| Part of a series on |
| Evolutionary biology |
|---|
|
Key topics
|
|
Natural history
|
|
Social implications
|
| Evolutionary Biology Portal Category • Related topics • Book |
Parapatry is a term from biogeography, referring to organisms whose ranges do not significantly overlap but are immediately adjacent to each other; they only occur together in the narrow contact zone, if at all. This geographical distribution is opposed to sympatry (same area) & allopatry or peripatry (2 cases of distinct areas).
This distribution may along time cause speciation into sister species, a process called parapatric speciation.
Contents |
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. 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).
Niches in this habitat can differ along an environmental gradient, hampering gene flow, and thus creating a cline. In parapatric speciation there is no specific extrinsic barrier to gene flow. The population is continuous, but nonetheless, it does not mate randomly. Individuals are more likely to mate with their geographic neighbors than with individuals in a different part of the population’s range. In this mode, divergence may happen because of reduced gene flow within the population as a whole and varying selection pressures across the population’s range.[1]
An example[2] of this is the grass Anthoxanthum, which has been known to undergo parapatric speciation in such cases as mine contamination of an area. This creates a selection pressure for tolerance to those metals. Flowering time generally changes (tending toward character displacement—strong selection against interbreeding—as the hybrids are generally ill-suited to the environment) and often plants will become self-pollinating.
Similarly, a recent study provided evidence for parapatric speciation in Tennessee cave salamanders, involving divergence with gene flow between cave and surface populations.[3]
Another example are ring species.
"Parapatric speciation." in Understanding Evolution at evolution.berkeley.edu
|
||||||||||||||
|
||||||||||||||||||||||||||||||||