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On one extreme is allopatry, in which the overlap is zero (no gene flow), and on the other extreme is sympatry, in which the ranges overlap completely (maximal gene flow). The varying definitions of sympatric speciation fall generally into two categories: definitions based on biogeography, or on population genetics.
In the range of overlap, only brown males of F. hypoleuca exist and are thought to have evolved the brown plumage to prevent hybridization, [17] though there is also evidence indicating that such character displacement is explained by heterospecific competition for territory rather than reinforcement. [18]
Hybridization among poplars is common where ever populations overlap, however the degree of introgression varies greatly depending on the species. One study exploring the extent of introgression among three species of poplar trees (P. balsamifera, P. angustifolia and P. trichocarpa) conducted along the Rock Mountain range in the U.S. and Canada ...
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.
Marah species hybridize freely where ranges overlap and this, in addition to intra-species leaf and fruit variability, makes definite identification of specimens a particular challenge. A proper genetic analysis of Marah phylogeny has not yet been undertaken. The standard taxonomy has been based on morphological comparisons and geographic ...
Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. [1]: 105 Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them., [2] and peripatric speciation may be considered one type or model of allopatric ...
The balm-of-Gilead (Populus × jackii), also known as P. × gileadensis, is the hybrid between P. balsamifera and the eastern cottonwood (P. deltoides), occurring occasionally where the two parental species' ranges overlap.
Arbutus unedo and A. andrachne hybridise naturally where their ranges overlap; the hybrid has been named Arbutus × andrachnoides (syn. A. × hybrida, or A. andrachne × unedo), [10] inheriting traits of both parent species, though fruits are not usually borne freely, and as a hybrid is unlikely to breed true from seed. It is sold in California ...