
Support for the reproductive character displacement hypothesis comes from observations of sympatric species in overlapping habitats in nature. Increased prezygotic isolation, which is associated with reproductive character displacement, has been observed in cicadas of genus Magicicada, stickleback fish, and the flowering plants of the genus Phlox.
A major aspect of speciation research is to determine the nature of the barriers that inhibit reproduction. Botanists often consider the zoological classifications of prezygotic and postzygotic barriers as inadequate. [259] The examples provided below give insight into the process of speciation.
Hence, prezygotic reproductive barriers to gene flow may be environment dependent. Postzygotic isolating barriers have also been shown to be important in a variety of hybrid lineages. Work on Helianthus sunflowers has revealed that intrinsic postzygotic factors can cause reproductive isolation against the parent species.
Allochronic speciation (also known as allochronic isolation, or temporal isolation) is a form of speciation (specifically ecological speciation) arising from reproductive isolation that occurs due to a change in breeding time that reduces or eliminates gene flow between two populations of a species.