becomes isolated (e.g. a population of birds on an oceanic island), selection can act on the population independent of the parent population. Given both geographic separation and enough time, speciation can result as a byproduct. It can be distinguished from allopatric speciation by three important features: 1) the size of the isolated population, 2) the strong selection imposed by the dispersal and colonization into novel environments, and 3) the potential effects of genetic drift on small populations. However, it can often be difficult for researchers to determine if peripatric speciation occurred as vicariant explanations can be invoked due to the fact that both models posit the absence of gene flow between the populations. The size of the isolated population is important because individuals colonizing a new habitat likely contain only a small sample of the genetic variation of the original population. This promotes divergence due to strong selective pressures, leading to the rapid fixation of an allele within the descendant population. This gives rise to the potential for genetic incompatibilities to evolve. These incompatibilities cause reproductive isolation, giving rise to rapid speciation events. Models of peripatry are supported mostly by species distribution patterns in nature. Oceanic islands and archipelagos provide the strongest empirical evidence that peripatric speciation occurs. Centrifugal Centrifugal speciation is a variant, alternative model of peripatric speciation. This model contrasts with peripatric speciation by virtue of the origin of the genetic novelty that leads to reproductive isolation. When a population of a species experiences a period of geographic range expansion and contraction, it may leave small, fragmented, peripherally isolated populations behind. These isolated populations will contain samples of the genetic variation from the larger parent population. This variation leads to a higher likelihood of ecological niche specialization and the evolution of reproductive isolation. Centrifugal speciation has been largely ignored in the scientific literature. Nevertheless, a wealth of evidence has been put forth by researchers in support of the model, much of which has not yet been refuted. One example is the possible center of origin in the Indo-West Pacific. Microallopatric Microallopatry refers to allopatric speciation occurring on a small geographic scale. Examples of microallopatric speciation in nature have been described. Rico and Turner found intralacustrine allopatric divergence of Pseudotropheus callainos (Maylandia callainos) within Lake Malawi separated only by 35 meters. Gustave Paulay found evidence that species in the subfamily Cryptorhynchinae have microallopatrically speciated on Rapa and its surrounding