Unformatted text preview: y for speciation to occur. Two populations of the same species living in the same area can become reproductively isolated (and sometimes quite rapidly). Reproductive Isolating Mechanism in Lacewing Fly LINK A small fly lays it eggs in the native hawthorne fruit. Females later lay their eggs in the fruit that they grew up in. Plus, males look for mates on the fruit they grew up on. However, 200 yrs ago a few females started to lay their eggs in apples instead. Now there are genetic differences between flies that lay eggs on apples vs. hawthornes. This is an example of potential: Clicker Question This is an example of potential: A) Sympatric speciation B) Allopatric speciation C) An invasive species D) An extinction for the original population E) A change in age structure of the original population Sympatric speciation Sympatric speciation does not require large-scale geographic distance to reduce gene flow between parts of a population. Merely exploiting a new niche may automatically reduce gene flow with individuals exploiting the other niche. This may occasionally happen when, for example, herbivorous insects try out a new host plant. 200 years ago, the ancestors of apple maggot flies laid their eggs only on hawthorns. Today, these flies lay eggs on hawthorns (which are native to America) and domestic apples (which were introduced to America by immigrants and bred). Apple spoiled by apple maggot larvae. Females generally choose to lay their eggs on the type of fruit they grew up in, and males tend to look for mates on the type of fruit they grew up in. So hawthorn flies generally end up mating with other hawthorn flies and apple flies generally end up mating with other apple flies. Is this the first step toward sympatric speciation? Emergence of Rhagoletis pomonella When there is secondary contact between two populations that show incomplete reproductive isolation, natural selection will directly favor the evolution of greater postzygotic isolating mechanisms. True False Hybrid Breakdown Postzygotic Isolation Hybrid Inferiority Reduced Hybrid Fertility Reduced Hybrid Viability Increasing Fitness Cost to Would-Be Hybridizers (going from bottom to top) Hybridization Attempted Gametic Isolation Mechanical Isolation Temporal Isolation Behavioral Isolation Habitat Isolation Geographical Isolation Prezygotic Isolating Mechanisms Has Genetic Component (right & above)...
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This note was uploaded on 03/19/2008 for the course BIOL 101 taught by Professor Annestork during the Fall '08 term at Ithaca College.
- Fall '08