Speciation and Reproductive Isolation

The formation of new species due to geographic isolation, where populations become separated by physical barriers.

The formation of new species in geographically adjacent populations, where gene flow between populations is limited by environmental gradients or barriers.

The occurrence of distinct populations of individuals belonging to different genotypes. Individuals with mixed genotypes may have characteristics of both populations.

The movement of genetic material between species, often occurring due to hybridization.

Areas of the genome that remain distinct between species, even in the presence of introgression, contributing to reproductive isolation.

The process by which speciation occurs despite ongoing gene flow between populations, often involving specialized adaptations to different environments.

The coexistence of closely related species in the same geographic area.

A group of closely related species with complex evolutionary relationships, often involving hybridization and gene flow.

The evolution of barriers to gene flow between populations, leading to the formation of new species.

Speciation where new species arise within the same geographical area, without physical isolation, driven by extremely strong divergent selection.

The reduction of genetic differences between populations due to the mixing of genes through interbreeding.

A situation where two or more genes are inherited together more often than expected by chance, meaning they're linked on a chromosome.

The process of species that have diverged in isolation coming back into contact and possibly interbreeding.

A process where natural selection favors individuals that mate with those from their own population, reducing the chances of interbreeding with other species.

Species can still be considered distinct even if there's some gene flow between them, as long as they maintain their unique identities.

The observation of different populations living together in the same area (sympatry) without merging, despite some gene flow, supports the idea that they are separate species.

The most fundamental way to classify reproductive isolation barriers is by whether they act before (prezygotic) or after (postzygotic) the formation of a zygote.

Pre-mating barriers prevent potential mates from even meeting or mating in the first place.

Post-mating, prezygotic barriers occur when potential mates try to mate but are unable to produce a zygote, often due to incompatibility in genitalia or gametes.

Postzygotic barriers lead to reduced fitness of hybrid offspring, either through intrinsic factors like sterility or lethality, or extrinsic factors like ecological mismatch or reduced mating success.

Pollinator differences can act as a pre-zygotic barrier to gene flow, as different species may rely on different pollinators for fertilization.

Multiple reproductive barriers can operate in sequence, contributing to the overall level of isolation between species. Some potential barriers may not even come into play.

A measure of how often individuals from different species mate compared to individuals from the same species.

Premating isolation mechanisms that act before mating occurs, preventing potential mates from meeting or interacting.

Differences in mating songs or calls between species that prevent successful mating.

Species that occupy the same geographic area but reproduce at different times, preventing gene flow.

Two coral species living in the same area, but releasing their gametes at different times, preventing interbreeding.

Mechanisms that occur before mating, preventing gene flow.

Differences in habitats, timing, or behavior prevent populations from meeting.

Intrinsic mechanisms that affect the survival or fertility of hybrids. Examples include hybrid lethality and sterility.

Extrinsic mechanisms that affect hybrid fitness due to the environment or social factors. Examples include ecological mismatches and mate recognition issues.

A model explaining the evolution of reproductive isolation based on incompatible gene combinations.

A specific type of genetic incompatibility that arises when two species hybridize, resulting in offspring with reduced fitness. It occurs when genes from different species interact in a way that disrupts proper function.

The process where natural selection favors traits that reduce interbreeding between species, often in areas where they overlap, due to the lower fitness of hybrids.

The evolution of differences in traits, particularly in a shared geographic area, that reduce hybridization and promote reproductive isolation. This can involve mating behaviors, physical characteristics, or other factors.