In populace hereditary qualities, quality stream (otherwise called quality relocation or allele stream) is the exchange of hereditary variety starting with one populace then onto the next. In the event that the pace of quality stream is sufficiently high, at that point two populaces are considered to have equal allele frequencies and consequently successfully be a solitary populace. It has been demonstrated that it takes just "One vagrant for each age" to keep populaces from wandering because of float. Quality stream is a significant instrument for moving hereditary decent variety among populaces. Transients change the dissemination of hereditary assorted variety inside the populaces, by adjusting the allele frequencies (the extent of individuals conveying a specific variation of a quality). High paces of quality stream can diminish the hereditary separation between the two gatherings, expanding homogeneity. Consequently, quality stream has been thought to compel speciation by consolidating the genetic stocks of the gatherings, subsequently forestalling the improvement of contrasts in hereditary variety that would have prompted full speciation. Sometimes relocation may likewise bring about the expansion of novel hereditary variations to the genetic stock of an animal varieties or populace.

There are various elements that influence the pace of quality stream between various populaces. Quality stream is relied upon to be lower in species that have low dispersal or versatility, that happen in divided living spaces, where there is significant distances among populaces, and when there are little populace sizes. Portability assumes a significant job in the relocation rate, as exceptionally versatile people will in general have more prominent transient possibilities. In spite of the fact that creatures are believed to be more versatile than plants, dust and seeds might be conveyed significant stretches by creatures or wind. At the point when quality stream is obstructed, there can be an expansion in inbreeding, estimated by the inbreeding coefficient (F) inside a populace. For instance, numerous island populaces have low paces of quality stream because of geographic seclusion and little populace sizes. The Black Footed Rock Wallaby has a few ingrained populaces that live on different islands off the bank of Australia. The populace is so unequivocally segregated that absence of quality stream has prompted high paces of inbreeding.