Reproductive isolation

Reproductive isolation occurs when barriers reduce or prevent gene flow between populations by limiting successful mating or the production of fertile offspring. It can contribute to the formation of new species.

Prezygotic barrier: A reproductive barrier that prevents mating or fertilization before a zygote forms. These barriers block gene flow before fertilization, through timing, behavior, habitat, or gamete incompatibility.
Gene flow: The transfer of alleles between populations through migration and reproduction. Reproductive isolation is defined by barriers that reduce this transfer.
Allopatric speciation: The formation of species after populations become geographically separated. Geographic separation can initiate divergence that later produces reproductive barriers.
Geographic isolation: The separation of populations by physical distance or landscape features that restrict movement. It limits encounters rather than directly preventing successful mating or fertile offspring.
Postzygotic barrier: A reproductive barrier that reduces hybrid survival or fertility after fertilization. These barriers allow fertilization but limit gene flow through weak, inviable, or sterile hybrids.
Population genetics: The study of genetic variation within and between populations and how it changes over time. It provides tools for measuring how barriers alter genetic exchange.
Sympatric speciation: The formation of species within the same geographic area, without physical separation. It shows reproductive isolation can evolve despite opportunities for populations to meet.
Premating isolation: Reproductive isolation caused by barriers that prevent mating between populations. It is one part of the broader prezygotic category, focused specifically on mating.
Assortative mating: A mating pattern in which individuals pair more often with similar than dissimilar individuals. Preference for similar mates can reduce gene flow even when populations overlap.
Biological species concept: A species concept that defines species as groups capable of interbreeding and reproductively isolated from others. It uses reproductive isolation as the boundary between species.

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