There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric, peripatric, parapatric, and sympatric.

Pied flycatchers can mimic the song of the Collared Flycatcher in sympatric populations ( Haavie et al.

In multicellular eukaryotic organisms, sympatric speciation is thought to be an uncommon but plausible process by which genetic divergence ( through reproductive isolation ) of various populations from a single parent species and inhabiting the same geographic region leads to the creation of new species.

The European cisco has also evolved into ecologically distinct sympatric populations or ecomorphs independently within several lakes ( e. g. autumn and spring spawning populations, normal and dwarf morphs ), which have been designated as distinct taxa, making the systematics complicated as with the North American Coregonus artedi complex.

In biology, two species or populations are considered sympatric when they exist in the same geographic area and thus regularly encounter one another.

Conversely, zoologist Michael JD White considered two populations sympatric if genetic interbreeding was viable within the habitat overlap.

The lack of geographic constraint in isolating sympatric populations implies that the emerging species avoid interbreeding via other mechanisms.

It is also apparent in the differences in levels of prezygotic isolation ( by factors that prevent formation of a viable zygote ) in both sympatric and allopatric populations.

This active isolation of individual populations helps maintain the genetic purity of the fungal colony, and this mechanism may lead to sympatric speciation within a shared habitat.

Current molecular studies in evolution and speciation indicate that although allopatric speciation seems to be the norm in groups ( such as in many invertebrates — especially in the insects ), there are numerous cases of sympatric speciation in groups with greater mobility ( such as the birds ).

The most widely accepted example of sympatric speciation is that of the cichlids of Lake Nabugabo in East Africa, which is thought to be due to sexual selection.

One example of evolution at work is the case of the hawthorn fly, Rhagoletis pomonella, also known as the apple maggot fly, which appears to be undergoing sympatric speciation.

The different species and subspecies of teosinte can be readily distinguished based on morphological, cytogenetic, protein, and DNA differences and on geographic origin, although the two perennials are sympatric and very similar.

The Lesser Grey Shrike ( L. minor, Balkans to Central Asia ) seems to be quite distinct indeed and is sympatric with the Grey Shrike superspecies between Eastern Europe and Central Asia ; it may be more closely related to the small brown shrikes and resemble the bold, aggressive and hard-to-catch grey shrikes because of Batesian mimicry.

There are a number of similar species, including the partly sympatric Arctic Tern, which can be separated on plumage details, leg and bill colour, or vocalisations.

But while they may exist unnoticed, they cannot be frequent, as the species are largely sympatric and closely related, yet remain distinct, with no signs of significant introgression.

The Corn Crake is sympatric with the African Crake on the wintering grounds, but can be distinguished by its larger size, paler upperparts, tawny upperwing and different underparts pattern.

In both the breeding and wintering ranges it is unlikely to be confused with any other rails, since sympatric species are smaller, with white markings on the upperparts, different underparts patterns and shorter bills.

By linking the specimens to type material through morphology and DNA barcoding, they determined that the species distributed from Costa Rica to southern Quebec and Ontario, should be called A. aurea, whereas the similar and marginally sympatric species found in Central America should be called A. pustulella.

If these organisms are closely related ( e. g. sister species ), such a distribution may be the result of sympatric speciation.

Rhagoletis pomonella, the apple maggot, may be currently undergoing sympatric or, more precisely, heteropatric ( see heteropatry ) speciation.

This species is commonly sympatric with Canyon Live Oak, and the two may be hard to distinguish because their spinose leaves are superficially similar.

While the similar plumage may be due to sheer chance – perhaps as an atavism of plesiomorphic patterns – the facts that such cases are commonplace in the Picinae and that the species involved are usually sympatric suggests that there may well be some as yet undiscovered benefit to either or all of the taxa involved.

O. ovalipes is almost identical to O. floridanus, which lives in the Gulf of Mexico, but can be separated from the sympatric O. stephensoni by the purple spots, which O. stephensoni lacks.

Possible interpretations of this phenomenon are: males may be polymorphic for rufous and white plumage colour ; rufous birds may be sub-adults ; and there may even be two sympatric species distinguishable only in the male.

The Corn Crake is sympatric with the African Crake on its wintering grounds, but can be distinguished by its larger size, paler upperparts, chestnut-coloured patch on the upperwing and different underparts pattern.

Furthermore, assortative mating may be required for sympatric speciation, meaning the evolution of a new species without geographic isolation.

L. emarginata is very similar to Libinia dubia with which it is largely sympatric.

Hyenas feature prominently in the folklore and mythology of human cultures with which they are sympatric.

It is sympatric with the impala only in certain corners of its range, such as Etosha National Park and the Pilanesberg area.

In sympatric speciation, species diverge while inhabiting the same place.

Often-cited examples of sympatric speciation are found in insects that become dependent on different host plants in the same area.

However, the existence of sympatric speciation as a mechanism of speciation is still hotly contested.

Scientists have argued that the evidences of sympatric speciation are in fact examples of micro-allopatric, or heteropatric speciation.

But there has been at least one study, in 2008, that suggests that sympatric speciation has occurred in Tennessee cave salamanders.

Grant ) and his current colleagues in British Columbia, were once thought to provide an intriguing example best explained by sympatric speciation.

** The fact that this pattern of speciation occurred the same way on three separate occasions suggests strongly that ecological factors in a sympatric population can cause speciation.

Some evidence, such as the fact that six out of thirteen allozyme loci are different, that hawthorn flies mature later in the season and take longer to mature than apple flies ; and that there is little evidence of interbreeding ( researchers have documented a 4-6 % hybridization rate ) suggests that sympatric speciation is occurring.

Reinforcement favoring reproductive isolation is required for both parapatric and sympatric speciation.

* Marti, Carl D .( 1974 ): Feeding ecology of four sympatric owls.

Parasites infect hosts that exist within their same geographical area ( sympatric ) more effectively.

In the experiment, the snails were infected by their sympatric parasites, allopatric parasites and mixed sources of parasites.

The results suggest that the parasites were more highly effective in infecting their sympatric snails than their allopatric snails.

Though the allopatric snails were still infected by the parasites, the infectivity was much less when compared to the sympatric snails.

In areas of Italy where the two animals are sympatric, the extent to which boars are preyed upon by wolves has led to them developing more aggressive behaviour toward both wolves and domestic dogs.

Polyploidization is a mechanism of sympatric speciation because polyploids are usually unable to interbreed with their diploid ancestors.

In the Oligocene, around 30 mya, advanced cyprinids began to out-compete catostomids wherever they were sympatric, causing a decline of the suckers.

In western Borneo, where they are sympatric, both K. minor and K. bicirrhis are collectively known as lais tipis in the Malay language, but when locals want to distinguish the two, they refer to the Glass Catfish as lais limpok.