Parapatric speciation is the evolution of geographically adjacent populations into distinct species.

# REDIRECT Parapatric speciation

Parapatric speciation is a form of speciation that occurs due to apparition of dimorphism between populations of a species, and simultaneous variation in the mating habits, within a continuous geographical area.

* " Parapatric speciation " in Understanding Evolution at evolution. berkeley. edu

# Rapid speciation: presence of one or more bursts in the emergence of new species around the time that ecological and phenotypic divergence is underway.

It is also involved in loss of cellular homeostasis associated with early events in cancer onset and in prion diseases as well as in the origin of new species ( speciation ).

The patterns of speciation in the Cucurbitales is diversified in a high number of species.

The turnover in this group is clearly marked at the species level .< ref > Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a sharp increase in extinctions than by a decrease in speciation .< ref > The K – T boundary record of dinoflagellates is not as well-understood, mainly because only microbial cysts provide a fossil record, and not all dinoflagellate species have cyst-forming stages, thereby likely causing diversity to be underestimated.

However, as the marine microbiota recovered, it is thought that increased speciation of benthic foraminifera resulted from the increase in food sources.

They wrote " History, as Hegel said, moves upward in a spiral of negations ," and that " punctuated equilibria is a model for discontinuous tempos of change ( in ) the process of speciation and the deployment of species in geological time.

His theory of peripatric speciation ( a more precise form of allopatric speciation which he advanced ), based on his work on birds, is still considered a leading mode of speciation, and was the theoretical underpinning for the theory of punctuated equilibrium, proposed by Niles Eldredge and Stephen Jay Gould.

Hybridization is, however, an important means of speciation in plants, since polyploidy ( having more than two copies of each chromosome ) is tolerated in plants more readily than in animals.

It is for this reason that gene flow strongly acts against speciation, by recombining the gene pools of the groups, and thus, repairing the developing differences in genetic variation that would have led to full speciation and creation of daughter species.

However, time is not a necessary distinguishing factormacroevolution can happen without gradual compounding of small changes ; whole-genome duplication can result in speciation occurring over a single generation-this is especially common in plants.

A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation, is the presence of heritable genetic variation that results in fitness differences.

When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis.

Philosopher Kim Sterelny adds, " In claiming that species typically undergo no further evolutionary change once speciation is complete, they are not claiming that there is no change at all between one generation and the next.

Whether genetic drift is a minor or major contributor to speciation is the subject matter of much ongoing discussion.

One example of natural speciation is the diversity of the three-spined stickleback, a marine fish that, after the last ice age, has undergone speciation into new freshwater colonies in isolated lakes and streams.

There is debate as to the rate at which speciation events occur over geologic time.

These included the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridization.

Contrary to the claims of some antievolution proponents, evolution of life forms beyond the species level (" macroevolution ", i. e. speciation ) has indeed been observed and documented by scientists on numerous occasions.

The process of speciation may fall within the purview of either, depending on the forces thought to drive it.

As few as two mutations can result in speciation: if each mutation has a neutral or positive effect on fitness when they occur separately, but a negative effect when they occur together, then fixation of these genes in the respective subgroups will lead to two reproductively isolated populations.

As time went on Gould moved away from wedding punctuated equilibrium to allopatric speciation, particularly as evidence accumulated in support of other modes of speciation.

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.

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

** 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.

The three-spine stickleback provides an example of how molecular biogeographic studies that rely solely on mtDNA can be misleading, and that consideration of the genealogical history of alleles from multiple unlinked markers ( i. e. nuclear genes ) is necessary to infer speciation histories.

His thinking changed from the view that species formed in isolated populations only, as on islands, to an emphasis on speciation without isolation ; that is, he saw increasing specialisation within large stable populations as continuously exploiting new ecological niches.

Despite this, Huxley strongly supported Darwin on evolution ; though he called for experiments to show whether natural selection could form new species, and questioned if Darwin's gradualism was sufficient without sudden leaps to cause speciation.

The science of ornithology has a long history and studies on birds have helped develop several key concepts in evolution, behaviour and ecology such as the definition of species, the process of speciation, instinct, learning, ecological niches, guilds, island biogeography, phylogeography and conservation.

Such whole genome sequencing projects allow for studies on evolutionary processes involved in speciation.

As part of the disagreement about whether natural selection alone was sufficient to explain speciation, George Romanes coined the term neo-Darwinism to refer to the version of evolution advocated by Alfred Russel Wallace and August Weismann with its heavy dependence on natural selection.

There is an increasing trend of using ICP-MS as a tool in speciation analysis, which normally involves a front end chromatograph separation and an elemental selective detector, such as AAS and ICP-MS. For example, ICP-MS may be combined with size exclusion chromatography and quantitative preparative native continuous polyacrylamide gel electrophoresis ( QPNC-PAGE ) for identifying and quantifying native metal cofactor containing proteins in biofluids.

The fragmentation of once more continuous rainforest facilitated isolation of populations and this likely caused the increase in the rate of speciation as found in the Lauraceae.

The fragmentation of once more continuous rainforest facilitated isolation of populations and this likely caused the increase in the rate of speciation.

In this model, the parent species lives in a continuous habitat, in contrast with allopatric speciation & peripatric speciation where subpopulations become geographically isolated, and sympatric speciation inside the same area ( and still contested ).

Most polyploids display heterosis relative to their parental species, and may display novel variation or morphologies that may contribute to the processes of speciation and eco-niche exploitation.

It is for this reason that gene flow strongly acts against speciation, by recombining the gene pools of the groups, and thus, repairing the developing differences in genetic variation that would have led to full speciation and creation of daughter species.

These adaptations, variations on habit, trunks, branches, branchlets, spines, leaves, or flowers, are plentiful in demonstrating how Pachypodium as a genus fosters greater variation in its speciation.

The significance of geographical variation is in that it may lead to allopatric speciation, whereas true polymorphism takes place in panmictic populations.

Owing to their widespread distribution and distinctive regional variation, they have become iconic examples of speciation by isolation and genetic drift.

Evidence for speciation, adaptation, variation, and optimization within narrow ranges via natural selection is not disputed.