Podcast
Questions and Answers
What type of selection favors individuals at the extremes of a phenotype distribution?
What type of selection favors individuals at the extremes of a phenotype distribution?
Which of the following is NOT a step in the process leading to adaptive speciation under disruptive selection?
Which of the following is NOT a step in the process leading to adaptive speciation under disruptive selection?
What ecological advantage results from disruptive selection in the context of trophic polymorphisms?
What ecological advantage results from disruptive selection in the context of trophic polymorphisms?
In the context of sympatric speciation, assortative mating leads to which outcome?
In the context of sympatric speciation, assortative mating leads to which outcome?
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Which of the following traits was NOT included in John Maynard-Smith's model of sympatric speciation?
Which of the following traits was NOT included in John Maynard-Smith's model of sympatric speciation?
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What is a common result of polymorphisms generated by disruptive selection?
What is a common result of polymorphisms generated by disruptive selection?
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Which of the following best describes a fitness landscape in the context of disruptive selection?
Which of the following best describes a fitness landscape in the context of disruptive selection?
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Which type of characters were observed in the beak types of black-bellied seedcrackers as a result of disruptive selection?
Which type of characters were observed in the beak types of black-bellied seedcrackers as a result of disruptive selection?
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What is a primary challenge for creating and maintaining associations between matching alleles at three gene loci during speciation?
What is a primary challenge for creating and maintaining associations between matching alleles at three gene loci during speciation?
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Which process makes sympatric speciation more conceivable according to recent models?
Which process makes sympatric speciation more conceivable according to recent models?
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What is the role of chemical cues in the host selection of the apple maggot fly?
What is the role of chemical cues in the host selection of the apple maggot fly?
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How does the fitness landscape influence speciation in fish populations in lake ecosystems?
How does the fitness landscape influence speciation in fish populations in lake ecosystems?
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What is a significant factor that could lead to temporal reproductive isolation in sympatric species?
What is a significant factor that could lead to temporal reproductive isolation in sympatric species?
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Which aspect is vital for sympatric speciation through adaptation in phytophagous insects?
Which aspect is vital for sympatric speciation through adaptation in phytophagous insects?
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What type of polymorphism is likely represented in populations adapting to new hosts in the case of the apple maggot fly?
What type of polymorphism is likely represented in populations adapting to new hosts in the case of the apple maggot fly?
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What represents assortative mating in fish populations adapting to different ecological conditions?
What represents assortative mating in fish populations adapting to different ecological conditions?
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What type of selection is involved in sympatric speciation as seen in Arctic Char trophic morphs?
What type of selection is involved in sympatric speciation as seen in Arctic Char trophic morphs?
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Which of the following best describes the outcome of disruptive selection in blackcaps regarding migratory traits?
Which of the following best describes the outcome of disruptive selection in blackcaps regarding migratory traits?
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What phenomenon explains the division of the red crossbill into multiple phylogenetic species?
What phenomenon explains the division of the red crossbill into multiple phylogenetic species?
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What best defines polymorphism in the context of Arctic Char trophic morphs?
What best defines polymorphism in the context of Arctic Char trophic morphs?
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Which mechanism of speciation involves the development of mating preferences due to divergent selection?
Which mechanism of speciation involves the development of mating preferences due to divergent selection?
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In the study of blackcaps, what is hypothesized to happen to offspring of parents with non-compatible migratory directions?
In the study of blackcaps, what is hypothesized to happen to offspring of parents with non-compatible migratory directions?
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Which of the following statements about mechanisms of speciation is true?
Which of the following statements about mechanisms of speciation is true?
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What role does ecological and behavioral incompatibility play in the reinforcement of speciation?
What role does ecological and behavioral incompatibility play in the reinforcement of speciation?
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Flashcards
Arctic Char trophic morphs
Arctic Char trophic morphs
Different types of Arctic Char fish that have evolved to eat different food sources.
Sympatric speciation
Sympatric speciation
Speciation occurring within the same geographic area, not requiring geographic isolation.
Disruptive selection
Disruptive selection
Natural selection that favors extreme forms of a trait.
Ecological speciation
Ecological speciation
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Resource use
Resource use
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Random mating
Random mating
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Non-random mating
Non-random mating
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Genetic drift
Genetic drift
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Fitness Landscape
Fitness Landscape
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Trophic Polymorphism
Trophic Polymorphism
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Assortative Mating
Assortative Mating
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Polymorphism
Polymorphism
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Ecological Morphs
Ecological Morphs
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Adaptive Speciation
Adaptive Speciation
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Allelic Association
Allelic Association
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Sexual Reproduction
Sexual Reproduction
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Quantitative Traits
Quantitative Traits
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Apple Maggot Fly
Apple Maggot Fly
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Host Switching
Host Switching
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Reproductive Isolation
Reproductive Isolation
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Study Notes
Mechanisms of Speciation
- Speciation involves the formation of new and distinct species in the course of evolution.
- There are multiple mechanisms driving this process.
Types of Speciation Mechanisms
- Evolution of incompatibilities: Genetic or behavioural incompatibilities can arise as a byproduct of neutral divergence (genetic drift) or as a product of adaptation (selection).
- Origin of incompatibility (reinforcement): Ecological and behavioural incompatibilities can emerge through direct selection.
- Divergence of mating preferences: Divergent or disruptive sexual selection can lead to the divergence of mating preferences.
Adaptive Speciation
- Adaptive speciation involves the origin of ecological incompatibility under direct selection in a geographical context.
- Disruptive selection is required. This is where extreme phenotypes are favored over intermediate ones.
Forms of Selection
- Unimodal fitness landscape: Directional selection—characterized by a single peak in the fitness landscape.
- Multimodal fitness landscape: Disruptive selection—characterized by multiple peaks in the fitness landscape. Stabilizing selection—characterized by a single peak in the fitness landscape.
Disruptive Selection and Polymorphisms
- Disruptive selection on multimodal fitness landscapes can create polymorphisms as a solution to low average fitness. Trophic polymorphisms are common in vertebrates (e.g. Arctic char, black-bellied seedcrackers).
- Examples include differences in beak sizes between seedcracker birds or variations in fish (e.g., planktivorous, piscivorous).
Sympatric Speciation
- Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same geographic region.
- Adaptation to alternative resources is a driving force in sympatric speciation in fish populations (e.g., Arctic char trophic morphs).
- The apple maggot fly (Rhagoletis pulmonella) provides an example of sympatric speciation through adaptation to alternative resources (hawthorne, apple, cherry).
Mathematical and Computer Models
- John Maynard-Smith developed early mathematical models, focusing on sympatric speciation occurring through assortative mating.
- Recent models suggest sympatric speciation is more likely when quantitative traits (determined by multiple genes) are considered.
Environments Affecting Speciation in Fish
- Environmental factors in lake ecosystems (e.g., temperature, water clarity, habitat structure), create selective pressures that shape the fitness landscape for fish species.
- Features such as water depth, habitat structure, and available food sources can drive speciation.
Classical Speciation Cases
- Numerous examples of speciation through divergent selection on resources illustrate scenarios without geographic isolation. These include: whitefish, sticklebacks, sockeye salmon, blue tits, etc.
Disruptive Selection in Migratory Patterns
- Disruptive selection can shape differences in migratory direction. The breeding and wintering ranges of blackcaps, for example, shows how migratory direction is a heritable trait.
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Description
Explore the various mechanisms of speciation, including the evolution of incompatibilities and adaptive speciation. This quiz examines how ecological factors and selective processes contribute to the formation of new species over time. Test your understanding of speciation dynamics and the role of selection.
