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Speciation is the evolutionary process by which populations evolve to become distinct species.The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages.
Independent speciation occurs when a single population on a single host undergoes speciation resulting in two sister lineages of parasite on a particular host. In other words, the parasite lineage speciates while the host lineage does not. This becomes complicated when the two lineages of parasites then undergo cospeciation with the host.
However, speciation has also a macroevolutionary aspect, because it produces the interspecific variation species selection operates on. [4] Another macroevolutionary aspect of speciation is the rate at which it successfully occurs, analogous to reproductive success in microevolution. [2]
Heteropatric speciation is a special case of sympatric speciation that occurs when different ecotypes or races of the same species geographically coexist but exploit different niches in the same patchy or heterogeneous environment. It is thus is a refinement of sympatric speciation, with a behavioral, rather than geographical barrier to the ...
Controversy exists as to whether Charles Darwin recognized a true geographical-based model of speciation in his publication On the Origin of Species. [5] In chapter 11, "Geographical Distribution", Darwin discusses geographic barriers to migration, stating for example that "barriers of any kind, or obstacles to free migration, are related in a close and important manner to the differences ...
The two populations may fuse back into one population. This tends to occur when there is little to no reproductive isolation between the two. During the process of fusion, a hybrid zone may occur. This is sometimes called introgressive hybridization or reverse speciation.
Macroevolution is guided by sorting of interspecific variation ("species selection" [2]), as opposed to sorting of intraspecific variation in microevolution. [3] Species selection may occur as (a) effect-macroevolution, where organism-level traits (aggregate traits) affect speciation and extinction rates, and (b) strict-sense species selection, where species-level traits (e.g. geographical ...
Partial sympatry in these whales is, therefore, not the result of speciation. Furthermore, killer whale populations that consist of all three types have been documented in the Atlantic, evidencing that interbreeding occurs among them. Thus, secondary contact does not always result in total reproductive isolation, as has often been predicted. [10]