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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]
The polyploid offspring occupy the same environment as the parent plants (hence sympatry), but are reproductively isolated. A number of models have been proposed for alternative modes of sympatric speciation. The most popular, which invokes the disruptive selection model, was first put forward by John Maynard Smith in 1966. [6]
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.
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 ...
Surveys using a phylogenetic species concept reported 48% more species and accordingly smaller populations and ranges than those using nonphylogenetic concepts; this was termed "taxonomic inflation", [145] which could cause a false appearance of change to the number of endangered species and consequent political and practical difficulties.
The species can also be distinguished by habitat: where the ranges overlap, common hackberry occurs primarily in upland areas, whereas sugarberry occurs mainly in bottomland areas. [3] Sugarberry's range extends from the Southeastern United States west to Texas and south to northeastern Mexico. [2] It is also found on the island of Bermuda. [4]
In genetics, a centimorgan (abbreviated cM) or map unit (m.u.) is a unit for measuring genetic linkage.It is defined as the distance between chromosome positions (also termed loci or markers) for which the expected average number of intervening chromosomal crossovers in a single generation is 0.01.
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 ...