What is speciation, and describe 3 types of speciation with examples

What is speciation?

Speciation is the process by which new species arise from existing ones. The genetic and ecological factors that contribute to speciation are complex and multifaceted, and different modes of speciation can occur under different circumstances. In this class note, we will explore the three main types of speciation: allopatric, sympatric, and parapatric speciation, as well as the factors contributing to each.

What is allopatric speciation?

Allopatric speciation occurs when a population is geographically isolated from the rest of its species. This can occur through a variety of mechanisms, including the formation of a mountain range, the opening of a new sea, or the formation of a glacier. Once isolated, the two populations may experience different selective pressures that lead to genetic differentiation. Over time, mutations, genetic drift, and natural selection can result in reproductive isolation between the two populations. This can occur through a variety of mechanisms, including differences in mating behavior, changes in genital morphology, or differences in gamete compatibility. Once reproductive isolation is complete, the two populations are considered different species.

Describe an example of allopatric speciation.

An example of allopatric speciation is the Galapagos finches. The finches on the different islands of the Galapagos archipelago are thought to have originated from a single ancestral species. Over time, the different populations of finches on each island adapted to their unique environments, resulting in different beak sizes and shapes. This adaptation eventually led to reproductive isolation, and the finches on each island are now considered different species.

What is sympatric speciation?

Sympatric speciation occurs when a new species arises within the range of an existing species without physically separating populations. This can occur through a variety of mechanisms, including changes in mating behavior, niche differentiation, or chromosomal changes. In order for sympatric speciation to occur, there must be strong selective pressures that lead to reproductive isolation between populations. This can occur through a variety of mechanisms, including differences in mating behavior, changes in genital morphology, or differences in gamete compatibility.

Describe an example of sympatric speciation.

An example of sympatric speciation is the apple maggot fly. This fly was originally a parasite of hawthorn fruit, but when apple trees were introduced to North America, a new host became available. The apple maggot fly rapidly adapted to this new host and became reproductively isolated from the hawthorn parasite fly. The two populations are now considered different species.

What is parapatric speciation?

Parapatric speciation occurs when populations of a species are distributed along a geographic gradient, with hybridization occurring at the edges of the populations. This can occur through various mechanisms, including selection for adaptations to different environments or niches. Over time, the populations at the edges of the range may become reproductively isolated due to selection against hybrids. This can occur through a variety of mechanisms, including hybrid breakdown, reduced hybrid viability, or reduced hybrid fertility.

Describe an example of parapatric speciation.

An example of parapatric speciation is the cline in the peppered moth. Prior to the industrial revolution, the light-colored form of the peppered moth was dominant in England, but as the country became more industrialized, the dark form became more common in polluted areas. This resulted in a cline of variation across the country, with the two forms interbreeding at the edges of the range. Over time, the two forms became reproductively isolated due to selection against hybrids.

In conclusion, speciation is a complex process that can occur through a variety of mechanisms. Allopatric, sympatric, and parapatric speciation are the three main types of speciation, and each is characterized by different factors that contribute to reproductive isolation. The study of speciation is important for understanding the diversity of life on Earth and the processes that shape it.