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Reinforcement's ubiquity is unknown, [4] but the patterns of reproductive character displacement are found across numerous taxa and is considered to be a common occurrence in nature. [18] Studies of reinforcement in nature often prove difficult, as alternative explanations for the detected patterns can be asserted.
For example, the secondary contact between Homo sapiens and Neanderthals, as well as the Denisovans, left traces of their genes in modern human. However, if hybridization is so common that the resulting population received significant amount of genetic contribution from both populations, the result should be considered a fusion.
[3]: 354 [4] [5] Differences in behavior or biology that inhibit formation of hybrid zygotes are termed prezygotic isolation. Reinforcement can be shown to be occurring (or to have occurred in the past) by measuring the strength of prezygotic isolation in a sympatric population in comparison to an allopatric population of the same species.
Reinforcement is the deliberate introduction and integration of an organism into an area where its species is already established. [1] This mode of translocation is implemented in populations whose numbers have dropped below critical levels, become dangerously inbred, or who need artificial immigration to maintain genetic diversity. [15]
Hybrid zones can form from secondary contact. A hybrid zone exists where the ranges of two interbreeding species or diverged intraspecific lineages meet and cross-fertilize. . Hybrid zones can form in situ due to the evolution of a new lineage [1] [page needed] but generally they result from secondary contact of the parental forms after a period of geographic isolation, which allowed their ...
Often-cited examples of sympatric speciation are found in insects that become dependent on different host plants in the same area. [38] [39] The best known example of sympatric speciation is that of the cichlids of East Africa inhabiting the Rift Valley lakes, particularly Lake Victoria, Lake Malawi and Lake Tanganyika. There are over 800 ...
Map of the world using hexagons of the same area, with landmasses and oceans categorized as different Lifezones, also arranged hexagonally. The Holdridge life zones system is a global bioclimatic scheme for the classification of land areas. It was first published by Leslie Holdridge in 1947, and updated in 1967.
Allopatric speciation (from Ancient Greek ἄλλος (állos) 'other' and πατρίς (patrís) 'fatherland') – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model [1]: 86 – is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow.