28-Speciation Flashcards
What is the difference between allopatric and sympatric speciation?
Allopatric speciation: A population forms a new species while geographically isolated from its parent population due to a barrier. It can occur through dispersal and vicariance.
Sympatric speciation: A subset of a population forms a new species without geographic separation.
What is the difference between dispersal and vicariance?
Dispersal: Movement to a new environment.
Vicariance: Encroaching physical feature such as a river, glacier, lava flow.
Give an example of dispersal and one of vicariance.
Dispersal: There are 3 species of a fly in the Hawaiian Islands.
Vicariance: The desert pupfish. Also, the Caribbean Sea and the Pacific Ocean used to be connected. This is indicated by the similar snapping shrimp on both sides. Also Madagascar and India used to be closer together (as seen by frog species)
How can sympatric speciation arise?
Mutation. Ex. Rhagoletis is a fly that used to use hawthorn as a host plant. When apples were introduced, there was a mutation that occured to male some use apples instead and this eventually turned into a new species.
Why are Hawaiian flies a good example of speciation by dispersal
Because they seemed to island hop. The oldest species are on the oldest island (Big Island)
How can autotetraploidy and allotetraploidy lead to speciation?
Autotetraploidy: Derived from same species.
Allotetraploidy: Dervied from some different species. have two sets of chromosomes
Occur because after chromosomes duplicate, they fail to divide. This gives rise to tetraploid tissue. Gametes produced are diploid. Offspring with tetraploid karyotypes may be viable and fertile.
What are reproductive isolating mechanisms and how do they affect fitness of females?
Prezygotic: no formation of embryo. Two snails spiral in different direction so genital opening cannot meet.
Postzygotic: no fertile offspring. Sea urchin gametes from red and purple are unable to fuse because proteins on the surfaces of eggs and sperm can not bind together.
What are hybrid zones?
A hybrid zone exists where the ranges of two interreeding species or diverged intraspecific lineages meet and cross-fertilize.
How is a hybrid zone illustrated by the toad and bird examples?
Toad: Change in allele frequency across the zone. No gene flow, hybrids have morphological abnormalities, poor survival.
Bird: Female pied flycatchers do not make mistake in zone of sympatry, but do make mistakes choosing males from zone of allopatry.
Can humans impact speciation in nature?
They can. They can stir sediments, which changes lighting that makes it harder for fish to choose the right mate (cichlid)
