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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]
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 ...
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 ...
D. baeomyces is related to Icmadophila ericetorum, the candy lichen, and the two species superficially resemble one another. [2] In some parts of North America where ranges overlap, both D. baeomyces and I. ericetorum are colloquially referred to as "fairy puke" lichen, leading to further confusion between the species.
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]
The two species are not genetically compatible: the result of over 27 attempts in Russia to hybridise the two species was just one stillborn kit, bred from the pairing of a male North American beaver and a female Eurasian beaver. The difference in chromosome count makes interspecific breeding unlikely in areas where the two species' ranges overlap.