Blog post: Module 11 reflection

 Speciation is the process by which reproductive isolation evolves between populations. The evolution of reproductive isolation is typically a gradual process that occurs along a gradient, starting from a single variable population, continuing to differentiated populations that are still connected by gene flow, and finally ending in distinct and reproductively isolated species. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, parapatric, and sympatric. In allopatric speciation, groups from an ancestral population evolve into separate species due to a period of geographical separation. In sympatric speciation, groups from the same ancestral population evolve into separate species without any geographical separation. In parapatric speciation, two subpopulations of a species evolve reproductive isolation from one another while continuing to exchange genes. Peripatric speciation is a special version of the allopatric speciation mode and happens when one of the isolated populations has very few individuals. I think the speed of speciation varies among different modes of speciation. When selection pressure is intense, rapid speciation is likely to occur; generation time can influence the speed of evolutionary change and hence the rate at which new species appear. One mode of speciation can be faster than another. The fastest known examples of speciation, taking several hundred generations, had been documented in certain insects.  New research, reported in the journal Science, describes a run of salmon that colonized a river and a lake beach and evolved partial reproductive isolation in fewer than 13 generations. Natural selection, it appears, can spur the emergence of new species far faster than expected.

https://www.scientificamerican.com/article/high-speed-speciation/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2605086/