Evolutionary Biology Lecture 15

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Questions and Answers

What is one proposed explanation for Haldane’s Rule regarding hybrid sterility in Drosophila?

Increased gene flow between species.

Chromosomal rearrangements are dominant in hybrids.

X-A incompatibilities in the heterogametic sex. (correct)

Environmental factors leading to hybrid invulnerability.

Which genes in Drosophila are associated with species incompatibility and show evidence of adaptive protein evolution?

Ods, Hmr, Nup96, and Nup160. (correct)

Dscam and Dicer.

Brd and Gpdh.

Ftz and Ubx.

What might be a consequence of ongoing genomic conflicts in hybrid Drosophila?

Speciation through sex-ratio meiotic drive. (correct)

Reduced introgression patterns between species.

Enhanced genetic diversity among populations.

Increased fertility and viability of hybrids.

What type of introgressions are indicated by red triangles in the sechellia genome model?

Male sterile introgressions. Signup and view all the answers

What role do the genes related to hybrid male sterility play in the context of Drosophila evolution?

They promote increased reproductive isolation. Signup and view all the answers

What is a potential outcome of the hybridization between G.conirostris and G.fortis in Galapagos finches?

The offspring will imprint on the distinct male song. Signup and view all the answers

How can strong selection affect species maintenance despite gene flow?

It can preserve distinct species even with gene flow. Signup and view all the answers

What does the presence of patterns of introgression across hybrid zones indicate?

They can reveal locations of genes that are incompatible in hybrids. Signup and view all the answers

What is still unclear regarding speciation with gene flow compared to strict allopatry?

The prevalence of speciation with gene flow is uncertain. Signup and view all the answers

Which mechanism allows favored alleles to move through hybridization events?

Selective introgression of advantageous traits. Signup and view all the answers

In the context of hybrid speciation, what does imprinting refer to?

The process of offspring learning specific songs from other species. Signup and view all the answers

What can be inferred about the success of hybridization events?

Hybridization can sometimes result in stable populations despite gene flow. Signup and view all the answers

What does the term 'speciation with gene flow' imply?

Gene flow among populations aids in the emergence of new species. Signup and view all the answers

What is a significant factor contributing to the rapid speciation in plants?

Hybridization leading to polyploidization Signup and view all the answers

Which organism is known for having speciation rates that may be slower compared to cichlids?

Passerine birds Signup and view all the answers

What is the consequence of crossing tetraploid plants with diploids?

Production of sterile offspring Signup and view all the answers

What does the 'large X-effect' refer to in Drosophila hybrids?

Disproportionate impact of the X chromosome on male hybrid sterility Signup and view all the answers

What mechanism can facilitate polyploid speciation in plants?

Selfing or vegetative propagation Signup and view all the answers

Which of these is NOT associated with speciation rates in the mentioned organisms?

Horseshoe crabs Signup and view all the answers

Which of the following refers specifically to hybridization resulting in a new species with an increased chromosome count?

Allopolyploidy Signup and view all the answers

Which statement about tetraploid mint Galeopsis tetrahit is accurate?

It was formed through hybridization of diploid species. Signup and view all the answers

Study Notes

Lecture 15 Objectives

Genetics of speciation
Dobzhansky-Muller incompatibilities
Speciation as an incidental effect of adaptation
Reinforcement
Sympatric speciation and leaky species boundaries

Dobzhansky-Muller Model of Species Incompatibility

Problem with single-locus models
Ancestral population splits followed by allopatric divergence
Different alleles fix
Hybrids may be sterile or inviable
Incompatibility arises from the interaction of alleles at different loci.

Additional Concepts

Observations from natural populations support the idea that isolation may be an incidental effect of directional selection
Variation in mating systems and the intensity of selection can affect speciation rates.
Ecological divergence is correlated with reproductive isolation.
Reinforcement - selection acts directly to increase isolation
Factors against reinforcement include gene flow into hybrid zones, deleterious pleiotropic effects of alleles increasing assortative mating, and weak genetic association.
Empirical examples of reinforcement
Sympatric speciation- in-situ evolution of reproductive isolation
High speciation rates in taxa exhibiting bioluminescent courtship (or displays)
Speciation associated with hybridization or gene flow
Haldane's Rule- the sex with the heterogametic sex is more likely to have a hybrid inviability or sterility.
X-chromosome may play a role for incompatibility
Time for speciation may vary across groups.
Polyploid speciation in plants
Nest parasites are a good example of sympatric isolation

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Explore key concepts in the genetics of speciation, including Dobzhansky-Muller incompatibilities and mechanisms of sympatric speciation. This quiz covers how adaptation influences speciation rates and the role of isolation in the evolutionary process. Test your knowledge on reinforcement and hybrid interactions in natural populations.