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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 ...
A hybrid zone may appear during secondary contact, meaning there would be an area where the two populations cohabitate and produce hybrids, often arranged in a cline. The width of the zone may vary from tens of meters to several hundred kilometers. A hybrid zone may be stable, or it may not.
Hybrizyme is a term coined to indicate novel or normally rare gene variants (or alleles) that are associated with hybrid zones, geographic areas where two related taxa (e.g. species or subspecies) meet, mate, and produce hybrid offspring. [1] The hybrizyme phenomenon is widespread and these alleles occur commonly, if not in all hybrid zones. [2]
It can occur across hybrid zones due to chance, selection or hybrid zone movement. [8] There is evidence that introgression is a ubiquitous phenomenon in plants and animals, [ 9 ] [ 10 ] including humans, [ 11 ] in which it may have introduced the microcephalin D allele.
A prediction of reinforcement is that assortive mating should be common in hybrid zones; a prediction that was confirmed in 19 of the 37 cases. [6] A survey of the rates of speciation in fish and their associated hybrid zones found similar patterns in sympatry, supporting the occurrence of reinforcement. [68]
Mathematical models, laboratory studies, and observational evidence supports the existence of parapatric speciation's occurrence in nature. The qualities of parapatry imply a partial extrinsic barrier during divergence; [2] thus leading to a difficulty in determining whether this mode of speciation actually occurred, or if an alternative mode (notably, allopatric speciation) can explain the data.
A tension zone is a transitional zone between two distinctive zones, the zones may be influenced by climatic factors, [1] [2] and geological variation. [ 3 ] creating a floristic tension zone. [ 4 ] A marine tension zone may be affected by variables such as depth, climate or salinity. [ 5 ]
Hybrid zones between races are semi-permeable barriers to gene flow, [11] see for example the chromosome races of the Auckland tree wētā. [12] Chromosomal race A population distinguished by having a unique karyotype, i.e., different chromosome numbers , or different chromosome structure. [9] Geographical race